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Guidelines for Preventing the Transmission of
Mycobacterium tuberculosis
in Health-Care Settings, 2005
Prepared by
Paul A. Jensen, PhD, Lauren A. Lambert, MPH, Michael F. Iademarco, MD, Renee Ridzon, MD
Division of Tuberculosis Elimination, National Center for HIV, STD, and TB Prevention
The material in this report originated in the National Center for HIV, STD, and TB Prevention, Kevin Fenton, MD, PhD, Director; and the Division
of Tuberculosis Elimination, Kenneth G. Castro, MD, Director.
Corresponding preparer: Paul A. Jensen, PhD, Division of Tuberculosis Elimination, National Center for HIV, STD, and TB Prevention, 1600
Clifton Rd., NE, MS E-10, Atlanta, GA 30333. Telephone: 404-639-8310; Fax: 404-639-8604; E-mail:
pej4@cdc.gov.
Summary
In 1994, CDC published the Guidelines for Preventing the Transmission of Mycobacterium tuberculosis
in HealthCare Facilities, 1994. The guidelines were issued in response to 1) a resurgence of tuberculosis (TB) disease
that occurred in the United States in the mid-1980s and early 1990s, 2) the documentation of several high-profile
health-care--associated (previously termed "nosocomial") outbreaks related to an increase in the prevalence of TB disease and
human immunodeficiency virus (HIV) coinfection, 3) lapses in infectioncontrol practices, 4) delays in the diagnosis and treatment
of persons with infectious TB disease, and 5) the appearance and transmission of multidrug-resistant (MDR) TB strains.
The 1994 guidelines, which followed statements issued in 1982 and 1990, presented recommendations for TBinfection
control based on a risk assessment process that classified health-care facilities according to categories of TB risk, with a
corresponding series of administrative, environmental, and respiratoryprotection control measures.
The TB infectioncontrol measures recommended by CDC in 1994 were implemented widely in health-care facilities in
the United States. The result has been a decrease in the number of TB outbreaks in health-care settings reported to CDC and
a reduction in health-care--associated transmission of
Mycobacterium tuberculosis to patients and health-care
workers (HCWs). Concurrent with this success, mobilization of the nation's TBcontrol programs succeeded in reversing the upsurge
in reported cases of TB disease, and case rates have declined in the subsequent 10 years. Findings indicate that although the
2004 TB rate was the lowest recorded in the United States since national reporting began in 1953, the declines in rates for
2003 (2.3%) and 2004 (3.2%) were the smallest since 1993. In addition, TB infection rates greater than the U.S.
average continue to be reported in certain racial/ethnic populations. The threat of MDR TB is decreasing, and the transmission of
M. tuberculosis in health-care settings continues to decrease because of implementation of infection-control measures
and reductions in community rates of TB.
Given the changes in epidemiology and a request by the Advisory Council for the Elimination of Tuberculosis (ACET)
for review and update of the 1994 TB infectioncontrol document, CDC has reassessed the TB infectioncontrol guidelines
for health-care settings. This report updates TB control recommendations reflecting shifts in the epidemiology of TB, advances
in scientific understanding, and changes in health-care practice that have occurred in the United States during the
preceding decade. In the context of diminished risk for health-care--associated transmission of
M. tuberculosis, this document places emphasis on actions to maintain momentum and expertise needed to avert another TB resurgence and to eliminate
the lingering threat to HCWs, which is mainly from patients or others with unsuspected and undiagnosed infectious TB
disease. CDC prepared the current guidelines in consultation with experts in TB, infection control, environmental control,
respiratory protection, and occupational health. The new guidelines have been expanded to address a broader concept;
health-care--associated settings go beyond the previously defined facilities. The term "health-care setting" includes many types, such
as inpatient settings, outpatient settings, TB clinics, settings in correctional facilities in which health care is delivered, settings
in which home-based health-care and emergency medical services are provided, and laboratories handling clinical specimens
that might contain M. tuberculosis. The term "setting" has been chosen over the term "facility," used in the previous guidelines,
to broaden the potential places for which these guidelines apply.
Introduction
Overview
In 1994, CDC published the Guidelines for Preventing the
Transmission of Mycobacterium tuberculosis in Health
Care Facilities, 1994 (1). The guidelines were issued in response to 1) a resurgence of tuberculosis (TB) disease that occurred in
the United States in the mid-1980s and early 1990s, 2) the documentation of multiple high-profile
health-care--associated (previously "nosocomial") outbreaks related to an increase in the prevalence of TB disease and human immunodeficiency
virus (HIV) coinfection, 3) lapses in infectioncontrol practices, 4) delays in the diagnosis and treatment of persons with
infectious TB disease (2,3), and 5) the appearance and transmission of multidrug-resistant (MDR) TB strains
(4,5).
The 1994 guidelines, which followed CDC statements
issued in 1982 and 1990 (1,6,7), presented recommendations for
TB infection control based on a risk assessment process. In this process, health-care facilities were classified according to
categories of TB risk,with a corresponding series of environmental and respiratoryprotection control measures.
The TB infectioncontrol measures recommended by CDC in 1994 were implemented widely in health-care
facilities nationwide (8--15). As a result, a decrease has occurred in
1) the number of TB outbreaks in health-care settings reported
to CDC and 2) health-care--associated transmission of
M. tuberculosis to patients and health-care workers (HCWs)
(9,16--23). Concurrent with this success, mobilization of the nation's TBcontrol programs succeeded in reversing the
upsurge in reported cases of TB disease, and case rates have declined in the subsequent 10 years
(4,5). Findings indicate that although the 2004
TB rate was the lowest recorded in the United States since national reporting began in 1953, the
declines in rates for 2003 (2.3%) and 2004 (3.2%) were the lowest since 1993. In addition, TB rates higher than the U.S. average continue to be reported
in certain racial/ethnic populations (24). The threat of MDR TB is decreasing, and the transmission of
M. tuberculosis in health-care settings continues to decrease because of implementation of
infection-control measures and reductions in
community rates of TB (4,5,25).
Despite the general decline in TB rates in recent years, a marked geographic variation in TB case rates persists, which
means that HCWs in different areas face different risks
(10). In 2004, case rates varied per 100,000 population: 1.0 in Wyoming,
7.1 in New York, 8.3 in California, and 14.6 in the District of Columbia
(26). In addition, despite the progress in the
United States, the 2004 rate of 4.9 per 100,000 population remained higher than the 2000 goal of 3.5. This goal was established
as part of the national strategic plan for TB elimination; the final goal is <1 case per 1,000,000 population by 2010
(4,5,26).
Given the changes in epidemiology and a request by the Advisory Council for the Elimination of Tuberculosis (ACET)
for review and updating of the 1994 TB infectioncontrol document, CDC has reassessed the TB infectioncontrol guidelines
for health-care settings. This report updates TBcontrol recommendations, reflecting shifts in the epidemiology of TB
(27), advances in scientific understanding, and changes in health-care practice that have occurred in the United States in
the previous decade (28). In the context of diminished risk for health-care--associated transmission of
M. tuberculosis, this report emphasizes actions to maintain momentum and
expertise needed to avert another TB resurgence and eliminate the
lingering threat to HCWs, which is primarily from patients or other persons with unsuspected and undiagnosed infectious TB disease.
CDC prepared the guidelines in this report in consultation with experts in TB, infection control, environmental
control, respiratory protection, and occupational health. This report replaces all previous CDC guidelines for TB infection control
in health-care settings (1,6,7). Primary references citing
evidence-based science are used in this report to
support explanatory material and recommendations. Review articles, which include primary references, are used for editorial style
and brevity.
The following changes differentiate this report from previous guidelines:
- The risk assessment process includes the assessment of additional aspects of infection control.
- The term "tuberculin skin tests" (TSTs) is used instead of purified protein derivative (PPD).
- The whole-blood interferon gamma release assay (IGRA),
QuantiFERON®TB Gold test (QFTG) (Cellestis
Limited, Carnegie, Victoria, Australia), is a Food and Drug Administration (FDA)--approved in vitro cytokine-based assay for
cell-mediated immune reactivity to M. tuberculosis
and might be used instead of TST in TB screening programs for
HCWs. This IGRA is an example of a blood assay for
M. tuberculosis (BAMT).
- The frequency of TB screening for HCWs has been
decreased in various settings, and the criteria for determination
of screening frequency have been changed.
- The scope of settings in which the guidelines apply has been broadened to include laboratories and additional
outpatient and nontraditional facilitybased settings.
- Criteria for serial testing for M. tuberculosis
infection of HCWs are more clearly defined. In certain settings, this change
will decrease the number of HCWs who need serial TB screening.
- These recommendations usually apply to an entire health-care setting rather than areas within a setting.
- New terms, airborne infection precautions (airborne precautions) and airborne infection isolation room (AII room),
are introduced.
- Recommendations for annual respirator training, initial respirator fit testing, and periodic respirator fit testing have
been added.
- The evidence of the need for respirator fit testing is summarized.
- Information on ultraviolet germicidal irradiation (UVGI) and room-air recirculation units has been expanded.
- Additional information regarding MDR TB and HIV infection has been included.
In accordance with relevant local, state, and federal laws, implementation of all recommendations must safeguard
the confidentiality and civil rights of all HCWs and patients who have been infected with
M. tuberculosis and TB disease.
The 1994 CDC guidelines were aimed primarily at
hospital-based facilities, which frequently refer to a physical building
or set of buildings. The 2005 guidelines have been expanded to address a broader concept. Setting has been chosen instead
of "facility" to expand the scope of potential places for which these guidelines apply (Appendix A). "Setting" is used
to describe any relationship (physical or organizational) in which HCWs might share air space with persons with TB disease or
in which HCWs might be in contact with clinical specimens. Various setting types might be present in a single
facility. Healthcare settings include inpatient settings, outpatient settings, and nontraditional facilitybased settings.
- Inpatient settings include patient rooms, emergency
departments (EDs), intensive care units (ICUs), surgical
suites, laboratories, laboratory procedure areas, bronchoscopy suites, sputum induction or inhalation therapy rooms,
autopsy suites, and embalming rooms.
- Outpatient settings include TB treatment facilities, medical offices, ambulatory-care settings, dialysis units, and
dental-care settings.
- Nontraditional facilitybased settings include emergency medical service (EMS), medical settings in correctional
facilities (e.g., prisons, jails, and detention centers), home-based health-care and outreach settings, long-term--care settings
(e.g., hospice-skilled nursing facilities), and homeless shelters. Other settings in which suspected and confirmed TB
patients might be encountered might include cafeterias, general stores, kitchens, laundry areas, maintenance shops,
pharmacies, and law enforcement settings.
HCWs Who Should Be Included in a TB Surveillance Program
HCWs refer to all paid and unpaid persons working in health-care settings who have the potential for exposure to
M. tuberculosis through air space shared with persons with infectious TB disease. Part time, temporary, contract, and full-time
HCWs should be included in TB screening programs. All HCWs who have duties that involve faceto-face contact with patients
with suspected or confirmed TB disease (including transport staff) should be included in a TB screening program.
The following are HCWs who should be included in a TB screening program:
- Administrators or managers
- Bronchoscopy staff
- Chaplains
- Clerical staff
- Computer programmers
- Construction staff
- Correctional officers
- Craft or repair staff
- Dental staff
- Dietician or dietary staff
- ED staff
- Engineers
- Food service staff
- Health aides
- Health and safety staff
- Housekeeping or custodial staff
- Homeless shelter staff
- Infectioncontrol staff
- ICU staff
- Janitorial staff
- Laboratory staff
- Maintenance staff
- Morgue staff
- Nurses
- Outreach staff
- Pathology laboratory staff
- Patient transport staff, including EMS
- Pediatric staff
- Pharmacists
- Phlebotomists
- Physical and occupational therapists
- Physicians (assistant, attending, fellow, resident, or intern), including
--- anesthesiologists
--- pathologists
--- psychiatrists
--- psychologists
- Public health educators or teachers
- Public safety staff
- Radiology staff
- Respiratory therapists
- Scientists
- Social workers
- Students (e.g., medical, nursing, technicians, and allied health)
- Technicians (e.g., health, laboratory, radiology, and animal)
- Veterinarians
- Volunteers
In addition, HCWs who perform any of the following
activities should also be included in the TB screening program.
- entering patient rooms or treatment rooms whether or not a patient is present;
- participating in aerosol-generating or aerosol-producing procedures (e.g., bronchoscopy, sputum induction,
and administration of aerosolized medications)
(29);
- participating in suspected or confirmed M. tuberculosis
specimen processing; or
- installing, maintaining, or replacing environmental
controls in areas in which persons with TB disease are
encountered.
Pathogenesis, Epidemiology, and Transmission of
M. tuberculosis
M. tuberculosis is carried in airborne particles called droplet nuclei that can be generated when persons who have
pulmonary or laryngeal TB disease cough, sneeze, shout, or sing
(30,31). The particles are approximately 1--5
µm; normal air currents can keep them airborne for prolonged periods and spread them throughout a room or building
(32). M. tuberculosis is usually transmitted only through air, not by surface contact. After the droplet nuclei are in the alveoli, local infection might
be established, followed by dissemination to draining lymphatics and hematogenous spread throughout the body
(33). Infection occurs when a susceptible person inhales droplet nuclei containing
M. tuberculosis, and the droplet nuclei traverse the
mouth or nasal passages, upper respiratory tract, and bronchi to reach the alveoli. Persons with TB pleural
effusions might also have concurrent unsuspected pulmonary or laryngeal TB disease.
Usually within 2--12 weeks after initial infection with
M. tuberculosis, the immune response limits additional
multiplication of the tubercle bacilli, and immunologic test results for
M. tuberculosis infection become positive. However, certain
bacilli remain in the body and are viable for multiple years. This condition is referred to as latent tuberculosis
infection (LTBI). Persons with LTBI are asymptomatic (they have no symptoms of TB disease) and are not infectious.
In the United States, LTBI has been diagnosed traditionally based on a PPD-based TST result after TB disease has
been excluded. In vitro cytokine-based immunoassays for the
detection of M. tuberculosis infection have been the focus of
intense research and development. One such blood assay for
M. tuberculosis (or BAMT) is an IGRA, the
QuantiFERON®TB test (QFT), and the subsequently developed version, QFTG. The QFTG measures cell-mediated immune responses to peptides from
two M. tuberculosis proteins that are not present in any Bacille Calmette-Guérin (BCG) vaccine strain and that are absent from
the majority of nontuberculous mycobacteria (NTM), also known as mycobacteria other than TB (MOTT). QFTG was
approved by FDA in 2005 and is an available option for detecting
M. tuberculosis infection. CDC recommendations for the United
States regarding QFT and QFTG have been published
(34,35). Because this field is rapidly evolving, in this report, BAMT will
be used generically to refer to the test currently available in the United States.
Additional cytokine-based immunoassays are under development and might be useful in the diagnosis of
M. tuberculosis infection. Future FDA-licensed products in combination with CDC-issued recommendations might provide
additional diagnostic alternatives. The latest CDC recommendations for guidance on diagnostic use of these and related technologies
are available at
http://www.cdc.gov/nchstp/tb/pubs/mmwrhtml/Maj_guide/Diagnosis.htm.
Typically, approximately 5%--10% of persons who become infected with
M. tuberculosis and who are not treated for
LTBI will develop TB disease during their lifetimes
(1). The risk for progression of LTBI to TB disease is highest during the
first several years after infection (36--38).
Persons at Highest Risk for Exposure to and Infection with
M. tuberculosis
Characteristics of persons exposed to M. tuberculosis
that might affect the risk for infection are not as well defined.
The probability that a person who is exposed to
M. tuberculosis will become infected depends primarily on the concentration
of infectious droplet nuclei in the air and the duration of
exposure to a person with infectious TB disease. The closer
the proximity and the longer the duration of exposure, the higher the risk is for being infected.
Close contacts are persons who share the same air space in a household or other enclosed environment for a
prolonged period (days or weeks, not minutes or hours) with a person with pulmonary TB disease
(39). A suspect TB patient is a person in whom a diagnosis of TB disease is being considered, whether or not antituberculosis treatment has been started.
Persons generally should not remain a suspect TB patient for >3 months
(30,39).
In addition to close contacts, the following persons are also at higher risk for exposure to and infection with
M. tuberculosis. Persons listed who are also close contacts should be top priority.
- Foreign-born persons, including children, especially those who have arrived to the United States within 5 years after
moving from geographic areas with a high incidence of TB disease (e.g., Africa, Asia, Eastern Europe, Latin America, and
Russia) or who frequently travel to countries with a high prevalence of TB disease.
- Residents and employees of congregate settings that are high risk (e.g., correctional facilities,
long-term--care facilities [LTCFs], and homeless shelters).
- HCWs who serve patients who are at high risk.
- HCWs with unprotected exposure to a patient with TB disease before the identification and correct airborne precautions
of the patient.
- Certain populations who are medically underserved and who have low income, as defined locally.
- Populations at high risk who are defined locally as having an increased incidence of TB disease.
- Infants, children, and adolescents exposed to adults in high-risk categories.
Persons Whose Condition is at High Risk for Progression From LTBI to TB Disease
The following persons are at high risk for progressing from LTBI to TB disease:
- persons infected with HIV;
- persons infected with M. tuberculosis within the previous 2 years;
- infants and children aged <4 years;
- persons with any of the following clinical conditions or other immunocompromising conditions
--- silicosis,
--- diabetes mellitus,
--- chronic renal failure,
--- certain hematologic disorders (leukemias and lymphomas),
--- other specific malignancies (e.g., carcinoma of the head, neck, or lung),
--- body weight >10% below ideal body weight,
--- prolonged corticosteroid use,
--- other immunosuppressive treatments (including tumor necrosis factor-alpha
[TNFa] antagonists),
--- organ transplant,
--- end-stage renal disease (ESRD), and
--- intestinal bypass or gastrectomy; and
- persons with a history of untreated or inadequately treated TB disease, including persons with chest radiograph
findings consistent with previous TB disease.
Persons who use tobacco or alcohol
(40,41), illegal drugs, including injection drugs and crack cocaine
(42--47), might also be at increased risk for infection and disease. However, because of multiple other potential risk factors that commonly
occur among such persons, use of these substances has been difficult to identify as separate risk factors.
HIV infection is the greatest risk factor for progression from LTBI to TB disease
(22,39,48,49). Therefore, voluntary HIV counseling, testing, and referral should be routinely offered to all persons at risk for LTBI
(1,50,51). Healthcare settings should be particularly aware of the need for preventing transmission of
M. tuberculosis in settings in which persons
infected with HIV might be encountered or might work
(52).
All HCWs should be informed regarding the risk for developing TB disease after being infected with
M. tuberculosis (1). However, the rate of TB disease among persons who are HIVinfected and untreated for LTBI in the United States
is substantially higher, ranging from 1.7--7.9 TB cases per 100 person-years
(53). Persons infected with HIV who are
already severely immunocompromised and who become newly
infected with M. tuberculosis have a greater risk for developing
TB disease, compared with newly infected persons without HIV infection
(39,53--57).
The percentage of patients with TB disease who are HIVinfected is decreasing in the United States because of
improved infectioncontrol practices and better diagnosis and treatment of both HIV infection and TB. With increased voluntary
HIV counseling and testing and the increasing use of treatment for LTBI, TB disease will probably continue to
decrease among HIVinfected persons in the United States
(58). Because the risk for disease is particularly high among HIVinfected
persons with M. tuberculosis infection, HIVinfected contacts of persons with infectious pulmonary or laryngeal TB disease must
be evaluated for M. tuberculosis infection, including the exclusion of TB disease, as soon as possible after learning of
exposure (39,49,53).
Vaccination with BCG probably does not affect the risk for infection after exposure, but it might decrease the risk
for progression from infection with M. tuberculosis
to TB disease, preventing the development of miliary and meningeal disease
in infants and young children (59,60). Although HIV infection increases the likelihood of progression from LTBI to TB
disease (39,49), whether HIV infection increases the risk for becoming infected if exposed to
M. tuberculosis is not known.
Characteristics of a Patient with TB Disease That Increase the Risk for Infectiousness
The following characteristics exist in a patient with TB disease that increases the risk for infectiousness:
- presence of cough;
- cavitation on chest radiograph;
- positive acid-fast bacilli (AFB) sputum smear result;
- respiratory tract disease with involvement of the larynx (substantially infectious);
- respiratory tract disease with involvement of the lung or pleura (exclusively pleural involvement is less infectious);
- failure to cover the mouth and nose when coughing;
- incorrect, lack of, or short duration of antituberculosis treatment; and
- undergoing cough-inducing or aerosol-generating procedures (e.g., bronchoscopy, sputum induction, and administration
of aerosolized medications) (29).
Environmental Factors That Increase the Risk for Probability of Transmission of
M. tuberculosis
The probability of the risk for transmission of
M. tuberculosis is increased as a result of various environmental factors.
- Exposure to TB in small, enclosed spaces.
- Inadequate local or general ventilation that results in
insufficient dilution or removal of infectious droplet
nuclei.
- Recirculation of air containing infectious droplet nuclei.
- Inadequate cleaning and disinfection of medical
equipment.
- Improper procedures for handling specimens.
Risk for Health-Care--Associated Transmission of
M. tuberculosis
Transmission of M. tuberculosis is a risk in health-care settings
(57,61--79). The magnitude of the risk varies by
setting, occupational group, prevalence of TB in the community,
patient population, and effectiveness of TB
infectioncontrol measures. Healthcare--associated transmission of
M. tuberculosis has been linked to close contact with persons with TB
disease during aerosol-generating or aerosol-producing procedures, including bronchoscopy
(29,63,80--82), endotracheal intubation, suctioning
(66), other respiratory procedures
(8,9,83--86), open abscess irrigation
(69,83), autopsy (71,72,77), sputum induction, and aerosol treatments that induce coughing
(87--90).
Of the reported TB outbreaks in health-care settings, multiple outbreaks involved transmission of MDR TB strains to
both patients and HCWs (56,57,70,87,91--94). The majority of the patients and certain HCWs were HIVinfected,
and progression to TB and MDR TB disease was rapid. Factors contributing to these outbreaks included delayed diagnosis of
TB disease, delayed initiation and inadequate airborne precautions, lapses in AII practices and precautions for cough-inducing
and aerosol-generating procedures, and lack of adequate respiratory protection. Multiple studies suggest that the decline in
health-care--associated transmission observed in specific institutions is associated with the rigorous implementation
of infectioncontrol measures (11,12,18--20,23,
95--97). Because various interventions were implemented
simultaneously, the effectiveness of each intervention could not be determined.
After the release of the 1994 CDC infectioncontrol guidelines, increased implementation of recommended
infectioncontrol measures occurred and was documented in multiple national surveys
(13,15,98,99). In a survey of approximately 1,000
hospitals, a TST program was present in nearly all sites, and 70% reported having an AII room
(13). Other surveys have documented improvement in the proportion of AII rooms meeting CDC criteria and proportion of HCWs using
CDC-recommended respiratory protection and receiving serial TST
(15,98). A survey of New York City hospitals with high caseloads of TB
disease indicated 1) a decrease in the time that patients with TB disease spent in EDs before being transferred to a hospital room, 2)
an increase in the proportion of patients initially placed in AII rooms, 3) an increase in the proportion of patients started
on recommended antituberculosis treatment and reported to the local or state health department, and 4) an increase in the use
of recommended respiratory protection and environmental controls
(99). Reports of increased implementation of recommended
TB infection controls combined with decreased reports of outbreaks of TB disease in health-care settings suggest that
the recommended controls are effective in reducing and preventing health-care--associated transmission of
M. tuberculosis (28).
Less information is available regarding the implementation of CDC-recommended TB infectioncontrol measures
in settings other than hospitals. One study identified major barriers to implementation that contribute to the costs of a
TST program in health departments and hospitals, including personnel costs, HCWs' time off from work for TST
administration and reading, and training and education of HCWs
(100). Outbreaks have occurred in outpatient settings (i.e.,
private physicians' offices and pediatric settings) where the guidelines were not followed
(101--103). CDC-recommended TB infectioncontrol measures are implemented in correctional facilities, and certain variations might relate to resources,
expertise, and oversight (104--106).
Fundamentals of TB Infection Control
One of the most critical risks for health-care--associated transmission of
M. tuberculosis in health-care settings is
from patients with unrecognized TB disease who are not promptly handled with appropriate airborne precautions
(56,57,93,104) or who are moved from an AII room too soon (e.g., patients with unrecognized TB and MDR TB)
(94). In the United States, the problem of MDR TB, which was amplified by health-care--associated transmission, has been substantially reduced by
the
use of standardized antituberculosis treatment regimens in the initial phase of therapy, rapid
drug-susceptibility testing, directly observed therapy (DOT), and improved infectioncontrol practices
(1). DOT is an adherence-enhancing strategy
in which an HCW or other specially trained health professional watches a patient swallow each dose of medication and
records the dates that the administration was
observed. DOT is the standard of care for all patients with TB disease and should
be used for all doses during the course of therapy for TB disease and for LTBI, whenever
feasible.
All health-care settings need a TB infectioncontrol program designed to ensure prompt detection, airborne precautions,
and treatment of persons who have suspected or confirmed TB disease (or prompt referral of persons who have suspected
TB disease for settings in which persons with TB disease are not expected to be encountered). Such a program is based on a
three-level hierarchy of controls, including
administrative, environmental, and respiratory protection
(86,107,108).
Administrative Controls
The first and most important level of TB controls is the use of administrative measures to reduce the risk for exposure
to persons who might have TB disease. Administrative controls consist of the following activities:
- assigning responsibility for TB infection control in the setting;
- conducting a TB risk assessment of the setting;
- developing and instituting a written TB infectioncontrol plan to ensure prompt detection, airborne precautions,
and treatment of persons who have suspected or confirmed TB disease;
- ensuring the timely availability of recommended laboratory processing, testing, and reporting of results to the
ordering physician and infectioncontrol team;
- implementing effective work practices for the management of patients with suspected or confirmed TB disease;
- ensuring proper cleaning and sterilization or disinfection of potentially contaminated equipment (usually endoscopes);
- training and educating HCWs regarding TB, with specific focus on prevention, transmission, and symptoms;
- screening and evaluating HCWs who are at risk for TB disease or who might be exposed to
M. tuberculosis (i.e., TB screening program);
- applying epidemiologic-based prevention principles,
including the use of setting-related infectioncontrol data;
- using appropriate signage advising respiratory hygiene and cough etiquette; and
- coordinating efforts with the local or state health department.
HCWs with TB disease should be allowed to return to work when they 1) have had three negative AFB sputum
smear results (109--112) collected 8--24 hours apart, with at least one being an early morning specimen because
respiratory secretions pool overnight; and 2) have responded to antituberculosis treatment that will probably be effective based
on susceptibility results. In addition, HCWs with TB disease should be allowed to return to work when a
physician knowledgeable and experienced in managing TB disease determines that HCWs are noninfectious (see Treatment
Procedures for LTBI and TB Disease). Consideration should also be given to the type of setting and the potential risk to patients
(e.g., general medical office versus HIV clinic) (see Supplements, Estimating the Infectiousness of a TB Patient;
Diagnostic Procedures for LTBI and TB Disease; and Treatment Procedures for LTBI and TB Disease).
Environmental Controls
The second level of the hierarchy is the use of environmental controls to prevent the spread and reduce the concentration
of infectious droplet nuclei in ambient air.
Primary environmental controls consist of controlling the source of infection by
using local exhaust ventilation (e.g., hoods, tents, or booths) and diluting and removing contaminated air by using general ventilation
Secondary environmental controls consist of controlling the airflow to prevent contamination of air in areas adjacent to
the source (AII rooms) and cleaning the air by using high efficiency particulate air (HEPA), filtration, or UVGI.
Respiratory-Protection Controls
The first two control levels minimize the number of areas in which exposure to
M. tuberculosis might occur and, therefore, minimize the number of persons exposed. These control levels also reduce, but do not eliminate, the risk for exposure in
the limited areas in which exposure can still occur. Because persons entering these areas might be exposed to
M. tuberculosis, the third level of the hierarchy is the use of respiratory protective equipment in situations that pose a high risk for exposure. Use
of respiratory protection can further reduce risk for exposure of HCWs to infectious droplet nuclei that have been expelled
into
the air from a patient with infectious TB disease (see Respiratory Protection). The following measures can be taken to
reduce the risk for exposure:
- implementing a respiratoryprotection program,
- training HCWs on respiratory protection, and
- training patients on respiratory hygiene and cough
etiquette procedures.
Relevance to Biologic Terrorism Preparedness
MDR M. tuberculosis is classified as a category C agent of biologic terrorism
(113). Implementation of the TB infectioncontrol guidelines described in this document is
essential for preventing and controlling transmission
of M. tuberculosis in health-care settings. Additional information is at
http://www.bt.cdc.gov and
http://www.idsociety.org/bt/toc.htm (114).
Recommendations for Preventing Transmission of
M. tuberculosis in Health-Care Settings
TB Infection-Control Program
Every health-care setting should have a TB infectioncontrol plan that is part of an overall infectioncontrol program.
The specific details of the TB infectioncontrol program will differ, depending on whether patients with suspected or
confirmed TB disease might be encountered in the setting or whether patients with suspected or confirmed TB disease will be
transferred to another health-care setting. Administrators making this distinction should obtain medical and epidemiologic
consultation from state and local health departments.
TB Infection-Control Program for Settings in Which Patients with Suspected or Confirmed
TB Disease Are Expected To Be Encountered
The TB infectioncontrol program should consist of
administrative controls, environmental controls, and
a respiratoryprotection program. Every setting in which services are provided to persons who have suspected or
confirmed infectious TB disease, including laboratories and nontraditional facilitybased settings, should have a TB
infection-control plan. The following steps should be taken to establish a TB infectioncontrol program in these settings:
- Assign supervisory responsibility for the TB infectioncontrol program to a designated person or group with expertise
in LTBI and TB disease, infection control, occupational health, environmental controls, and respiratory protection.
Give the supervisor or supervisory body the support and authority to conduct a TB risk assessment, implement and
enforce TB infectioncontrol policies, and ensure recommended training and education of HCWs.
--- Train the persons responsible for implementing and enforcing the TB infectioncontrol program.
--- Designate one person with a back-up as the TB
resource person to whom questions and problems should
be addressed, if supervisory responsibility is assigned to a committee.
- Develop a written TB infectioncontrol plan that outlines a protocol for the prompt recognition and initiation
of airborne precautions of persons with suspected or confirmed TB disease, and update it annually.
- Conduct a problem evaluation (see Problem Evaluation) if a case of suspected or confirmed TB disease is not
promptly recognized and appropriate airborne precautions not initiated, or if administrative, environmental,
or respiratoryprotection controls fail.
- Perform a contact investigation in collaboration with the local or state health department if
health-care--associated transmission of M. tuberculosis
is suspected (115). Implement and monitor corrective action.
- Collaborate with the local or state health department to develop administrative controls consisting of the risk
assessment, the written TB infectioncontrol plan, management of patients with suspected or confirmed TB
disease, training and education of HCWs, screening and
evaluation of HCWs, problem evaluation, and coordination.
- Implement and maintain environmental controls, including AII room(s) (see Environmental Controls).
- Implement a respiratoryprotection program.
- Perform ongoing training and education of HCWs (see Suggested Components of an Initial TB Training and
Education Program for HCWs).
- Create a plan for accepting patients who have suspected or confirmed TB disease if they are transferred
from another setting.
TB Infection-Control Program for Settings in Which Patients with Suspected or Confirmed
TB Disease Are Not Expected To Be Encountered
Settings in whichT patients might stay before transfer should still have a TB infectioncontrol program in place consisting
of administrative, environmental, and respiratoryprotection controls. The following steps should be taken to establish a
TB infectioncontrol program in these settings:
- Assign responsibility for the TB infectioncontrol program to appropriate personnel.
- Develop a written TB infectioncontrol plan that outlines a protocol for the prompt recognition and transfer of
persons who have suspected or confirmed TB disease to another health-care setting. The plan should indicate procedures
to follow to separate persons with suspected or confirmed infectious TB disease from other persons in the setting until
the time of transfer. Evaluate the plan annually, if possible, to ensure that the setting remains one in which persons who
have suspected or confirmed TB disease are not encountered and that they are promptly transferred.
- Conduct a problem evaluation (see Problem Evaluation) if a case of suspected or confirmed TB disease is not
promptly recognized, separated from others, and transferred.
- Perform an investigation in collaboration with the local or state health department if health-care--associated
transmission of M. tuberculosis is suspected.
- Collaborate with the local or state health department to develop administrative controls consisting of the risk
assessment and the written TB infectioncontrol plan.
TB Risk Assessment
Every health-care setting should conduct initial and ongoing evaluations of the risk for transmission of
M. tuberculosis, regardless of whether or not patients with suspected or confirmed TB disease are expected to be encountered in the
setting. The TB risk assessment determines the types of administrative, environmental, and respiratoryprotection controls needed
for a setting and serves as an ongoing evaluation tool of the quality of TB infection control and for the identification of
needed improvements in infectioncontrol measures. Part of the risk assessment is similar to a program review that is conducted by
the local TBcontrol program (42). The TB Risk Assessment Worksheet (Appendix B) can be used as a guide for conducting a
risk assessment. This worksheet frequently does not specify values for acceptable performance indicators because of the lack
of scientific data.
TB Risk Assessment for Settings in Which Patients with Suspected or Confirmed TB Disease
Are Expected To Be Encountered
The initial and ongoing risk assessment for these settings should consist of the following steps:
- Review the community profile of TB disease in collaboration with the state or local health department.
- Consult the local or state TBcontrol program to
obtain epidemiologic surveillance data necessary to conduct a TB
risk assessment for the health-care setting.
- Review the number of patients with suspected or confirmed TB disease who have been encountered in the
setting during at least the previous 5 years.
- Determine if persons with unrecognized TB disease have been admitted to or were encountered in the setting during
the previous 5 years.
- Determine which HCWs need to be included in a TB screening program and the frequency of screening (based on
risk classification) (Appendix C).
- Ensure the prompt recognition and evaluation of suspected episodes of health-care--associated transmission of
M. tuberculosis.
- Identify areas in the setting with an increased risk for health-care--associated transmission of
M. tuberculosis, and target them for improved TB infection controls.
- Assess the number of AII rooms needed for the setting. The risk classification for the setting should help to make
this determination, depending on the number of TB patients examined. At least one AII room is needed for settings
in which TB patients stay while they are being treated, and additional AII rooms might be needed, depending on
the magnitude of patient-days of cases of suspected or confirmed TB disease. Additional AII rooms might be considered
if options are limited for transferring patients with suspected or confirmed TB disease to other settings with AII rooms.
- Determine the types of environmental controls needed other than AII rooms (see TB Airborne Precautions).
- Determine which HCWs need to be included in the respiratoryprotection program.
- Conduct periodic reassessments (annually, if possible) to ensure
--- proper implementation of the TB infectioncontrol plan,
--- prompt detection and evaluation of suspected TB cases,
--- prompt initiation of airborne precautions of suspected infectious TB cases,
--- recommended medical management of patients with suspected or confirmed TB disease
(31),
--- functional environmental controls,
--- implementation of the respiratoryprotection
program, and
--- ongoing HCW training and education regarding TB.
- Recognize and correct lapses in infection control.
TB Risk Assessment for Settings in Which Patients with Suspected or Confirmed TB Disease
Are Not Expected To Be Encountered
The initial and ongoing risk assessment for these settings should consist of the following steps:
- Review the community profile of TB disease in collaboration with the local or state health department.
- Consult the local or state TBcontrol program to obtain epidemiologic surveillance data necessary to conduct a TB
risk assessment for the health-care setting.
- Determine if persons with unrecognized TB disease were encountered in the setting during the previous 5 years.
- Determine if any HCWs need to be included in the TB screening program.
- Determine the types of environmental controls that are currently in place, and determine if any are needed in the
setting (see Environmental Controls; Appendices A and D).
- Document procedures that ensure the prompt recognition and evaluation of suspected episodes of
health-care--associated transmission of M.
tuberculosis.
- Conduct periodic reassessments (annually, if possible) to ensure 1) proper implementation of the TB infectioncontrol plan; 2) prompt detection and evaluation of suspected TB cases; 3) prompt initiation of airborne precautions
of suspected infectious TB cases before transfer; 4) prompt transfer of suspected infectious TB cases; 5) proper
functioning of environmental controls, as applicable; and 6) ongoing TB training and education for HCWs.
- Recognize and correct lapses in infection control.
Use of Risk Classification to Determine Need for TB Screening and Frequency of Screening HCWs
Risk classification should be used as part of the risk assessment to determine the need for a TB screening program
for HCWs and the frequency of screening (Appendix C). A risk classification usually should be determined for the entire
setting. However, in certain settings (e.g., health-care organizations that encompass multiple sites or types of services), specific
areas defined by geography, functional units, patient population, job type, or location within the setting might have separate
risk classifications. Examples of assigning risk classifications have been provided (see Risk Classification
Examples).
TB Screening Risk Classifications
The three TB screening risk classifications are low risk, medium risk, and potential ongoing transmission. The
classification of low risk should be applied to settings in which persons with TB disease are not expected to be encountered, and,
therefore, exposure to M. tuberculosis is unlikely. This classification should also be applied to HCWs who will never be exposed
to persons with TB disease or to clinical specimens that might contain
M. tuberculosis.
The classification of medium risk should be applied to settings in which the risk assessment has determined that HCWs
will or will possibly be exposed to persons with TB disease or to clinical specimens that might contain
M. tuberculosis.
The classification of potential ongoing transmission should be temporarily applied to any setting (or group of HCWs)
if evidence suggestive of personto-person (e.g.,
patient-to-patient, patient-to-HCW, HCWto-patient, or
HCWto-HCW) transmission of M. tuberculosis has occurred in the setting during the preceding year. Evidence of
personto-person transmission of M. tuberculosis
includes 1) clusters of TST or BAMT conversions, 2) HCW with confirmed TB
disease, 3) increased rates of TST or BAMT conversions,
4) unrecognized TB disease in patients or HCWs, or 5) recognition of
an identical strain of M. tuberculosis in patients or HCWs with TB disease identified by deoxyribonucleic acid
(DNA) fingerprinting.
If uncertainty exists regarding whether to classify a setting as low risk or medium risk, the setting typically should
be classified as medium risk.
TB Screening Procedures for Settings (or HCWs) Classified as Low Risk
- All HCWs should receive baseline TB screening upon hire, using two-step TST or a single BAMT to test for infection
with M. tuberculosis.
- After baseline testing for infection with M.
tuberculosis, additional TB screening is not necessary unless an exposure to
M. tuberculosis occurs.
- HCWs with a baseline positive or newly positive test
result for M. tuberculosis infection (i.e., TST or BAMT)
or documentation of treatment for LTBI or TB disease should receive one chest radiograph result to exclude TB disease
(or an interpretable copy within a reasonable time frame, such as 6 months). Repeat radiographs are not needed
unless symptoms or signs of TB disease develop or unless recommended by a clinician
(39,116).
TB Screening Procedures for Settings (or HCWs) Classified as Medium Risk
- All HCWs should receive baseline TB screening upon hire, using two-step TST or a single BAMT to test for infection
with M. tuberculosis.
- After baseline testing for infection with M.
tuberculosis, HCWs should receive TB screening annually (i.e., symptom screen
for all HCWs and testing for infection with M. tuberculosis
for HCWs with baseline negative test results).
- HCWs with a baseline positive or newly positive test
result for M. tuberculosis infection or documentation of
previous treatment for LTBI or TB disease should receive one chest radiograph result to exclude TB disease. Instead of
participating in serial testing, HCWs should receive a symptom screen annually. This screen should be accomplished by educating
the HCW about symptoms of TB disease and instructing the HCW to report any such symptoms immediately to
the occupational health unit. Treatment for LTBI should be considered in accordance with CDC guidelines
(39).
TB Screening Procedures for Settings (or HCWs) Classified as Potential Ongoing Transmission
- Testing for infection with M. tuberculosis
might need to be performed every 8--10 weeks until lapses in infection
control have been corrected, and no additional evidence of ongoing transmission is apparent.
- The classification of potential ongoing transmission should be used as a temporary classification only. It warrants
immediate investigation and corrective steps. After a determination that ongoing transmission has ceased, the setting should
be reclassified as medium risk. Maintaining the classification of medium risk for at least 1 year is recommended.
Settings Adopting BAMT for Use in TB Screening
Settings that use TST as part of TB screening and want to adopt BAMT can do so directly (without any overlapping TST)
or in conjunction with a period of evaluation (e.g., 1 or 2 years) during which time both TST and BAMT are used. Baseline
testing for BAMT would be established as a single step test.
As with the TST, BAMT results should be recorded in detail. The
details should include date of blood draw, result in specific units, and the laboratory interpretation (positive, negative,
or indeterminate---and the concentration of cytokine measured, for example, interferon-gamma
[IFN-g]).
Risk Classification Examples
Inpatient Settings with More Than 200 Beds
If less than six TB patients for the preceding year, classify as low risk. If greater than or equal to six TB patients for
the preceeding year, classify as medium risk.
Inpatient Settings with Less Than 200 Beds
If less than three TB patients for the proceeding year, classify as low risk. If greater than or equal to three TB patients for
the preceeding year, classify as medium risk.
Outpatient, Outreach, and Home-Based Health-Care Settings
If less than three TB patients for the preceding year, classify as low risk. If greater than or equal to three TB patients for
the preceeding year, classify as medium risk.
Hypothetical Risk Classification Examples
The following hypothetical situations illustrate how assessment data are used to assign a risk classification. The risk
classifications are for settings in which patients with suspected or confirmed infectious TB disease are expected to be encountered.
Example A. The setting is a 150-bed hospital located in a small city. During the preceding year, the hospital admitted
two patients with a diagnosis of TB disease. One was admitted directly to an AII room, and one stayed on a medical ward for
2 days before being placed in an AII room. A contact
investigation of exposed HCWs by hospital infectioncontrol personnel
in consultation with the state or local health department
did not identify any health-care--associated transmission-.
Risk classification: low risk.
Example B. The setting is an ambulatory-care site in which a TB clinic is held 2 days per week. During the preceding
year, care was delivered to six patients with TB disease and approximately 50 persons with LTBI. No instances of transmission
of M. tuberculosis were noted. Risk classification: medium
risk (because it is a TB clinic).
Example C. The setting is a large publicly funded hospital in a major metropolitan area. The hospital admits an average
of 150 patients with TB disease each year, comprising 35% of the city burden. The setting has a strong TB infectioncontrol program (i.e., annually updates infectioncontrol plan, fully implements infectioncontrol plan, and has enough AII
rooms [see Environmental Controls]) and an annual conversion rate (for tests for
M. tuberculosis infection) among HCWs of
0.5%. No evidence of health-care--associated transmission is apparent. The hospital has strong collaborative linkages with the state
or local health department. Risk classification: medium
risk (with close ongoing surveillance for episodes of transmission
from unrecognized cases of TB disease, test conversions for
M. tuberculosis infection in HCWs as a result of
health-care--associated transmission, and specific groups or areas in which a higher risk for health-care--associated transmission exists).
Example D. The setting is an inpatient area of a correctional facility. A proportion of the inmates were born in
countries where TB disease is endemic. Two cases of TB disease were diagnosed in inmates during the preceding year. Risk
classification: medium risk (Correctional facilities should be classified as at least medium risk).
Example E. A hospital located in a large city admits 35 patients with TB disease per year, uses QFT-G to
measure M. tuberculosis infection, and has an overall HCW
M. tuberculosis infection test conversion rate of 1.0%. However, on
annual testing, three of the 20 respiratory therapists tested had QFT-G conversions, for a rate of 15%. All of the respiratory
therapists who tested positive received medical evaluations, had TB disease excluded, were diagnosed with LTBI, and were offered
and completed a course of treatment for LTBI. None of the respiratory therapists had known exposures to
M. tuberculosis outside the hospital. The problem evaluation revealed that 1) the respiratory therapists who converted had spent part of their time
in the pulmonary function laboratory where induced sputum specimens were collected, and 2) the ventilation in the
laboratory was inadequate. Risk classification: potential ongoing transmission for the respiratory
therapists (because of evidence of health-care--associated transmission). The rest of the setting was classified as medium risk. To address the problem, booths
were installed for sputum induction. On subsequent testing for
M. tuberculosis infection, no conversions were noted at the
repeat testing 3 months later, and the respiratory therapists were then reclassified back to medium risk.
Example F. The setting is an ambulatory-care center associated with a large health maintenance organization (HMO).
The patient volume is high, and the HMO is located in the inner city where TB rates are the highest in the state. During
the preceding year, one patient who was known to have TB disease was evaluated at the center. The person was recognized as a
TB patient on his first visit and was promptly triaged to an ED with an AII room capacity. While in the
ambulatory-care center, the patient was held in an area separate from HCWs and other patients and instructed to wear a surgical or procedure mask,
if possible. QFT-G was used for infection-control surveillance purposes, and a contact investigation was conducted
among exposed staff, and no QFT-G conversions were noted. Risk classification: low risk.
Example G. The setting is a clinic for the care of persons infected with HIV. The clinic serves a large metropolitan area
and a patient population of 2,000. The clinic has an AII room and a TB infectioncontrol program. All patients are screened
for TB disease upon enrollment, and airborne precautions are promptly initiated for anyone with respiratory complaints while
the patient is being evaluated. During the preceding year, seven patients who were encountered in the clinic were
subsequently determined to have TB disease. All patients were promptly put into an AII room, and no contact investigations
were performed. The local health department was promptly notified in all cases. Annual TST has determined a conversion rate
of 0.3%, which is low compared with the rate of the hospital with which the clinic is associated. Risk classification: medium
risk (because persons infected with HIV might be encountered).
Example H. A home health-care agency employs 125 workers, many of whom perform duties, including nursing,
physical therapy, and basic home care. The agency did not care for any patients with suspected or confirmed TB disease during
the preceding year. Approximately 30% of the agency's workers are foreign-born, many of whom have immigrated within
the previous 5 years. At baseline two-step testing, four had a positive initial TST result, and two had a positive second-step
TST result. All except one of these workers was foreign-born. Upon further screening, none were determined to have TB
disease. The home health-care agency is based in a major metropolitan area and delivers care to a community where the
majority persons are poor and medically underserved and TB case rates are higher than the community as a whole. Risk
classification: low risk (because HCWs might be from populations at higher risk for LTBI and subsequent progression to TB disease
because of foreign birth and recent immigration or HIVinfected clients might be overrepresented, medium risk could be considered).
Screening HCWs Who Transfer to Other Health-Care Settings
All HCWs should receive baseline TB screening, even in settings considered to be low risk. Infectioncontrol plans
should address HCWs who transfer from one health-care setting to another and consider that the transferring HCWs might be at
an equivalent or higher risk for exposure in different settings. Infectioncontrol plans might need to be customized to balance
the assessed risks and the efficacy of the plan based on consideration of various logistical factors. Guidance is provided based
on different scenarios.
Because some institutions might adopt BAMT for the purposes of testing for
M. tuberculosis infection, infectioncontrol programs might be confronted with interpreting historic and current TST and BAMT results when HCWs transfer to
a different setting. On a case-by-case basis, expert medical opinion might be needed to interpret results and refer patients
with discordant BAMT and TST baseline results. Therefore, infectioncontrol programs should keep all records when
documenting previous test results. For example, an infectioncontrol program using a BAMT strategy should request and keep historic
TST results of a HCW transferring from a previous setting. Even if the HCW is transferring from a setting that used BAMT to
a setting that uses BAMT, historic TST results might be needed when in the future the HCW transfers to a setting that
uses TST. Similarly, historic BAMT results might be needed when the HCW transfers from a setting that used TST to a
setting that uses BAMT.
HCWs transferring from low-risk to low-risk settings.
After a baseline result for infection with M. tuberculosis
is established and documented, serial testing for
M. tuberculosis infection is not necessary.
HCWs transferring from low-risk to medium-risk settings.
After a baseline result for infection with M. tuberculosis
is established and documented, annual TB screening (including a symptom screen and TST or BAMT for persons
with previously negative test results) should be performed.
HCWs transferring from low- or medium-risk settings to settings with a temporary classification of
potential ongoing transmission. After a baseline result for infection with
M. tuberculosis is established, a decision should be
made regarding follow-up screening on an individual basis. If transmission seems to be ongoing, consider including the HCW in
the screenings every 8--10 weeks until a determination has been made that ongoing transmission has ceased. When the setting
is reclassified back to medium-risk, annual TB screening should be resumed.
Calculation and Use of Conversion Rates for M. tuberculosis
Infection
The M. tuberculosis infection conversion rate is the percentage of HCWs whose test result for
M. tuberculosis infection has converted within a specified period. Timely detection of
M. tuberculosis infection in HCWs not only facilitates treatment
for LTBI, but also can indicate the need for a source case investigation and a revision of the risk assessment for the
setting. Conversion in test results for M.
tuberculosis, regardless of the testing method used, is usually interpreted as
presumptive
evidence of new M. tuberculosis infection, and recent infections are associated with an increased risk for progression to
TB disease.
For administrative purposes, a TST conversion is
>10 mm increase in the size of the TST induration during a 2-year
period in 1) an HCW with a documented negative (<10 mm) baseline two-step TST result or 2) a person who is not an HCW with
a negative (<10 mm) TST result within 2 years.
In settings conducting serial testing for M. tuberculosis
infection (medium-risk settings), use the to estimate the risk for
test conversion in HCWs.
- Calculate a conversion rate by dividing the number of conversions among HCWs in the setting in a specified
period (numerator) by the number of HCWs who received tests in the setting over the same period (denominator) multiplied
by 100 (see Use of Conversion Test Data for M. tuberculosis
Infection To Identify Lapses in Infection Control).
- Identify areas or groups in the setting with a potentially high risk for
M. tuberculosis transmission by comparing
conversion rates in HCWs with potential exposure to patients with TB disease to conversion rates in HCWs for whom
health-care--associated exposure to M. tuberculosis
is not probable.
Use of Conversion Test Data for M. tuberculosis
Infection To Identify Lapses in Infection Control
- Conversion rates above the baseline level (which will be different in each setting) should instigate an investigation to
evaluate the likelihood of health-care--associated transmission. When testing for
M. tuberculosis infection, conversions are
determined to be the result of well-documented community exposure or probable false-positive test results; the risk classification of
the setting does not need to be adjusted.
- For settings that no longer perform serial testing for
M. tuberculosis infection among HCWs, reassessment of the risk for
the setting is essential to ensure that the infectioncontrol program is effective. The setting should have ongoing
communication with the local or state health department regarding incidence and epidemiology of TB in the population served and
should ensure that timely contact investigations are performed for HCWs or patients with unprotected exposure to a person with
TB disease.
Example Calculation of Conversion Rates
Medical Center A is classified as medium risk and uses TST for annual screening. At the end of 2004, a total of
10,051 persons were designated as HCWs. Of these, 9,246 had negative baseline test results for
M. tuberculosis infection. Of the HCWs tested, 10 experienced an increase in TST result by
>10 mm. The overall setting conversion rate for 2004 is 0.11%.
If five of the 10 HCWs whose test results converted were among the 100 HCWs employed in the ICU of Hospital X
(in Medical Center A), then the ICU setting-specific conversion rate for 2004 is 5%.
Evaluation of HCWs for LTBI should include information from a serial testing program, but this information must
be interpreted as only one part of a full assessment. TST or BAMT conversion criteria for administrative (surveillance)
purposes are not applicable for medical evaluation of HCWs for the diagnosis of LTBI (see Supplement, Surveillance and Detection
of M. tuberculosis Infections in HealthCare Workers [HCWs]).
Evaluation of TB InfectionControl Procedures and Identification of Problems
Annual evaluations of the TB infectioncontrol plan are needed to ensure the proper implementation of the plan and
to recognize and correct lapses in infection control. Previous hospital admissions and outpatient visits of patients with TB
disease should be noted before the onset of TB symptoms. Medical records of a sample of patients with suspected and confirmed
TB disease who were treated or examined at the setting should be reviewed to identify possible problems in TB infection control.
The review should be based on the factors listed on the TB Risk Assessment Worksheet (Appendix B).
- Time interval from suspicion of TB until initiation of airborne precautions and antituberculosis treatment.
--- suspicion of TB disease and patient triage to proper AII room or referral center for settings that do not provide care
for patients with suspected or confirmed TB disease;
--- admission until TB disease was suspected;
--- admission until medical evaluation for TB disease was performed;
--- admission until specimens for AFB smears and polymerase chain reaction (PCR)--based nucleic
acid amplification (NAA) tests for M. tuberculosis
were ordered;
--- admission until specimens for mycobacterial culture were ordered;
--- ordering of AFB smears, NAA tests, and mycobacterial culture until specimens were collected;
--- collection of specimens until performance and AFB smear results were reported;
--- collection of specimens until performance and culture results were reported;
--- collection of specimens until species identification was reported;
--- collection of specimens until drug-susceptibility test results were reported;
--- admission until airborne precautions were initiated; and
--- admission until antituberculosis treatment was
initiated.
- Duration of airborne precautions.
- Measurement of meeting criteria for discontinuing airborne precautions. Certain patients might be correctly
discharged from an AII room to home.
- Patient history of previous admission.
- Adequacy of antituberculosis treatment regimens.
- Adequacy of procedures for collection of follow-up sputum specimens.
- Adequacy of discharge planning.
- Number of visits to outpatient setting from the start of symptoms until TB disease was suspected (for outpatient settings).
Work practices related to airborne precautions should be observed to determine if employers are enforcing all practices,
if HCWs are adhering to infectioncontrol policies, and if patient adherence to airborne precautions is being enforced.
Data from the case reviews and observations in the annual risk assessment should be used to determine the need to modify
1) protocols for identifying and initiating prompt airborne precautions for patients with suspected or confirmed infectious
TB disease, 2) protocols for patient management, 3) laboratory procedures, or 4) TB training and education programs for HCWs.
Environmental Assessment
- Data from the most recent environmental evaluation should be reviewed to determine if recommended
environmental controls are in place (see Suggested Components of an Initial TB Training and Education Program for HCWs).
- Environmental control maintenance procedures and logs should not be reviewed to determine if maintenance is
conducted properly and regularly.
- Environmental control design specifications should be compared with guidelines from the American Institute of
Architects (AIA) and other ventilation guidelines
(117,118) (see Risk Classification Examples) and the
installed system performance.
- Environmental data should be used to assist building managers and engineers in evaluating the performance of the
installed system.
- The number and types of aerosol-generating or aerosol-producing procedures (e.g., specimen processing and
manipulation, bronchoscopy, sputum induction, and administration
of aerosolized medications) performed in the setting should
be assessed.
- The number of AII rooms should be suitable for the setting based on AIA Guidelines and the setting risk assessment.
The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) has adapted the AIA guidelines
when accrediting facilities (118).
Suggested Components of an Initial TB Training and Education Program for HCWs
The following are suggested components of an initial TB training and education program:
1. Clinical Information
Basic concepts of M. tuberculosis transmission, pathogenesis, and diagnosis, including the difference between LTBI and
TB disease and the possibility of reinfection after previous infection with
M. tuberculosis or TB disease.
- Symptoms and signs of TB disease and the importance of a high index of suspicion for patients or HCWs with
these symptoms.
- Indications for initiation of airborne precautions of
inpatients with suspected or confirmed TB disease.
- Policies and indications for discontinuing airborne precautions.
- Principles of treatment for LTBI and for TB disease
(indications, use, effectiveness, and potential adverse
effects).
2. Epidemiology of TB
- Epidemiology of TB in the local community, the United States, and worldwide.
- Risk factors for TB disease.
3. Infection-Control Practices to Prevent and Detect
M. tuberculosis Transmission in Health-Care Settings
- Overview of the TB infectioncontrol program.
- Potential for occupational exposure to infectious TB disease in health-care settings.
- Principles and practices of infection control to reduce the risk for transmission of
M. tuberculosis, including the hierarchy of TB infectioncontrol measures, written policies and procedures, monitoring, and control measures for HCWs
at increased risk for exposure to M.
tuberculosis.
- Rationale for infectioncontrol measures and documentation evaluating the effect of these measures in
reducing occupational TB risk exposure and M. tuberculosis
transmission.
- Reasons for testing for M. tuberculosis infection, importance of a positive test result for
M. tuberculosis infection, importance of participation in a TB screening program, and importance of retaining documentation of previous test result for
M. tuberculosis infection, chest radiograph results, and treatment for LTBI and TB disease.
- Efficacy and safety of BCG vaccination and principles of screening for
M. tuberculosis infection and interpretation in
BCG recipients.
- Procedures for investigating an M. tuberculosis
infection test conversion or TB disease occurring in the workplace.
- Joint responsibility of HCWs and employers to ensure prompt medical evaluation after
M. tuberculosis test conversion or development of symptoms or signs of TB disease in HCWs.
- Role of HCW in preventing transmission of M. tuberculosis.
- Responsibility of HCWs to promptly report a diagnosis of TB disease to the setting's administration and
infectioncontrol program.
- Responsibility of clinicians and the infectioncontrol program to report to the state or local health department a
suspected case of TB disease in a patient (including
autopsy findings) or HCW.
- Responsibilities and policies of the setting, the local health department, and the state health department to
ensure confidentiality for HCWs with TB disease or LTBI.
- Responsibility of the setting to inform EMS staff who transported a patient with suspected or confirmed TB disease.
- Responsibilities and policies of the setting to ensure that an HCW with TB disease is noninfectious before
returning to duty.
- Importance of completing therapy for LTBI or TB disease to protect the HCW's health and to reduce the risk to others.
- Proper implementation and monitoring of environmental controls (see Environmental Controls).
- Training for safe collection, management, and disposal of clinical specimens.
- Required Occupational Safety and Health Administration (OSHA) record keeping on HCW test conversions for
M. tuberculosis infection.
- Record-keeping and surveillance of TB cases among
patients in the setting.
- Proper use of (see Respiratory Protection) and the need to inform the infectioncontrol program of factors that might
affect the efficacy of respiratory protection as required
by OSHA.
- Success of adherence to infectioncontrol practices in
decreasing the risk for transmission of M. tuberculosis
in health-care settings.
4. TB and Immunocompromising Conditions
- Relationship between infection with M. tuberculosis
and medical conditions and treatments that can lead
to impaired immunity.
- Available tests and counseling and referrals for persons with HIV infection, diabetes, and other
immunocompromising conditions associated with an increased risk for progression to TB disease.
- Procedures for informing employee health or infectioncontrol personnel of medical conditions associated
with immunosuppression.
- Policies on voluntary work reassignment options for immunocompromised HCWs.
- Applicable confidentiality safeguards of the health-care setting, locality, and state.
5. TB and Public Health
- Role of the local and state health department's TBcontrol program in screening for LTBI and TB disease,
providing treatment, conducting contact investigations and outbreak investigations, and providing education, counseling,
and responses to public inquiries.
- Roles of CDC and of OSHA.
- Availability of information, advice, and counseling from community sources, including universities, local experts,
and hotlines.
- Responsibility of the setting's clinicians and infection-control program to promptly report to the state or local
health department a case of suspected TB disease or a cluster of TST or BAMT conversions.
- Responsibility of the setting's clinicians and infectioncontrol program to promptly report to the state or local
health department a person with suspected or confirmed TB disease who leaves the setting against medical advice.
Managing Patients Who Have Suspected or Confirmed TB Disease:
General Recommendations
The primary TB risk to HCWs is the undiagnosed or unsuspected patient with infectious TB disease. A high index
of suspicion for TB disease and rapid implementation of precautions are essential to prevent and interrupt transmission.
Specific precautions will vary depending on the setting.
Prompt Triage
Within health-care settings, protocols should be implemented and enforced to promptly identify, separate from others,
and either transfer or manage persons who have suspected or confirmed infectious TB disease. When patients' medical histories
are taken, all patients should be routinely asked about 1) a history of TB exposure, infection, or disease; 2) symptoms or signs
of TB disease; and 3) medical conditions that increase their risk for TB disease (see Supplements, Diagnostic Procedures for
LTBI and TB Disease; and Treatment Procedures for LTBI and TB Disease). The medical evaluation should include an
interview conducted in the patient's primary language, with the assistance of a qualified medical
interpreter, if necessary. HCWs who are the first point of contact should be trained to ask questions that will facilitate
detection of persons who have suspected or confirmed infectious TB disease. For assistance with language interpretation, contact the local and state health
department. Interpretation resources are also available
(119) at http://www.atanet.org;
http://www.languageline.com; and
http://www.ncihc.org.
A diagnosis of respiratory TB disease should be considered for any patient with symptoms or signs of infection in the
lung, pleura, or airways (including larynx), including coughing for >3 weeks, loss of appetite, unexplained weight loss, night
sweats, bloody sputum or hemoptysis, hoarseness,
fever, fatigue, or chest pain. The index of suspicion for TB disease will vary
by geographic area and will depend on the population served by the setting. The index of suspicion should be substantially
high for geographic areas and groups of patients characterized by high TB incidence
(26).
Special steps should be taken in settings other than TB clinics. Patients with symptoms suggestive of undiagnosed
or inadequately treated TB disease should be promptly referred so that they can receive a medical evaluation. These
patients should not be kept in the setting any longer than required to arrange a referral or transfer to an AII room. While in the
setting, symptomatic patients should wear a surgical or procedure mask, if possible, and should be instructed to observe
strict respiratory hygiene and cough etiquette procedures (see Glossary)
(120--122).
Immunocompromised persons, including those who are HIVinfected, with infectious TB disease should be
physically separated from other persons to protect both themselves and others. To avoid exposing HIVinfected or otherwise
severely immunocompromised persons to M.
tuberculosis, consider location and scheduling issues to avoid exposure.
TB Airborne Precautions
Within health-care settings, TB airborne precautions should be initiated for any patient who has symptoms or signs of
TB disease, or who has documented infectious TB disease and has not completed antituberculosis treatment. For patients
placed in AII rooms because of suspected infectious TB disease of the lungs, airway, or larynx, airborne precautions may
be discontinued when infectious TB disease is considered unlikely and either 1) another diagnosis is made that explains
the clinical syndrome or 2) the patient has three consecutive, negative AFB sputum smear results
(109--112,123). Each of the
three sputum specimens should be collected in 8--24-hour intervals
(124), and at least one specimen should be an
early morning specimen because respiratory secretions pool overnight. Generally, this method will allow patients with
negative sputum smear results to be released from airborne precautions in 2 days.
The classification of the risk assessment of the health-care setting is used to determine how many AII rooms each
setting needs, depending on the number of TB patients examined. At least one AII room is needed for settings in which
TB patients stay while they are being treated, and additional AII rooms might be needed depending on the magnitude of
patient-days of persons with suspected or confirmed TB disease
(118). Additional rooms might be considered if options are limited
for transferring patients with suspected or confirmed TB disease to other settings with AII rooms. For
example, for a hospital with 120 beds, a minimum of one AII room is needed, possibly more, depending on how many TB patients are examined in 1 year.
TB Airborne Precautions for Settings in Which Patients with Suspected or Confirmed TB Disease Are Expected To
Be Encountered
Settings that plan to evaluate and manage patients with TB disease should have at least one AII room or enclosure
that meets AII requirements (see Environmental Controls; and Supplement, Environmental Controls). These settings
should develop written policies that specify 1) indications for airborne precautions, 2) persons authorized to initiate and
discontinue airborne precautions, 3) specific airborne precautions, 4) AII room-monitoring procedures, 5) procedures for
managing patients who do not adhere to airborne precautions, and 6) criteria for discontinuing airborne precautions.
A high index of suspicion should be maintained for TB disease. If a patient has suspected or confirmed TB disease,
airborne precautions should be promptly initiated. Persons with suspected or confirmed TB disease who are inpatients should remain
in AII rooms until they are determined to be noninfectious and have demonstrated a clinical response to a standard
multidrug antituberculosis treatment regimen or until an alternative diagnosis is made. If the alternative diagnosis cannot be
clearly established, even with three negative sputum smear results, empiric treatment of TB disease should strongly be considered
(see Supplement, Estimating the Infectiousness of a TB Patient). Outpatients with suspected or confirmed infectious TB
disease should remain in AII rooms until they are transferred or until their visit is complete.
TB Airborne Precautions for Settings in Which Patients with Suspected or Confirmed TB Disease Are Not
Expected To Be Encountered
Settings in which patients with suspected or confirmed TB disease are not expected to be encountered do not need an
AII room or a respiratoryprotection program for the prevention of transmission of
M. tuberculosis. However, follow the
following steps in these settings.
A written protocol should be developed for referring
patients with suspected or confirmed TB disease to a
collaborating referral setting in which the patient can be evaluated and managed properly. The referral setting should
provide documentation of intent to collaborate. The protocol should be reviewed routinely and revised as needed.
Patients with suspected or confirmed TB disease should be placed in an AII room, if available, or in a room that meets
the requirements for an AII room, or in a separate room with the door closed, apart from other patients and not in an
open waiting area. Adequate time should elapse to ensure removal of
M. tuberculosis--contaminated room air before allowing
entry by staff or another patient (see Environmental Controls;
Tables 1 and 2).
If an AII room is not available, persons with suspected or confirmed infectious TB disease should wear a surgical
or procedure mask, if possible. Patients should be instructed to keep the mask on and to change the mask if it becomes wet.
If patients cannot tolerate a mask, they should observe strict respiratory hygiene and cough etiquette procedures.
AII Room Practices
AII rooms should be single-patient rooms in which environmental factors and entry of visitors and HCWs are controlled
to minimize the transmission of M.
tuberculosis. All HCWs who enter an AII room should wear at least N95
disposable respirators (see Respiratory Protection). Visitors may be offered respiratory protection (i.e., N95) and should be instructed
by HCWs on the use of the respirator before entering an AII room. AII rooms have specific requirements for
controlled ventilation, negative pressure, and air filtration
(118) (see Environmental Controls). Each inpatient AII room should have
a private bathroom.
Settings with AII Rooms
Health-care personnel settings with AII rooms should
- keep doors to AII rooms closed except when patients, HCWs, or others must enter or exit the room
(118);
- maintain enough AII rooms to provide airborne precautions of all patients who have suspected or confirmed TB
disease. Estimate the number of AII rooms needed based on the results of the risk assessment for the setting;
- monitor and record direction of airflow (i.e., negative pressure) in the room on a daily basis, while the room is being
used for TB airborne precautions. Record results in an electronic or readily retrievable document;
- consider grouping AII rooms in one part of the health-care setting to limit costs, reduce the possibility of transmitting
M. tuberculosis to other patients, facilitate the care of TB patients, and facilitate the installation and maintenance of
optimal environmental controls (particularly ventilation). Depending on the architecture and the
environmental control systems of a particular setting, AII rooms might be grouped either horizontally (e.g., a wing of a facility) or vertically (e.g., the
last few rooms of separate floors of a facility);
- perform diagnostic and treatment procedures (e.g., sputum collection and inhalation therapy) in an AII room.
- ensure patient adherence to airborne precautions. In their primary language, with the assistance of a qualified
medical interpreter, if necessary, educate patients (and family and visitors) who are placed in an AII room
about M. tuberculosis transmission and the reasons for airborne precautions. For assistance with language interpretation,
contact the local and state health department. Interpretation resources are available
(119) at http://www.atanet.org;
http://www.languageline.com; and
http://www.ncihc.org. Facilitate patient adherence by using incentives (e.g.,
provide telephones, televisions, or radios in AII rooms; and grant special dietary requests) and other measures.
Address problems that could interfere with adherence (e.g., management of withdrawal from addictive substances, including tobacco); and
- ensure that patients with suspected or confirmed infectious TB disease who must be transported to another area of
the setting or to another setting for a medically essential procedure bypass the waiting area and wear a surgical or
procedure mask, if possible. Drivers, HCWs, and other
staff who are transporting persons with suspected or confirmed infectious
TB disease might consider wearing an N95 respirator. Schedule procedures on patients with TB disease when a
minimum number of HCWs and other patients are present and as the last procedure of the day to maximize the time available
for removal of airborne contamination (see Environmental Controls;
Tables 1 and 2).
Diagnostic Procedures
Diagnostic procedures should be performed in settings with appropriate infectioncontrol capabilities. The
following recommendations should be applied for diagnosing TB disease and for evaluating patients for potential infectiousness.
Clinical Diagnosis
A complete medical history should be obtained, including symptoms of TB disease, previous TB disease and
treatment, previous history of infection with M.
tuberculosis, and previous treatment of LTBI or exposure to persons with TB disease.
A physical examination should be performed, including chest radiograph, microscopic examination, culture, and,
when indicated, NAA testing of sputum
(39,53,125,126). If possible, sputum induction with aerosol inhalation is
preferred, particularly when the patient cannot produce sputum. Gastric aspiration might be necessary for those patients,
particularly children, who cannot produce sputum, even with aerosol inhalation
(127--130). Bronchoscopy might be needed for
specimen collection, especially if sputum specimens have been nondiagnostic and doubt exists as to the diagnosis
(90,111, 127,128,131--134).
All patients with suspected or confirmed infectious TB disease should be placed under airborne precautions until they
have been determined to be noninfectious (see Supplement, Estimating the Infectiousness of a TB Patient). Adult and
adolescent patients who might be infectious include persons who are coughing; have cavitation on chest radiograph; have positive
AFB sputum smear results; have respiratory tract disease with involvement of the lung, pleura or airways, including larynx, who
fail to cover the mouth and nose when coughing; are not on antituberculosis treatment or are on incorrect
antituberculosis treatment; or are undergoing cough-inducing or aerosol-generating procedures (e.g., sputum induction, bronchoscopy,
and airway suction) (30,135).
Persons diagnosed with extrapulmonary TB disease should be evaluated for the presence of concurrent pulmonary
TB disease. An additional concern in infection control with children relates to adult household members and visitors who
might be the source case (136). Pediatric patients, including adolescents, who might be infectious include those who have
extensive pulmonary or laryngeal involvement, prolonged cough, positive sputum AFB smears results, cavitary TB on chest
radiograph
(as is typically observed in immunocompetent adults with TB disease), or those for whom
cough-inducing or aerosol-generating procedures are performed
(136,137).
Although children are uncommonly infectious, pediatric patients should be evaluated for infectiousness by using the
same criteria as for adults (i.e., on the basis of pulmonary or laryngeal involvement). Patients with suspected or confirmed
TB disease should be immediately reported to the local public health authorities so that arrangements can be made for
tracking their treatment to completion, preferably through a case management system, so that DOT can be arranged and
standard procedures for identifying and evaluating TB contacts can be initiated. Coordinate efforts with the local or state
health department to arrange treatment and long-term follow-up and evaluation of contacts.
Laboratory Diagnosis
To produce the highest quality laboratory results, laboratories performing mycobacteriologic tests should be skilled in
both the laboratory and the administrative aspects of specimen processing. Laboratories should use or have prompt
access to the most rapid methods available: 1) fluorescent
microscopy and concentration for AFB smears; 2) rapid NAA testing for
direct detection of M. tuberculosis in patient specimens
(125); 3) solid and rapid broth culture methods for isolation of
mycobacteria; 4) nucleic acid probes or high pressure liquid chromatography (HPLC) for species identification; and 5) rapid broth
culture methods for drug susceptibility testing. Laboratories should incorporate other more rapid or sensitive tests as they
become available, practical, and affordable (see Supplement, Diagnostic Procedures for LTBI and TB Disease)
(138,139).
In accordance with local and state laws and regulations, a system should be in place to ensure that laboratories report
any positive results from any specimens to clinicians within 24 hours of obtaining the result
(139,140). Certain settings perform AFB smears on-site for rapid results (and results should be reported to clinicians within 24 hours) and then send specimens
or cultures to a referral laboratory for identification and drug-susceptibility testing. This referral practice can speed the receipt
of smear results but delay culture identification and drug-susceptibility results. Settings that cannot provide the full range
of mycobacteriologic testing services should contract with their referral laboratories to ensure rapid results while
maintaining proficiency for on-site testing. In addition, referral laboratories should be instructed to store isolates in case additional
testing is necessary.
All drug susceptibility results on M. tuberculosis
isolates should be reported to the local or state health department as soon
as these results are available. Laboratories that rarely
receive specimens for mycobacteriologic analysis should refer specimens to
a laboratory that performs these tests routinely. The reference laboratory should provide rapid testing and
reporting. Out-of-state reference laboratories should provide all results to the local or state health department from which the
specimen originated.
Special Considerations for Persons Who Are at High Risk for TB Disease or in Whom TB Disease Might Be
Difficult to Diagnose
The probability of TB disease is higher among patients who 1) previously had TB disease or were exposed to
M. tuberculosis, 2) belong to a group at high risk for TB disease or, 3) have a positive TST or BAMT result. TB disease is strongly suggested
if the diagnostic evaluation reveals symptoms or signs of TB disease, a chest radiograph consistent with TB disease, or AFB
in sputum or from any other specimen. TB disease can occur simultaneously in immunocompromised persons
who have pulmonary infections caused by other organisms (e.g.,
Pneumocystis jaroveci [formerly P.
carinii] and M. avium complex) and should be considered in the diagnostic evaluation of all such patients with symptoms or signs of TB disease
(53).
TB disease can be difficult to diagnose in persons who have HIV infection
(49) (or other conditions associated with severe
suppression of cell mediated immunity) because of nonclassical or normal radiographic presentation or
the simultaneous occurrence of other pulmonary infections (e.g.,
P. jaroveci or M. avium complex)
(2). Patients who are HIV-infected are also at greater risk for having extrapulmonary TB
(2). The difficulty in diagnosing TB disease in HIVinfected
can be compounded by the possible lower sensitivity and specificity of sputum smear results for detecting AFB
(53,141) and the overgrowth of cultures with
M. avium complex in specimens from patients infected with both
M. tuberculosis and M. avium complex. The TST in patients with advanced HIV infection is unreliable and cannot be used in clinical
decision making (35,53,142).
For immunocompromised patients who have respiratory symptoms or signs that are attributed initially to infections
or conditions other than TB disease, conduct an evaluation for coexisting TB disease. If the patient does not respond
to recommended treatment for the presumed cause of the pulmonary abnormalities, repeat the evaluation (see
Supplement,
Diagnostic Procedures for LTBI and TB Disease). In certain settings in which immunocompromised patients and
patients with TB disease are examined, implementing airborne precautions might be prudent for all persons at high risk. These
persons include those infected with HIV who have an abnormal chest radiograph or respiratory symptoms, symptomatic
foreign-born persons who have immigrated within the previous 5 years from TBendemic countries, and persons with pulmonary
infiltrates on chest radiograph, or symptoms or signs of TB disease.
Initiation of Treatment
For patients who have confirmed TB disease or who are considered highly probable to have TB disease, promptly
start antituberculosis treatment in accordance with current guidelines (see Supplements, Diagnostic Procedures for LTBI and
TB Disease; and Treatment Procedures for LTBI and TB Disease)
(31). In accordance with local and state regulations,
local health departments should be notified of all cases of suspected TB.
DOT is the standard of care for all patients with TB disease and should be used for all doses during the course of therapy
for treatment of TB disease. All inpatient medication should be administered by DOT and reported to the state or local
health department. Rates of relapse and development of drug-resistance are decreased when DOT is used
(143--145). All patients on intermittent (i.e., once or twice per week) treatment for TB disease or LTBI should receive DOT. Settings should
collaborate with the local or state health department on decisions concerning inpatient DOT and arrangements for outpatient DOT
(31).
Managing Patients Who Have Suspected or Confirmed TB Disease:
Considerations for Special Circumstances and Settings
The recommendations for preventing transmission of
M. tuberculosis are applicable to all health-care
settings, including those that have been described (Appendix A). These settings should each have independent risk assessments if
they are stand-alone settings, or each setting should have a detailed section written as part of the risk assessment for the
overall setting.
Minimum Requirements
The specific precautions for the settings included in this section vary, depending on the setting.
Inpatient Settings
Emergency Departments (EDs)
The symptoms of TB disease are usually symptoms for which patients might seek treatment in EDs. Because TB
symptoms are common and nonspecific, infectious TB disease could be encountered in these settings. The use of ED-based TB
screening has not been demonstrated to be consistently effective
(146).
The amount of time patients with suspected or confirmed infectious TB disease spend in EDs and urgent-care
settings should be minimized. Patients with suspected or confirmed infectious TB disease should be promptly identified,
evaluated, and separated from other patients. Ideally, such patients should be placed in an AII room. When an AII room is not
available, use a room with effective general ventilation, and use air cleaning technologies (e.g., a portable HEPA filtration system),
if available, or transfer the patient to a setting or area with recommended infectioncontrol capacity. Facility
engineering personnel with expertise in heating, ventilation, and air conditioning (HVAC) and air handlers have evaluated how this
option is applied to ensure no over pressurization of
return air or unwanted alternations exists in design of air flow in the zone.
EDs with a high volume of patients with suspected or confirmed TB disease should have at least one AII room (see TB
Risk Assessment). Air-cleaning technologies (e.g., HEPA filtration and UVGI) can be used to increase equivalent air changes
per hour (ACH) in waiting areas (Table 1). HCWs entering an AII room or any room with a patient with infectious TB
disease should wear at least an N95 disposable respirator. After a patient with suspected or confirmed TB disease exits a room,
allow adequate time to elapse to ensure removal of
M. tuberculosis-contaminated room air before allowing
entry by staff or another patient (see Environmental Controls; Tables 1 and
2).
Before a patient leaves an AII room, perform an assessment of 1) the patient's need to discontinue airborne precautions,
2) the risk for transmission and the patient's ability to observe strict respiratory hygiene, and 3) cough etiquette
procedures. Patients with suspected or confirmed infectious
TB who are outside an AII room should wear a surgical or procedure mask,
if
possible. Patients who cannot tolerate masks because of medical conditions should observe strict respiratory hygiene
and cough etiquette procedures.
Intensive Care Units (ICUs)
Patients with infectious TB disease might become sick enough to require admission to an ICU. Place ICU patients
with suspected or confirmed infectious TB disease in an AII room, if possible. ICUs with a high volume of patients with
suspected or confirmed TB disease should have at least one AII room (see TB Risk Assessment Worksheet) [Appendix B].
Air-cleaning technologies (e.g., HEPA filtration and UVGI) can be used to increase equivalent ACH in waiting areas (see
Environmental Controls).
HCWs entering an AII room or any room with a patient with infectious TB disease should wear at least an N95
disposable respirator. To help reduce the risk for contaminating a ventilator or discharging
M. tuberculosis into the ambient air when mechanically ventilating (i.e., with a ventilator or manual resuscitator) a patient with suspected or confirmed TB disease,
place a bacterial filter on the patient's endotracheal tube (or at the expiratory side of the breathing circuit of a ventilator)
(147--151). In selecting a bacterial filter, give preference to models specified by the manufacturer to filter particles 0.3
µm in size in both the unloaded and loaded states with a filter efficiency of >95% (i.e., filter penetration of <5%) at the maximum
design flow rates of the ventilator for the service life of the filter, as specified by the manufacturer.
Surgical Suites
Surgical suites require special infectioncontrol considerations for preventing transmission of
M. tuberculosis. Normally, the direction of airflow should be from the operating room (OR) to the hallway (positive pressure) to minimize contamination
of the surgical field. Certain hospitals have procedure rooms with reversible airflow or pressure, whereas others have
positive-pressure rooms with a negative pressure anteroom. Surgical staff, particularly those close to the surgical field, should
use respiratory protection (e.g., a valveless N95 disposable respirator) to protect themselves and the patient
undergoing surgery.
When possible, postpone non-urgent surgical procedures on patients with suspected or confirmed TB disease until
the patient is determined to be noninfectious or determined to not have TB disease. When surgery cannot be
postponed, procedures should be performed in a surgical suite with recommended ventilation controls. Procedures should be
scheduled for patients with suspected or confirmed TB disease when a minimum number of HCWs and other patients are present in
the surgical suite, and at the end of the day to maximize the time available for removal of airborne contamination
(see Environmental Controls; Tables 1 and 2).
If a surgical suite or an OR has an anteroom, the anteroom should be either 1) positive pressure compared with both
the corridor and the suite or OR (with filtered supply air) or 2) negative pressure compared with both the corridor and the
suite or OR. In the usual design in which an OR has no anteroom, keep the doors to the OR closed, and minimize traffic into
and out of the room and in the corridor. Using additional air-cleaning technologies (e.g., UVGI) should be considered to
increase the equivalent ACH. Air-cleaning systems can be placed in the room or in surrounding areas to minimize contamination
of the surroundings after the procedure
(114) (see Environmental Controls).
Ventilation in the OR should be designed to provide a sterile environment in the surgical field while
preventing contaminated air from flowing to other areas in the health-care setting. Personnel steps should be taken to reduce the risk
for contaminating ventilator or anesthesia equipment or discharging tubercle bacilli into the ambient air when operating on
a patient with suspected or confirmed TB disease
(152). A bacterial filter should be placed on the patient's endotracheal tube
(or at the expiratory side of the breathing circuit of a ventilator or anesthesia machine, if used)
(147--151). When selecting a bacterial filter, give preference to models specified by the manufacturer to filter particles 0.3 µm in size in both
the unloaded and loaded states with a filter efficiency of
>95% (i.e., filter penetration of <5%) at the maximum design flow
rates of the ventilator for the service life of the filter, as specified by the manufacturer.
When surgical procedures (or other procedures that require a sterile field) are performed on patients with suspected
or confirmed infectious TB, respiratory protection should be worn by HCWs to protect the sterile field from the
respiratory secretions of HCWs and to protect HCWs from the
infectious droplet nuclei generated from the patient. When
selecting respiratory protection, do not use valved or positive-pressure respirators, because they do not protect the sterile field.
A respirator with a valveless filtering facepiece (e.g., N95 disposable respirator) should be used.
Postoperative recovery of a patient with suspected or confirmed TB disease should be in an AII room in any location
where the patient is recovering (118). If an AII or comparable room is not available for surgery or postoperative recovery,
air-cleaning
technologies (e.g., HEPA filtration and UVGI) can be used to increase the number of equivalent ACH (see
Environmental Controls); however, the infectioncontrol committee should be involved in the selection and placement of these
supplemental controls.
Laboratories
Staff who work in laboratories that handle clinical specimens encounter risks not typically present in other areas of a
health-care setting (153--155). Laboratories that handle TB specimens include 1) pass-through facilities that forward specimens
to reference laboratories for analysis; 2) diagnostic laboratories that process specimens and perform acid-fast staining and
primary culture for M. tuberculosis; and 3) facilities that perform extensive identification, subtyping, and susceptibility studies.
Procedures involving the manipulation of specimens or
cultures containing M. tuberculosis introduce additional
substantial risks that must be addressed in an effective TB infection-control program. Personnel who work with
mycobacteriology specimens should be thoroughly trained in methods that minimize the production of aerosols and
undergo periodic competency testing to include direct observation of their work practices. Risks for transmission of
M. tuberculosis in laboratories include aerosol formation during any specimen or isolate manipulation and percutaneous inoculation
from accidental exposures. Biosafety recommendations for laboratories performing diagnostic testing for TB have been
published (74,75,138,156,157).
In laboratories affiliated with a health-care setting (e.g., a hospital) and in free-standing laboratories, the laboratory
director, in collaboration with the infectioncontrol staff for the setting, and in consultation with the state TB laboratory, should develop
a risk-based infectioncontrol plan for the laboratory that minimizes the risk for exposure to
M. tuberculosis. Consider factors including 1) incidence of TB disease (including drug-resistant TB) in the community and in patients served by settings
that submit specimens to the laboratory, 2) design of the laboratory, 3) level of TB diagnostic service offered, 4) number of
specimens processed, and 5) whether or not aerosol-generating or aerosol-producing procedures are performed and the frequency at
which they are performed. Referral laboratories should store isolates in case additional testing is necessary.
Biosafety level (BSL)-2 practices and procedures, containment equipment, and facilities are required for
nonaerosol-producing manipulations of clinical specimens (e.g., preparing direct smears for acid-fast staining when done in
conjunction with training and periodic checking of competency)
(138). All specimens suspected of containing
M. tuberculosis (including specimens processed for other microorganisms) should be handled in a Class I or II biological safety cabinet (BSC)
(158,159). Conduct all aerosol-generating activities (e.g.,
inoculating culture media, setting up biochemical and
antimicrobic susceptibility tests, opening centrifuge cups, and performing sonication) in a Class I or II BSC
(158).
For laboratories that are considered at least medium risk (Appendix C), conduct testing for
M. tuberculosis infection at least annually among laboratorians who perform TB diagnostics or manipulate specimens from which
M. tuberculosis is commonly isolated (e.g., sputum, lower respiratory secretions, or tissues) (Appendix D). More frequent testing for
M. tuberculosis is recommended in the event of a documented conversion among laboratory staff or a laboratory accident that poses a risk
for exposure to M. tuberculosis (e.g., malfunction of a centrifuge leading to aerosolization of a sample).
Based on the risk assessment for the laboratory, employees should use personal protective equipment (including
respiratory protection) recommended by local regulations for each activity. For activities that have a low risk for generating
aerosols, standard personal protective equipment consists of protective laboratory coats, gowns, or smocks designed specifically for
use in the laboratory. Protective garments should be left in the laboratory before going to nonlaboratory areas.
For all laboratory procedures, disposable gloves should be worn. Gloves should be disposed of when work is completed,
the gloves are overtly contaminated, or the integrity of the glove is compromised. Local or state regulations
should determine procedures for the disposal of gloves. Face protection (e.g., goggles, full-facepiece respirator, face shield, or
other splatter guard) should also be used when manipulating specimens inside or outside a BSC. Use respiratory protection
when performing procedures that can result in aerosolization outside a BSC. The minimum level of respiratory protection is an
N95 filtering facepiece respirator. Laboratory workers who use respiratory protection should be provided with the same training
on respirator use and care and the same fit testing as other HCWs.
After documented laboratory accidents, conduct an investigation of exposed laboratory workers. Laboratories in
which specimens for mycobacteriologic studies (e.g., AFB smears and cultures) are processed should follow the AIA and
CDC/National Institute of Health guidelines
(118,159) (see Environmental Controls). BSL-3 practices, containment equipment,
and facilities are recommended for the propagation and
manipulation of cultures of M. tuberculosis
complex (including M. bovis) and for animal studies in which primates that are experimentally or naturally infected with
M. tuberculosis or M. bovis are
used.
Animal studies in which guinea pigs or mice are used can be conducted at animal BSL-2. Aerosol infection methods
are recommended to be conducted at BSL-3
(159).
Bronchoscopy Suites
Because bronchoscopy is a cough-inducing procedure that might be performed on patients with suspected or confirmed
TB disease, bronchoscopy suites require special attention
(29,81,160,161). Bronchoscopy can result in the transmission of
M. tuberculosis either through the airborne route
(29,63,81,86,162) or a contaminated bronchoscope
(80,82,163--170). Closed and effectively filtered ventilatory circuitry and minimizing opening of such circuitry in intubated and mechanically
ventilated patients might minimize exposure (see Intensive Care Units)
(149).
If possible, avoid bronchoscopy on patients with suspected or confirmed TB disease or postpone the procedure until
the patient is determined to be noninfectious, by confirmation of the three negative AFB sputum smear results
(109--112). When collection of spontaneous sputum specimen is not adequate or possible, sputum induction has been demonstrated to
be equivalent to bronchoscopy for obtaining specimens for culture
(110). Bronchoscopy might have the advantage
of confirmation of the diagnosis with histologic specimens, collection of additional specimens, including post
bronchoscopy sputum that might increase the diagnostic yield, and the opportunity to confirm an alternate diagnosis. If the diagnosis of
TB disease is suspected, consideration should be given to empiric antituberculosis treatment.
A physical examination should be performed, and a chest radiograph, microscopic examination, culture, and NAA testing
of sputum or other relevant specimens should also be
obtained, including gastric aspirates (125), as indicated
(53,126,131,130). Because 15%--20% of patients with TB disease have negative TST results, a negative TST result is of limited value in
the evaluation of the patient with suspected TB disease, particularly in patients from high TB incidence groups in whom
TST positive rates exceed 30% (31).
Whenever feasible, perform bronchoscopy in a room that meets the ventilation requirements for an AII room (same as
the AIA guidelines parameters for bronchoscopy rooms) (see Environmental Controls). Air-cleaning technologies (e.g.,
HEPA filtration and UVGI) can be used to increase equivalent ACH.
If sputum specimens must be obtained and the patient cannot produce sputum, consider sputum induction
before bronchoscopy (111). In a patient who is intubated and mechanically ventilated, minimize the opening of circuitry. At
least N95 respirators should be worn by HCWs while present during a bronchoscopy procedure on a patient with suspected
or confirmed infectious TB disease. Because of the increased risk for
M. tuberculosis transmission during the performance
of bronchoscopy procedures on patients with TB disease, consider using a higher level of respiratory protection than an
N95 disposable respirator (e.g., an elastomeric full-facepiece respirator or a powered air-purifying respirator [PAPR]
[29]) (see Respiratory Protection).
After bronchoscopy is performed on a patient with suspected or confirmed infectious TB disease, allow adequate time
to elapse to ensure removal of M.
tuberculosis--contaminated room air before performing another procedure in the same
room (see Environmental Controls; Tables 1 and
2). During the period after bronchoscopy when the patient is still coughing,
collect at least one sputum for AFB to increase the yield of the procedure. Patients with suspected or confirmed TB disease who
are undergoing bronchoscopy should be kept in an AII room until coughing subsides.
Sputum Induction and Inhalation Therapy Rooms
Sputum induction and inhalation therapy induces coughing, which increases the potential for transmission
of M. tuberculosis (87,88,90). Therefore, appropriate precautions should be taken when working with patients with suspected
or confirmed TB disease. Sputum induction procedures for persons with suspected or confirmed TB disease should be
considered after determination that self-produced sputum collection is inadequate and that the AFB smear result on other
specimens collected is negative. HCWs who order or perform sputum induction or inhalation therapy in an environment without
proper controls for the purpose of diagnosing conditions other than TB disease should assess the patient's risk for TB disease.
Cough-inducing or aerosol-generating procedures in patients with diagnosed TB should be conducted only after an
assessment of infectiousness has been considered for each patient and should be conducted in an environment with proper controls.
Sputum induction should be performed by using local exhaust ventilation (e.g., booths with special ventilation) or alternatively in a
room that meets or exceeds the requirements of an AII room (see Environmental Controls)
(90). At least an N95 disposable respirator should be worn by HCWs performing sputum inductions or inhalation therapy on a patient with suspected or
confirmed
infectious TB disease. Based on the risk assessment, consideration should be given to using a higher level of respiratory
protection (e.g., an elastomeric full-facepiece respirator or a PAPR) (see Respiratory Protection)
(90).
After sputum induction or inhalation therapy is performed on a patient with suspected or confirmed infectious TB
disease, allow adequate time to elapse to ensure removal of
M. tuberculosis--contaminated room air before
performing another procedure in the same room (see Environmental Controls;
Tables 1 and 2). Patients with suspected or confirmed
TB disease who are undergoing sputum induction or inhalation therapy should be kept in an AII room until coughing subsides.
Autopsy Suites
Autopsies performed on bodies with suspected or confirmed TB disease can pose a high risk for transmission
of M. tuberculosis, particularly during the performance of
aerosol-generating procedures (e.g., median sternotomy). Persons
who handle bodies might be at risk for transmission of
M. tuberculosis (77,78,171--177). Because certain procedures performed
as part of an autopsy might generate infectious aerosols, special airborne precautions are required.
Autopsies should not be performed on bodies with suspected or confirmed TB disease without adequate protection for
those performing the autopsy procedures. Settings in which autopsies are performed should meet or exceed the requirements of
an AII room, if possible (see Environmental Controls), and the drawing in the American Conference of Governmental
Industrial Hygienists® (ACGIH) Industrial Ventilation Manual VS-99-07
(178). Air should be exhausted to the outside of the
building. Air-cleaning technologies (e.g., HEPA filtration or UVGI) can be used to increase the number of equivalent ACH
(see Environmental Controls).
As an added administrative measure, when performing
autopsies on bodies with suspected or confirmed TB
disease, coordination between attending physicians and pathologists is needed to ensure proper infection control and
specimen collection. The use of local exhaust ventilation should be considered to reduce exposures to infectious aerosols (e.g.,
when using a saw, including Striker saw). For HCWs performing an autopsy on a body with suspected or confirmed TB disease,
at least N95 disposable respirators should be worn (see Respiratory Protection). Based on the risk assessment, consider using
a higher level of respiratory protection than an N95 disposable respirator (e.g., an elastomeric full-facepiece respirator or
a PAPR) (see Respiratory Protection).
After an autopsy is performed on a body with suspected or confirmed TB disease, allow adequate time to elapse to
ensure removal of M. tuberculosis--contaminated room air before performing another procedure in the same room (see
Environmental Controls; Tables 1 and 2). If time delay is not feasible, the autopsy staff should continue to wear respirators while they are
in the room.
Embalming Rooms
Embalming procedures performed on bodies with suspected or confirmed TB disease can pose a high risk for
transmission of M. tuberculosis, particularly during the performance of aerosol-generating procedures. Persons who handle corpses might
be at risk for transmission of M. tuberculosis
(77,78,171--176). Because certain procedures performed as part of
embalming might generate infectious aerosols, special airborne precautions are required.
Embalming should not be performed on bodies with suspected or confirmed TB disease without adequate protection for
the persons performing the procedures. Settings in which embalming is performed should meet or exceed the requirements of
an AII room, if possible (see Environmental Controls), and the drawing in the ACGIH Industrial Ventilation Manual
VS-99-07 (178). Air should be exhausted to the outside of the building. Air-cleaning technologies (e.g., HEPA filtration or UVGI)
can be used to increase the number of equivalent ACH (see Environmental Controls). The use of local exhaust ventilation
should be considered to reduce exposures to infectious aerosols (e.g., when using a saw,
including Striker saw) and vapors from embalming fluids.
When HCWs embalm a body with suspected or confirmed TB disease, at least N95 disposable respirators should be
worn (see Respiratory Protection). Based on the risk assessment, consider using a higher level of respiratory protection than an
N95 disposable respirator (e.g., an elastomeric full-facepiece respirator or a PAPR) (see Respiratory Protection).
After embalming is performed on a body with suspected or confirmed TB disease, allow adequate time to elapse to
ensure removal of M. tuberculosis--contaminated room air before performing another procedure in the same room (see
Environmental Controls). If time delay is not feasible, the embalming staff should continue to wear respirators while in the room.
Outpatient Settings
Outpatient settings might include TB treatment facilities, dental-care settings, medical offices, ambulatory-care settings,
and dialysis units. Environmental controls should be implemented based on the types of activities that are performed in
the setting.
TB Treatment Facilities
TB treatment facilities might include TB clinics, infectious disease clinics, or pulmonary clinics. TB clinics and
other settings in which patients with TB disease and LTBI are examined on a regular basis require special attention. The
same principles of triage used in EDs and ambulatory-care settings (see Minimum Requirements) should be applied to
TB treatment facilities. These principles include prompt identification, evaluation, and airborne precautions of patients
with suspected or confirmed infectious TB disease.
All TB clinic staff, including outreach workers, should be screened for
M. tuberculosis infection (Appendix C). Patients
with suspected or confirmed infectious TB disease should be physically separated from all patients, but especially from those
with HIV infection and other immunocompromising conditions that increase the likelihood of development of TB disease
if infected. Immunosuppressed patients with suspected or confirmed infectious TB disease need to be physically separated
from others to protect both the patient and others.
Appointments should be scheduled to avoid exposing HIV-infected or
otherwise severely immunocompromised persons to
M. tuberculosis. Certain times of the day should be designated for appointments
for patients with infectious TB disease or treat them in locations in areas in which immunocompromised persons are not treated.
Persons with suspected or confirmed infectious TB disease should be promptly placed in an AII room to minimize exposure
in the waiting room and other areas of the clinic, and they should be instructed to observe strict respiratory hygiene and
cough etiquette procedures. Clinics that provide care for
patients with suspected or confirmed infectious TB disease should have at
least one AII room. The need for additional AII rooms should be based on the risk assessment for the setting.
All cough-inducing and aerosol-generating procedures should be performed using environmental controls (e.g., in a
booth or an AII room) (see Environmental Controls). Patients should be left in the booth or AII room until coughing
subsides. Another patient or HCW should not be allowed to
enter the booth or AII room until sufficient time has elapsed for
adequate removal of M. tuberculosis-contaminated air (see Environmental Controls). A respiratoryprotection program should
be implemented for all HCWs who work in the TB clinic and who enter AII rooms, visit areas in which persons with
suspected or confirmed TB disease are located, or transport patients with suspected or confirmed TB disease in
vehicles. When persons with suspected or confirmed infectious TB disease are in the TB clinic and not in an AII room, they should wear a surgical
or procedure mask, if possible.
Medical Offices and Ambulatory-Care Settings
The symptoms of TB disease are usually symptoms for which patients might seek treatment in a medical office.
Therefore, infectious TB disease could possibly be encountered in certain medical offices and ambulatory-care settings.
Because of the potential for M. tuberculosis
transmission in medical offices and ambulatory-care settings, follow the
general recommendations for management of patients with suspected or confirmed TB disease and the specific recommendations
for EDs (see Intensive Care Units [ICUs]). The risk assessment may be used to determine the need for or selection
of environmental controls and the frequency of testing HCWs for
M. tuberculosis infection.
Dialysis Units
Certain patients with TB disease need chronic dialysis for treatment of ESRD
(179--181). The incidence of TB disease and infection in patients with ESRD might be higher than in the general population
(181--183) and might be compounded by the overlapping risks for ESRD and TB disease among patients with diabetes mellitus
(39). In addition, certain dialysis patients
or patients who are otherwise immunocompromised (e.g., patients with organ transplants) might be on
immunosuppressive medications (162,183). Patients with ESRD who need chronic dialysis should have at least one test for
M. tuberculosis infection to determine the need for treatment of LTBI. Annual re-screening is indicated if ongoing exposure of ESRD
patients to M. tuberculosis is probable.
Hemodialysis procedures should be performed on hospitalized patients with suspected or confirmed TB disease in an
AII room. Dialysis staff should use recommended respiratory protection, at least an N95 disposable respirator. Patients
with suspected or confirmed TB disease who need chronic hemodialysis might need referral to a hospital or other setting with
the
ability to perform dialysis procedures in an AII room
until the patient is no longer infectious or another diagnosis is
made. Certain antituberculosis medications are prescribed differently for hemodialysis patients
(31).
Dental-Care Settings
The generation of droplet nuclei containing M. tuberculosis
as a result of dental procedures has not been
demonstrated (184). Nonetheless, oral manipulations during dental procedures could stimulate coughing and dispersal of
infectious particles. Patients and dental HCWs share the same air space for varying periods, which contributes to the potential
for transmission of M. tuberculosis in dental settings
(185). For example, during primarily routine dental procedures in a
dental setting, MDR TB might have been transmitted between two dental workers
(186).
To prevent the transmission of M. tuberculosis
in dental-care settings, certain recommendations should be
followed (187,188). Infectioncontrol policies for each dental health-care setting should be developed, based on the community TB
risk assessment (see TB Risk Assessment Worksheet
[Appendix B]), and the periodically should be reviewed
annually, if possible. The policies should include appropriate screening for LTBI and TB disease for dental HCWs, education on the risk
for transmission to the dental HCWs, and provisions for detection and management of patients who have suspected or
confirmed TB disease.
When taking a patient's initial medical history and at periodic updates, dental HCWs should routinely document
whether the patient has symptoms or signs of TB disease. If urgent dental care must be provided for a patient who has suspected
or confirmed infectious TB disease, dental care should be provided in a setting that meets the requirements for an AII room
(see Environmental Controls). Respiratory protection (at least N95 disposable respirator) should be used while
performing procedures on such patients.
In dental health-care settings that routinely provide care to populations at high risk for TB disease, using
engineering controls (e.g., portable HEPA units) similar to those used in waiting rooms or clinic areas of health-care settings with
a comparable community-risk profile might be beneficial.
During clinical assessment and evaluation, a patient with suspected or confirmed TB disease should be instructed to
observe strict respiratory hygiene and cough etiquette procedures
(122). The patient should also wear a surgical or procedure mask,
if possible. Non-urgent dental treatment should be postponed, and these patients should be promptly referred to an
appropriate medical setting for evaluation of possible infectiousness. In addition, these patients should be kept in the dental
health-care setting no longer than required to arrange
a referral.
Nontraditional Facility-Based Settings
Nontraditional facilitybased settings include EMS, medical settings in correctional facilities, home-based health-care
and outreach settings, long-term--care settings (e.g., hospices and skilled nursing facilities), and homeless shelters.
Environmental controls should be implemented based on the types of activities that are performed in the setting.
TB is more common in the homeless population than in the general population
(189--192). Because persons who visit homeless shelters frequently share exposure and risk characteristics of TB patients who are treated in outpatient
clinics, homeless shelters with clinics should observe the same TB infectioncontrol measures as outpatient clinics. ACET
has developed recommendations to assist health-care providers, health departments, shelter operators and workers, social
service agencies, and homeless persons to prevent and control TB in this population
(189).
Emergency Medical Services (EMS)
Although the overall risk is low (193), documented transmission of
M. tuberculosis has occurred in EMS
occupational settings (194), and approaches to reduce this risk have been described
(193,195). EMS personnel should be included in
a comprehensive screening program to test for M. tuberculosis
infection and provide baseline screening and follow-up testing
as indicated by the risk classification of the setting. Persons with suspected or confirmed infectious TB disease who
are transported in an ambulance should wear a surgical or procedure mask, if possible, and drivers, HCWs, and other staff
who are transporting the patient might consider wearing an N95 respirator.
The ambulance ventilation system should be operated in the nonrecirculating mode, and the maximum amount of
outdoor air should be provided to facilitate dilution. If the vehicle has a rear exhaust fan, use this fan during transport. If the vehicle
is equipped with a supplemental recirculating ventilation unit that passes air through HEPA filters before
returning it to the vehicle, use this unit to increase the number of ACH
(188). Air should flow from the cab (front of vehicle), over the
patient,
and out the rear exhaust fan. If an ambulance is not used, the ventilation system for the vehicle should bring in as
much outdoor air as possible, and the system should be set to nonrecirculating. If possible, physically isolate the cab from the rest
of the vehicle, and place the patient in the rear seat
(194).
EMS personnel should be included in the follow-up contact investigations of patients with infectious TB disease. The
Ryan White Comprehensive AIDS Resource Emergency Act of 1990 (Public law 101--381) mandates notification of
EMS personnel after they have been exposed to a patient with suspected or confirmed infectious TB disease (Title 42 U.S.
Code 1994) (http://hab.hrsa.gov/data2/adap/introduction.htm).
Medical Settings in Correctional Facilities
TB is a substantial health concern in correctional facilities; employees and inmates are at high risk
(105,196--205). TB outbreaks in correctional facilities can lead to transmission in surrounding communities
(201,206,207). ACET recommends that all correctional facilities have a written TB infectioncontrol plan
(196), and multiple studies indicate that
screening correctional employees and inmates is a vital TB control measure
(204,208,209).
The higher risk for M. tuberculosis transmission in health-care settings in correctional facilities (including jails and prisons)
is a result of the disproportionate number of inmates with risk factors for TB infection and TB disease
(203,210). Compared with the general population, TB prevalence is higher among inmates and is associated with a higher prevalence of
HIV infection (197), increased illicit substance use, lower socioeconomic status
(201), and their presence in settings that are at
high risk for transmission of M.
tuberculosis.
A TB infectioncontrol plan should be developed specifically for that setting, even if the institution is part of a
multifacility system (196,211). Medical settings in correctional facilities should be classified as at least medium risk; therefore,
all correctional facility health-care personnel and other staff, including correctional officers should be screened for TB at
least annually (201,203,208).
Correctional facilities should collaborate with the local or state health department to decide on TB contact
investigations and discharge planning
(105,212) and to provide TB training and education to inmates and employees
(196). Corrections staff should be educated regarding symptoms and signs of TB disease and encouraged to facilitate prompt evaluation
of inmates with suspected infectious TB disease
(206).
At least one AII room should be available in the correctional facility. Any inmate with suspected or confirmed infectious
TB disease should be placed in an AII room immediately or transferred to a setting with an AII room; base the number
of additional AII rooms needed on the risk assessment for the setting. Sputum samples should be collected in
sputum induction booths or AII rooms, not in inmates' cells. Sputum collection can also be performed safely outside, away from
other persons, windows, and ventilation intakes.
Inmates with suspected or confirmed infectious TB disease who must be transported outside an AII room for
medically essential procedures should wear a surgical or procedure mask during transport, if possible. If risk assessment indicates
the need for respiratory protection, drivers, medical or security staff, and others who are transporting patients with suspected
or confirmed infectious TB disease in an enclosed vehicle should consider wearing an N95 disposable respirator.
A respiratoryprotection program, including training, education, and fit-testing in the correctional facility's
TB infectioncontrol program should be implemented. Correctional facilities should maintain a tracking system for inmate
TB screening and treatment and establish a mechanism for sharing this information with state and local health departments
and other correctional facilities
(196,201). Confidentiality of inmates should be ensured the confidentiality of inmates
during screening for symptoms or signs of TB disease and risk factors.
Home-Based Health-Care and Outreach Settings
Transmission of M. tuberculosis has been documented in staff who work in home-based health-care and outreach
settings (213,214). The setting's infectioncontrol plan should include training that reminds HCWs who provide medical services
in the homes of patients or other outreach settings of the importance of early evaluation of symptoms or signs of TB disease
for early detection and treatment of TB disease. Training should also include the role of the HCW in educating patients
regarding the importance of reporting symptoms or signs of TB disease and the importance of reporting any adverse effects to
treatment for LTBI or TB disease.
HCWs who provide medical services in the homes of
patients with suspected or confirmed TB disease can help
prevent transmission of M. tuberculosis by 1) educating patients and other household members regarding the importance of
taking
medications as prescribed, 2) facilitating medical evaluation of symptoms or signs of TB disease, and 3) administering
DOT, including DOT for treatment of LTBI, whenever feasible.
HCWs who provide medical services in the homes of
patients should not perform cough-inducing or
aerosol-generating procedures on patients with suspected or confirmed infectious TB disease, because recommended infection
controls probably will not be in place. Sputum collection should be performed outdoors, away from other persons, windows,
and ventilation intakes.
HCWs who provide medical services in the homes of
patients with suspected or confirmed infectious TB disease
should instruct TB patients to observe strict respiratory
hygiene and cough etiquette procedures. HCWs who enter homes of
persons with suspected or confirmed infectious TB disease or who transport such persons in an enclosed vehicle should
consider wearing at least an N95 disposable respirator (see Respiratory Protection).
Long-Term--Care Facilities (LTCFs)
Infection with M. tuberculosis poses a health risk to patients, HCWs, visitors, and volunteers in LTCFs (e.g., hospices
and skilled nursing facilities) (215,216). Transmission of
M. tuberculosis has occurred in LTCF
(217--220), and pulmonary TB disease has been documented in HIVinfected
patients and other immunocompromised persons residing in
hospices (218,221,222). New employees and residents to these settings should receive a symptom screen and possibly a test for
M. tuberculosis infection to exclude a diagnosis of TB disease (see TB Risk Assessment Worksheet).
LTCFs must have adequate administrative and environmental controls, including airborne precautions capabilities and
a respiratoryprotection program, if they accept patients with suspected or confirmed infectious TB disease. The setting
should have 1) a written protocol for the early identification of patients with symptoms or signs of TB disease and 2) procedures
for referring these patients to a setting where they can be evaluated and managed. Patients with suspected or confirmed
infectious TB disease should not stay in LTCFs unless adequate administrative and environmental controls and a
respiratoryprotection program are in place. Persons with TB disease who are determined to be noninfectious can remain in the LTCF and do
not need to be in an AII room.
Training and Educating HCWs
HCW training and education regarding infection with
M. tuberculosis and TB disease is an essential part of
administrative controls in a TB surveillance or infectioncontrol program. Training physicians and nurse managers is especially
essential because of the leadership role they frequently fulfill in infection control. HCW training and education can
increase adherence to TB infectioncontrol measures. Training and education should emphasize the increased risks posed by an
undiagnosed person with TB disease in a health-care setting and the specific measures to reduce this risk. HCWs receive various types
of training; therefore, combining training for TB infection control with other related trainings might be preferable.
Initial TB Training and Education
The setting should document that all HCWs, including physicians, have received initial TB training relevant to their work
setting and additional occupation-specific education. The level and detail of baseline training will vary according to the responsibilities of
the HCW and the risk classification of the setting.
Educational materials on TB training are available from various sources at no cost in printed copy, on videotape
(223), on compact discs, and the Internet. The local or state health department should have access to additional materials and
resources and might be able to help develop a setting-specific TB education program. Suggested components of a baseline TB
training program for HCWs have been described previously. CDC's TB website provides information regarding training and
education materials (http://www.cdc.gov/tb). Additional training and education materials are available on CDC's TB Education
and Training Resources website (http://www.findtbresources.org) and on other TBrelated websites and resources (Appendix E).
Physicians, trainees, students, and other HCWs who work in a health-care setting but do not receive payment from
that setting should receive baseline training in TB infectioncontrol policies and practices, the TB screening program,
and procedures for reporting an M. tuberculosis
infection test conversion or diagnosis of TB disease. Initial TB training should
be provided before the HCW starts working.
Follow-Up TB Training and Education
All settings should conduct an annual evaluation of the need for follow-up training and education for HCWs based on
the number of untrained and new HCWs, changes in the organization and services of the setting, and availability of new
TB infectioncontrol information.
If a potential or known exposure to M. tuberculosis
occurs in the setting, prevention and control measures should
include retraining HCWs in the infectioncontrol procedures established to prevent the recurrence of exposure. If a potential or
known exposure results in a newly recognized positive TST or BAMT result, test conversion, or diagnosis of TB disease,
education should include information on 1) transmission of
M. tuberculosis, 2) noninfectiousness of HCWs with LTBI, and 3)
potential infectiousness of HCWs with TB disease.
OSHA requires annual respiratoryprotection training for HCWs who use respiratory devices (see Respiratory
Protection). HCWs in settings with a classification of potential
ongoing transmission should receive additional training and education
on 1) symptoms and signs of TB disease, 2) M. tuberculosis
transmission, 3) infectioncontrol policies, 4) importance of
TB screening for HCWs, and 5) responsibilities of employers and employees regarding
M. tuberculosis infection test conversion and diagnosis of TB disease.
TB Infection-Control Surveillance
HCW Screening Programs for TB Support Surveillance and Clinical Care
TB screening programs provide critical information for caring for individual HCWs and information that
facilitates detection of M. tuberculosis transmission. The screening program consists of four major components: 1) baseline testing for
M. tuberculosis infection, 2) serial testing for
M. tuberculosis infection, 3) serial screening for symptoms or signs of TB disease,
and 4) TB training and education.
Surveillance data from HCWs can protect both HCWs and patients. Screening can prevent future transmission
by identifying lapses in infection control and expediting treatment for persons with LTBI or TB disease. Tests to screen for
M. tuberculosis infection should be administered, interpreted, and
recorded according to procedures in this report
(see Supplement, Diagnostic Procedures for LTBI and TB Disease). Protection of privacy and maintenance of confidentiality
of HCW test results should be ensured. Methods to screen for infection with
M. tuberculosis are available
(30,31,39).
Baseline Testing for M. tuberculosis Infection
Baseline testing for M. tuberculosis infection is recommended for all newly hired HCWs, regardless of the risk
classification of the setting and can be conducted with the TST or BAMT. Baseline testing is also recommended for persons who
will receive serial TB screening (e.g., residents or staff of correctional facilities or LTCFs)
(39,224). Certain settings, with the support of the infectioncontrol committee, might choose not to perform baseline or serial TB screening for HCWs who
will never be in contact with or have shared air space with patients who have TB disease (e.g., telephone operators who work in
a separate building from patients) or who will never be in contact with clinical specimens that might contain
M. tuberculosis.
Baseline test results 1) provide a basis for comparison in the event of a potential or known exposure to
M. tuberculosis and 2) facilitate the detection and treatment of LTBI or TB disease in an HCW before employment begins and reduces the risk
to patients and other HCWs. If TST is used for baseline testing, two-step testing is recommended for HCWs whose initial
TST results are negative (39,224). If the first-step TST result is negative, the second-step TST should be administered 1--3
weeks after the first TST result was read. If either 1) the baseline first-step TST result is positive or 2) the first-step TST result
is negative but the second-step TST result is positive, TB disease should be excluded, and if it is excluded, then the HCW
should be evaluated for treatment of LTBI. If the first and second-step TST results are both negative, the person is classified as
not infected with M. tuberculosis.
If the second test result of a two-step TST is not read within 48--72 hours, administer a TST as soon as possible (even
if several months have elapsed) and ensure that the result is read within 48--72 hours
(39). Certain studies indicate that
positive TST reactions might still be measurable from 4--7 days after testing
(225,226). However, if a patient fails to return
within 72 hours and has a negative test result, the TST should be repeated
(42).
A positive result to the second step of a baseline two-step TST is probably caused by boosting as opposed to
recent infection with M. tuberculosis. These responses might result from remote infections with
M. tuberculosis, infection with an
NTM (also known as MOTT), or previous BCG vaccination. Two-step testing will minimize the possibility that boosting
will lead to an unwarranted suspicion of transmission of
M. tuberculosis with subsequent testing. A second TST is not needed if
the HCW has a documented TST result from any time during the previous 12 months (see Baseline Testing for
M. tuberculosis Infection After TST Within the Previous 12 Months).
A positive TST reaction as a result of BCG wanes after 5 years. Therefore, HCWs with previous BCG vaccination
will frequently have a negative TST result
(74,227--232). Because HCWs with a history of BCG are frequently from
high TBprevalence countries, positive test results for
M. tuberculosis infection in HCWs with previous BCG vaccination should
be interpreted as representing infection with M. tuberculosis
(74,227--233). Although BCG reduces the occurrence of
severe forms of TB disease in children and overall might reduce the risk for progression from LTBI to TB disease
(234,235), BCG is not thought to prevent
M. tuberculosis infection (236). Test
results for M. tuberculosis infection for HCWs with a history of BCG should
be interpreted by using the same diagnostic cut points used for HCWs without a history of BCG vaccination.
BAMT does not require two-step testing and is more specific than skin testing. BAMT that uses
M. tuberculosis-specific antigens (e.g., QFTG) are not expected to result in false-positive results in persons vaccinated with BCG. Baseline
test results should be documented, preferably within 10 days of HCWs starting employment.
Baseline Testing for M. tuberculosis Infection After TST Within the Previous 12 Months
A second TST is not needed if the HCW has a documented TST result from any time during the previous 12 months. If
a newly employed HCW has had a documented negative TST result within the previous 12 months, a single TST can
be administered in the new setting (Box 1). This additional TST represents the second stage of two-step testing. The second
test decreases the possibility that boosting on later testing will lead to incorrect suspicion of transmission of
M. tuberculosis in the setting.
A recent TST (performed in <12 months) is not a contraindication to a subsequent TST unless the test was associated
with severe ulceration or anaphylactic shock, which are substantially rare adverse events
(30,237--239). Multiple TSTs are safe and do not increase the risk for a false-positive result or a TST conversion in persons without infection with mycobacteria
(39).
Baseline Documentation of a History of TB Disease, a Previously Positive Test Result for
M. tuberculosis Infection, or Completion of Treatment for LTBI or TB Disease
Additional tests for M. tuberculosis infection do not need to be performed for HCWs with a documented history of
TB disease, documented previously positive test result for
M. tuberculosis infection, or documented completion of treatment
for LTBI or TB disease. Documentation of a previously positive test result for
M. tuberculosis infection can be substituted for
a baseline test result if the documentation includes a recorded TST result in millimeters (or BAMT result), including
the concentration of cytokine measured (e.g.,
IFN-g). All other HCWs should undergo baseline testing for
M. tuberculosis infection to ensure that the test result on record in the setting has been performed and measured using the
recommended diagnostic the recommended procedures (see Supplement, Diagnostic Procedures for LTBI and TB Disease).
A recent TST (performed in <12 months) is not a contraindication to the administration of an additional test unless
the TST was associated with severe ulceration or anaphylactic shock, which are substantially rare adverse events
(30,237,238). However, the recent test might complicate interpretation of subsequent test results because of the possibility of boosting.
Serial Follow-Up of TB Screening and Testing for
M. tuberculosis Infection
The need for serial follow-up screening for groups of HCWs with negative test results for
M. tuberculosis infection is an institutional decision that is based on the setting's risk classification. This decision and changes over time based on
updated risk assessments should be official and documented. If a serial follow-up screening program is required, the risk assessment
for the setting (see TB Risk Assessment Worksheet [Appendix B]) will determine which HCWs should be included in
the program and the frequency of screening. Two-step TST testing should not be performed for follow-up testing.
If possible, stagger follow-up screening (rather than testing all HCWs at the same time each year) so that all HCWs who
work in the same area or profession are not tested in the same month. Staggered screening of HCWs (e.g., on the anniversary of
their employment or on their birthdays) increases opportunities for early recognition of infectioncontrol problems that can lead
to conversions in test results for M. tuberculosis
infection. Processing aggregate analysis of TB screening data on a periodic
regular basis is important for detecting problems.
HCWs with a Newly Recognized Positive Test Result for
M. tuberculosis Infection or Symptoms or Signs of TB Disease
Clinical Evaluation
Any HCW with a newly recognized positive test result for
M. tuberculosis infection, test conversion, or symptoms or signs
of TB disease should be promptly evaluated. The evaluation should be arranged with employee health, the local or state
health department, or a personal physician. Any physicians who evaluate HCWs with suspected TB disease should be
familiar with current diagnostic and therapeutic guidelines for LTBI and TB disease
(31,39).
The definitions for positive test results for
M. tuberculosis infection and test conversion in HCWs are included in this
report (see Supplement, Diagnostic Procedures for LTBI and TB Disease). Symptoms of disease in the lung, pleura, or airways,
and the larynx include coughing for >3 weeks, loss of appetite, unexplained weight loss, night sweats, bloody sputum
or hemoptysis, hoarseness, fever, fatigue, or chest pain. The evaluation should include a clinical examination and symptom
screen (a procedure used during a clinical evaluation in which patients are asked if they have experienced any symptoms or signs
of TB disease), chest radiograph, and collection of sputum specimens.
If TB disease is diagnosed, begin antituberculosis treatment immediately, according to published guidelines
(31). The diagnosing clinician (who might not be a physician with the institution's infectioncontrol program) should notify the
local or state health department in accordance with disease reporting laws, which generally specify a 24-hour time limit.
If TB disease is excluded, offer the HCW treatment for LTBI in accordance with published guidelines (see
Supplements, Diagnostic Procedures for LTBI and TB Disease; and Treatment Procedures for LTBI and TB Disease
[39,240]). If the HCW has already completed treatment for LTBI and is part of a TB screening program, instead of participating in serial skin testing,
the HCW should be monitored for symptoms of TB disease and should receive any available training, which should
include information on the symptoms of TB disease and
instructing the HCW to report any such symptoms immediately to
occupational health. In addition, annual symptom screens should be performed, which can be administered as part of other HCW
screening and education efforts. Treatment for LTBI should be offered to HCWs who are eligible
(39).
HCWs with a previously negative test result who have an increase of
>10 mm induration when examined on
follow-up testing probably have acquired M. tuberculosis
infection and should be evaluated for TB disease. When disease is
excluded, HCWs should be treated for LTBI unless medically contraindicated
(39,240).
Chest Radiography
HCWs with a baseline positive or newly positive TST or BAMT result should receive one chest radiograph to exclude
a diagnosis of TB disease (or an interpretable copy within a reasonable time frame, such as 6 months). After this baseline
chest radiograph is performed and the result is documented, repeat radiographs are not needed unless symptoms or signs of
TB disease develop or a clinician recommends a repeat chest radiograph
(39,116). Instead of participating in serial testing for
M. tuberculosis infection, HCWs with a positive test result for
M. tuberculosis infection should receive a symptom screen.
The frequency of this symptom screen should be determined by the risk classification for the setting.
Serial follow-up chest radiographs are not recommended for HCWs with documentation of a previously positive test
result for M. tuberculosis infection, treatment for LTBI or TB disease, or for asymptomatic HCWs with negative test results for
M. tuberculosis infection. HCWs who have a previously positive test result for
M. tuberculosis infection and who change
jobs should carry documentation of a baseline chest radiograph result (and the positive test result for
M. tuberculosis infection) to their new employers.
Workplace Restrictions
HCWs with a baseline positive or newly positive test result for
M. tuberculosis infection should receive one chest
radiograph result to exclude TB disease (or an interpretable copy within a reasonable time frame, such as 6 months).
HCWs with confirmed infectious pulmonary, laryngeal, endobroncheal, or tracheal TB disease, or a draining TB skin
lesion pose a risk to patients, HCWs, and others. Such HCWs should be excluded from the workplace and should be allowed
to return to work when the following criteria have been met: 1) three consecutive sputum samples
(109--112) collected in 8--24-hour intervals that are negative, with at least one sample from an early morning specimen (because respiratory secretions
pool overnight); 2) the person has responded to antituberculosis treatment that will probably be effective (can be based
on susceptibility results); and 3) the person is determined to be noninfectious by a physician knowledgeable and experienced
in
managing TB disease (see Supplements, Estimating the Infectiousness of a TB Patient; Diagnostic Procedures for LTBI
and TB Disease; and Treatment Procedures for LTBI and TB Disease).
HCWs with extrapulmonary TB disease usually do not need to be excluded from the workplace as long as no
involvement of the respiratory track has occurred. They can be confirmed as noninfectious and can continue to work if
documented evidence is available that indicates that concurrent pulmonary TB disease has been excluded.
HCWs receiving treatment for LTBI can return to work immediately. HCWs with LTBI who cannot take or do not
accept or complete a full course of treatment for LTBI should not be excluded from the workplace. They should be
counseled regarding the risk for developing TB disease and
instructed to report any TB symptoms immediately to the
occupational health unit.
HCWs who have a documented positive TST or BAMT result and who leave employment should be counseled again,
if possible, regarding the risk for developing TB disease and instructed to seek prompt evaluation with the local
health department or their primary care physician if symptoms of TB disease develop. Consider mailing letters to former HCWs
who have LTBI. This information should be recorded in the HCWs' employee health record when they leave employment.
Asymptomatic HCWs with a baseline positive or newly positive TST or BAMT result do not need to be excluded from
the workplace. Treatment for LTBI should be considered in accordance with CDC guidelines
(39).
Identification of Source Cases and Recording of Drug-Susceptibility Patterns
If an HCW experiences a conversion in a test result for
M. tuberculosis infection, evaluate the HCW for a history
of suspected or known exposure to M. tuberculosis
to determine the potential source. When the source case is identified,
also identify the drug susceptibility pattern of the
M. tuberculosis isolate from the source. The drug-susceptibility pattern should
be recorded in the HCW's medical or employee health record to guide the treatment of LTBI or TB disease, if indicated.
HCWs with Medical Conditions Associated with Increased Risk for Progression to TB Disease
In settings in which HCWs are severely immunocompromised, additional precautions must be taken. HIV infection is
the highest risk factor for progression from LTBI to TB disease
(22,39,42,49). Other immunocompromising
conditions, including diabetes mellitus, certain cancers, and certain drug treatments, also increase the risk for rapid progression from
LTBI to TB disease. TB disease can also adversely affect the clinical course of HIV infection and acquired
immunodeficiency syndrome (AIDS) and can complicate HIV treatment
(31,39,53).
Serial TB screening beyond that indicated by the risk classification for the setting is not indicated for persons with
the majority of medical conditions that suppress the immune system or otherwise increase the risk for infection with
M. tuberculosis progressing to TB disease
(58). However, consideration should be given to repeating the TST for
HIVinfected persons whose initial TST result was negative and whose immune function has improved in response to highly
active antiretroviral therapy (HAART) (i.e., those whose CD4-T lymphocyte count has increased to >200 cells/mL).
All HCWs should, however, be encouraged during their initial TB training to determine if they have such a medical
condition and should be aware that receiving medical treatment can improve cell-mediated immunity. HCWs should be
informed concerning the availability of counseling, testing, and referral for HIV
(50,51). In addition, HCWs should know whether they
are immunocompromised, and they should be aware of the risks from exposure to
M. tuberculosis (1). In certain cases,
reassignment to areas in which exposure is minimized or nonexistent might be medically advisable or desirable.
Immunocompromised HCWs should have the option of an assignment in an area or activity where the risk for exposure
to M. tuberculosis is low. This choice is a personal decision for the immunocompromised HCW
(241) (http://www.eeoc.gov/laws/ada.html). Healthcare settings should provide education and follow infectioncontrol recommendations
(70).
Information provided by HCWs regarding their immune status and request for voluntary work assignments should
be treated confidentially, according to written procedures on the confidential handling of such information. All HCWs should
be made aware of these procedures at the time of employment and during initial TB training and education.
Problem Evaluation
Contact investigations might be initiated in response to 1) conversions in test results in HCWs for
M. tuberculosis infection, 2) diagnosis of TB disease in an HCW, 3) suspected personto-person transmission of
M. tuberculosis, 4) lapses in TB infectioncontrol practices that expose HCWs and
patients to M. tuberculosis, or 5) possible TB outbreaks identified
using
automated laboratory systems (242). In these situations, the objectives of a contact investigation might be to 1) determine
the likelihood that transmission of M. tuberculosis
has occurred; 2) determine the extent of M. tuberculosis
transmission; 3) identify persons who were exposed, and, if possible, the sources of potential transmission; 4) identify factors that could
have contributed to transmission, including failure of environmental infectioncontrol measures, failure to follow
infectioncontrol procedures, or inadequacy of current measures or procedures; 5) implement recommended interventions; 6) evaluate
the effectiveness of the interventions; and 7) ensure that exposure to
M. tuberculosis has been terminated and that the
conditions leading to exposure have been eliminated.
Earlier recognition of a setting in which M. tuberculosis
transmission has occurred could be facilitated through
innovative approaches to TB contact investigations (e.g., network analysis and genetic typing of isolates). Network analysis makes use
of information (e.g., shared locations within a setting that might not be collected in traditional TB contact investigations)
(45). This type of information might be useful during contact investigations involving hospitals or correctional settings to
identify any shared wards, hospital rooms, or cells. Genotyping of isolates is universally available in the United States and is a
useful adjunct in the investigation of M. tuberculosis
transmission (44,89,243,244). Because the situations prompting
an investigation are likely to vary, investigations should be tailored to the individual circumstances. Recommendations
provide general guidance for conducting contact investigations
(34,115).
General Recommendations for Investigating Conversions in Test Results for
M. tuberculosis Infection in HCWs
A test conversion might need to be reported to the health department, depending on state and local regulations.
Problem evaluation during contact investigations should be accomplished through cooperation between infectioncontrol
personnel, occupational health, and the local or state TBcontrol program. If a test conversion in an HCW is detected as a result of
serial screening and the source is not apparent, conduct a source case investigation to determine the probable source and
the likelihood that transmission occurred in the health-care setting
(115).
Lapses in TB infection control that might have contributed to the transmission of
M. tuberculosis should be corrected. Test conversions and TB disease among HCWs should be recorded and reported, according to OSHA requirements
(http://www.osha.gov/recordkeeping). Consult Recording and Reporting Occupational Injuries and
Illness (OSHA standard 29 Code of Federal Regulations [CFR], 1904) to
determine recording and reporting requirements
(245).
Investigating Conversions in Test Results for
M. tuberculosis Infection in HCWs: Probable
Source Outside the Health-Care Setting
If a test conversion in an HCW is detected and exposure outside the health-care setting has been documented by
the corresponding local or state health department, terminate the investigation within the health-care setting.
Investigating Conversions in Test Results for
M. tuberculosis Infection in HCWs: Known Source
in the Health-Care Setting
An investigation of a test conversion should be performed in collaboration with the local or state health department. If
a conversion in an HCW is detected and the HCW's history does not document exposure outside the health-care setting
but does identify a probable source in the setting, the following steps should be taken: 1) identify and evaluate close contacts
of the suspected source case, including other patients and visitors; 2) determine possible reasons for the exposure; 3)
implement interventions to correct the lapse(s) in infection control; and 4) immediately screen HCWs and patients if they were
close contacts to the source case. For exposed HCWs and patients in a setting that has chosen to screen for infection with
M. tuberculosis by using the TST, the following steps should be taken:
- administer a symptom screen;
- administer a TST to those who had previously negative TST results; baseline two-step TST should not be performed
in contact investigations;
- repeat the TST and symptom screen 8--10 weeks after the end of exposure, if the initial TST result is negative
(33);
- administer a symptom screen, if the baseline TST result is positive;
- promptly evaluate (including a chest radiograph) the
exposed person for TB disease, if the symptom screen or the initial
8--10-week follow-up TST result is positive; and
- conduct additional medical and diagnostic evaluation (which includes a judgment about the extent of exposure) for LTBI,
if TB disease is excluded;
If no additional conversions in the test results for
M. tuberculosis are detected in the follow-up testing, terminate
the investigation. If additional conversions in the tests for
M. tuberculosis are detected in the follow-up testing, transmission
might still be occurring, and additional actions are needed: 1) implement a classification of potential ongoing transmission for
the specific setting or group of HCWs; 2) the initial cluster of test conversions should be reported promptly to the local or
state health department; 3) possible reasons for exposure and transmission; should be reassessed and 4) the degree of adherence
to the interventions implemented should be evaluated.
Repeat testing for M. tuberculosis infection should be
repeated 8--10 weeks after the end of exposure for HCW contacts
who previously had negative test results, and the circle of contacts should be expanded to include other persons who might
have been exposed. If no additional TST conversions are detected on the second round of follow-up testing, terminate
the investigation. If additional TST conversions are
detected on the second round of follow-up testing, maintain a classification
of potential ongoing transmission and consult the local or state health department or other persons with expertise in
TB infection control for assistance.
The classification of potential ongoing transmission should be used as a temporary classification only. This
classification warrants immediate investigation and corrective steps. After determination has been made that ongoing transmission
has ceased, the setting should be reclassified as medium risk. Maintaining the classification of medium risk for at least 1 year
is recommended.
Investigating a Conversion of a Test Result for
M. tuberculosis Infection in an HCW with an Unknown Exposure
If a test conversion in an HCW is detected and the HCW's history does not document exposure outside the
health-care setting and does not identify a probable source of exposure in the setting, additional investigation to identify a probable
source in the health-care setting is warranted.
If no source case is identified, estimate the interval during which the HCW might have been infected. The interval is usually
8--10 weeks before the most recent negative test result through 2 weeks before the first positive test result. Laboratory
and infectioncontrol records should be reviewed to identify all
patients (and any HCWs) who have had suspected or
confirmed infectious TB disease and who might have transmitted
M. tuberculosis to the HCW. If the investigation identifies a
probable source, identify and evaluate contacts of the suspected source. Close contacts should be the highest priority for
screening.
The following steps should be taken in a setting that uses TST or BAMT to screen for
M. tuberculosis: 1) administer a symptom screen and the test routinely used in the setting (i.e., TST or BAMT) to persons who previously had negative
results; 2) if the initial result is negative, the test and symptom screen should be repeated 8--10 weeks after the end of exposure; 3)
if the symptom screen, the first test result, or the 8--10-week follow-up test result is positive, the presumed exposed
person should be promptly evaluated for TB disease, including the use of a chest radiograph; and 4) if TB disease is
excluded, additional medical and diagnostic evaluation for LTBI is needed, which includes a judgment regarding the extent of
exposure (see Investigating Conversions in Test Results for
M. tuberculosis Infection in HCWs: Known Source in the
HealthCare Setting).
Investigations That Do Not Identify a Probable Source
If serial TB screening is performed in the setting, review the results of screening of other HCWs in the same area of the
health-care setting or same occupational group. If serial TB screening is not performed in the setting or if insufficient numbers of
recent results are available, conduct additional TB screening of other HCWs in the same area or occupational group. If the review
and screening yield no additional test conversions, and no evidence to indicate health-care--associated transmission exists, then
the investigation should be terminated.
Whether HCW test conversions resulted from exposure in the setting or elsewhere or whether true infection
with M. tuberculosis has even occurred is uncertain. However, the absence of other data implicating
health-care--associated transmission suggests that the conversion could have resulted from 1) unrecognized exposure to
M. tuberculosis outside the health-care setting; 2) cross reactivity with another antigen (e.g., BCG or nontuberculous mycobacteria); or 3) errors
in applying, reading, or interpreting the test result for
M. tuberculosis infection. If the review and screening identify
additional test conversions, health-care--associated transmission is more
probable.
Evaluation of the patient identification process, TB infectioncontrol policies and practices, and environmental controls
to identify lapses that could have led to exposure and transmission should be conducted. If no problems are identified,
a classification of potential ongoing transmission should be identified, and the local or state health department or other
persons with expertise in TB infection control should be consulted for assistance. If problems are identified, implement
recommended interventions and repeat testing for
M. tuberculosis infection 8--10 weeks after the end of exposure for HCWs with
negative test results. If no additional test conversions are detected in the follow-up testing, terminate the
investigation.
Conversions in Test Results for M. tuberculosis
Infection Detected in Follow-Up Testing
In follow-up testing, a classification of potential ongoing transmission should be maintained. Possible reasons
for exposure and transmission should be reassessed, and the
appropriateness of and degree of adherence to the
interventions implemented should be evaluated. For HCWs with negative test results, repeat testing for
M. tuberculosis infection 8--10 weeks after the end of exposure. The local or state health
department or other persons with expertise in TB infection
control should be consulted.
If no additional conversions are detected during the second round of follow-up testing, terminate the investigation.
If additional conversions are detected, continue a classification of potential ongoing transmission and consult the local or
state health department or other persons with expertise in TB infection control.
The classification of potential ongoing transmission should be used as a temporary classification only. This
classification warrants immediate investigation and corrective steps. After a determination that ongoing transmission has ceased, the
setting should be reclassified as medium risk. Maintaining the classification of medium risk for at least 1 year is recommended.
Investigating a Case of TB Disease in an HCW
Occupational health services and other physicians in the setting should have procedures for immediately notifying
the local administrators or infectioncontrol personnel if an HCW is diagnosed with TB disease so that a problem evaluation can
be initiated. If an HCW is diagnosed with TB disease and does not have a previously documented positive test result
for M. tuberculosis infection, conduct an investigation to identify the probable sources and circumstances for transmission
(see General Recommendations for Investigating Conversions in Test Results for
M. tuberculosis Infection in HCWs). If an HCW
is diagnosed with TB disease, regardless of previous test result status, an additional investigation must be conducted to
ascertain whether the disease was transmitted from this HCW to others, including other HCWs, patients, and visitors.
The potential infectiousness of the HCW, if potentially
infectious, and the probable period of infectiousness (see
Contact Investigations) should be determined. For HCWs with suspected or confirmed infectious TB disease, conduct
an investigation that includes 1) identification of contacts (e.g., other HCWs, patients, and visitors), 2) evaluation of contacts
for LTBI and TB disease, and 3) notification of the local or state health department for consultation and investigation
of community contacts who were exposed outside the health-care setting.
M. tuberculosis genotyping should be performed so that the results are promptly available.
M. tuberculosis results are useful adjuncts to epidemiologically based public health investigations of contacts and possible source cases (especially in
determining the role of laboratory contamination)
(89,166,243,246--261). When confidentiality laws prevent the local or state
health department from communicating information regarding a patient's identity, health department staff should work
with hospital staff and legal counsel, and the HCW to determine how the hospital can be notified without
breaching confidentiality.
Investigating Possible Patient-to-Patient Transmission of
M. tuberculosis
Information concerning TB cases among patients in the setting should be routinely recorded for risk classification and
risk assessment purposes. Documented information by location and date should include results of sputum smear and culture,
chest radiograph, drug-susceptibility testing, and
adequacy of infectioncontrol measures.
Each time a patient with suspected or confirmed TB disease is encountered in a health-care setting, an assessment of
the situation should be made and the focus should be on 1) a determination of infectiousness of the patient, 2) confirmation
of compliance with local public health reporting requirements (including the prompt reporting of a person with suspected
TB disease as required), and 3) assessment of the adequacy
of infection control.
A contact investigation should be initiated in situations where infection control is inadequate and the patient is
infectious. Patients with positive AFB sputum smear results are more infectious than patients with negative AFB sputum smear
results,
but the possibility exists that patients with negative sputum smear results might be infectious
(262). Patients with negative AFB sputum smear results but who undergo aerosol-generating or aerosol-producing procedures (including
bronchoscopy) without adequate infectioncontrol measures create a potential for exposure. All investigations should be conducted
in consultation with the local public health department.
If serial surveillance of these cases reveals one of the following conditions, patient-to-patient transmission might
have occurred, and a contact investigation should be initiated:
- A high proportion of patients with TB disease were
admitted to or examined in the setting during the year preceding
onset of their TB disease, especially when TB disease is identified in patients who were otherwise
unlikely to be exposed to M. tuberculosis.
- An increase occurred in the number of TB patients diagnosed with drug-resistant TB, compared with the previous year.
- Isolates from multiple patients had identical and characteristic drug susceptibility or DNA fingerprint patterns.
Surveillance of TB Cases in Patients Indicates Possible Patient-to-Patient Transmission of
M. tuberculosis
Healthcare settings should collaborate with the local or state health department to conduct an investigation. For settings
in which HCWs are serially tested for M. tuberculosis
infection, review HCW records to determine whether an increase in
the number of conversions in test results for M. tuberculosis
infection has occurred. Patient surveillance data and medical
records should be reviewed for additional cases of TB disease. Settings should look for possible exposures from previous or
current admissions that might have exposed patients with newly diagnosed TB disease to other patients with TB disease,
determining if the patients were admitted to the same room or area, or if they received the same procedure or went to the same
treatment area on the same day.
If the investigation suggests that transmission has occurred, possible causes of transmission of
M. tuberculosis (e.g., delayed diagnosis of TB disease, institutional barriers to implementing timely and correct airborne precautions,
and inadequate environmental controls) should be evaluated. Possible exposure to other patients or HCWs should be
determined, and if exposure has occurred, these persons should be evaluated for LTBI and TB disease (i.e., test for
M. tuberculosis infection and administer a symptom screen).
If the local or state health department was not previously contacted, settings should notify the health department so that
a community contact investigation can be initiated, if necessary. The possibility of laboratory errors in diagnosis or
the contamination of bronchoscopes (82,169) or other equipment should be considered
(136).
Contact Investigations
The primary goal of contact investigations are to identify secondary cases of TB disease and LTBI among contacts so
that therapy can be initiated as needed
(263--265). Contact investigations should be collaboratively conducted by
both infectioncontrol personnel and local TBcontrol program personnel.
Initiating a Contact Investigation
A contact investigation should be initiated when 1) a person with TB disease has been examined at a health-care setting,
and TB disease was not diagnosed and reported quickly, resulting in failure to apply recommended TB infection controls;
2) environmental controls or other infectioncontrol measures have malfunctioned while a person with TB disease was in
the setting; or 3) an HCW develops TB disease and exposes other persons in the setting.
As soon as TB disease is diagnosed or a problem is recognized, standard public health practice should be implemented
to prioritize the identification of other patients, HCWs, and visitors who might have been exposed to the index case before
TB infectioncontrol measures were correctly applied
(52). Visitors of these patients might also be contacts or the source case.
The following activities should be implemented in collaboration with or by the local or state health department
(34,266): 1) interview the index case and all persons who might have been exposed; review the medical records of the index case;
determine the exposure sites (i.e., where the index case lived, worked, visited, or was hospitalized before being placed under
airborne precautions); and determine the infectious period of the index case, which is the period during which a person with TB
disease is considered contagious and most capable of transmitting
M. tuberculosis to others.
For programmatic purposes, for patients with positive AFB sputum smear results, the infectious period can be considered
to begin 3 months before the collection date of the first positive AFB sputum smear result or the symptom onset date
(whichever
is earlier). The end of the infectious period is the date the patient is placed under airborne precautions or the date of
collection of the first of consistently negative AFB sputum smear results (whichever is earlier). For patients with negative AFB
sputum smear results, the infectious period can begin 1 month before the symptom onset date and end when the patient is
placed under airborne precautions.
The exposure period, the time during which a person shared the same air space with a person with TB disease for
each contact, should be determined as well as whether transmission occurred from the index patient to persons with whom
the index patient had intense contact. In addition, the following should be determined: 1) intensity of the exposure based
on proximity; 2) overlap with the infectious period of the
index case; 3) duration of exposure, 4) presence or absence
of infectioncontrol measures, 5) infectiousness of the index case; 6) performance of procedures that could increase the risk
for transmission during contact (e.g., sputum induction, bronchoscopy, and airway suction); and 7) the exposed cohort
of contacts for TB screening.
The most intensely exposed HCWs and patients should be screened as soon as possible after exposure to
M. tuberculosis has occurred and 8--10 weeks after the end of exposure if the initial TST result is negative. Close contacts should be the
highest priority for screening.
For HCWs and patients who are presumed to have been exposed in a setting that screens for infection with
M. tuberculosis using the TST, the following activities should be implemented:
- performing a symptom screen;
- administering a TST to those who previously had negative TST results;
- repeating the TST and symptom screen 8--10 weeks after the end of exposure, if the initial TST result is negative;
- promptly evaluating the HCW for TB disease, including performing a chest radiograph, if the symptom screen or the
initial or 8--10-week follow-up TST result is positive; and
- providing additional medical and diagnostic evaluation for LTBI, including determining the extent of exposure, if
TB disease is excluded.
For HCWs and patients who are presumed to have been exposed in a setting that screens for infection with
M. tuberculosis using the BAMT, the following activities should be implemented (see Supplement, Surveillance and Detection of
M. tuberculosis Infections in HealthCare Settings). If the most intensely exposed persons have test conversions or positive
test results for M. tuberculosis infection in the absence of a previous history of a positive test result or TB disease, expand
the investigation to evaluate persons with whom the index patient had less contact. If the evaluation of the most intensely
exposed contacts yields no evidence of transmission, expanding testing to others is not necessary.
Exposed persons with documented previously positive test results for
M. tuberculosis infection do not require
either repeat testing for M. tuberculosis infection or a chest radiograph (unless they are immunocompromised or otherwise at
high risk for TB disease), but they should receive a symptom screen. If the person has symptoms of TB disease, 1) record
the symptoms in the HCW's medical chart or employee health record, 2) perform a chest radiograph, 3) perform a full
medical evaluation, and 4) obtain sputum samples for smear and culture, if indicated.
The setting should determine the reason(s) that a TB diagnosis or initiation of airborne precautions was delayed
or procedures failed, which led to transmission of
M. tuberculosis in the setting. Reasons and corrective actions taken should
be recorded, including changes in policies, procedures, and TB training and education practices.
Collaboration with the Local or State Health Department
For assistance with the planning and implementation of TBcontrol activities in the health-care setting and for names
of experts to help with policies, procedures, and program evaluation, settings should coordinate with the local or state
TBcontrol program . By law, the local or state health department must be notified when TB disease is suspected or confirmed in a
patient or HCW so that follow up can be arranged and a community contact investigation can be conducted. The local or state
health department should be notified as early as possible before the patient is discharged to facilitate followup and continuation
of therapy by DOT (31). For inpatient settings, coordinate a discharge plan with the patient (including a patient who is
an HCW with TB disease) and the TBcontrol program of the local or state health department.
Environmental Controls
Environmental controls are the second line of defense in the TB infectioncontrol program, after administrative
controls. Environmental controls include technologies for the removal or inactivation of airborne
M. tuberculosis. These technologies include local exhaust ventilation, general ventilation, HEPA filtration, and UVGI. These controls help to prevent the
spread and reduce the concentration of infectious droplet nuclei in the air. A summary of environmental controls and their use
in prevention of transmission of M. tuberculosis
is provided in this report (see Supplement, Environmental Controls),
including detailed information concerning the application of environmental controls.
Local Exhaust Ventilation
Local exhaust ventilation is a source-control technique used for capturing airborne contaminants (e.g., infectious
droplet nuclei or other infectious particles) before they are dispersed into the general environment. In local exhaust
ventilation methods, external hoods, enclosing booths, and tents are used. Local exhaust ventilation (e.g., enclosed, ventilated
booth) should be used for cough-inducing and aerosol-generating procedures. When local exhaust is not feasible, perform
cough-inducing and aerosol-generating procedures in a room that meets the requirements for an AII room.
General Ventilation
General ventilation systems dilute and remove contaminated air and control airflow patterns in a room or setting. An
engineer or other professional with expertise in ventilation should be included as part of the staff of the health-care setting or hire
a consultant with expertise in ventilation engineering specific to health-care settings. Ventilation systems should be designed
to meet all applicable federal, state, and local requirements.
A single-pass ventilation system is the preferred choice in areas in which infectious airborne droplet nuclei might be
present (e.g., AII rooms). Use HEPA filtration if recirculation of air is necessary.
AII rooms in existing health-care settings should have an airflow of
>6 ACH. When feasible, the airflow should
be increased to 12 ACH by 1) adjusting or modifying the ventilation system or 2) using air-cleaning methods (e.g.,
room-air recirculation units containing HEPA filters or UVGI systems that increase the equivalent ACH). New construction
or renovation of health-care settings should be designed so that AII rooms achieve an airflow of
>12 ACH. Ventilation rates for other areas in health-care settings should meet certain specifications (see Risk Classification Examples). If a variable air
volume (VAV) ventilation system is used in an AII room,
design the system to maintain the room under negative pressure at all
times. The VAV system minimum set point must be adequate to maintain the recommended mechanical and outdoor ACH and
a negative pressure >0.01 inch of water gauge compared with adjacent areas.
Based on the risk assessment for the setting, the required number of AII rooms, other negative-pressure rooms,
and local exhaust devices should be determined. The location of these rooms and devices will depend partially on
where recommended ventilation conditions can be achieved. Grouping AII rooms in one area might facilitate the care of
patients with TB disease and the installation and maintenance of optimal environmental controls.
AII rooms should be checked for negative pressure by using smoke tubes or other visual checks before occupancy, and
these rooms should be checked daily when occupied by a patient with suspected or confirmed TB disease. Design, construct,
and maintain general ventilation systems so that air flows from clean to less clean (more contaminated) areas. In addition,
design general ventilation systems to provide optimal airflow patterns within rooms and to prevent air stagnation or
short-circuiting of air from the supply area to the exhaust area.
Healthcare settings serving populations with a high prevalence of TB disease might need to improve the existing
general ventilation system or use air-cleaning technologies in general-use areas (e.g., waiting rooms, EMS areas, and radiology
suites). Applicable approaches include 1) single-pass, nonrecirculating systems that exhaust air to the outside, 2) recirculation systems
that pass air through HEPA filters before recirculating it to the general ventilation system, and 3) room-air recirculation units
with HEPA filters and UVGI systems.
Air-Cleaning Methods
High-Efficiency Particulate Air (HEPA) Filters
HEPA filters can be used to filter infectious droplet nuclei from the air and must be used 1) when discharging air from
local exhaust ventilation booths or enclosures directly into the surrounding room or area and 2) when discharging air from an
AII
room (or other negative-pressure room) into the general ventilation system (e.g., in settings in which the ventilation system
or building configuration makes venting the exhaust to the outside impossible).
HEPA filters can be used to remove infectious droplet
nuclei from air that is recirculated in a setting or exhausted directly
to the outside. HEPA filters can also be used as a safety measure in exhaust ducts to remove droplet nuclei from air
being discharged to the outside. Air can be recirculated through HEPA filters in areas in which 1) no general ventilation system
is present, 2) an existing system is incapable of providing sufficient ACH, or 3) air-cleaning (particulate
removal) without affecting the fresh-air supply or negative-pressure system is desired. Such uses can increase the number of equivalent ACH
in the room or area.
Recirculation of HEPA filtered air can be achieved by
exhausting air from the room into a duct, passing it through a
HEPA filter installed in the duct, and returning it to the room or the general ventilation system. In addition, recirculation can
be achieved by filtering air through HEPA recirculation systems installed on the wall or ceiling of the room or filtering
air through portable room-air recirculation units.
To ensure adequate functioning, install HEPA filters carefully and maintain the filters according to the instructions of
the manufacturer. Maintain written records of all prefilter and HEPA maintenance and monitoring
(114). Manufacturers of room-air recirculation units should provide installation
instructions and documentation of the filtration efficiency and of
the overall efficiency of the unit in removing airborne particles from a space of a given size.
UVGI
UVGI is an air-cleaning technology that can be used in a room or corridor to irradiate the air in the upper portion of the
room (upper-air irradiation) and is installed in a duct to irradiate air passing through the duct (duct irradiation) or incorporated
into room air-recirculation units. UVGI can be used in ducts that recirculate air back into the same room or in ducts that exhaust
air directly to the outside. However, UVGI should not be used in place of HEPA filters when discharging air from isolation
booths or enclosures directly into the surrounding room or area or when discharging air from an AII room into the general
ventilation system. Effective use of UVGI ensures that
M. tuberculosis, as contained in an infectious
droplet, is exposed to a sufficient dose of ultraviolet-C
(UV-C) radiation at 253.7 nanometers (nm) to result in inactivation. Because dose is a function of irradiance
and time, the effectiveness of any application is determined by its ability to deliver sufficient irradiance for enough time to result
in inactivation of the organism within the infectious droplet. Achieving a sufficient dose can be difficult with airborne
inactivation because the exposure time can be substantially limited; therefore,
attaining sufficient irradiance is essential.
For each system, follow design guidelines to maximize UVGI effectiveness in equivalent ACH. Because air velocity,
air mixing, relative humidity, UVGI intensity, and lamp position all affect the efficacy of UVGI systems, consult a UVGI
system designer before purchasing and installing a UVGI system. Experts who might be consulted include industrial
hygienists, engineers, and health physicists.
To function properly and minimize potential hazards to HCWs and other room occupants, upper-air UVGI systems
should be properly installed, maintained, and labeled. A person knowledgeable in the use of ultraviolet (UV) radiometers
or actinometers should monitor UV irradiance levels to
ensure that exposures in the work area are within safe exposure levels.
UV irradiance levels in the upper-air, where the air disinfection is occurring, should also be monitored to determine that
irradiance levels are within the desired effectiveness range.
UVGI tubes should be changed and cleaned according to the instructions of the manufacturer or when
irradiance measurements indicate that output is reduced below effective levels. In settings that use UVGI systems, education of
HCWs should include 1) basic principles of UVGI systems (mechanism and limitations), 2) potential hazardous effects of UVGI
if overexposure occurs, 3) potential for photosensitivity associated with certain medical conditions or use of certain
medications, and 4) the importance of maintenance procedures and record-keeping. In settings that use UVGI systems,
patients and visitors should be informed of the purpose of UVGI systems and be warned about the potential hazards and safety precautions.
Program Issues
Personnel from engineering, maintenance, safety and infection control, and environmental health should collaborate
to ensure the optimal selection, installation, operation, and maintenance of environmental controls. A written maintenance
plan should be developed that outlines the responsibility and
authority for maintenance of the environmental controls
and addresses HCW training needs. Standard operating procedures should include the notification of infectioncontrol
personnel before performing maintenance on ventilation systems servicing TB patient-care areas.
Personnel should schedule routine preventive maintenance for all components of the ventilation systems (e.g., fans,
filters, ducts, supply diffusers, and exhaust grills) and air-cleaning
devices. Quality control (QC) checks should be conducted to
verify that environmental controls are operating as designed and that records are current. Provisions for emergency electrical
power should be made so that the performance of essential
environmental controls is not interrupted during a power failure.
Respiratory Protection
The first two levels of the infectioncontrol hierarchy,
administrative and environmental controls, minimize the number
of areas in which exposure to M. tuberculosis
might occur. In addition, these administrative and environmental controls
also reduce, but do not eliminate, the risk in the few areas in which exposures can still occur (e.g., AII rooms and rooms
where cough-inducing or aerosol-generating procedures are performed). Because persons entering these areas might be exposed
to airborne M. tuberculosis, the third level of the hierarchy is the use of respiratory protective equipment in situations that pose
a high risk for exposure (see Supplement, Respiratory Protection).
On October 17, 1997, OSHA published a proposed standard for occupational exposure to
M. tuberculosis (267). On December 31, 2003, OSHA announced the termination of rulemaking for a TB standard
(268). Previous OSHA policy permitted the use of any Part 84 particulate filter respirator for protection against TB disease
(269). Respirator use for TB had been regulated by OSHA under CFR Title 29, Part 1910.139 (29CFR1910.139)
(270) and compliance policy directive (CPL) 2.106 (Enforcement Procedures and Scheduling for Occupational Exposure to Tuberculosis). Respirator use for TB is
regulated under the general industry standard for respiratory protection (29 CFR 1910.134,
http://www.osha.gov/SLTC/respiratoryprotection/index.html)
(271). General information concerning respiratory protection for aerosols,
including M. tuberculosis, has been published
(272--274).
Indications for Use
Respiratory protection should be used by the following persons:
- all persons, including HCWs and visitors, entering rooms in which patients with suspected or confirmed infectious
TB disease are being isolated;
- persons present during cough-inducing or
aerosol-generating procedures performed on patients with suspected or
confirmed infectious TB disease; and
- persons in other settings in which administrative and
environmental controls probably will not protect them from
inhaling infectious airborne droplet nuclei. These persons might also include persons who transport patients with suspected
or confirmed infectious TB disease in vehicles (e.g., EMS vehicles or, ideally, ambulances) and persons who provide
urgent surgical or dental care to patients with suspected or confirmed infectious TB disease (see Supplement, Estimating
the Infectiousness of a TB Patient).
Laboratorians conducting aerosol-producing procedures might require respiratory protection. A decision concerning use
of respiratory protection in laboratories should be made on an individual basis, depending on the type of ventilation in use
for the laboratory procedure and the likelihood of aerosolization of viable mycobacteria that might result from the
laboratory procedure.
Respiratory-Protection Program
OSHA requires health-care settings in which HCWs use respiratory protection to develop, implement, and maintain
a respiratoryprotection program. All HCWs who use respiratory protection should be included in the program
(see Supplement, Respiratory Protection).
Training HCWs
Annual training regarding multiple topics should be conducted for HCWs, including the nature, extent, and hazards of
TB disease in the health-care setting. The training can be conducted in conjunction with other related training
regarding infectious disease associated with airborne transmission. In addition, training topics should include the 1) risk
assessment process and its relation to the respirator program,
including signs and symbols used to indicate that respirators are required
in certain areas and the reasons for using respirators; 2) environmental controls used to prevent the spread and reduce
the concentration of infectious droplet nuclei; 3) selection of a particular respirator for a given hazard (see
Selection of
Respirators); 4) operation, capabilities, and limitations of respirators; 5) cautions regarding facial hair and respirator
use (275,276); and 6) OSHA regulations regarding respirators, including assessment of employees' knowledge.
Trainees should be provided opportunities to handle and wear a respirator until they become proficient (see Fit
Testing). Trainees should also be provided with 1) copies or summaries of lecture materials for use as references and 2) instructions
to refer all respirator problems immediately to the respiratory program administrator.
Selection of Respirators
Respiratory protective devices used in health-care settings for protection against
M. tuberculosis should meet the following criteria
(277,278):
- certified by CDC/National Institute for Occupational Safety and Health (NIOSH) as a nonpowered particulate
filter respirator (N-, R-, or P-95, 99, or 100), including disposable respirators, or PAPRs with high efficiency filters
(279);
- ability to adequately fit respirator wearers (e.g., a fit factor of >100 for disposable and half-mask respirators) who
are included in a respiratoryprotection program; and
- ability to fit the different facial sizes and characteristics of HCWs. (This criterion can usually be met by making
respirators available in different sizes and models.)
The fit of filtering facepiece respirators varies because of different facial types and respirator characteristics
(10,280--289). Assistance with selection of respirators should be
obtained through consultation with respirator fit-testing
experts, CDC, occupational health and infectioncontrol professional organizations, peer-reviewed research, respirator manufacturers,
and advanced respirator training courses.
Fit Testing
A fit test is used to determine which respirator fits the user adequately and to ensure that the user knows when the
respirator fits properly. After a risk assessment is conducted to validate the need for respiratory protection, perform fit testing during
the initial respiratoryprotection program training and periodically thereafter in accordance with federal, state, and
local regulations (http://www.osha.gov/SLTC/respiratoryprotection/index.html).
Fit testing provides a means to determine which respirator model and size fits the wearer best and to confirm that the
wearer can don the respirator properly to achieve a good fit. Periodic fit testing for respirators used in TB environments can serve
as an effective training tool in conjunction with the content included in employee training and retraining. The frequency
of periodic fit testing should be supplemented by the occurrence of 1) risk for transmission of
M. tuberculosis, 2) facial features of the wearer, 3) medical condition that would affect respiratory function, 4) physical characteristics of respirator (despite
the same model number), or 5) model or size of the assigned respirator
(281).
Respirator Options: General Recommendations
In situations that require respiratory protection, the minimum respiratory protection device is a filtering
facepiece (nonpowered, air-purifying, half-facepiece) respirator (e.g., an N95 disposable respirator). This
CDC/NIOSH-certified respirator meets the minimum filtration performance for respiratory protection in areas in which patients with suspected
or confirmed TB disease might be encountered. For situations in which the risk for exposure to
M. tuberculosis is especially high because of cough-inducing and aerosol-generating procedures, more protective respirators might be needed (see
Respirator Options: Special Circumstances).
Respirator Options: Special Circumstances
Visitors to AII rooms and other areas with patients who have suspected or confirmed infectious TB disease may be
offered respirators and should be instructed by an HCW on the use of the respirator before entering an AII room
(Supplement, Frequently Asked Questions [FAQs] User-Seal Check in Respiratory Protection section). Particulate respirators
vary substantially by model, and fit testing is usually not easily available to visitors.
The risk assessment for the setting might identify a limited number of circumstances (e.g., bronchoscopy or autopsy
on persons with suspected or confirmed TB disease and selected laboratory procedures) for which a level of respiratory
protection that exceeds the minimum level provided by an N95 disposable respirator should be considered. In such
circumstances, consider providing HCWs with a level of respiratory protection that both exceeds the minimum criteria and is
compatible with patient care delivery. Such protection might include more protective respirators (e.g., full-facepiece respirators or
PAPRs)
(see Supplement, Respiratory Protection). Detailed information regarding these and other respirators has been
published (272,273,278,290).
In certain settings, HCWs might be at risk for both inhalation exposure to
M. tuberculosis and mucous membrane exposure
to bloodborne pathogens. In these situations, the HCW might wear a nonfluid-resistant respirator with a
full-face shield or the combination product surgical mask/N95 disposable respirator to achieve both respiratory protection and
fluid protection.
When surgical procedures (or other procedures requiring a sterile field) are performed on persons with suspected
or confirmed infectious TB disease, respiratory protection worn by HCWs must also protect the surgical field. The
patient should be protected from the HCW's respiratory secretions and the HCW from infectious droplet nuclei that might
be expelled by the patient or generated by the procedure. Respirators with exhalation valves and PAPRs do not protect the
sterile field.
Settings in which patients with suspected or confirmed
infectious TB disease will not be encountered do not need
a respiratoryprotection program for exposure to
M. tuberculosis. However, these settings should have written protocols for
the early identification of persons with symptoms or signs of TB disease and procedures for referring these patients to a
setting where they can be evaluated and managed. Filtering facepiece respirators should also be available for emergency use by
HCWs who might be exposed to persons with suspected or confirmed TB disease before transfer. In addition, respirators and
the associated respiratoryprotection program might be needed to protect HCWs from other infectious diseases or exposures
to harmful vapors and gases. Their availability or projected need for other exposures should be considered in the selection
of respirators for protection against TB to minimize replication of effort.
Surgical or procedure masks are designed to prevent respiratory secretions of the wearer from entering the air. To
reduce the expulsion of droplet nuclei into the air, persons with suspected or confirmed TB disease should be instructed to
observe respiratory hygiene and cough etiquette procedures
(122) and should wear a surgical or procedure mask, if possible, when
they are not in AII rooms. These patients do not need to wear particulate respirators.
Patients with suspected or confirmed TB disease should never wear any kind of respiratory protection that has
an exhalation valve. This type of respirator does not prevent droplet nuclei from being expelled into the air.
Cough-Inducing and Aerosol-Generating Procedures
General Recommendations
Procedures that involve instrumentation of the lower respiratory tract or induction of sputum can increase the
likelihood that droplet nuclei will be expelled into the air. These cough-inducing procedures include endotracheal intubation,
suctioning, diagnostic sputum induction, aerosol treatments (e.g., pentamidine therapy and nebulized treatments), bronchoscopy,
and laryngoscopy, gastric aspiration and nasogastric tube placement can also induce cough in certain patients. Other
procedures that can generate aerosols include irrigating TB abscesses, homogenizing or lyophilizing tissue, performing autopsies
on cadavers with untreated TB disease, and other processing of tissue that might contain tubercle bacilli and TB
laboratory procedures.
If possible, postpone cough-inducing or aerosol-generating procedures on patients with suspected or confirmed
infectious TB disease unless the procedure can be performed with recommended precautions. When a cough-inducing or
aerosol-generating procedure must be performed on a patient with suspected or confirmed infectious TB disease, use a
local exhaust ventilation device (e.g., booth or special enclosure). If using this device is not feasible, perform the procedure in
a room that meets the ventilation requirements for an AII room.
After completion of cough-inducing procedures, keep
patients in the AII room or enclosure until coughing subsides.
Patients should be given tissues and instructed to cover the mouth and nose with tissues when coughing. Tissues should be disposed of
in accordance with the infectioncontrol plan.
Before the booth, enclosure, or room is used for another patient, allow enough time for the removal of
>99% of airborne contaminants. This interval will vary based on the efficiency of the ventilation or filtration system (see
Supplement, Environmental Controls; Table 2).
For postoperative recovery, do not place the patient in a recovery room with other patients; place the patient in a room
that meets the ventilation requirements for an AII room. If the room does not meet the ventilation requirements for an AII
room,
air-cleaning technologies (e.g., HEPA filtration and UVGI) can be used to increase the number of equivalent ACH
(see Supplement, Environmental Controls).
Perform all manipulations of suspected or confirmed
M. tuberculosis specimens that might generate aerosols in a BSC.
When in rooms or enclosures in which cough-inducing or aerosol-generating procedures are being performed, respiratory
protection should be worn.
Special Considerations for Bronchoscopy
Bronchoscopy can result in the transmission of
M. tuberculosis either through the airborne route
(63,81,86,162) or a contaminated bronchoscope
(80,82,163--169). Whenever feasible, perform bronchoscopy in a room that meets the
ventilation requirements for an AII room (see Supplement, Environmental Controls). Air-cleaning technologies can be used to
increase equivalent ACH. If a bronchoscopy must be performed in a positive-pressure room (e.g., OR), exclude TB disease
before performing the procedure. Examine three spontaneous or induced sputum specimens for AFB (if possible) to exclude
a diagnosis of TB disease before bronchoscopy is considered as a diagnostic procedure
(110,291).
In a patient who is intubated and mechanically ventilated, minimize the opening of circuitry. For HCWs present
during bronchoscopic procedures on patients with suspected or confirmed TB disease, a respirator with a level of protection of at
least an N95 disposable respirator should be worn. Protection greater than an N95 disposable respirator (e.g., a
full-facepiece elastomeric respirator or PAPR) should be considered.
Special Considerations for Administration of Aerosolized Pentamidine and Other Medications
Patients receiving aerosolized pentamidine (or other aerosolized medications) who are immunocompromised and have
a confirmed or suspected pulmonary infection (i.e., pneumocystis pneumonia [PCP] or pneumonia caused by
P. jaroveci, formerly P. carinii) are also at risk for TB disease. Patients receiving other aerosolized medications might have
an immunocompromising condition that puts them at greater risk for TB disease. Patients should be screened for TB
disease before initiating prophylaxis with aerosolized pentamidine; a medical history, test for infection with
M. tuberculosis, and a chest radiograph should be performed.
Before each subsequent treatment with aerosolized pentamidine, screen patients for symptoms or signs of TB disease.
If symptoms or signs are present, evaluate the patient for TB disease. Patients with suspected or confirmed TB disease should
be administered oral prophylaxis for P.
jaroveci instead of aerosolized pentamidine if clinically practical. Patients receiving
other aerosolized medication might have immunocompromising conditions; therefore, if warranted, they should be
similarly screened and evaluated, and treatment with oral medications should be considered.
Supplements
Estimating the Infectiousness of a TB Patient
General Principles
Transmission of M. tuberculosis is most likely to result from exposure to persons who have 1) unsuspected pulmonary
TB disease and are not receiving antituberculosis treatment, 2) diagnosed TB disease and are receiving inadequate therapy, or
3) diagnosed TB disease and are early in the course of effective therapy. Administration of effective antituberculosis treatment
has been associated with decreased infectiousness among persons who have TB disease
(292). Effective treatment reduces coughing, the amount of sputum produced, the number of organisms in the sputum, and the viability of
the organisms in the sputum. However, the duration of therapy required to decrease or eliminate infectiousness varies
(293). Certain TB patients are never infectious, whereas those with unrecognized or inadequately treated drug-resistant TB
disease might remain infectious for weeks or months
(2,3,87,94,162,294--297). In one study, 17% of transmission occurred
from persons with negative AFB smear results
(262). Rapid laboratory methods, including PCR-based techniques, can
decrease diagnostic delay and reduce the duration of
infectiousness (298).
The infectiousness of patients with TB correlates with the number of organisms they expel into the air
(299). The number of organisms expelled are related to the following factors: 1) presence of cough lasting >3 weeks; 2) cavitation on
chest radiograph; 3) positive AFB sputum smear result; 4) respiratory tract disease with involvement of the lung or
airways,
including larynx; 5) failure to cover the mouth and nose when coughing; 6) lack of incorrect or short duration
of antituberculosis treatment (300); or 7) undergoing cough-inducing or aerosol-generating procedures (e.g., sputum
induction, bronchoscopy, and airway suction). Closed and effectively filtered ventilatory circuitry and minimized opening of
such circuitry in intubated and mechanically ventilated patients might minimize exposure (see Intensive Care Units [ICUs]).
Persons with extrapulmonary TB disease usually are not infectious unless they have concomitant pulmonary
disease, nonpulmonary disease located in the oral cavity or the larynx, or extrapulmonary disease that includes an open abscess
or lesion in which the concentration of organisms is high, especially if drainage from the abscess or lesion is extensive, or
if aerosolization of drainage fluid is performed
(69,72,77, 83,301). Persons with TB pleural effusions might also have
concurrent unsuspected pulmonary or laryngeal TB disease. These patients should be considered infectious until pulmonary TB disease
is excluded. Patients with suspected TB pleural effusions or extrapulmonary TB disease should be considered pulmonary
TB suspects until concomitant pulmonary disease is excluded
(302).
Although children with TB disease usually are less likely than adults to be infectious, transmission from young children
can occur (135,137). Therefore, children and adolescents with TB disease should be evaluated for infectiousness by using
the majority of the same criteria as for adults. These criteria include presence of cough lasting >3 weeks; cavitation on
chest radiograph; or respiratory tract disease with involvement of lungs, airways, or larynx. Infectiousness would be increased if
the patient were on nonstandard or short duration of antituberculosis treatment
(300) or undergoing cough-inducing or
aerosol-generating procedures (e.g., sputum induction, bronchoscopy, and airway suction). Although gastric lavage is useful in
the diagnosis of pediatric TB disease, the grade of the positive AFB smear result does not correlate with infectiousness.
Pediatric patients who might be infectious include those who are not on antituberculosis treatment, who have just been started
on treatment or are on inadequate treatment, and who have extensive pulmonary or laryngeal involvement (i.e., coughing
>3 weeks, cavitary TB disease, positive AFB sputum smear results, or undergoing
cough-inducing or aerosol-generating procedures). Children who have typical primary TB lesions on chest radiograph and do not have any of these indicators
of infectiousness might not need to be placed in an AII room.
No data exist on the transmission of M. tuberculosis
and its association with the collection of gastric aspirate
specimens. Children who do not have predictors for infectiousness do not need to have gastric aspirates obtained in an AII room or
other special enclosure; however, the procedure should not be performed in an area in which persons infected with HIV might
be exposed. Because the source case for pediatric TB patients might be a member of the infected child's family, parents and
other visitors of all hospitalized pediatric TB patients
should be screened for TB disease as soon as possible to ensure that they
do not become sources of health-care--associated transmission of
M. tuberculosis (303--306).
Patients who have suspected or confirmed TB disease and who are not on antituberculosis treatment usually should
be considered infectious if characteristics include
- presence of cough;
- cavitation on chest radiograph;
- positive AFB sputum smear result;
- respiratory tract disease with involvement of the lung or airways, including larynx;
- failure to cover the mouth and nose when coughing; and
- undergoing cough-inducing or aerosol-generating procedures (e.g., sputum induction, bronchoscopy, and airway suction).
If a patient with one or more of these characteristics is on standard multidrug therapy with documented
clinical improvement usually in connection with smear conversion over multiple weeks, the risk for infectiousness is reduced.
Suspected TB Disease
For patients placed under airborne precautions because of suspected infectious TB disease of the lungs, airway, or
larynx, airborne precautions can be discontinued when infectious TB disease is considered unlikely and either 1) another diagnosis
is made that explains the clinical syndrome or 2) the patient has three negative AFB sputum smear results
(109--112). Each of the three consecutive sputum specimens should be collected in 8--24-hour intervals
(124), and at least one specimen should be an early morning specimen because respiratory secretions pool overnight. Generally, this method will allow patients
with negative sputum smear results to be released from airborne precautions in 2 days.
Hospitalized patients for whom the suspicion of TB disease remains after the collection of three negative AFB sputum
smear results should not be released from airborne precautions until they are on standard multidrug antituberculosis treatment
and are clinically improving. If the patient is believed
to not have TB disease because of an alternate diagnosis or because
clinical
information is not consistent with TB disease, airborne precautions may be discontinued. Therefore, a patient suspected
of having TB disease of the lung, airway, or larynx is symptomatic with cough and not responding clinically to
antituberculosis treatment should not be released from an AII room into a non-AII room, and additional sputum specimens should
be collected for AFB examination until three negative AFB sputum smear results are obtained
(30,31). Additional diagnostic approaches might need to be considered (e.g., sputum induction) and, after sufficient time on treatment, bronchoscopy.
Confirmed TB Disease
A patient who has drug-susceptible TB of the lung, airway, or larynx, who is on standard multidrug
antituberculosis treatment, and who has had a substantial clinical and bacteriologic response to therapy (i.e., reduction in cough, resolution
of fever, and progressively decreasing quantity of AFB on smear result) is probably no longer infectious. However, because
culture and drug-susceptibility results are not usually known when the decision to discontinue airborne precautions is made,
all patients with suspected TB disease should remain under airborne precautions while they are hospitalized until they have
had three consecutive negative AFB sputum smear results, each collected in 8--24-hour intervals, with at least one being an
early morning specimen; have received standard multidrug antituberculosis treatment (minimum of 2 weeks); and
have demonstrated clinical improvement.
Discharge to Home of Patients with Suspected or Confirmed TB Disease
If a hospitalized patient who has suspected or confirmed TB disease is deemed medically stable (including patients
with positive AFB sputum smear results indicating pulmonary TB disease), the patient can be discharged from the
hospital before converting the positive AFB sputum smear results to negative AFB sputum smear results, if the following
parameters have been met:
- a specific plan exists for follow-up care with the local TBcontrol program;
- the patient has been started on a standard multidrug antituberculosis treatment regimen, and DOT has been arranged;
- no infants and children aged <4 years or persons with immunocompromising conditions are present in the household;
- all immunocompetent household members have been previously exposed to the patient; and
- the patient is willing to not travel outside of the home except for health-care--associated visits until the patient has
negative sputum smear results.
Patients with suspected or confirmed infectious TB disease should not be released to health-care settings or homes in
which the patient can expose others who are at high risk for progressing to TB disease if infected (e.g., persons infected with HIV
or infants and children aged <4 years). Coordination with the local health department TB program is indicated in
such circumstances.
Drug-Resistant TB Disease
Because the consequences of transmission of MDR TB are severe, certain infectioncontrol practitioners might choose
to keep persons with suspected or confirmed MDR TB disease under airborne precautions during the entire hospitalization
or until culture conversion is documented, regardless of sputum smear results. The role of drug resistance in transmission
is complex. Transmission of drug-resistant organisms to persons with and without HIV infection has been documented
(54,307--309). In certain cases, transmission from patients with TB disease caused by drug-resistant organisms might
be extensive because of prolonged infectiousness as a result of delays in diagnosis and delays in initiation of effective
therapy (53,94,98,101,255,310,311).
HIV-Associated TB Disease
Although multiple TB outbreaks among HIVinfected persons have been reported
(51,52,99), the risk for transmission does not appear to be increased from patients with TB disease and HIV infection, compared with TB patients without
HIV infection (54,312--315). Whether persons infected with HIV are more likely to be infected with
M. tuberculosis if exposed is unclear; however, after infected with
M. tuberculosis, the risk for progression to TB disease in persons infected with HIV
is high (316). Progression to TB disease can be rapid, as soon as 1 month after exposure
(51,53,54,101).
Diagnostic Procedures for LTBI and TB Disease
LTBI is a condition that develops after exposure to a person with infectious TB disease, and subsequent infection
with M. tuberculosis occurs where the bacilli are alive but inactive in the body. Persons who have LTBI but who do not have
TB disease are asymptomatic (i.e., have no symptoms), do not feel sick, and cannot spread TB to other persons.
Use of QFT-G for Diagnosing M. tuberculosis
Infections in Health-Care Workers (HCWs)
In the United States, LTBI has been traditionally diagnosed based on a positive TST result after TB disease has
been excluded. In vitro cytokine-based immunoassays for the
detection of M. tuberculosis infection have been the focus of
intense research and development. This document uses the term "BAMT" to refer to blood assay for
M. tuberculosis infection currently available in the United States.
TB disease should be considered for any patient who has symptoms or signs of disease, including coughing for >3
weeks, loss of appetite, unexplained weight loss, night sweats, bloody sputum or hemoptysis, hoarseness, fever, fatigue, or chest
pain. The index of suspicion for TB disease will vary by individual risk factors, geographic area, and prevalence of TB disease in
the population served by the health-care setting. Persons
exposed to patients with infectious TB disease might acquire
LTBI, depending on host immunity and the degree and duration of exposure. Diagnostic tests for TB disease include
chest radiography and laboratory tests of sputum (examination for AFB and culture). The treatment of persons with TB
disease involves vital aspects of TB control by stopping transmission of
M. tuberculosis and preventing persons with LTBI
from developing infectious TB disease (36).
In the majority of the U.S. population, targeted testing for LTBI and TB disease is performed to identify persons with
LTBI and TB disease who would benefit from treatment. Therefore, all testing activities should be accompanied by a plan
for follow-up care of persons with LTBI or TB disease. A decision to test for infection with
M. tuberculosis should be based on a commitment to treat LTBI after a medical examination
(39). Healthcare agencies or other settings should consult with
the local or state health department before starting a program to test HCWs for
M. tuberculosis infection. This step ensures
that adequate provisions are in place for the evaluation and treatment of persons whose test results are positive, including
the medical supervision of the course of treatment for those who are treated for LTBI or TB disease.
Groups that are not at high risk for LTBI or TB disease should not be tested routinely because testing in populations at
low risk diverts resources from other priority activities. In addition, testing persons at low risk for
M. tuberculosis infection is discouraged because a substantial proportion of persons from populations at low risk who have positive TST results
might actually have false-positive TST results and might not represent true infection with
M. tuberculosis (39,316). Testing
for infection with M. tuberculosis should be performed for well-defined groups at high risk. These groups can be divided into
two categories: 1) persons at higher risk for exposure to and infection with
M. tuberculosis and 2) persons at higher risk
for progression from LTBI to TB disease (see TB
Infection-Control Program for Settings in Which Patients with Suspected
or Confirmed TB Disease Are Expected To Be
Encountered; and TB InfectionControl Program for Settings in Which
Patients with Suspected or Confirmed TB Disease Are Not Expected To Be Encountered).
Flexibility is needed in defining high-priority groups for TB screening. The changing epidemiology of TB indicates that
the risk for TB among groups currently considered as high priority might decrease over time, and groups currently not
identified originally as being at high risk might be considered as high priority.
Use of Tuberculin Skin Test (TST) for Diagnosing
M. tuberculosis Infections in HCWs
The TST is frequently the first step of a TB diagnostic evaluation that might lead to diagnosing LTBI. Although
currently available preparations of PPD used in TST are <100% sensitive and specific for the detection of LTBI, the TST is
currently the most widely used diagnostic test for
M. tuberculosis infection in the United States. The TST is less sensitive in patients
who have TB disease.
The TST, like all medical tests, is subject to variability
(74,228,317), but many of the inherent variations in
administering and reading TST results can be avoided by training and attention to detail
(318). Details of TST administration and
TST result reading procedures are suggested in this
report to improve the technical aspects of TST placement and reading,
thus reducing observer variations and improving test reliability (Appendix F). These checklists were developed for the
National Health and Nutrition Examination Survey (NHANES) to standardize TST placement and reading for research purposes.
The suggested TST training recommendations are not mandatory.
Adherence to TST
Operational policies, procedures, and practices at health-care settings can enhance HCW adherence to serial TST. In
2002, one focus group study identified potential barriers and facilitators to adherence with routine TST
(319). HCWs identified structural factors (e.g., inconvenient TST screening schedules and locations and long waiting times) that negatively
affected adherence. Facilitators to help HCWs adhere to routine TST included active follow-up by supervisors and occupational
health staff and work-site visits for TST screening. Misinformation and stigma concerning TB also emerged in the
discussions, indicating the need for additional training and education for HCWs.
Administering the TST
For each patient, a risk assessment should be conducted that takes into consideration recent exposure to
M. tuberculosis, clinical conditions that increase risk for TB disease if infected, and the program's capacity to deliver treatment for LTBI
to determine if the TST should be administered.
The recommended method for TST is the Mantoux method (Appendix F)
(223,318,320--322). Mantoux TST
training materials supporting the guidance in this report are available at
http://www.cdc.gov/tb
(223,318,320--325). Multipuncture tests (e.g.,
Tine® tests) are not as reliable as the Mantoux method of skin testing and should not be used as a diagnostic test
in the United States (30). Contact the state and local health
department for TST resources.
Reading the TST Result
The TST result should be read by a designated, trained HCW 48--72 hours after the TST is placed
(39,326,327). If the TST was not read between 48--72 hours, ideally, another TST should be placed as soon as possible and read within
48--72 hours (39). Certain studies indicate that positive TST
reactions might still be measurable from 4--7 days after
testing (225,226,328). However, if a patient fails to return within 72 hours and has a negative test result, the TST should be
repeated (42). Patients and HCWs should not be allowed to read their own TST results. HCWs do not typically measure their
own TST results reliably (48).
Reading the TST result consists of first determining the presence or absence of induration (hard, dense, and
raised formation) and, if induration is present, measuring the diameter of induration transverse (perpendicular) to the long axis
of the forearm (Figure 1) (39,318). Erythema or redness of the skin should not be considered when reading a TST
result (Appendix F).
Interpreting TST Results
The positive-predictive value of a TST is the probability that a person with a positive TST result is actually infected with
M. tuberculosis. The positive predictive value is dependent on the prevalence of infection with
M. tuberculosis in the population being tested and the sensitivity and specificity of the test
(228,329,330).
In populations with a low prevalence of M. tuberculosis
infection, the probability that a positive TST result represents
true infection with M. tuberculosis can be substantially low, especially if the cut point is set too low (i.e., the test is not
adequately specific and a low prevalence exists in the population). In populations with a high prevalence of infection with
M. tuberculosis and inadequate test specificity, the probability that a positive TST result using the same cut point represents true
infection with M. tuberculosis is much higher.
Interpreting TST Results in HCWs
TST result interpretation depends on two factors: 1) measured TST induration in millimeters and 2) the person's risk
for being infected with M. tuberculosis and risk for progression to TB disease if infected.
The purpose of the test (Box 2) should be used to determine whether the TST result should be classified as positive or
negative. A TST result with no induration (0 mm) or a measured induration below the defined cut point for each category is considered
to signify absence of infection with M.
tuberculosis.
In the context of TST screening as part of a TB infection-control program, the interpretation of TST results occurs in
two distinct parts. The first is the interpretation by standard criteria, without regard to personal risk factors or
setting-specific factors of the TST results for infection control, surveillance, and referral purposes. The second is the interpretation
by individualized criteria to determine the need for treatment of LTBI.
Determining the need for treatment of LTBI is a subsequent and separate task. For infectioncontrol and
surveillance purposes, TST results should be interpreted and recorded under strict criteria, without considering setting-based or
personal
risk factors (see Supplement, Diagnostic Procedures for LTBI and TB Disease). Any HCW with a positive TST result
from serial TB screening should be referred to a medical provider for an evaluation and to determine the need for treatment of
LTBI based on individual risk (see Supplements, Diagnostic Procedures for LTBI and TB Disease; and Treatment Procedures
for LTBI and TB Disease; Box 2).
Interpreting the TST Result for Infection Control and Surveillance
On baseline TST testing, a TST result of
>10 mm is considered positive for the majority of HCWs, and a TST result of
>5 mm is considered positive for HCWs who are infected with HIV or who have other immunocompromising conditions
(see Supplement, Diagnostic Procedures for LTBI and TB Disease; Box 2). All HCWs with positive baseline TST results should
be referred for medical and diagnostic evaluation; additional skin testing does not need to be performed.
On serial screening for the purposes of infectioncontrol surveillance, TST results indicating an increase of
>10 mm within 2 years should be interpreted and recorded as a TST conversion. For the purposes of assessing and monitoring
infection control, TST conversion rates should be regularly determined. Healthcare settings with a substantial number of HCWs to be
tested might have systems in place that can accurately determine the TST conversion rate every month (e.g., from among a group
of HCWs tested annually), whereas smaller settings might have imprecise estimates of their TST conversion rate even
with annual assessments.
The precision of the setting's TST conversion rate and any analysis assessing change from baseline TST results
will depend on the number and frequency of HCWs tested. These factors should be considered when establishing a
regular interval for TB screening for HCWs.
After a known exposure in a health-care setting, close HCW contacts who have TST results of
>5 mm should be considered to have positive TST results, which should be interpreted as new infections only in HCWs whose previous TST result is
0 mm. However, HCWs 1) with a baseline or follow-up TST result of >0 mm but <10 mm with a
health-care--associated exposure to M. tuberculosis
and 2) who then have an increase of
>10 mm should be considered to have a TST
conversion because of a new infection (see Supplement, Diagnostic Procedures for LTBI and TB Disease;
Box 2).
In a contact investigation, a follow-up TST should be
administered 8--10 weeks after the end of exposure (rather than
1--3 weeks later, as in two-step testing). In this instance, a change from a negative TST result to a positive TST result should not
be interpreted as a boosted reaction. The change in the TST result indicates a TST conversion, recent exposure, transmission,
and infection.
All HCWs who are immunocompromised should be referred for a medical and diagnostic evaluation for any TST result
of >5 mm on baseline or follow-up screening. Because infectioncontrol staff will usually not know the immune status of
the HCWs being tested, HCWs who have TST results of 5--9 mm should be advised that such results can be an indication
for referral for medical evaluation for HCWs who have HIV infection or other causes of severe immunosuppression.
After an HCW has met criteria for a positive TST result, including HCWs who will not receive treatment for LTBI,
repeat TSTs are not necessary because the results would not provide any additional information
(30). This approach applies to HCWs who have positive TST results but who will not receive treatment for LTBI after medical evaluation. For future
TB screening in settings that are medium risk, instead of participating in serial skin testing, the HCW should
receive a medical evaluation and a symptom screen annually.
Interpreting the TST Result for Medical and Diagnostic Referral and Evaluation
HCWs who have positive TST results and who meet the criteria for referral should have a medical and
diagnostic evaluation. For HCWs who are at low risk (e.g., those from low-incidence settings), a baseline result of
>15 mm of induration (instead of
>10 mm) might possibly be the cut point. The criteria used to determine the need for treatment of LTBI has
been presented (Box 2).
When making decisions for the diagnosis and treatment of LTBI, setting-based risk factors (e.g., the prevalence of
TB disease and personal risk factors such as having an immunocompromising condition or known contact with a TB case)
should be assessed when choosing the cut point for a positive TST result. The medical evaluation can occur in different
settings, including an occupational health clinic, local or state health department, or private medical clinic (Box 2)
When 15 mm is used as the cut point, TST results of 10--14 mm can be considered clinically negative
(331). These HCWs should not have repeat TST, and the referring physician might not recommend treatment for LTBI. This issue of
false-positive TST results might be especially true in areas of the country where the prevalence of infection with NTM is high.
HCWs who have TST results of 5--9 mm on baseline two-step testing should be advised that such results might be
an indication for treatment of LTBI if the HCW is a contact of a person with infectious TB disease, has HIV infection, or
has other causes of severe immunosuppression (e.g., organ transplant and receipt of the equivalent of
>15 mg/day of prednisone for >1 month). The risk for TB disease in persons treated with corticosteroids increases with higher dose and longer
duration of corticosteroid use. TNFa antagonists also substantially increase the risk for progression to TB disease in persons with
LTBI (332).
HCWs with negative baseline two-step TST results who are referred for medical evaluation for an increase of
>10 mm induration on follow-up TST screening, including those who are otherwise at low risk for TB disease, probably
acquired M. tuberculosis infection since receiving the previous TST and should be evaluated for TB disease. If disease is excluded,
the HCW should be offered treatment for LTBI if they have no contraindication to treatment (Box 2).
QC Program for Techniques for TST Administration and Reading TST Results
Random variation (i.e., differences in procedural techniques) in TST administration and reading TST results can cause
false-positive or false-negative TST results. Many of the variations in administering and reading TST results can be avoided
by conducting training and maintaining attention to details. HCWs who are responsible for TST procedures should be trained
to reduce variation by following standardized operational procedures and should be observed by an expert TST trainer. All
TST procedures (i.e., administering, reading, and recording the results) should be supervised and controlled to detect and
correct variation. Corrective actions might include coaching and demonstration by the TST trainer. Annual
re-training is recommended for HCWs responsible for
administering and reading TST results.
One strategy to identify TST procedure variation is to use a QC tool (see Supplement, Diagnostic Procedures for LTBI
and TB Disease; Appendix F). The expert TST trainer should observe the procedures and indicate procedural variation on
the observation checklists. An expert trainer includes persons who have documented training experience.
QC for Administering TST by the Mantoux Method
Ideally, the TST trainer should participate in QC TST
administrations with other TST trainers to maintain TST
trainer certification. State regulations specify who is qualified to administer the test by injection. The TST trainer should first
ensure antigen stability by maintaining the manufacturer's recommended cold chain (i.e., controlling antigen exposure to heat
and light from the time it is out of refrigeration until the time it is placed back into refrigeration or until the vial is empty
or expired). The TST trainer should prevent infection during an injection by preparing the skin and preventing contamination
of solution, needle, and syringe.
The TST trainer should prevent antigen administration
errors by controlling the five rights of administration: 1)
right antigen; 2) right dose; 3) right patient; 4) right route; and
5) right time for TST administration, reading, and
clinical evaluation (333). Finally, the TST trainer should observe and coach the HCW trainee in administering multiple
intradermal injections by the Mantoux method. The TST trainer should record procedural variation on the observation checklist
(see Supplement, Diagnostic Procedures for LTBI and TB Disease;
Appendix F). TST training and coaching should continue
until more than 10 correct skin test placements (i.e.,
>6 mm wheal) are achieved.
For training purposes, normal saline for injection can be used instead of PPD for intradermal injections. Volunteers
are usually other HCWs who agree to be tested. Attempt to recruit volunteers who have known positive TST results so
the trainees can practice reading positive TST results. A previous TST is not a contraindication to a subsequent TST unless
the test was associated with severe ulceration or anaphylactic shock, which are substantially rare adverse events
(30,237,238).
Model TST Training Program
A model TST training program for placing TST and reading TST results has been produced by NHANES
(326). The number of hours, sessions, and blinded independent duplicate reading (BIDR) readings should be determined by the
setting's TB risk assessment. The following information can be useful for a model TST training program.
Initial training for a TST placer ideally consists of three components.
- Introductory lecture and demonstration by an expert TST placer or trainer. An expert TST trainer is a qualified HCW
who has received training on administering multiple TST and reading multiple TST results (consider 3 hours of lecture).
- Supervised practical work using procedural checklists observed and coached by the expert TST trainer (see
Supplement, Diagnostic Procedures for LTBI and TB Disease; Appendix F) (consider 9 hours of practical work).
- Administration of more than 10 total skin tests on volunteers by using injectable saline and producing more than 10
wheals that measure 6--10 mm.
TST training should include supervised TST administration, which is a procedure in which an expert TST trainer
supervises a TST trainee during all steps on the procedural observation checklist for TST administration (see Supplement,
Diagnostic Procedures for LTBI and TB Disease; Appendix F). Wheal size should be checked for all supervised TST
administrations, and skin tests should be repeated if wheal size is inadequate (i.e., <6 mm). TST training and coaching should continue until
more than10 correct skin test placements (i.e., >6 mm wheal) are achieved.
QC for Reading TST Results by the Palpation Method
The TST trainer should participate in QC readings with other TST trainers to maintain TST trainer certification.
When training HCWs to read TST results, providing measurable TST responses is helpful (i.e., attempt to recruit volunteers
who have known positive TST results so that the trainees can practice reading positive TST results).
TST readers should correctly read both measurable (>0 mm) and nonmeasurable responses (0 mm) (e.g., consider
reading more than 20 TST results [at least 10 measurable and at least 10 nonmeasurable], if possible). The TST trainer
should observe and coach the HCW in reading multiple TST results by the Palpation method and should record procedure
variation on the observation checklist (see Supplement, Diagnostic Procedures for LTBI and TB Disease;
Appendix F).
The TST trainer should conduct BIDRs for comparison with the HCW's reading. BIDRs are performed when two or
more consecutive TST readers immediately measure the same TST result by standard procedures, without consulting or
observing one another's readings, and record results independently (may use recommended procedural observation checklist;
Appendix F). BIDRs help ensure that TST readers continue to read TST results correctly.
Initial training for a TST reader ideally should consist of multiple components.
- Receiving an introductory lecture and demonstration by an expert TST reader. Training materials are available from
CDC (223,318) and CDC-sponsored Regional Model and Training Centers and should also be available at the local or
state health department (consider 6 hours for lecture and demonstration).
- Receiving four sessions of supervised practical work
using procedural checklists (observed and coached by an expert
TST reader) (consider16 hours of practical work).
- Performing BIDR readings (consider more than 80, if possible). TST trainers should attempt to organize the sessions so
that at least 50% of the TST results read have a result of >0 mm according to the expert TST reader.
- Performing BIDR readings on the last day of TST training (consider more than 30 BIDR readings out of the total
80 readings, if possible). TST trainers should attempt to ensure that at least 25% of persons tested have a TST result of
>0 mm, according to the expert TST reader.
- Missing no more than two items on the procedural
observation checklist (Appendix F) for three random
observations by an expert TST reader.
- Performing all procedures on the checklist correctly during the final observation.
TST training and coaching should continue until the HCW is able to perform all procedures correctly and until
a satisfactory measurement is achieved (i.e., the trainer and the trainee read the TST results within 2 mm of each other).
For example, if the trainer reads the TST result as 11 mm (this might be considered the gold standard reading), the
trainee's reading should be between 9--13 mm to be considered correct. Only a single measurement, in millimeters, should be
recorded (not 11 mm x 11 mm or 11 mm x 15 mm). QC Procedural Observation Checklists (Appendix F) are recommended by
CDC as a tool for use during TST training.
Special Considerations in TST
Anergy. The absence of a reaction to a TST does not
exclude a diagnosis of TB disease or infection with
M. tuberculosis. In immunocompromised persons, delayed-type hypersensitivity (DTH) responses (e.g., tuberculin reactions) can decrease
or disappear more rapidly, and a limited number of otherwise healthy persons apparently are incapable of reacting to
tuberculin even after diagnosed infection with M.
tuberculosis. This condition, called anergy, can be caused by multiple factors
(e.g., advanced HIV infection, measles infection, sarcoidosis, poor nutrition, certain medications, vaccinations, TB disease
itself, and other factors) (307,334--338). However, anergy skin in conjunction with skin testing is no longer recommended
routinely for screening for M. tuberculosis
infection (336).
Anergy testing is not useful in screening for diagnosing LTBI or asymptomatic TB disease
(339). In addition, anergy testing is not routinely recommended for anyone infected with HIV or who is otherwise immunocompromised, because TST
results alone, positive or negative, are not sensitive or specific enough to guide clinical decision making
(336).
Reconstitution of DTH in HIVinfected persons taking antiretroviral therapy (ART).
In one prospective study (340), TB patients who initially had negative TST results had positive TST results after initiation of HAART. HCWs must be
aware of the potential public health and clinical implications of restored TST reactivity among persons who have not been
diagnosed with TB disease but who might have LTBI. After the initiation of HAART repeat testing for infection with
M. tuberculosis is recommended for HIVinfected persons previously known to have negative TST results
(58). Recommendations on the prevention and treatment of TB in HIVinfected persons have been published
(39,53,240).
Pregnancy. Tens of thousands of pregnant women have
received TST since the test was developed, and no
documented episodes of TST-related fetal harm have been reported
(341). No evidence exists that the TST has adverse effects on
the pregnant mother or fetus (39). Pregnant HCWs should be included in serial skin testing as part of an
infectioncontrol program or a contact investigation because no contraindication for skin testing exists
(342). Guidelines issued by the American College of Obstetricians and Gynecologists (ACOG) emphasize that postponement of the diagnosis of
infection with M. tuberculosis during pregnancy is unacceptable
(343).
Booster phenomenon and two-step testing. In certain persons with LTBI, the DTH responsible for TST reactions
wanes over time. Repeated TST can elicit a reaction called boosting in which an initial TST result is negative, but a subsequent
TST result is positive. For example, a TST administered years after infection with
M. tuberculosis can produce a false-negative
result. This TST might stimulate (or boost) the person's ability to react to tuberculin, resulting in a positive result to a subsequent
test (including the second step of a two-step procedure)
(36,74,316,342,343). With serial testing, a boosted reaction on
a subsequent TST might be misinterpreted as a newly acquired infection, compared with the
false-negative result from the initial TST. Misinterpretation of a boosted reaction as a new infection with
M. tuberculosis or TST conversion might
prompt unnecessary investigations to find the source case, unnecessary treatment for the person tested, and unnecessary testing
of other HCWs. The booster phenomenon can occur in anyone, but it is more likely to occur in older persons, persons
with remote infection with M. tuberculosis (i.e., infected years ago), persons infected with NTM, and persons with previous
BCG vaccination (39,229,234,344,345).
All newly employed HCWs who will be screened with TST should receive baseline two-step TST upon hire, unless
they have documentation of either a positive TST result or treatment for LTBI or TB disease
(39,224). Any setting might have HCWs at risk for boosting, and a rate of boosting even as low as 1% can result in unnecessary investigation of
transmission. Therefore, two-step TSTs are needed to establish a baseline for persons who will receive serial TST (e.g., residents or staff
of correctional facilities or LTCFs). This procedure is especially important for settings that are classified as low risk where
testing is indicated only upon exposure. A reliable baseline test result is necessary to detect
health-care--associated transmission of M.
tuberculosis. Guidance for baseline TST for HCWs is included in this report (Box 2). To estimate the frequency of boosting
in a particular setting, a four-appointment schedule of TST administration and reading (i.e., appointments for
TST administration and reading both TST results) is necessary, rather than the three-appointment schedule (i.e., appointments
for the administration of both tests, with reading of the second-step TST result only)
(196).
Two-step testing should be used only for baseline screening, not in contact investigations. In a contact investigation,
for persons with a negative TST, a follow-up test should be administered 8--10 weeks after the end of exposure (rather than
1--3 weeks later, as in a two-step TST). In this instance, a change from a negative to a positive TST result suggests that
recent exposure, transmission, and infection occurred and should not be interpreted as a boosted response.
After a known exposure in a health-care setting (close contact to a patient or HCW with infectious TB disease), TST
results of >5 mm should be considered positive and interpreted as a new infection in HCWs whose previous TST
result is 0 mm. If an HCW has a baseline or follow-up TST result of >0 mm but
<10 mm, a health-care--associated exposure to
M. tuberculosis, and an increase in the TST size of >10 mm, the result should be interpreted as the HCW having a TST conversion because
of new infection.
BCG vaccination. In the United States, vaccination with BCG is not recommended routinely for anyone, including
HCWs or children (227). Previous BCG vaccination is not a contraindication to having a TST or two-step skin testing
administered. HCWs with previous BCG vaccination should receive baseline and serial skin testing in the same manner as those
without BCG vaccination (233) (see Supplement,
Diagnostic Procedures for LTBI and TB Disease; Box 1).
Previous BCG vaccination can lead to boosting in baseline two-step testing in certain persons
(74,231,344--346). Distinguishing a boosted TST reaction resulting from BCG vaccination (a false-positive TST result) and a TST result
because of previous infection with M. tuberculosis
(true positive TST result) is not possible
(39). Infectioncontrol programs should refer HCWs with positive TST results for medical evaluation as soon as possible (see Supplement, Diagnostic Procedures
for LTBI and TB Disease; Box 2).
Previous BCG vaccination increases the probability of a boosted reaction that will probably be uncovered on initial
two-step skin testing. For an HCW with a negative baseline two-step TST result who is a known contact of a patient who has
suspected or confirmed infectious TB disease, treatment for LTBI should be considered if the follow-up TST result is
>5 mm, regardless of BCG vaccination status.
PPD preparations for diagnosing infection with
M. tuberculosis. Two PPD preparations are available in the
United States: Tubersol® (Aventis Pasteur, Switftwater, Pennsylvania)
(237) and APLISOL® (Parkdale Pharmaceuticals,
Rochester, Michigan) (238). Compared with the U.S. reference PPD, no difference exists in TST interpretation between the
two preparations (347). However, when Tubersol and Aplisol were compared with each other, a slight difference in reactivity
was observed. Aplisol produced slightly larger reactions than Tubersol, but this difference was not statistically significant
(347). The difference in specificity, 98% versus 99%, is limited. However, when applied in large institutional settings that test thousands
of workers annually who are at low risk for infection
with M. tuberculosis, this difference in specificity might affect the rate
of positive TST results observed.
TB screening programs should use one antigen consistently and should realize that changes in products might make serial
changes in TST results difficult to interpret. In one report, systematic changes in product use resulted in a cluster of pseudoconversions
that were believed to have erroneously indicated a health-care--associated outbreak
(348). Persons responsible for making decisions
about the choice of pharmacy products should seek advice from the local or state health department's TB infectioncontrol program
before switching PPD preparations and should inform program staff of any changes.
Chest Radiography
Chest radiographic abnormalities can suggest pulmonary TB disease. Radiographic abnormalities that are consistent
with pulmonary TB disease include upper-lobe infiltration, cavitation, and effusion. Infiltrates can be patchy or nodular
and observed in the apical (in the top part of the lungs) or subapical posterior upper lobes or superior segment of the lower
lobes in the lungs. HCWs who have positive test results for
M. tuberculosis infection or symptoms or signs of TB disease,
regardless of test results for M. tuberculosis
infection, should have a chest radiograph performed to exclude a diagnosis of TB
disease. However, a chest radiograph is not a substitute for tests for
M. tuberculosis infection in a serial TB screening program
for HCWs.
Persons who have LTBI or cured TB disease should not have repeat chest radiographs performed routinely
(116). Repeat radiographs are not needed unless symptoms or signs of TB disease develop or a clinician recommends a repeat
chest radiograph (39,116).
A chest radiograph to exclude pulmonary TB disease is
indicated for all persons being considered for treatment of LTBI.
If chest radiographs do not indicate pulmonary TB and if no symptoms or signs of TB disease are present, persons with
a positive test result for infection with M. tuberculosis
might be candidates for treatment of LTBI. In persons with LTBI,
the chest radiograph is usually normal, although it might demonstrate abnormalities consistent with previous healed TB disease
or other pulmonary conditions. In patients with symptoms or signs of TB disease, pulmonary infiltrates might only be
apparent on a computed tomography (CT) scan. Previous, healed TB disease can produce radiographic findings that might differ
from those associated with current TB disease, although a substantial overlap might exist. These findings
include nodules, fibrotic scars, calcified granulomas, or basal pleural thickening. Nodules and fibrotic scars might contain slowly multiplying
tubercle bacilli and pose a high risk for progression to TB disease. Calcified nodular lesions (calcified granulomas) and apical
pleural thickening pose a lower risk for progression to TB disease
(31).
Chest Radiography and Pregnancy
Because TB disease is dangerous to both mother and fetus, pregnant women who have a positive TST result or who
are suspected of having TB disease, as indicated by symptoms or other concerns, should receive chest radiographs (with
shielding consistent with safety guidelines) as soon as feasible, even during the first trimester of pregnancy
(31,39,341).
Chest Radiography and HIV-Infected Persons
The radiographic presentation of pulmonary TB in persons infected with HIV might be apical; however, apical
cavitary disease is less common among such patients. More common chest radiograph findings for HIVinfected persons are
infiltrates in any lung zone, mediastinal or hilar adenopathy, or, occasionally, a normal chest radiograph. Typical and cavitary lesions
are usually observed in patients with higher CD4 counts, and more atypical patterns are observed in patients with lower
CD4 counts (31,49,94,142,349--354). In patients with symptoms and signs of TB, a negative chest radiograph result does
not exclude TB. Such patients might be candidates for airborne precautions during medical evaluation.
Evaluation of Sputum Samples
Sputum examination is a critical diagnostic procedure for pulmonary TB disease
(30) and is indicated for the following persons:
- anyone suspected of having pulmonary or laryngeal TB disease;
- persons with chest radiograph findings consistent with TB disease (current, previous, or healed TB);
- persons with symptoms of infection in the lung, pleura, or airways, including larynx;
- HIVinfected persons with any respiratory symptoms or signs, regardless of chest radiograph findings; and
- persons suspected of having pulmonary TB disease for whom bronchoscopy is planned.
Sputum Specimen Collection
Persons requiring sputum collection for smear and culture should have at least three consecutive sputum
specimens obtained, each collected in 8--24-hours intervals
(124), with at least one being an early morning specimen
(355). Specimens should be collected in a sputum induction booth or in an AII room. In resource-limited settings without
environmental containment or when an AII room is not available, sputum collection can be performed safely outside of a building,
away from other persons, windows, and ventilation intakes. Patients should be instructed on how to produce an adequate
sputum specimen (containing little saliva) and should be supervised and observed by an HCW during the collection of sputum,
if possible (30). If the patient's specimen is determined to be inadequate, it should still be sent for bacteriologic testing,
although the inadequate nature of the specimen should be recorded. The HCW should wear an N95 disposable respirator
during sputum collection.
Sputum Induction
For patients who are unable to produce an adequate sputum specimen, expectoration can be induced by inhalation of
an aerosol of warm, hypertonic saline. Because sputum
induction is a cough-inducing procedure, pre-treatment with
a bronchodilator should be considered in patients with a history of asthma or other chronic obstructive airway diseases.
Medical assistance and bronchodilator medication should be available during any sputum induction in the event
of induced bronchospasm (109,356,357).
The patient should be seated in a small, well-ventilated sputum induction booth or in an AII room (see
Environmental Controls; and Supplement, Environmental Controls). For best results, an ultrasonic nebulizer that generates an aerosol
of approximately 5 mL/minute should be used. A 3% hypertonic saline is commercially available, and its safety has
been demonstrated. At least 30 mL of 3% saline should be administered; administration of smaller volumes will have a lower
yield. Higher concentrations can be used with an adjustment in the dose and closer monitoring for adverse effects.
Patients should be instructed to breathe deeply and cough intermittently. Sputum induction should be continued for up
to 15 minutes or until an adequate specimen (containing little saliva) is produced. Induced sputum will often be clear
and watery. Any expectorated material produced should be labeled as expectorated sputum and sent to the laboratory.
Laboratory Examination
Detection of AFB in stained smears by microscopy can provide the first bacteriologic indication of TB disease.
Laboratories should report any positive smear results within 24 hours of receipt of the specimen
(30). A positive result for AFB in a sputum smear is predictive of increased infectiousness. Smears allow presumptive detection of mycobacteria, but
definitive identification, strain typing, and drug-susceptibility testing of
M. tuberculosis require that a culture be performed
(30). Negative AFB sputum smear results do not exclude a diagnosis of TB disease, especially if clinical suspicion of disease is
high. In the United States, approximately 63% of patients with
reported positive sputum culture results have positive AFB
sputum smear results (26).
A culture of sputum or other clinical specimen that contains
M. tuberculosis provides a definitive diagnosis of TB disease.
In the majority of cases, identification of M. tuberculosis
and drug-susceptibility results are available within 28 days (or
4--6 weeks) when recommended rapid methods such as liquid culture and DNA probes are used. Negative culture results
are obtained in approximately 14% of patients with confirmed pulmonary TB disease
(4,5). Testing sputum with rapid techniques (e.g., NAA) facilitates the rapid detection and identification of
M. tuberculosis but should not replace culture and
drug-susceptibility testing in patients with suspected TB disease
(30,125,358). Mixed mycobacterial infection can obscure
the identification of M. tuberculosis during the laboratory evaluation (e.g., because of cross-contamination or dual infections)
and can be distinguished by the use of mycobacterial species-specific DNA probes
(359). Examination of colony morphology on solid culture media can also be useful.
Drug-susceptibility tests should be performed on initial isolates from all patients to assist in identifying an
effective antituberculosis treatment regimen. Drug-susceptibility tests should be repeated if sputum specimens continue to be
culture-positive after 3 months of antituberculosis treatment or if culture results become positive for
M. tuberculosis after a period of negative culture results
(30,31).
Bronchoscopy
If possible, bronchoscopy should be avoided in patients with a clinical syndrome consistent with pulmonary or laryngeal
TB disease because bronchoscopy substantially increases the risk for transmission either through an airborne
route (63,80,81,162,360) or a contaminated bronchoscope
(80,82,163--169), including in persons with negative AFB
sputum smear results. Microscopic examination of three consecutive sputum specimens obtained in 8--24-hour intervals, with at
least one obtained in the early morning, is recommended instead of bronchoscopy, if possible. In a patient who is intubated
and mechanically ventilated, closed circuitry can reduce the risk for exposure.
If the suspicion for pulmonary TB disease is high or if the patient is seriously ill with a disorder, either pulmonary
or extrapulmonary, that is believed to be TB disease, multidrug antituberculosis treatment using one of the
recommended regimens should be initiated promptly, frequently before AFB smear results are known
(31). Obtaining three sputum samples is safer than performing bronchoscopy. For AFB smear and culture results, three sputum samples have an increased
yield compared with a single specimen
(110,357), and induced specimens have better yield than specimens obtained
without induction. Sputum induction is well-tolerated
(90,109,132, 133,357,361,362), even in children
(134,356), and sputum specimens (either spontaneous or induced) should be obtained in all cases before a bronchoscopy
(109,356,363,364).
In circumstances where a person who is suspected of having TB disease is not on a standard antituberculosis
treatment regimen and the sputum smear results (possibly including
induced specimens) are negative and a reasonably high suspicion
for TB disease remains, additional consideration to initiate treatment for TB disease should be given. If the underlying cause of
a radiographic abnormality remains unknown, additional evaluation with bronchoscopy might be indicated; however, in
cases where TB disease remains a diagnostic possibility, initiation of a standard antituberculosis treatment regimen for a
period before bronchoscopy might reduce the risk for transmission. Bronchoscopy might be valuable in establishing the diagnosis;
in addition, a positive culture result can be both of clinical and public health importance to obtain
drug-susceptibility results. Bronchoscopy in patients with suspected or confirmed TB disease should not be undertaken until after consideration of
the risks for transmission of M. tuberculosis
(30,63,81,162,360). If bronchoscopy is performed, because it is a
cough-inducing procedure, additional sputum samples for AFB smear and culture should be collected after the procedure to increase
the diagnostic yield.
Treatment Procedures for LTBI and TB Disease
Treatment for LTBI
Treatment for LTBI is essential to control and eliminate TB disease in the United States because it substantially reduces
the risk that infection with M. tuberculosis
will progress to TB disease (10,28). Certain groups of persons are at substantially
high risk for developing TB disease after being infected, and every effort should be made to begin treatment for LTBI and to
ensure that those persons complete the entire course of treatment (see Supplement, Treatment Procedures for LTBI and TB
Disease; Box 2).
Before beginning treatment of LTBI, a diagnosis of TB disease should be excluded by history, medical examination,
chest radiography, and, when indicated, bacteriologic studies. In addition, before offering treatment of LTBI, ensure that the
patient has not experienced adverse reactions with previous isoniazid (INH) treatment
(215).
Candidates for Treatment of LTBI
Persons in the following groups at high risk should be
administered treatment for LTBI if their TST result is
>5 mm, regardless of age (31,39):
- persons infected with HIV,
- recent contacts with a person with TB disease,
- persons with fibrotic changes on chest radiograph consistent with previous TB disease,
- organ transplant recipients, and
- other immunosuppressed persons (e.g., persons receiving
>15 mg/day of prednisone for >1 month).
Persons in the following groups at high risk should be considered for treatment of LTBI if their TST result is
>10 mm, or if the BAMT result is positive:
- persons with TST or BAMT conversions;
- persons born or who have lived in developing countries or countries with a high-incidence of TB disease;
- persons who inject illicit drugs;
- residents and employees in congregate settings that are at high risk (i.e., correctional facilities and LTCFs [e.g., hospices
and skilled nursing facilities]), hospitals and other health-care facilities, residential settings for persons with HIV/AIDS
or other immunocompromising conditions, and homeless shelters;
- personnel from mycobacteriology laboratories;
- persons with any of the following clinical conditions or other immunocompromising conditions that place them at high
risk for TB disease:
--- silicosis,
--- diabetes mellitus,
--- chronic renal failure,
--- certain hematologic disorders (e.g., leukemias and lymphomas),
--- other specific malignancies (e.g., carcinoma of the head, neck, or lung),
--- unexplained weight loss of >10% of ideal body weight,
--- gastrectomy, or
--- jejunoileal bypass;
- persons living in areas with high incidence of TB disease;
- children aged <4 years; and
- infants, children, and adolescents exposed to adults at high risk for developing TB disease.
Persons who use tobacco or alcohol
(40,41), illegal drugs, including injection drugs and crack cocaine
(43--48), might also be at increased risk for infection and disease, but because of the multiple other potential risk factors that commonly
occur among such persons, use of these substances has been difficult to identify as separate risk factors.
Persons with no known risk factors for TB disease can be considered for treatment of LTBI if their TST result is
>15 mm. However, programs to screen HCWs for infection with
M. tuberculosis should only be conducted among groups at high
risk. All testing activities should be accompanied by a plan for follow-up care for persons with LTBI or, if it is found, TB disease.
A decision to test for infection with M. tuberculosis
should be based on a commitment to treat LTBI after a medical
examination (39).
Persons who might not be good candidates for treatment of LTBI include those with a previous history of liver injury or
a history of excessive alcohol consumption. Active hepatitis and ESLD are relative contraindications to the use of INH
for treatment of LTBI (39,240). If the decision is made to treat such patients, baseline and follow-up monitoring of
serum aminotransaminases should be considered.
For persons who have previous positive TST or BAMT
results and who completed treatment for LTBI previously,
treating them again is not necessary. Documentation of completed therapy for LTBI is critical. Instead of participating in serial
skin testing, the HCW should receive a medical evaluation and a symptom screen annually. A symptom screen is a procedure
used
during a clinical evaluation in which patients are asked if they have experienced any departure from normal in
function, appearance, or sensation related to TB disease (e.g., cough)..
Screening HCWs for infection with M. tuberculosis
is an essential administrative measure for the control of transmission
of M. tuberculosis in health-care settings. By conducting TB screening, ongoing transmission of
M. tuberculosis can be detected, and future transmission can be prevented by identifying lapses in infection control and identifying persons
infected with M. tuberculosis and TB disease. The majority of individual HCWs, however, do not have the risk factors for progression to
disease that serve as the basis for the current recommendations for targeted testing and treatment of LTBI. The majority of HCWs
in the United States do not provide care in areas in which the prevalence of TB is high. Therefore, HCWs should be tested,
as determined by risk classification for the health-care setting, and can be categorized as having a positive test result or
conversion for M. tuberculosis infection. HCWS can be categorized as part of the TB infectioncontrol program for the purpose
of surveillance and referral, but they might not necessarily be a candidate for treatment of LTBI.
In the context of TST screening as part of an infection-control program, the interpretation of TST results in HCWs
occurs in multiple steps. HCWs should receive baseline two-step TST testing (see Supplement, Diagnostic Procedures for LTBI
and TB Disease; Box 2). In the context of BAMT screening, HCWs should receive only one baseline test.
HCWs should receive serial screening for infection
with M. tuberculosis (either TST or BAMT), as determined by
the health-care setting's risk classification (Appendix D). For infectioncontrol purposes, the results of the testing should
be recorded and interpreted as part of the TB infectioncontrol
program as either a 1) negative TST result, 2)
previously documented positive TST or BAMT result, or 3) TST or BAMT conversion. All recordings should also document the size of
the induration in millimeters, not simply as negative or
positive. BAMT results should be recorded in detail. The details
should include date of blood draw, result in specific units, and the laboratory interpretation (positive, negative, or
indeterminate---and the concentration of cytokine measured [e.g.,
IFN-g]).
To determine whether treatment for LTBI should be indicated, HCWs should be referred for medical and
diagnostic evaluation according to the TST result criteria (Box 2). In conjunction with a medical and diagnostic evaluation, HCWs
with positive test results for M. tuberculosis
should be considered for treatment of LTBI (Box 2) after TB disease has been
excluded by further medical evaluation. HCWs cannot be compelled to take treatment for LTBI, but they should be encouraged to
do so if they are eligible for treatment.
HCWs' TST or BAMT results might be considered positive as part of the TB infectioncontrol program for the purposes
of surveillance and referral (i.e., meet the criterion for a conversion), and this occurrence is important to note. However, not
all of these HCWs may be considered candidates for treatment of LTBI, according to the individual medical and
diagnostic evaluation. After an HCW has been classified as having a positive result or conversion for
M. tuberculosis infection,
additional testing is not necessary.
Treatment Regimens for LTBI
For persons suspected of having LTBI, treatment of LTBI should not begin until TB disease has been excluded.
Persons highly suspected of having TB disease should receive the standard multidrug antituberculosis treatment regimen for TB
disease until the diagnosis is confirmed or excluded. Standard regimens for the treatment of LTBI have been presented
(Table 3); however, modifications to those regimens should be considered under certain circumstances, including HIV
infection, suspected drug resistance, and pregnancy
(47,365).
Reports of severe liver injury and death associated with the combination of rifampin and pyrazinamide (RZ) for treatment
of LTBI (366--368) prompted the American Thoracic Society and CDC to revise previous recommendations
(39,53) to indicate that RZ generally should not be offered for the treatment of LTBI
(240). If the potential benefits substantially outweigh
the demonstrated risk for severe liver injury and death associated with this regimen and the patient has no contraindications,
a physician with experience treating LTBI and TB disease should be consulted before using this regimen
(246). Clinicians should continue the appropriate use of rifampin and pyrazinamide in standard multidrug antituberculosis treatment regimens for
the treatment of TB disease (31).
For all regimens for treatment of LTBI, nonadherence to
intermittent dosing (i.e., once or twice weekly) results in a
larger proportion of total doses missed than daily dosing. DOT should be used for all doses during the course of treatment of
LTBI whenever feasible. Collaborate with the local or state health department on decisions regarding DOT arrangements
(31).
Contacts of patients with drug-susceptible TB disease.
Persons with a previously negative TST or BAMT result who
are contacts of patients with drug-susceptible TB disease and who subsequently have a positive TST result
(>5 mm) or positive
BAMT result should be evaluated for treatment of LTBI, regardless of age. The majority of persons who are infected with
M. tuberculosis will have a positive TST result within 6 weeks of exposure
(74,228,369--371). Therefore, contacts of patients
with drug-susceptible TB disease with negative TST (or BAMT) results should be retested 8--10 weeks after the end of exposure
to a patient with suspected or confirmed TB disease. Persons
infected with M. tuberculosis should be advised that they
possibly can be reinfected with M. tuberculosis
if re-exposed (246,372--375). Persons infected with HIV, persons
receiving immunosuppressive therapy, regardless of TST result, and persons with a previous positive TST or BAMT result who are
close contacts of a person with suspected or confirmed TB disease should be considered for treatment of LTBI.
The interpretation of TST results is more complicated in a contact investigation among HCWs who have negative
baseline TST results from two-step testing but where the
induration was >0 mm on the baseline TST or subsequent serial
testing. Differences in the TST results between the contact investigation and previous baseline and serial TST could be a result of
1) inter-test variability in reaction size; 2) intervening exposure to NTM, BCG, or
M. tuberculosis; and 3) reversion. In
practice, TST, only inter-test variability and exposure to or infection with NTM or
M. tuberculosis are likely.
Treatment of LTBI should not be started until a diagnosis of TB disease has been excluded. If uncertainty exists
concerning the presence of TB disease because of an ambiguous chest radiograph, a standard multidrug antituberculosis
treatment regimen can be started and adjusted as necessary based on the results of sputum cultures and the patient's clinical
response (31). If cultures are obtained without initiating therapy, treatment for LTBI should not be initiated until all culture results
are reported as negative.
Contacts of patients with drug-resistant TB disease.
Treatment for LTBI caused by drug-resistant or MDR TB disease
is complex and should be conducted in consultation with the local or state health department's infectioncontrol program
and experts in the medical management of drug-resistant TB. In certain instances, medical decision making for the person
with LTBI will benefit from the results of drug susceptibility testing of the isolate of the index TB case. Treatment should be
guided by susceptibility test results from the isolate to which the patient was exposed and presumed to be infected
(31,376,377).
Pretreatment Evaluation and Monitoring of Treatment
The pretreatment evaluation of persons who are targeted for treatment of LTBI provides an opportunity for
health-care providers to 1) establish rapport with patients; 2) discuss details of the patient's risk for progression from LTBI to TB
disease; 3) explain the benefits of treatment and the importance of adhering to the drug regimen; 4) review possible adverse effects
of the regimen, including interactions with other medications; and 5) establish an optimal follow-up plan.
Monitoring for adverse effects of antituberculosis medications must be individualized. Persons receiving treatment for
LTBI should be specifically instructed to look for symptoms associated with the most common reactions to the medications they
are taking (39). Laboratory testing should be performed to evaluate possible adverse effects
(31,39). Routine laboratory monitoring during treatment of LTBI is indicated for patients with abnormal baseline test results and for persons with a
risk for hepatic disease. Baseline laboratory testing is indicated for persons infected with HIV, pregnant women, women in
the immediate postpartum period (usually within 3 months of delivery), persons with a history of liver disease, persons who
use alcohol regularly, and those who have or are at risk for chronic liver disease.
All patients being treated for LTBI should be clinically monitored at least monthly, including a brief clinical
assessment conducted in the person's primary language for signs of hepatitis (e.g., nausea, vomiting, abdominal pain, jaundice, and
yellow or brown urine). Patients receiving treatment for LTBI should be advised about the adverse effects of the drugs and the
need for prompt cessation of treatment and clinical evaluation if adverse effects occur.
Because of the risk for serious hepatic toxicity and death, the use of the combination of RZ for the treatment of LTBI
generally should not be offered. If RZ is used, a physician with experience treating LTBI and TB disease should be consulted before the
use of this regimen. In addition, more extensive biochemical and clinical monitoring is recommended
(240).
Treatment for TB Disease
Suspected or confirmed TB cases must be reported to the local or state health department in accordance with laws
and regulations. Case management for TB disease should be coordinated with officials of the local or state health
department. Regimens for treatment of TB disease must contain multiple drugs to which the organisms are susceptible. For persons
with TB disease, treatment with a single drug can lead to the development of mycobacterial resistance to that drug.
Similarly, adding a single drug to a failing antituberculosis treatment regimen can lead to resistance to the added drug
(31).
For the majority of patients, the preferred regimen for treating TB disease consists of an initiation 2-month phase of
four drugs (INH, rifampin, pyrazinamide, and ethambutol) and at least a 4-month continuation phase of INH and rifampin (for
a minimum total treatment of 6 months). Ethambutol may be discontinued if supporting drug susceptibility results
are available. Completion of therapy is based on the number of doses taken within a maximal period and not simply 6
months (31). Persons with cavitary pulmonary TB disease and positive culture results of sputum specimens at the completion of
2 months of therapy should receive a longer (7-month continuation) phase because of the significantly higher rate of
relapse (31).
TB treatment regimens might need to be altered for persons infected with HIV who are on ART
(49). Whenever feasible, the care of persons with both TB disease and HIV infection should be provided by or in consultation with experts in
the management of both TB and HIV-related disease
(31). To prevent the emergence of rifampin-resistant organisms, persons
with TB disease, HIV infection, and CD4 cell counts of <100
cells/mm3 should not be treated with highly intermittent (i.e., once
or twice weekly) regimens. These patients should receive daily treatment during the intensive phase by DOT (if feasible) and daily
or three times weekly by DOT during the continuation phase
(378). Detailed information on TB treatment for persons
infected with HIV has been published and is available (http://www.dhfs.state.wi.us/AIDS-HIV/Resources/Overviews/AIDS_HIV.htm,
http://www.hiv-druginteractions.org, and
http://www.cdc.gov/nchstp/tb/TB_HIV_Drugs/TOC.htm) and published
(31,53).
Drug-susceptibility testing should be performed on all initial isolates from patients with TB disease. When results from
drug-susceptibility tests become available, the antituberculosis treatment regimen should be reassessed, and the drugs used in
combination should be adjusted accordingly
(376,377,379--381). If drug resistance is present, clinicians who are not experts in the
management of patients with drug-resistant TB disease should seek expert consultation
(31) and collaborate with the local or state
health department for treatment decisions.
The major determinant of the outcome of treatment is
adherence to the drug regimen. Therefore, careful attention
should be paid to measures designed to enable and foster
adherence (31,319,382). DOT is an adherence-enhancing strategy in
which a trained HCW or other specially trained person watches a patient swallow each dose of medication and records the dates
that the DOT was observed. DOT is the standard of care for all patients with TB disease and should be used for all doses
during the course of therapy for TB disease and for LTBI, whenever feasible. Plans for DOT should be coordinated with the local
or state health department (31).
Reporting Serious Adverse Events
HCWs should report serious adverse events associated with the administration of tuberculin antigen or treatment of
LTBI or TB disease to the FDA MedWatch (Adverse Event Reporting System) [AERS], telephone: 800-FDA-1088, fax:
800-FDA-0178, http://www.fda.gov/medwatch. Report Form 3500, Physicians' Desk Reference. Specific instructions for the types
of adverse events that should be reported are included
in MedWatch report forms.
Surveillance and Detection of M. tuberculosis
Infections in Health-Care Settings
In the United States, LTBI has been traditionally diagnosed on the basis of a positive PPD-based TST result after TB
disease has been excluded. In vitro cytokine-based immunoassays for the detection of
M. tuberculosis infection have been the focus
of research and development. One such BAMT is QFT (which is PPD-based)
and the subsequently developed version, QFTG. QFTG measures cell-mediated immune responses to peptides representative of two
M. tuberculosis proteins that are not
present in any BCG vaccine strain and are absent from the majority of nontuberculosis mycobacteria. This assay was approved by FDA
in 2005 and is an available option for detecting
M. tuberculosis infection. CDC recommendations for the United States on QFT
and QFTG have been published (35).
QFTG is an in vitro test based on measuring interferon-gamma
(IFN-g) released in heparinized whole blood when incubated overnight with mitogen (serving as a positive control), Nil (i.e., all reagents except antigens, which sets a
baseline), and peptide simulating ESAT-6 (6-kDa early secretory antigenic target) and CFP-10 (10-kDa culture filtrate
protein) (measured independently), two different proteins with similar amino acid sequences specific for
M. tuberculosis (Box 3). The sequences of ESAT-6 and CFP-10 are not related to each other. The genes encoding these two proteins are usually found
next to each other in an operon (i.e., are coexpressed and translated from an mRNA product containing both genes).
Although mycobacterial genomes contain multiple copies of each family, QFTG and Elispot detect immunoreactivity associated
only
with the ESAT-6 protein and CFP-10 protein encoded by the genes in the region of deletion (RDI). In addition,
virulence attributes are associated with the RD1 genes only and not the other homologues.
Specific antigens of these two proteins are found in
M. tuberculosis--complex organisms (i.e.,
M. tuberculosis, M. bovis, M.
africanum, M. microti, and M. canetti, M. caprae,
and M. pinnipedii), but not in the majority of other mycobacteria or
in vaccine-variant M. bovis, BCG. Lymphocytes from the majority of persons who have been infected by
M. tuberculosis complex indicate their sensitivity to ESAT-6 or
CFP-10 by releasing IFN-g, whereas infection by the majority of other
mycobacteria, including BCG, does not appear to cause this sensitivity.
The blood tests using IFN-g methods require one less
patient visit, assess responsiveness to M. tuberculosis
antigens, and do not boost anamnestic immune responses. Interpretation of the BAMT result is less subjective than interpretation of a skin
test result, and the BAMT result might be affected less by previous BCG vaccination and sensitization to
environmental mycobacteria (e.g., M. avium complex) than the PPD-based TST. BAMT might be more efficient and cost effective than
TST (35). Screening programs that use BAMT might eliminate the need for two-step testing because this test does not
boost sensitization.
Other cytokine-based immunoassays are under development and might be useful in the diagnosis of
M. tuberculosis infection. Future FDA-approved products, in combination with CDC-issued recommendations, might provide
additional diagnostic alternatives. For guidance on the use of these and related technologies, CDC plans to periodically
publish recommendations on the diagnosis of M. tuberculosis
infection. BAMT can be used in both testing and
infectioncontrol surveillance programs for HCWs.
Baseline Testing with BAMT
For the purposes of establishing a baseline, a single negative BAMT result is sufficient evidence that the HCW is
probably not infected with M. tuberculosis (Box 1). However, cautions regarding making medical care decisions for persons
whose conditions are at increased risk for progressing to TB disease from
M. tuberculosis infection have been presented
(Box 4).
If BAMT is used for baseline testing of HCWs, including those in settings that are low risk, one negative BAMT result
is sufficient to demonstrate that the HCW is not infected with
M. tuberculosis (Box 2). Perform and document the
baseline BAMT result preferably within 10 days of starting employment. HCWs with positive baseline results should be referred for
a medical and diagnostic evaluation to exclude TB disease and then treatment for LTBI should be considered in accordance
with CDC guidelines. Persons with a positive BAMT result do not need to be tested again for surveillance. For HCWs who
have indeterminate test results, providers should consult the responsible laboratorian for advice on interpreting the result
and making additional decisions (383).
Serial Testing with BAMT for Infection-Control Surveillance
When using BAMT for serial testing, a conversion for
administrative purposes is a change from a negative to a
positive result (Box 2). For HCWs who have indeterminate test results, providers should consult the responsible laboratorian for
advice on interpreting the result and making additional decisions
(383). Persons with indeterminate results should not be counted
for administrative calculations of conversion rates.
Exposure of HCWs and Patients to M. tuberculosis
Known and Presumed Exposure
For HCWs with known and presumed exposure to
M. tuberculosis, administer a symptom screen and obtain the
BAMT result. A BAMT conversion probably indicates recent
M. tuberculosis infection; therefore, TB disease must be
excluded. Experience with BAMT in contact investigations is limited. Specific attention is needed in the management of
certain populations (e.g., infants and children aged <4 years and immunocompromised persons, including those who
are HIVinfected) (Box 4).
If the symptom screen or the BAMT result is positive, the exposed person should be evaluated for TB disease promptly,
which includes a chest radiograph. If TB disease is excluded, additional medical and diagnostic evaluation for LTBI is needed,
which includes a judgment regarding the extent of exposure.
Performing QFT-G
The QFTG should be performed as described in the product insert provided with the BAMT kit. This insert is
also available from the manufacturer's website (http://www.cellestis.com).
Interpretation of BAMT Results and Referral for Evaluation
HCWs who meet the criteria for referral should have a medical and diagnostic evaluation (see Supplements, Estimating
the Infectiousness of a TB Patient; Diagnostic Procedures for LTBI and TB Disease; and Treatment Procedures for LTBI and
TB Disease). The factors affecting treatment decisions during medical and diagnostic evaluation by risk for infection with
M. tuberculosis have been presented (Box 5). In addition, because BAMT and other indirect tests for
M. tuberculosis infection are diagnostic aids, the test results must be interpreted in the context of epidemiologic, historical, physical, and
diagnostic findings. A higher likelihood of infection, as estimated from historical or epidemiologic details (e.g., exposure
to M. tuberculosis) or because of the presence of an illness consistent with TB disease, increases the predictive value of a
positive result. Setting-based risk factors (e.g., the prevalence of TB disease in the setting) should be considered when making
decisions regarding the diagnosis and treatment of LTBI.
Medical conditions that impair or alter immune function (Box 4) decrease the predictive value of a negative result,
and additional diagnostic methods (e.g., bacteriology, radiography, and histology) are required as evidence before excluding
M. tuberculosis infection when the BAMT result is negative. Medical evaluations can occur in different settings, including
an occupational health clinic, local or state health department, hospital, or private medical clinic.
Indeterminate QFTG results are reported for either of two test conditions.
- The IFN-g responses to all antigens (ESAT-6, CFP-10, and mitogen) are below a cut-off threshold. The weak response
to mitogen could be caused by nonstandard storage or transportation of the blood sample, by laboratory errors, or
by lymphocytic insensitivity caused by immune dysfunction.
OR,
- The IFN-g response to the Nil exceeds a specified threshold, and the responses to both ESAT-6 and CFP-10 do not
exceed the response to Nil by at least 50%. This response
could be caused by nonstandard storage or transportation,
laboratory errors, or circulating IFN-g, which can be increased in ill HCWs or patients. For HCWs who have indeterminate
test results, providers should consult the responsible laboratorian for advice on interpreting the result and making
further decisions (383).
Interpreting the BAMT Result for Infection Control and Surveillance
BAMT conversion rates should be determined routinely. The precision of the BAMT conversion rate will depend, in
part, on the number of HCWs tested, which should be considered when establishing a regular interval for evaluation
and monitoring of HCWs with BAMT. Healthcare settings with a substantial number of HCWs might have testing
schedules that can accurately determine the BAMT conversion rate each month (i.e., from annual results of an HCW cohort
tested within the given month), if testing is staggered throughout the year. BAMT conversion rates are more difficult to calculate
in settings with fewer test results.
QC Program for the BAMT
Multiple processes are necessary to assure quality BAMT results: specimen collection, transport and handling,
and conducting the test in the laboratory. BAMT must meet performance parameters for a valid test result to be achieved. QC
is an ongoing laboratory issue. The infectioncontrol team should assist the laboratory in assuring that all requisite conditions
are present. The laboratory performing the BAMT will be required to validate its performance of the test before processing
clinical samples. State and federal laboratory requirements regulate laboratory-testing procedures.
Additional Considerations
An indeterminate QFTG result does not mean that the test has failed; it indicates that the specimen has
inadequate responsiveness for the test to be performed. This result might reflect the condition of the HCW or patient, who, for
example, might be immunosuppressed. Alternatively, the specimen might have been handled incorrectly. For HCWs who
have indeterminate test results, providers should consult the responsible laboratorian for advice on interpreting the result
and making further decisions (383). Skin testing for cutaneous anergy is not useful in screening for asymptomatic LTBI or
for diagnosing TB disease (339).
QFTG use with HIVinfected persons taking ART. The effect of HIV infection and of ART on the performance of
the QFTG have not been fully evaluated.
Persons aged <17 years or pregnant women. The use of the QFTG has not been evaluated in persons aged <17 years
or pregnant women (35).
Booster phenomenon and BAMT. BAMT does not involve
the injection of any substance into the persons being
tested and is not affected by the booster phenomenon.
BCG vaccination. In the United States, vaccination with BCG is not routinely recommended
(227). However, BCG is the most commonly used vaccine in the world. Foreign-born persons are commonly employed in the United States as
HCWs. Previous BCG vaccination is not a contraindication to having a BAMT performed. BCG does not influence BAMT
results with the version of the test approved in 2005 (i.e., QFTG). HCWs who have received BCG vaccination should receive
a baseline BAMT in the same manner as those without BCG vaccination, and the test result should be interpreted
without reference to BCG.
Environmental Controls
Overview
Environmental controls include the following technologies to remove or inactivate
M. tuberculosis: local exhaust ventilation,
general ventilation, HEPA filtration, and UVGI. These controls help to prevent the spread and reduce the concentration of
airborne infectious droplet nuclei. Environmental controls are the second line of defense in the TB infectioncontrol program, and they
work in harmony with administrative controls.
The reduction of occupational exposures to M. tuberculosis
can be facilitated through the effective use of environmental
controls at the source of exposure (e.g., coughing patient or laboratory specimen) or in the general workplace environment. Source
control is amenable to situations where the source has been identified and the generation of the contaminant is localized.
Source-control techniques can prevent or reduce the spread of infectious droplet nuclei into the air by collecting infectious particles as they
are released. These techniques are especially critical during procedures that will probably generate infectious aerosols
(e.g., bronchoscopy, sputum induction, endotracheal intubation, suctioning, irrigating TB abscesses, aerosol treatments, autopsies
on cadavers with untreated TB disease, and certain laboratory specimen manipulations) and when patients with infectious TB
disease are coughing or sneezing.
Unsuspected and undiagnosed cases of infectious TB disease are believed to represent a substantial proportion of the
current risk to HCWs (10,85). In such situations, source control is not a feasible option. Instead, general ventilation and air
cleaning must be relied upon for control. General ventilation can be used to dilute the air and remove air contaminants and to
control airflow patterns in rooms or in a health-care setting. Air-cleaning technologies include HEPA filtration to reduce
the concentration of M. tuberculosis droplet nuclei and UVGI to kill or inactivate the microorganisms so that they no longer
pose a risk for infection.
Ventilation systems for health-care settings should be
designed, and modified when necessary, by ventilation engineers
in collaboration with infectioncontrol practitioners and occupational health staff. Recommendations for designing
and operating ventilation systems have been published
(117,118,178). The multiple types and conditions for use of
ventilation systems in health-care settings and the needs of persons in these settings preclude the provision of extensive guidance in
this document.
The information (see Environmental Controls; and Supplement, Environmental Controls) is conceptual and intended
to educate HCWs regarding environmental controls and how these controls can be used in the TB infectioncontrol
program. This information should not be used in place of consultation with experts who can give advice on ventilation system
design, selection, installation, and maintenance. Because
environmental controls will fail if they are not properly operated
and maintained, routine training and education of staff are key components to a successful TB infectioncontrol program.
These guidelines do not specifically address mechanical ventilators in detail (see Intensive Care Units [ICUs]).
Local Exhaust Ventilation
Local exhaust ventilation captures airborne contaminants at or near their source and removes the contaminants
without exposing persons in the area to infectious agents. This method is considered the most efficient way to remove
airborne
contaminants because it captures them before they can disperse. In local exhaust devices, hoods are typically used. Two
types of hoods are 1) enclosing devices, in which the hood either partially or fully encloses the infectious source; and 2)
exterior devices, in which the infectious source is near but outside the hood. Fully enclosed hoods, booths, or tents are
always preferable to exterior devices because of their superior ability to prevent contaminants from escaping into the
HCW's breathing space. Descriptions of both enclosing and exterior devices have been published
(178).
Enclosing Devices
Enclosing devices for local exhaust ventilation include 1) booths for sputum induction or administration of
aerosolized medications (see Environmental Controls;
Figure 2), 2) tents or hoods for enclosing and isolating a patient, and 3)
BSCs (165). These devices are available in various configurations. The simplest device is a tent placed over the patient; the tent
has an exhaust connection to the room-discharge exhaust system. The most complex device is an enclosure with a
self-contained airflow and recirculation system (see Environmental Controls; Figure 2).
Tents and booths should have sufficient airflow to remove at least 99% of airborne particles during the interval between
the departure of one patient and the arrival of the next (see Environmental Controls; Table 1). The time required to
remove 99% or 99.9% of airborne particles from an enclosed
space depends on 1) the number of ACH, which is a function of the
volume (number of cubic feet of air) in the room or booth and the rate at which air is exiting the room or booth at the intake
source; 2) the location of the ventilation inlet and outlet; and 3) the configuration of the room or booth. The surfaces of tents
and booths should be periodically cleaned in accordance with recommendations and guidance from the manufacturers
(see Supplement, Cleaning, Disinfecting, and Sterilizing Patient-Care Equipment and Rooms).
Exterior Devices
Exterior devices for local exhaust ventilation are usually hoods that are near to but not enclosing an infectious patient.
The airflow produced by these devices should be sufficient to prevent cross-currents of air near the patient's face
from allowing droplet nuclei to escape. Whenever possible, the
patient should face directly into the opening of the hood to
direct any coughing or sneezing into the hood. The device should maintain an air velocity of 200 feet per minute (fpm) at
the patient's breathing zone to ensure the capture of droplet nuclei. Smoke tubes should be used to verify that the control
velocity at the typical location of the patient's breathing zone is adequate to provide capture for the condition of highest
expected cross-drafts and then the patient's breathing zone should be maintained at this location for the duration of the treatment.
Discharge of Exhaust from Booths, Tents, and Hoods
Air from booths, tents, and hoods is either discharged into the room in which the device is located or to the outside. If
the exhaust air is discharged into the room, a HEPA filter should be incorporated at the discharge duct or vent of the device.
The exhaust fan should be located on the discharge side of the HEPA filter to ensure that the air pressure in the filter housing
and booth is negative compared with adjacent areas. Uncontaminated air from the room will flow into the booth through
all openings, preventing infectious droplet nuclei in the booth from escaping into the room. Additional information on
the installation, maintenance, and monitoring of HEPA filters is included in this report (Appendix A).
The majority of commercially available booths, tents, and hoods are fitted with HEPA filters; additional HEPA filtration
is not needed with these devices. If a device does not incorporate a HEPA filter, the air from the device should be
exhausted directly to the outside and away from air-intake vents, persons, and animals, in accordance with applicable federal, state,
and local regulations on environmental discharges.
General Ventilation
General ventilation is used to 1) dilute and remove contaminated air, 2) control the direction of airflow in a
health-care setting, and 3) control airflow patterns in rooms.
Dilution and Removal of Contaminated Air
General ventilation maintains air quality by both air dilution and removal of airborne contaminants.
Uncontaminated supply air mixes with contaminated room air (dilution), and air is subsequently removed from the room by the exhaust
system (removal). These processes reduce the concentration of droplet nuclei in the room air.
Ventilation systems for air dilution and removal.
Two types of general ventilation systems are used to dilute and
remove contaminated air: single-pass air systems and recirculating air systems.
In a single-pass air system, the supply air is either outside air that has been heated or cooled or air that is
uncontaminated from a central system that supplies multiple areas. After air passes through the room or area, 100% of the air is
exhausted to the outside. A single-pass system is the preferred choice for an AII room because the system prevents contaminated air
from being recirculated to other areas of the health-care setting. In a recirculating air system, a limited portion of the exhaust air
is discharged directly to the outside and replaced
with fresh outside air, which mixes with the portion of exhaust air that was
not discharged. If the resulting air mixture is not treated, it can contain a substantial proportion of contaminated air when it
is recirculated to areas serviced by the system. This air mixture can be recirculated into the general ventilation, and
infectious particles can be carried from contaminated areas to uncontaminated areas. Alternatively, the air mixture could be
recirculated in a specific room or area so that other areas are not affected. The use of air-cleaning technologies for removing or
inactivating infectious particles in recirculated air systems has been discussed (Appendix A).
Delivery of general ventilation. General ventilation is delivered by either constant air volume (CAV) systems or
VAV systems. In general, CAV systems are best for AII rooms and other negative-pressure rooms because the
negative-pressure differential is easier to maintain. VAV systems are acceptable if provisions are made to maintain the minimum mechanical
and outside ACH and a negative pressure
>0.01 inch of water gauge compared with adjacent areas at all times.
Ventilation rates. Recommended ventilation rates (air change rates) for health-care settings are usually expressed
in numbers of ACH, which is the ratio of the volume of air entering the room per hour to the room volume. ACH equals
the exhaust airflow (Q cubic feet per minute [cfm]) divided by the room volume
(V
cubic feet) multiplied by 60.
ACH = (Q ÷ V
) x 60
Ventilation recommendations for selected areas in new or renovated health-care settings have been presented (Table 2). These recommendations have been adapted from those published by AIA
(118). The feasibility of achieving a
specific ventilation rate depends on the construction and operational requirements of the ventilation system and might differ
for retrofitted and newly constructed facilities. The expense and effort of achieving a high ventilation rate might be reasonable
for new construction but less reasonable when retrofitting an existing setting.
In existing settings, air-cleaning technologies (e.g., fixed or portable room-air recirculation units [also called portable
air cleaners] or UVGI) can be used to increase the equivalent ACH. This equivalent ventilation concept has been used to
compare microbial inactivation by UVGI with
particle-removal by mechanical ventilation
(384,385) and to compare particle removal by HEPA filtration of recirculated air with particle removal by mechanical ventilation. The equivalent ventilation
approach does not, however, negate the requirement to provide sufficient fresh outside air for occupant comfort (see
Supplement, Environmental Controls; Table 2).
To dilute the concentration of normal room-air contaminants and minimize odors, a portion of the supply air should
come from the outdoors (see Supplement, Environmental Controls, Table 2). Healthcare settings should consult the
American Society of Heating, Refrigerating, and
Air-Conditioning Engineers, Inc. (ASHRAE), Standard 62.1, Ventilation for
Acceptable Indoor Air Quality, for outside air recommendations in areas not listed in this report
(386).
Control of Airflow Direction in a Health-Care Setting
Airflow direction is controlled in health-care settings to contain contaminated air and prevent its spread to
uncontaminated areas.
Directional airflow. The general ventilation system should be designed and balanced so that air flows from
less contaminated (more clean) to more contaminated (less clean) areas
(118,117). For example, air should flow from
corridors (cleaner areas) into AII rooms (less clean areas) to prevent the spread of contaminants. In certain rooms in which surgical
and invasive procedures are performed and in protective environment (PE) rooms, the direction of airflow should be from
the room to the hallway. Environmental control recommendations for situations involving the care and treatment of patients
with TB disease in ORs and PE rooms have been presented (see Other Selected Settings). Cough-inducing or
aerosol-generating procedures should not be performed on patients with suspected or confirmed TB disease in rooms where air
flows from the room to the hallway.
Negative pressure for achieving directional airflow.
The direction of airflow is controlled by creating a lower
(negative) pressure in the area into which the flow of air is desired. Negative pressure is the approximate air-pressure difference
between two areas in a health-care setting. For air to flow from one area to another, the air pressure in the two areas must be
different. Air will flow from a higher pressure area to a lower pressure area. A room that is under negative pressure has a lower
pressure
than adjacent areas, which keeps air flowing from the adjacent rooms or areas into the room. Negative pressure is achieved
by exhausting air at a higher volumetric rate than the rate that the air is being supplied.
Control of Airflow Patterns in Rooms
General ventilation systems should be designed to provide controlled patterns of airflow in rooms and to prevent
air stagnation or short-circuiting of air from the supply to the
exhaust (i.e., passage of air directly from the air supply to
the exhaust). To provide controlled airflow patterns, the air supply and exhaust should be located so that clean air flows first
to parts of the room where HCWs probably work and then across the infectious source and into the exhaust. Therefore,
HCWs are not positioned between the infectious source and the exhaust. This configuration is not always possible but should be
used whenever feasible.
One way to achieve a controlled airflow pattern is to supply air at the side of the room opposite the patient and exhaust
it from the side where the patient is located (see Environmental Controls;
Figure 3). Another method, which is most effective when the supply air is cooler than the room air, is to supply air near the ceiling and exhaust it near the floor (see
Supplements, Environmental Controls; Figure 3). Care must be taken to ensure that furniture or moveable equipment does not block
the low exhausts. Airflow patterns are affected by air temperature differentials, location of the supply diffusers and exhaust
grilles, location of furniture, movement of HCWs and
patients, and the configuration of the space.
If the room ventilation is not designed for a plug-flow type of airflow pattern (Figure 3), then adequate mixing must
be maintained to minimize air stagnation. The majority of rooms with properly installed supply diffusers and exhaust grilles
will have adequate mixing. A qualitative measure of mixing is the visualization of air movement with smoke tubes at
multiple locations in the room. Smoke movement in all areas of the room indicates good mixing. Additional sophisticated studies
can be conducted by using a tracer gas to quantify air-mixing and air-exchange rates.
If areas of air stagnation are present, air mixing can be
improved by adding a circulating fan or repositioning the supply
and exhaust vents. Room-air recirculation units positioned in the room or installed above the ceiling can also improve air
mixing. If supply or exhaust vents circulating fans or room-air recirculation units are placed incorrectly, HCWs might not
be adequately protected.
Achieving Negative Pressure in Rooms
Negative pressure is needed to control the direction of airflow between selected rooms in a health-care setting and
their adjacent spaces to prevent contaminated air from escaping from the room into other areas
(118) (Figure 4). Control of a room's differential airflow and total leakage area is critical to achieving and maintaining negative pressure. Differential
airflow, differential pressure, and leakage area are interrelated. This relation is illustrated (Figure 4) and is expressed in an
empirical equation (387).
AE = 0.01138 * (DQ
1.170/DP0.602)
In the equation, AE is the leakage area in square inches; DQ is the differential airflow rate in cfm; and DP is the
differential pressure drop in inches of water gauge. This empirical equation was used (Figure 4), which indicates that changing
one parameter will influence one or both of the other parameters. For example, the control of differential pressure can
frequently be improved by increasing the air tightness or seal of a room, HVAC system, and ensuring continuous monitoring. In a
room that is already substantially tight (e.g., with 10 square inches of leakage), however, a small change in differential pressure
will have a substantial affect on differential airflow. Similarly, a room with a more substantial leakage area (e.g., 300 square
inches of leakage) requires a higher differential airflow rate to achieve a pressure differential of 0.01 inch of water gauge. Reducing
the leakage in a room with 300 square inches of leakage can help achieve a pressure differential of 0.01 inch of water gauge
(Figure 4). If the leakage area is reduced to approximately 40 square inches, a pressure differential of 0.01 inch of water gauge can
be achieved by exhausting approximately 100 cubic feet per minute (cfm) more air from the room than is supplied to the room.
Room leakage can occur through cracks or spaces near doors, windows, ceiling, and utility connections. Steps should
be taken to minimize these leaks. Changes in the performance of the HVAC system will affect the pressure differential in a
room and can potentially cause a negative-pressure room to become positive-pressure. Therefore, each of these parameters
requires close monitoring to ensure that minor changes in the performance of the HVAC system do not adversely affect the
entire system (388,389).
Pressure differential. To achieve negative pressure in a room that has a normally functioning ventilation system,
first measure and balance the supply and exhaust airflows to achieve an exhaust flow higher than the supply flow. Next,
measure
the pressure differential across the closed door. Although the minimum pressure difference needed for airflow into a room
is substantially small (regarding 0.001 inch of water gauge), a pressure differential of
>0.01 inch of water gauge (2.5 Pascals
[Pa]) is recommended. This higher pressure differential is easier to measure and offers a margin of safety for maintaining
negative pressure as the pressure in surrounding areas changes
because of the opening and closing of doors, operation of
elevators, stack effect (rising of warm air, similar to a chimney), ventilation system fluctuations, and other factors. The
higher pressurization value is consistent with the most recent
AIA recommendations for airborne precautions in health-care settings
(118) and is the generally accepted level of negative pressurization for microbiology and biomedical laboratories
(390).
Opening doors and windows can substantially affect the negative pressure in an AII room. Infectioncontrol criteria
requires AII room windows and doors to remain closed,
except when doors must be opened for persons to enter or leave the
room. Keeping certain doors in the corridor outside the AII rooms closed might be necessary to maintain the
negative-pressure differential between an AII room and the corridor. Pressurization cannot be maintained in rooms or spaces that are
not enclosed.
If >0.01 inch of water gauge is not achieved and cannot be achieved by increasing the flow differential (within the limits
of the ventilation system), the room should be inspected for leakage. The total room leakage is based on the previously
measured pressure, and air flow differentials can be estimated (Figure 4). If the room leakage is too substantial (e.g., 300 square
inches), maintaining a negative-pressure differential as high as 0.01 inch of water gauge might be difficult. A lower value is
acceptable if air-pressure monitoring indicates that negative pressure is always maintained (or airflow indicators consistently
demonstrate that air is flowing in the desired
direction). If negative pressure cannot be maintained, the leakage area might need to
be reduced by sealing cracks around windows or replacing porous suspended ceiling panels with gasketed or sealed solid panels.
Because negative pressure in an AII room can be affected by even minimal changes in the operation of the
ventilation system, negative pressure can be difficult to maintain with a VAV ventilation system. To maintain negative pressure, a
VAV supply system should be coupled with a compensating exhaust system that increases when the supply flow rate
increases. Alternatively, the exhaust can be set at a fixed rate that ensures negative pressure throughout the VAV supply cycle. The
VAV minimum flow rate must also be adequate to maintain the recommended minimum mechanical and outdoor ACH
(see Supplement, Environmental Controls; Table 2).
Alternate methods for achieving negative pressure.
An anteroom is not a substitute for negative pressure in an AII
room. However, an anteroom can reduce the escape of droplet nuclei during the opening and closing of the door to an AII room
and can buffer an AII room from pressure fluctuations in the corridor. To function properly, an anteroom must have more
air exhausted from the room than supplied to remove
M. tuberculosis that can enter from the AII room. An anteroom can
also have its own supply diffuser, if needed, to balance the pressure with the corridor. If an anteroom is unventilated or
not properly ventilated, it will function only as a lesser contaminated vestibule between the AII room and the corridor and
might not prevent the escape of droplet nuclei into the corridor. To adjust airflow and pressure differentials, health-care
settings should consult a ventilation engineer who is knowledgeable regarding all applicable regulations, including building fire codes.
If the desired negative pressure cannot be achieved because a room does not have a separate ventilation system or a
system that can provide the proper airflow, steps should be taken to provide a method to discharge air from an AII room.
One method to achieve negative pressure in a room is to add a supplemental exhaust unit. If an AII room has a window or
an outside wall, a small exhaust fan can be used. An engineer should be consulted to evaluate the potential for negative effects
on surrounding areas (e.g., disruption of exhaust airflow in adjoining bathrooms) and to ensure the provision of
the recommended amounts of outdoor air. The exhaust must not be discharged where it can immediately re-enter the building
or pose a hazard to persons outside.
Fixed room-air recirculation systems (i.e., systems that
recirculate the air in an entire AII room) can be designed to
achieve negative pressure by discharging a portion of the air to the outside. Some portable room-air recirculation units are
also designed to discharge air to the outside to achieve negative pressure. These air cleaners must be designed specifically for
this purpose.
Monitoring negative pressure. Negative pressure must be monitored to ensure that air is always flowing from the
corridor (or surrounding area) into the AII room. Negative pressure can be monitored either continuously or periodically.
Monitoring methods include chemical aerosols (e.g., smoke tube), differential pressure-sensing devices (e.g., manometer), and
physical indicators (e.g., flutter strips).
A chemical aerosol resembling smoke can be used to
observe airflow between a room and the surrounding area, or within
a room. Devices called smoke tubes generate the chemical aerosol resembling smoke, which follows the local air
currents wherever it is released. To check the negative pressure in a room, hold a smoke tube approximately 2 inches in front of
the base of the closed door of the AII room or in front of the air transfer grille, if the door has such a feature. Hold the smoke
tube parallel to the door. A small amount of smoke should be generated slowly to ensure that the velocity of smoke emanating
from the tube does not overpower the air velocity (see Supplement, Environmental Controls;
Figure 5). If the room is under negative pressure, the smoke will travel into the room (from higher to lower pressure). If the room is not under
negative pressure, the smoke will be blown outward or stay in front of the door. Room air cleaners in the room should be
operating. Persons using smoke tubes should avoid inhaling the smoke, because direct inhalation of high concentrations of the smoke
can be irritating (391) (Figure 5).
Manometers are used to monitor negative pressure. They provide either periodic (noncontinuous) pressure measurements
or continuous pressure monitoring. A continuous monitoring indicator can simply be a visible or audible warning
signal indicating that air pressure is positive. Both periodic and continuous pressure detectors generate a digital or analog signal
that can be recorded for later verification or used to automatically adjust the room's ventilation control system.
Physical indicators (e.g., flutter strips) are occasionally used to provide a continuous visual sign that a room is
under negative pressure. These simple and inexpensive devices are placed directly in the door and can be useful in identifying
a pressure differential problem.
Pressure-measuring devices should sense the pressure just inside the airflow path into the AII room (e.g., at the base of
the door). Unusual airflow patterns can cause pressure variations. For example, the air can be under negative pressure at
the middle of a door and under positive pressure at the base of the same door. The ideal location of a pressure-measuring
device has been illustrated (Figure 6). If the pressure-sensing ports of the device cannot be located directly across the airflow
path, validating that the negative pressure at the sensing point is and remains the same as the negative pressure across the flow
path might be necessary.
Pressure-sensing devices should incorporate an audible warning with a time delay to indicate an open door. When a door
is open, the negative pressure cannot be maintained, but this situation should not generate an alarm unless the door is left
open. Therefore, the time delay should allow adequate time for persons to enter or leave an AII room without activating the alarm.
The pressure differentials used to achieve low negative pressure (<0.005 inch) require the use of substantially
sensitive mechanical devices, electronic devices, or pressure gauges to ensure accurate measurements. Pressure-measuring
and monitoring devices can give false readings if the calibration has drifted. For example, a sensor might indicate that the
room pressure is slightly negative compared with the corridor, but, because air current momentum effects or "drift" of the
electrical signal, air might actually be flowing out of the AII room through the opening at the base of the door. In one study of 38
AII rooms with electrical or mechanical devices to continuously monitor air pressurization, one half had airflow at the door in
the opposite direction of that indicated by the continuous monitors
(392). The investigators attributed this problem
to instrument limitations and device malfunction. A negative pressure differential of
>0.01 inch of water gauge (compared with the previously recommended 0.001 inch of water gauge) might help to minimize this problem.
Periodic checks are required to maintain the desired negative pressure and the optimal operation of monitoring devices.
- AII rooms should be checked for negative pressure before occupancy.
- When occupied by a patient, an AII room should be checked daily with smoke tubes or other visual checks for
negative pressure.
- If pressure-sensing devices are used in AII rooms occupied by patients with suspected or confirmed TB disease,
negative pressure should be checked daily by using smoke tubes or other visual checks.
- If the AII rooms are not being used for patients who have suspected or confirmed TB disease but potentially could be
used for such patients, the negative pressure should be checked monthly.
- Laboratories should be checked daily for negative pressure.
AII Rooms and Other Negative-Pressure Rooms
AII rooms are used to 1) separate patients who probably have infectious TB from other persons, 2) provide an
environment in which environmental factors are controlled to
reduce the concentration of droplet nuclei, and 3) prevent the escape
of droplet nuclei from such rooms into adjacent areas using directional airflow. Other negative-pressure
rooms
include bronchoscopy suites, sputum induction rooms,
selected examination and treatment rooms, autopsy suites, and
clinical laboratories.
Preventing the escape of droplet nuclei. AII rooms used for TB isolation should be single-patient rooms with
negative pressure, compared with the corridor or other areas connected to the room. Opening doors and windows can
substantially affect the negative pressure in an AII room. Infectioncontrol criteria require AII room windows and doors to remain
closed, except when doors must be opened for persons to enter or leave the room. It might also be necessary to keep certain doors
in the corridor outside the AII rooms closed and also might be necessary to maintain the negative-pressure differential
between an AII room and the corridor. The use of self-closing doors is recommended. The openings in the room (e.g., windows,
and electrical and plumbing entries) should be sealed as much as possible, with the exception of a small gap (1/8--1/2 inch) at
the base of the door to provide a controlled airflow path. Proper use of negative pressure will prevent contaminated air
from escaping the room (393,394).
Reducing the concentration of droplet nuclei. AII rooms in existing health-care settings should have an airflow of
>6 mechanical ACH. Whenever feasible, this airflow rate should be increased to
>12 mechanical ACH by adjusting or
modifying the ventilation system or should be increased to
>12 equivalent ACH by supplementing with air-cleaning technologies
(e.g., fixed or portable room-air recirculation systems or UVGI systems). New construction or renovation of existing
health-care settings should be designed so that AII rooms achieve a total air change rate of
>12 mechanical ACH. These
recommendations are consistent with guidelines by ASHRAE and AIA that recommend
>12 mechanical ACH for AII rooms
(117,118). Ventilation recommendations for other negative-pressure rooms in new or renovated health-care settings have been
presented (see Risk Classification Examples).
To dilute the concentration of normal room air contaminants and minimize odors, a portion of the supply air should
come from the outdoors. A minimum of 2 ACH of outdoor air should be provided to AII rooms and other
negative-pressure rooms (117,118).
Exhaust from AII rooms and other negative-pressure rooms.
Air from AII rooms and other negative-pressure rooms
for patients with suspected or confirmed TB disease should be exhausted directly to the outside and away from air-intake
vents, persons, and animals, in accordance with applicable federal, state, and local regulations on environmental discharges.
Exhaust ducts should be located away from areas (e.g., sidewalks or windows that can be opened). Ventilation system
exhaust discharges and inlets should be designed to prevent the re-entry of exhausted air. Wind blowing over a building creates
a substantially turbulent recirculation zone that can cause exhausted air to re-enter the building. Exhaust flow should
be discharged above this zone. Design guidelines for proper placement of exhaust ducts have been published
(395). If recirculation of air from such rooms into the general ventilation system is unavoidable, the air should be passed through
a HEPA filter before recirculation.
Alternatives to negative-pressure rooms. AII can also be achieved by the use of negative-pressure enclosures (e.g., tents
or booths). These enclosures can provide patient isolation in EDs and medical testing and treatment areas and can
supplement AII in designated negative-pressure rooms.
Other Selected Settings
Operating rooms, autopsy suites, sputum-induction rooms, and aerosolized treatment rooms pose potential hazards
from infectious aerosols generated during procedures on patients with TB disease
(72,90,396--398). Recommended
administrative, environmental, and respiratoryprotection controls for these and other selected settings have been summarized
(Appendix B). Additional or specialized TB infection controls that are applicable to special circumstances and types of health-care
delivery settings have also been described (see Managing Patients Who Have Suspected or Confirmed TB Disease: Considerations
for Special Circumstances and Settings). Ventilation recommendations for these settings in new or renovated health-care
facilities have been included in this report (Table 2). Existing facilities might need to augment the current ventilation system or use
the air-cleaning methods to increase the number of equivalent ACH.
Patients with TB disease who also require a PE room (e.g., severely immunocompromised patients) are special cases.
These patients require protection from common airborne
infectious microorganisms and must be placed in a room that has
HEPA-filtered supply air and is under positive pressure compared with its surroundings
(118). If an anteroom is not available, the
use of other air-cleaning methods should be considered to increase the equivalent ACH. The air-cleaning systems can be placed
in the room and in surrounding areas to minimize contamination of the surroundings. Similar controls can be used in ORs
that
are used for patients with TB disease because these rooms must be maintained under positive pressure, compared with
their surroundings to maintain a sterile field.
Air-Cleaning Methods
HEPA Filtration
HEPA filtration can be used to supplement other recommended ventilation measures by providing a
minimum removal efficiency of 99.97% of particles equal 0.3 µm in diameter. This air-cleaning method is considered an adjunct to
other ventilation measures. Used alone, this method neither provides outside air for occupant comfort nor satisfies
other recommended ventilation measures (e.g., using source control whenever possible and minimizing the spread of
contaminants in a setting through control of airflow patterns and pressure differentials).
HEPA filters have been demonstrated to reduce the concentration of
Aspergillus spores (range in size: 5--6
µm) to below measurable levels
(399--401). Because infective droplet nuclei generated by TB patients are believed to range from
1--5 µm in diameter (300) (comparable in size to Aspergillus spores)
(402), HEPA filters will remove M.
tuberculosis--containing infectious droplet nuclei from contaminated air. HEPA filters can be used to clean air before it is 1) exhausted
to the outside, 2) recirculated to other areas of a health-care setting, or 3) recirculated in an AII room. Because electrostatic
filters can degrade over time with exposure to humid environments and ambient aerosols
(403), their use in systems that
recirculate air back into the general ventilation system from AII rooms and treatment rooms should be avoided. If used, the
filter manufacturer should be consulted regarding the performance of the filter to ensure that it maintains the desired
filtration efficiency over time and with loading.
Use of HEPA filtration when exhausting air to the outside. HEPA filters can be used as an added safety measure to
clean air from AII rooms and local exhaust devices (e.g., booths, tents, and hoods) before exhausting it to the outside. This
added measure is not necessary, however, if the exhaust air cannot re-enter the ventilation system supply and does not pose a risk
to persons and animals where it is exhausted.
Exhaust air frequently is not discharged directly to the outside; instead, the air is directed through heat-recovery
devices (e.g., heat wheels or radiator-like devices). Heat wheels are frequently used to reduce the costs of operating ventilation
systems (404). As the wheel rotates, energy is transferred into or removed from the supply inlet air stream. If a heat wheel is used
with a system, a HEPA filter should also be used. The HEPA filter should be placed upstream from the heat wheel because of
the potential for leakage across the seals separating the inlet and exhaust chambers and the theoretical possibility that
droplet nuclei might be impacted on the wheel by the exhaust air and subsequently stripped off into the supply air.
Recirculation of HEPA-filtered air. Air from AII rooms and other negative-pressure rooms should be exhausted directly
to the outside. In certain instances, however, recirculation of air into the general ventilation system from such rooms
is unavoidable (e.g., settings in which the ventilation system or building configuration causes venting the exhaust to the
outside impossible). In such cases, HEPA filters should be
installed in the exhaust duct exiting the room to
remove infectious organisms from the air before it is returned to the general ventilation system.
Person room-air recirculation can be used in areas in which no general ventilation system exists, where an existing system
is incapable of providing sufficient ACH, or where
air-cleaning (particulate removal) is desired without affecting the fresh
air supply or negative-pressure system. Recirculation of HEPA-filtered air in a room can be achieved by 1) exhausting air from
the room into a duct, passing it through a HEPA filter installed in the duct, and returning it to the room (see
Supplement, Environmental Controls; Figure 7);
2) filtering air through HEPA recirculation systems installed on the wall or ceiling of
the room (see Supplement, Environmental Controls;
Figure 8); or 3) filtering air through portable HEPA recirculation systems.
In this report, the first two approaches are referred to as fixed room-air recirculation systems because the recirculation systems
are not easily movable.
Fixed room-air recirculation systems. The preferred method of recirculating HEPA-filtered air is by using a built-in
system in which air is exhausted from the room into a duct, filtered through a HEPA filter, and returned to the room (see
Supplement Environmental Controls; Figure 7). This technique can add equivalent ACH in areas in which the recommended
minimum ACH is difficult to meet with general ventilation. This equivalent ventilation concept compares particle removal by
HEPA filtration of the recirculated air with particle clearance from exhaust ventilation. Because the air does not have to
be conditioned, airflow rates that are higher than those produced by the general ventilation system can usually be achieved.
An alternative is to install HEPA filtration units on the wall or ceiling (see Supplement, Environmental Controls; Figure 8).
Fixed recirculation systems are preferred to portable (free-standing) units because they can be installed with a higher
degree of reliability. In addition, certain fixed systems have a higher airflow capacity than portable systems, and the potential
for short-circuiting of air is reduced as the distance
between the air intake and exhaust is increased.
Portable room-air recirculation systems.
Portable room-air recirculation units with HEPA filters (also called portable
air cleaners) can be considered when 1) a room has no general ventilation system, 2) the system cannot provide adequate ACH,
or 3) increased effectiveness in airflow is needed. Effectiveness depends on the ability of the portable room-air recirculation
unit to circulate as much of the air in the room as possible through the HEPA filter. Effectiveness can vary
depending on the room's configuration, the furniture and persons in the room, the placement of the HEPA filtration unit compared with the
supply diffusers and exhaust grilles, and the degree of mixing of air within the room.
Portable room-air recirculation units have been demonstrated to be effective in removing bioaerosols and
aerosolized particles from room air
(405--410). Findings indicate that various commercially available units are useful in reducing
the concentration of airborne particles and are therefore helpful in reducing airborne disease transmission. The performance of
14 units was evaluated for volumetric airflow, airborne particle reduction, noise level, and other parameters
(406). The range of volumetric airflow rates is 110 cfm--1,152 cfm, and the equivalent ACH range was an average of 8--22 in a
standard-sized, substantially well-mixed, single-patient room. Recommendations were provided to make subsequent models safer,
more effective, quieter, and easier to use and service. Purchasers should be aware that the majority of manufacturer
specifications indicated flow rates of free-wheeling fans and not the fan under the load of a filter.
Portable HEPA filtration units should be designed to 1) achieve
>12 equivalent ACH, 2) ensure adequate air mixing in
all areas of the rooms, and 3) be compatible with the ventilation system. An estimate of the ability of the unit to circulate the
air in a room can be made by visualizing airflow patterns (estimating room air mixing [see Supplements,
Environmental Controls; and General Ventilation]). If the air movement is adequate in all areas of the room, the unit should be effective.
If portable devices are used, units with high volumetric airflow rates that provide maximum flow through the HEPA
filter are preferred. Placement should be selected to optimize the recirculation of AII room air through the HEPA filter.
Careful consideration must be given to obstacles (e.g., furnishings, medical equipment, and walls) that could disrupt airflow and
to system specifications (e.g., physical dimensions, airflow capacity, locations of air inlet and exhaust, and noise) to
maximize performance of the units, minimize short-circuiting
of air, and reduce the probability that the units will be switched off
by room occupants.
Installing, maintaining, and monitoring HEPA filters.
The performance of HEPA filters depends on proper
installation, testing, and meticulous maintenance
(411), especially if the system recirculates air to other parts of the health-care
setting. Improper design, installation, or maintenance could allow infectious particles to circumvent filtration and escape into
the general ventilation system (117). These failures also could impede proper ventilation performance.
HEPA filters should be installed to prevent leakage between filter segments and between the filter bed and its frame.
A regularly scheduled maintenance program is required to monitor filters for possible leakage and filter loading. A
quantitative filter performance test (e.g., the dioctyl phthalate penetration test
[412,413]) should be performed at the initial
installation and each time the filter is changed. Records should be maintained for all filter changes and testing. A leakage test using
a particle counter or photometer should be performed every 6--12 months for filters in general-use areas and in areas
with systems that will probably be contaminated with
M. tuberculosis (e.g., AII rooms).
A manometer or other pressure-sensing device should be installed in the filter system to provide an accurate and
objective means of determining the need for filter replacement. Pressure-drop characteristics of the filter are supplied by
the manufacturer. Installation of the filter should allow for maintenance that will not contaminate the delivery system or the
area served. For general infectioncontrol purposes, special care should be taken to avoid jarring or dropping the filter
element during or after removal.
The scheduled maintenance program should include procedures for installation, removal, and disposal of filter elements.
HEPA filter maintenance should be performed only by
adequately trained personnel and only while the ventilation system or
room-air recirculation unit is not being operated.
Laboratory studies indicate that re-aerosolization of viable mycobacteria from filter material (HEPA filters and
N95 disposable respirator filter media) is not probable under normal conditions
(414--416). Although these studies indicate
that M. tuberculosis becoming an airborne hazard is not probable after it is removed by a HEPA filter (or other high efficiency
filter material), the risks associated with handling loaded HEPA filters in ventilation systems under field-use conditions have
not
been evaluated. Therefore, persons performing maintenance and replacing filters on any ventilation system that is
probably contaminated with M. tuberculosis should wear a respirator (see Respiratory Protection) in addition to eye protection
and gloves. When feasible, HEPA filters can be disinfected in 10% bleach solution or other appropriate mycobacteriacide
before removal (417). In addition, filter housing and ducts leading to the housing should be labeled clearly with the
words "TBContaminated Air" or other similar warnings. Disposal of filters and other potentially contaminated materials should
be in accordance with applicable local or state regulations.
One or more lower-efficiency disposable pre-filters installed upstream can extend the life of a HEPA filter by at least 25%.
If the disposable filter is replaced by a 90% extended surface filter, the life of the HEPA filter can be extended by
approximately 900% (178). Pre-filters should be handled and disposed of in the same manner as the HEPA filter.
UVGI
UVGI is a form of electromagnetic radiation with wavelengths between the blue region of the visible spectrum and
the radiograph region. UV-C radiation (short wavelengths; range: 100--280 nm)
(418) can be produced by various artificial sources (e.g., arc lamps and metal halide lamps). The majority of commercially available UV lamps used for
germicidal purposes are low-pressure mercury vapor lamps that emit radiant energy in the UV-C range, predominantly at a wavelength
of 253.7 nm (418).
Research has demonstrated that UVGI is effective in killing or inactivating
M. tuberculosis under experimental
conditions (292,385,419--423) and in reducing transmission of other infectious agents in hospitals
(424), military housing (425), and classrooms
(426--428). Because of the results of multiple studies
(384,429--432) and the experiences of clinicians
and mycobacteriologists during the preceding decades, UVGI has been recommended as a supplement or adjunct to other
TB infectioncontrol and ventilation measures in settings in which the need to kill or inactivate
M. tuberculosis is essential
(6,7,196,433,434). UVGI alone does not provide outside air or circulate interior air, both of which are essential in
achieving acceptable air quality in occupied spaces.
Applications of UVGI. UVGI is considered a method of air cleaning because it can kill or inactivate microorganisms
so that they are no longer able to replicate and form colonies. UVGI is not a substitute for HEPA filtration before exhausting
the air from AII rooms back into the general circulation. UVGI lamps can be placed in ducts, fixed or
portable room air-recirculation units, or upper-air irradiation systems. The use of this air-cleaning technique has increased, particularly
in substantial open areas in which unsuspected or undiagnosed patients with TB disease might be present (e.g., ED
waiting rooms, shelters, and correctional facilities), and the costs of conditioning substantial volumes of outdoor air are prohibitive.
For each UVGI system, guidelines should be followed to maximize effectiveness. Effectiveness can be expressed in terms
of an equivalent air change rate
(427,435--437), comparing the ability of UVGI to inactivate organisms with removal
through general ventilation. Initially, understanding and characterizing the application for which UVGI will be used is
vital. Because the effectiveness of UVGI systems will vary, the use of UVGI must be carefully evaluated and the level of efficacy
clearly defined and monitored.
The effective use of UVGI is associated with exposure of
M. tuberculosis, as contained in an infectious droplet, to a
sufficient dose of UV-C at 253.7 nm to ensure inactivation.
Because dose is a function of irradiance and time, the effectiveness of
any application is determined by its ability to deliver sufficient irradiance for enough time to result in inactivation of the
organism within the infectious droplet. Achieving a sufficient dose can be difficult with airborne inactivation because the exposure
time can be substantially limited; therefore, attaining sufficient irradiance is essential.
The number of persons who are properly trained in the
design and installation of UVGI systems is limited. One
critical recommendation is that health-care facility managers consult a UVGI system designer to address safety and
efficacy considerations before such a system is procured and installed. Experts who can be consulted include industrial
hygienists, engineers, and health physicists.
Duct irradiation. Duct irradiation is designed to kill or
inactivate M. tuberculosis without exposing persons to UVGI. In
duct irradiation systems, UVGI lamps are placed inside ducts to disinfect the exhaust air from AII rooms or other areas in which
M. tuberculosis might be present before it is recirculated to the same room (desirable) or to other areas served by the system
(less desirable). When UVGI duct systems are not properly designed, installed, and maintained, high levels of UVGI can be
produced in the duct that can potentially cause high UVGI exposures during maintenance operations.
Duct-irradiation systems depend on the circulation of as much of the room air as possible through the duct.
Velocity profiles and mixing are important factors in determining the UVGI dose received by airborne particles. Design velocity for
a
typical UVGI unit is approximately 400 fpm
(438). The particle residence time must be sufficient for inactivation of
the microorganisms.
Duct irradiation can be used in three ways.
- Ventilation systems serving AII rooms to recirculate air from the room, through a duct containing UV lamps, and back
into the same room. UVGI duct systems should not be used either in place of HEPA filters, if air from AII rooms must
be recirculated to other areas of a setting, or as a substitute for HEPA filtration of air from booths, tents, or hoods used
for cough-inducing or aerosol-generating procedures.
- Return air ducts serving patient rooms, waiting rooms, EDs, and general-use areas in which patients with undiagnosed
TB disease could potentially contaminate the recirculated air.
- Recirculating ventilation systems serving rooms or areas in which ceiling heights are too low for the safe and effective use
of upper-air UVGI.
Upper-air irradiation. In upper-air irradiation, UVGI lamp fixtures are suspended from the ceiling and installed on
walls. The base of the lamps are shielded to direct the radiation upward and outward to create an intense zone of UVGI in the
upper air while minimizing the levels of UVGI in the lower part of the room where the occupants are located. The system
depends on air mixing to move the air from the lower part of the room to the upper part where microbial-contaminated air can
be irradiated.
A major consideration is the placement of UVGI fixtures to achieve sufficient irradiance of the upper-air space. The
ceiling should be high enough (>8 feet) for a substantial volume of upper air to be irradiated without overexposing occupants in
the lower part of the room to UVGI. System designers must consider the mechanical ventilation system, room geometry,
and emission characteristics of the entire fixture.
Upper-air UVGI can be used in various settings.
- AII rooms and rooms in which aerosol-generating or aerosol-producing procedures (e.g., bronchoscopy, sputum
induction, and administration of aerosolized medications) are performed.
- Patient rooms, waiting rooms, EDs, corridors, central
areas, and other substantial areas in which patients with
undiagnosed TB disease could potentially contaminate the air.
- Operating rooms and adjacent corridors where procedures are performed on patients with TB disease.
- Medical settings in correctional facilities.
UVGI-containing--portable room air
cleaners. In portable room air-recirculation units containing UVGI, a fan moves
a volume of room air across UVGI lamps to disinfect the air before it is recirculated back to the room. Some
portable units contain both a HEPA filter (or other high efficiency filter) and UVGI lamps.
In addition to the guidelines described for the use of
portable room air-recirculation systems containing HEPA
filtration, consideration must be given to the volume of room air that passes through the unit, the UVGI levels, particle residence
time, and filtration efficiency (for devices with a filter). One study in which a bioaerosol chamber was used demonstrated
that portable room air cleaners with UVGI lamps as the primary air-cleaning mechanism are effective (>99%) in inactivating
or killing airborne vegetative bacteria
(439). Additional studies need to be performed in rooms with
portable air cleaners that rely only on UVGI for air cleaning.
Portable room air cleaners with UVGI can be used in 1) AII rooms as an adjunct method of air cleaning and 2)
waiting rooms, EDs, corridors, central areas, or other substantial
areas in which patients with undiagnosed TB disease
could potentially contaminate the air.
Effectiveness of UVGI. Air mixing, air velocity, relative humidity, UVGI intensity, and lamp configuration affect
the efficacy of all UVGI applications. For example, with upper-air systems, airborne microorganisms in the lower, occupied
areas of the room must move to the upper part of the room to be killed or inactivated by upper-air UVGI. Air mixing can
occur through convection caused by temperature differences, fans, location of supply and exhaust ducts, or movement of persons.
Air-mixing. UVGI has been demonstrated to be effective in killing bacteria in the upper-air applications under
conditions in which air mixing was accomplished primarily by convection. In a 1976 study on aerosolization of
M. bovis. BCG (a surrogate for M.
tuberculosis) in a room without mechanical ventilation that relied primarily on convection and
infiltration resulted in 10--25 equivalent ACH, depending on the number of UVGI fixtures used
(384). Other early studies examined the effect of air-mixing on UVGI efficacy
(440,441). These studies indicated that the efficacy of UVGI was substantially
increased if cold supply air relative to the lower portion of the room entered through diffusers in the ceiling. The findings indicated
that
substantial temperature gradients between the upper and lower portions of the room favored (cold air in the upper portion
of the room) or inhibited (hot air in the upper portion of the room) vertical mixing of air between the two zones.
When large-bladed ceiling fans were used to promote mixing in the experimental room, the ability of UVGI to
inactivate Serratia marcescens, an organism known to be highly sensitive to UVGI, was doubled
(442,443). Similar effects were reported in studies conducted during 2000--2002 in which louvered UVGI fixtures were used. One study documented an increase in
UVGI effectiveness of 16% at 2 ACH and 33% at 6 ACH when a mixing fan was used
(444). Another study conducted in a
simulated health-care room determined that 1) at 0 ACH, a high degree of efficacy of upper-air UVGI was achieved in the absence
or presence of mixing fans when no temperature gradient was created; and 2) at 6 ACH, bringing in warm air at the ceiling
resulted in a temperature gradient with cooler room air near the floor and a UVGI efficacy of only 9%
(422). Turning on box fans under these winter conditions increased UVGI efficacy nearly 10-fold (to 89%)
(445).
To reduce variability in upper-air UVGI efficacy caused by temperature gradients in the room, a fan should be
routinely used to continually mix the air, unless the room has been
determined to be well mixed under various conditions of
operation. Use of a fan would also reduce or remove the variable winter versus summer ACH requirements for optimal upper-air
UVGI efficacy (446).
Relative humidity. In studies conducted in bioaerosol chambers, the ability of UVGI to kill or inactivate
microorganisms declined substantially when the relative humidity exceeded 60%
(447--450). In room studies, declines in the ability of
upper-air UVGI to kill or inactivate microorganisms at high relative humidity (65%, 75%, and 100%)
(384,422) have also been reported. The exact mechanism responsible for the
reduced effectiveness of UVGI at these higher levels of relative humidity
is unknown but does not appear to be related to changes in UV irradiance levels. Relative humidity changes from
55%--90% resulted in no corresponding changes in measured UVGI levels
(437). In another study, an increase in relative humidity
from 25%--67% did not reduce UVGI levels
(422). Bacteria have been demonstrated to absorb substantial amounts of water
from the air as the relative humidity increases. At high humidity, the UV irradiance levels required to inactivate bacteria
might approach the higher levels that are needed for liquid suspensions of bacteria
(448). The ability of bacteria to repair
UVGI damage to their DNA through photoreactivation has also been reported to increase as relative humidity increases
(422,448).
For optimal efficacy of upper-air UVGI, relative humidity should be maintained at
<60%, a level that is consistent with recommendations for providing
acceptable indoor air quality and minimizing environmental microbial contamination
in indoor environments (386,451).
Ventilation rates. The relation between ventilation and UVGI has also been evaluated. Certain predicted inactivation
rates have been calculated and published for varying flow rates, UV intensity, and distances from the lamp, based on radiative
heat transfer theory (438). In room studies with substantially well-mixed air, ventilation rates (0 ACH, 3 ACH, and 6 ACH)
were combined with various irradiation levels of
upper-air UVGI. All experiments were conducted at 50% relative humidity
and 70º F (21.2° C). When M.
parafortuitum is used as a surrogate for M.
tuberculosis, ventilation rates usually had no
adverse effect on the efficiency of upper-air UVGI. The combined effect of both environmental controls was primarily additive in
this artificial environment, with possibly a small loss of upper-air UVGI efficiency at 6 ACH
(422). Therefore, ventilation rates of up to 6 ACH in a substantially well-mixed room might achieve
>12 ACH (mechanical ACH plus equivalent ACH)
by combining these rates with the appropriate level of upper-air irradiation
(422). Higher ventilation rates (>6 ACH)
might, however, decrease the time the air is irradiated and, therefore, decrease the killing of bacteria
(429,452).
Ventilation rates up to six mechanical ACH do not appear to adversely affect the performance of upper-air UVGI in
a substantially well-mixed room. Additional studies are needed to examine the combined effects of mechanical ventilation
and UVGI at higher room-air exchange rates.
UVGI intensity. UVGI intensity field plays a primary role in the performance of upper-air UVGI systems. The UVGI
dose received by microorganisms is a function of UVGI times duration of exposure. Intensity is influenced by the lamp
wattage, distance from the lamp, surface area, and presence of
reflective surfaces. The number of lamps, location, and UVGI
level needed in a room depends on the room's geometry, area, and volume, and the location of supply air diffusers
(422,436). UVGI fixtures should be spaced to reduce overlap while maintaining an even irradiance zone in the upper air.
The emission profile of a fixture is a vital determinant of UVGI effectiveness. Information regarding total UVGI output
for a given fixture (lamp plus housing and louvers) should be requested from the manufacturer and used for comparison
when selecting UVGI systems. Information concerning only the UVGI output of the lamp is inadequate; the lamp output will
be higher than the output for the fixture because of losses from reflectors and nonreflecting surfaces and the presence of
louvers
and other obstructions (436,437). In addition, information provided by the manufacturer reflects ideal laboratory
conditions; damage to fixtures or improper installation will affect UV output. Because old or dust-covered UVGI lamps are less
effective, routine maintenance and cleaning of UVGI lamps and fixtures is essential. UVGI system designers should consider
room geometry, fixture output, room ventilation, and the desired level of equivalent ACH in determining the types, numbers,
and placement of UVGI fixtures in a room to achieve target irradiance levels in the upper air.
Health and safety issues. Short-term overexposure to UV radiation can cause erythema (i.e., abnormal redness of the
skin), photokeratitis (inflammation of the cornea), and conjunctivitis (i.e., inflammation of the conjunctiva)
(453). Symptoms of photokeratitis and conjunctivitis include a feeling of sand in the eyes, tearing, and sensitivity to light. Photokeratitis
and conjunctivitis are reversible conditions, but they can be debilitating while they run their course. Because the health effects
of UVGI are usually not evident until after exposure has ended (typically 6--12 hours later), HCWs might not recognize them
as occupational injuries.
In 1992, UV-C (100--280 nm) radiation was classified by the International Agency for Research on Cancer as
"probably carcinogenic to humans (Group 2A)"
(454). This classification was based on studies indicating that UV-C radiation
can induce skin cancers in animals and create DNA damage, chromosomal aberrations, and sister chromatid exchange
and transformation in human cells in vitro. In addition, DNA damage in mammalian skin cells in vivo can be caused. In
the animal studies, a contribution of UV-C radiation to the
tumor effects could not be excluded, but the effects were higher
than expected for UV-B radiation alone (454). Certain studies have demonstrated that UV radiation can activate HIV
gene promoters (i.e., genes in HIV that prompt replication of the virus) in laboratory samples of human cells
(455--460). The potential for UV-C radiation to cause cancer and promote HIV in humans is unknown, but skin penetration might be
an important factor. According to certain reports, only 20% of incident 250 nm UV penetrates the stratum corneum,
compared with approximately 30--60% of 300 nm UV (UV-B) radiation
(461).
In upper-air UVGI systems, fixtures must be designed and installed to ensure that UVGI exposures to occupants
are below current safe exposure levels. Healthhazard evaluations have identified potential problems at some settings using
UVGI systems. These problems include overexposure of HCWs to UVGI and inadequate maintenance, training,
labeling, and use of personal protective equipment (PPE)
(398,462,463).
An improperly maintained (unshielded) germicidal lamp was believed to be the cause of dermatosis or photokeratitis in
five HCWs in an ED (464) and three HCWs who were inadvertently exposed to an unshielded UVGI lamp in a room that
had been converted from a sputum induction room to an office
(465). These case reports highlight the importance of
posting warning signs to identify the presence of UVGI (see Supplement, Labeling and Posting) and are reminders that
shielding should be used to minimize UVGI exposures to
occupants in the lower room. In the majority of applications,
properly designed, installed, and maintained UVGI fixtures provide protection from the majority of, if not all, the direct UVGI in
the lower room. However, radiation reflected from glass, polished metal, and high-gloss ceramic paints can be harmful to
persons in the room, particularly if more than one UVGI fixture is in use. Surfaces in irradiated rooms that can reflect UVGI
into occupied areas of the room should be covered with non-UV--reflecting material.
Although more studies need to be conducted, lightweight clothing made of tightly woven fabric and
UV-absorbing sunscreens with solar-protection factors (SPFs) of
>15 might help protect photosensitive persons. Plastic eyewear containing
a UV inhibitor that prevents the transmission of
>95% of UV radiation in the 210--405 nm range is commercially
available. HCWs should be advised that any eye or skin irritation that develops after UVGI exposure should be evaluated by
an occupational health professional.
Exposure criteria. In 1972, CDC published a recommended exposure limit (REL) for occupational exposure to
UV radiation (453). REL is intended to protect HCWs from the acute effects of UV light exposure. Photosensitive persons
and those exposed concomitantly to photoactive chemicals might not be protected by the recommended standard.
The CDC/NIOSH REL for UV radiation is wavelength dependent because different wavelengths have
different adverse effects on the skin and eyes
(453). At 254 nm, the predominant wavelength for germicidal UV lamps, the
CDC/NIOSH REL is 0.006 joules per square centimeter (J/cm2) for a daily 8-hour work shift. ACGIH has a Threshold
Limit Value® for UV radiation that is identical to the REL for this spectral region
(466). HCWs frequently do not stay in one
place in the setting during the course of their work and, therefore, are not exposed to UV irradiance levels for 8 hours.
Permissible exposure times (PET) for HCWs with unprotected eyes and skin can be calculated for various irradiance levels as follows:
PET (seconds) = 0.006 J/cm2 (the CDC/NIOSH REL at 254 nm)
Measured irradiance level (at 254 nm) in
W/cm2
Exposures exceeding the CDC/NIOSH REL require the use of PPE to protect the skin and eyes.
Labeling, Maintenance, and Monitoring
Labeling and posting. Healthcare settings should post warning signs on UV lamps and wherever high-intensity
(i.e., UVGI exposure greater than the REL) UVGI irradiation is present to alert maintenance staff, HCWs, and the general
public of the hazard. The warning signs should be written in the languages of the affected persons
(Box 6).
Maintenance. Because the UVGI output of the lamps
decline with age, a schedule for replacing the lamps should
be developed in accordance with manufacturer recommendations. The schedule can be determined from a time-use log, a
system based on cumulative time, or routinely (e.g., at least
annually). UVGI lamps should be checked monthly for dust
build-up, which lessens radiation output. A dirty UVGI lamp should be allowed to cool and then should be cleaned in
accordance with the manufacturer recommendations so that no residue remains.
UVGI lamps should be replaced if they stop glowing, if they flicker, or if the measured irradiance (see
Supplement, Environmental Controls) drops below the performance criteria or minimum design criterion set forth by the design
engineers. Maintenance personnel must switch off all UVGI lamps before entering the upper part of the room or before accessing
ducts for any purpose. Only limited seconds of direct exposure to the intense UVGI in the upper-air space or in ducts can
cause dermatosis or photokeratitis. Protective clothing and equipment (e.g., gloves, goggles, face shield, and sunscreen) should
be worn if exposure greater than the recommended levels is possible or if UVGI radiation levels are unknown.
Banks of UVGI lamps can be installed in ventilation system ducts. Safety devices and lock-out or tag-out protocols
should be used on access doors to eliminate exposures of maintenance personnel. For duct irradiation systems, the access door
for servicing the lamps should have an inspection window through which the lamps are checked periodically for dust
build-up and to ensure that they are functioning properly. The access door should have a warning sign written in appropriate
languages to alert maintenance personnel to the health hazard of looking directly at bare UV lamps. The lock for this door should
have an automatic electric switch or other device that turns off the lamps when the door is opened.
Types of fixtures used in upper-air irradiation include wall-mounted, corner-mounted, and ceiling-mounted fixtures
that have louvers or baffles to block downward radiation and ceiling-mounted fixtures that have baffles to block
radiation below the horizontal plane of the fixtures. If possible, light switches that can be locked should be used to prevent injury
to persons who might unintentionally turn the lamps on during maintenance procedures. Because lamps must be discarded
after use, consideration should be given to selecting germicidal lamps that are manufactured with relatively low amounts (i.e.,
<5 mg) of mercury. UVGI products should be listed with the Underwriters Laboratories (UL) or Electrical Testing
Laboratories (ETL) for their specific application and installed in accordance with the National Electric Code.
Monitoring. UVGI intensity should be measured by an industrial hygienist or other person knowledgeable in the use of
UV radiometers with a detector designed to be most sensitive at 254 nm. Equipment used to measure UVGI should
be maintained and calibrated on a regular schedule, as recommended by the manufacturer.
UVGI should be measured in the lower room to ensure that exposures to occupants are below levels that could result
in acute skin and eye effects. The monitoring should consider typical duties and locations of the HCWs and should be done
at eye level. At a minimum, UVGI levels should be measured at the time of initial installation and whenever fixtures are
moved or other changes are made to the system that could affect UVGI. Changes to the room include those that might result
in higher exposures to occupants (e.g., addition of UV-reflecting materials or painting of walls and ceiling). UVGI
monitoring information, lamp maintenance, meter calibration, and lamp and fixture change-outs should be recorded.
UVGI measurements should also be made in the upper air to define the area that is being irradiated and determine if
target irradiance levels are met (467). Measurements can be made using UVGI radiometers or other techniques (e.g.,
spherical actinometry), which measures the UVGI in an omnidirectional manner to estimate the energy to which
microorganisms would be exposed (468). Because high levels of UVGI can be measured in the upper air, persons making the
measurements should use adequate skin and eye protection. UVGI radiation levels close to the fixture source can have permissible
exposure times on the order of seconds or minutes for HCWs with unprotected eyes and skin. Therefore, overexposures can occur
with brief UVGI exposures in the upper air (or in ventilation system ducts where banks of unshielded UV lamps are placed)
in HCWs who are not adequately protected.
Upper-air UVGI systems and portable room-air recirculation units.
A study in 2002 examined the relation between three
portable room-air recirculation units with different capture or inactivation mechanisms and an upper-air UVGI
system
in a simulated health-care room (409). The study determined that the equivalent ACH produced by the recirculation
units and produced by the upper-air UVGI system were approximately additive. For example, one test using aerosolized
M. parafortuitum provided an equivalent ACH for UVGI of 17 and an equivalent ACH for the recirculation unit of 11; the
total experimentally measured equivalent ACH for the two systems was 27. Therefore, the use of
portable room-air recirculation units in conjunction with upper-air UVGI systems might increase the overall removal of
M. tuberculosis droplet nuclei from room air.
Environmental Controls: Program Concerns
To be most effective, environmental controls must be
installed, operated, and maintained correctly. Ongoing maintenance
is a critical part of infection control that should be addressed in the written TB infectioncontrol plan. The plan should
outline the responsibility and authority for maintenance and address staff training needs. At one hospital,
improperly functioning ventilation controls were believed to be an important factor in the transmission of MDR TB disease to three patients and
a correctional officer, three of whom died
(469). In three other multihospital studies evaluating the performance of AII
rooms, failure to routinely monitor air-pressure differentials or a failure of the continuous monitoring devices installed in the
AII rooms resulted in a substantial percentage of the rooms being under positive pressure
(57,392,470,471).
Routine preventive maintenance should be scheduled and should include all components of the ventilation systems
(e.g., fans, filters, ducts, supply diffusers, and exhaust grilles) and any air-cleaning devices in use. Performance monitoring should
be conducted to verify that environmental controls are operating as designed. Performance monitoring can include 1)
directional airflow assessments using smoke tubes and use of pressure monitoring devices that are sensitive to pressures as low
as approximately 0.005 inch of water gauge and 2) measurement of supply and exhaust airflows to compare with
recommended air change rates for the respective areas of the setting. Records should be kept to document all preventive maintenance
and repairs.
Standard procedures should be established to ensure that maintenance staff notifies infectioncontrol personnel
before performing maintenance on ventilation systems servicing
patient-care areas. Similarly, infectioncontrol staff
should request assistance from maintenance personnel in checking the operational status of AII rooms and local exhaust devices
(e.g., booths, hoods, and tents) before use. A protocol that is well-written and followed will help to prevent unnecessary
exposures of HCWs and patients to infectious aerosols. Proper labeling of ventilation system components (e.g., ducts, fans, and
filters) will help identify air-flow paths. Clearly labeling which fan services a given area will help to prevent accidental
shutdowns (472).
In addition, provisions should be made for emergency power to avoid interruptions in the performance of
essential environmental controls during a power failure.
Respiratory Protection
Considerations for Selection of Respirators
The overall effectiveness of respiratory protection is affected by 1) the level of respiratory protection selected (e.g.,
the assigned protection factor), 2) the fit characteristics of the respirator model, 3) the care in donning the respirator, and 4)
the adequacy of the fit-testing program. Although data on the effectiveness of respiratory protection from various
hazardous airborne materials have been collected, the precise level of
effectiveness in protecting HCWs from M. tuberculosis
transmission in health-care settings has not been determined.
Information on the transmission parameters of
M. tuberculosis is also incomplete. Neither the smallest infectious dose of
M. tuberculosis nor the highest level of exposure to
M. tuberculosis at which transmission will not occur has been
defined conclusively (159,473,474). In addition, the size distribution of droplet nuclei and the number of particles
containing viable M. tuberculosis organisms that are expelled by patients with infectious TB disease have not been adequately defined,
and accurate methods of measuring the concentration of
infectious droplet nuclei in a room have not been
developed. Nonetheless, in certain settings (e.g., AII rooms and ambulances during the transport of persons with suspected or
confirmed infectious TB disease), administrative and environmental controls alone might not adequately protect HCWs from
infectious airborne droplet nuclei.
On October 17, 1997, OSHA published a proposed standard for occupational exposure to
M. tuberculosis (267). On December 31, 2003, OSHA announced the termination of rulemaking for a TB standard
(268). Previous OSHA policy permitted the use of any Part 84 particulate filter respirator for protection against infection with
M. tuberculosis (269). Respirator usage for TB had been regulated by OSHA under CFR Title 29, Part 1910.139 (29 CFR 1910.139)
(270) and compliance policy directive (CPL) 2.106 (Enforcement Procedures and Scheduling for Occupational Exposure
to Tuberculosis). Respirator usage for TB is now regulated under the general industry standard for respiratory protection
(29 CFR 1910.134) (271). General information on respiratory protection for aerosols, including
M. tuberculosis, has been published
(272--274).
Performance Criteria for Respirators
Performance criteria for respirators are derived from data on 1) effectiveness of respiratory protection against
noninfectious hazardous materials in workplaces other than health-care settings and an interpretation of how these data can be applied
to respiratory protection against M.
tuberculosis, 2) efficiency of respirator filters in filtering biologic aerosols, 3) face-seal
leakage, and 4) characteristics of respirators used in conjunction with administrative and environmental controls in outbreak settings
to stop transmission of M. tuberculosis to HCWs and patients.
Particulate filter respirators certified by CDC/NIOSH,
either nonpowered respirators with N95, N99, N100, R95,
R99, R100, P95, P99, and P100 filters (including disposable respirators), or PAPRs with high efficiency filters can be used
for protection against airborne M.
tuberculosis.
The most essential attribute of a respirator is the ability to fit the different facial sizes and characteristics of HCWs.
Studies have demonstrated that fitting characteristics vary substantially among respirator models. The fit of filtering
facepiece respirators varies because of different facial types and respirator characteristics
(10,280--289). Selection of respirators can
be done through consultation with respirator fit-testing
experts, CDC, occupational health and infectioncontrol
professional organizations, peer-reviewed research, respirator manufacturers, and from advanced respirator training courses. Data
have determined that fit characteristics cannot be determined solely by physical appearance of the respirator
(282).
Types of Respiratory Protection for TB
Respirators encompass a range of devices that vary in complexity from flexible masks covering only the nose and mouth,
to units that cover the user's head (e.g., loose-fitting or hooded PAPRs), and to those that have independent air supplies
(e.g., airline respirators). Respirators must be selected from those approved by CDC/NIOSH under the provisions of 42 CFR,
Part 84 (475).
Nonpowered air-purifying respirators. Nine classes of nonpowered, air-purifying, particulate-filter respirators are
certified under 42 CFR 84. These include N-, R-, and
P-series respirators of 95%, 99%, and 100% (99.7%) filtration efficiency
when challenged with 0.3 µm particles (filters are generally least efficient at this size) (see Supplement, Respiratory Protection;
Table 4). The N, R, and P classifications are based on the capacity of the filter to withstand exposure to oil. All of these
respirators meet or exceed CDC's filtration efficiency performance criteria during the service life of the filter
(1,272,273).
Nonpowered air-purifying respirators work by drawing ambient air through the filter during inhalation. Inhalation
causes negative pressure to develop in the tight-fitting facepiece and allows air to enter while the particles are captured on the
filter. Air leaves the facepiece during exhalation because positive pressure develops in the facepiece and forces air out of the
mask through the filter (disposable) or through an exhalation valve (replaceable and certain ones are disposable).
The classes of certified nonpowered air-purifying respirators include both filtering facepiece (disposable) respirators
and elastomeric (rubber-like) respirators with filter cartridges. The certification test for filtering facepieces and filter
cartridges consists only of a filter performance test. It does not address respirator fit. Although all N-, R-, and P-series respirators
are recommended for protection against M. tuberculosis
infection in health-care settings and other workplaces that are usually
free of oil aerosols that could degrade filter efficiency, well-fitting N-series respirators are usually less expensive than R- and
P-series respirators (272,273). All respirators should be replaced as needed, based on hygiene considerations, increased
breathing resistance, time-use limitations specified in the CDC/NIOSH approval guidelines, and respirator damage, in accordance
with manufacturer specifications.
PAPRs. PAPR uses a blower that draws air through the filters into the facepiece. PAPRs can be equipped with a
tight-fitting or loose-fitting facepiece, a helmet, or a hood. PAPR filters are classified as high efficiency and are different from
those presented in this report (Table 4). A hooded PAPR high efficiency filter meets the N100, R100, and P100 criteria at
the
beginning of their service life. No loading tests using 0.3
µm particles are conducted as part of certification. PAPRs can
be useful for persons with facial hair or other conditions that prevent an adequate face to facepiece seal
(476).
Atmosphere-supplying respirators. Positive-pressure airline (supplied-air) respirators are provided with air from
a stationary source (compressor) or an air tank.
Effectiveness of Respiratory-Protection Devices
Data on the effectiveness of respiratory protection against hazardous airborne materials are based on experience in
the industrial setting; data on protection against transmission of
M. tuberculosis in health-care settings are not available.
The parameters used to determine the effectiveness of a respiratory protective device are face-seal efficacy and filter efficiency.
Face-seal leakage. Face-seal leakage is the weak link that limits a respirator's protective ability. Excessive face-seal
leakage compromises the ability of particulate respirators to protect HCWs from airborne materials
(477). A proper seal between the respirator's sealing surface and the face of the person wearing the res-pirator is essential for the effective and
reliable performance of any tight-fitting, negative-pressure respirator.
For tight-fitting, negative-pressure respirators (e.g., N95 disposable respirators), the amount of face-seal leakage
is determined by 1) the fit characteristics of the respirator, 2) the care in donning the respirator, and 3) the adequacy of the
fit-testing program. Studies indicate that a well-fitting respirator and a fit test produces better results than a well-fitting
respirator without a fit test or a poor-fitting respirator with a fit test. Increased face-seal leakage can result from additional
factors, including incorrect facepiece size, failure to follow the manufacturer's instructions at each use, beard growth, perspiration
or facial oils that can cause facepiece slippage, improper maintenance, physiological changes of the HCW, and respirator damage.
Face-seal leakage is inherent in tight-fitting
negative-pressure respirators. Each time a person wearing a
nonpowered particulate respirator inhales, negative pressure (relative to the workplace air) is created inside the facepiece. Because of
this negative pressure, air containing contaminants can leak into the respirator through openings at the face-seal interface
and avoid the higher-resistance filter material. A half-facepiece respirator, including an N95 disposable respirator, should
have <10% leakage. Full facepiece, nonpowered respirators have the same leakage (<2%) as PAPRs with tight-fitting full-facepieces.
The more complex PAPRs and positive-pressure airline respirators reduce or eliminate this negative facepiece pressure
and, therefore, reduce leakage into the respirator and enhance protection. A PAPR is equipped with a blower that forcibly
draws ambient air through high efficiency filters and then delivers the filtered air to the facepiece. This air is blown into the facepiece
at flow rates that generally exceed the expected inhalation flow rates. The pressure inside the facepiece reduces face-seal leakage
to low levels, particularly during the relatively low inhalation rates expected in health-care settings. PAPRs with a
tight-fitting facepiece have <2% face-seal leakage under routine conditions
(278). PAPRs with loose-fitting facepieces, hoods,
or helmets have <4% inward leakage under routine conditions
(278). Therefore, a PAPR might offer lower levels of face-seal
leakage than nonpowered, half-mask respirators.
Filter penetration. Aerosol penetration through respirator filters depends on at least five independent variables: 1)
filtration characteristics for each type of filter, 2) size distribution of the droplets in the aerosol, 3) linear velocity through the
filtering material, 4) filter loading (i.e., amount of contaminant deposited on the filter), and 5) electrostatic charges on the filter and
on the droplets in the aerosol (284).
When N95 disposable respirators are used, filter penetration might approach 5% (50% of the allowable leakage of 10%
for an N95 disposable respirator). When high efficiency filters are used in PAPRs or for half-facepiece respirators, filter
efficiency is high (effectively 100%), and filter penetration is less of a consideration. Therefore, for high efficiency or
100-series filter respirators, the majority of inward leakage of droplet nuclei occurs at the respirator's faceseal or exhalation valve.
Implementing a Respiratory-Protection Program
If respirators are used in a health-care setting, OSHA
requires the development, implementation, administration,
and periodic reevaluation of a respiratoryprotection program
(271,277,278). The most critical elements of a
respiratory protection program include 1) assigning of responsibility, 2) training, and 3) fit testing
(1). All HCWs who use respirators for protection against infection with
M. tuberculosis should be included in the respiratoryprotection program.
Visitors to AII rooms and other areas with patients who have suspected or confirmed infectious TB disease may be
offered respirators (e.g., N95 disposable respirators) and should be instructed by an HCW on the use of the respirator before
entering an AII room (see Respiratory Protection section for User-Seal Check FAQs). The health-care setting should
develop a policy on use of respirators by visitors.
The number of HCWs included in the respiratory protection program will vary depending on the 1) number of
persons who have suspected or confirmed TB disease examined in a setting, 2) number of rooms or areas in which patients
with suspected or confirmed infectious TB disease stay or are encountered, and 3) number of HCWs needed to staff these rooms
or areas. In settings in which respiratoryprotection programs are required, enough HCWs should be included to
provide adequate care for patients with suspected or confirmed TB disease. However, administrative measures should be used to
limit the number of HCWs exposed to M. tuberculosis
(see Prompt Triage).
Information on the development and management of a respiratoryprotection program is available in technical
training courses that cover the basics of respiratory protection. Such courses are offered by OSHA, the American
Industrial Hygiene Association, universities, manufacturers, and private contractors. To be effective and reliable,
respiratoryprotection programs must include at least the following elements
(274,277,278).
Assignment of Responsibility
One person (the program administrator) must be in charge of the respiratoryprotection program and be given
the authority and responsibility to manage all aspects of the program. The administrator must have sufficient
knowledge (obtained by training or experience) to develop and implement a respiratoryprotection program. Preferably, the
administrator should have a background in industrial hygiene, safety, health care, or engineering. The administrator should report to
the highest official possible (e.g., manager of the safety
department, supervisor of nurses, HCWs' health manager,
or infectioncontrol manager) and should be allocated sufficient time to administer the respiratoryprotection program
in addition to other assigned duties.
Standard Operating Procedures
The effectiveness of a respiratoryprotection program
requires the development of written standard procedures.
These procedures should include information and guidance for the proper selection, use, and care of respirators
(274).
Screening
HCWs should not be assigned a task requiring use of respirators unless they are physically able to perform job duties
while wearing the respirator. HCWs who might need to use a respirator should be screened by a physician or other licensed
health-care professional for pertinent medical conditions at the time they are hired and then re-screened periodically
(274). The screening process should begin with a screening questionnaire for pertinent medical conditions, the results of which should
be used to identify HCWs who need further evaluation (see Supplement, Respiratory Protection;
Appendix G). Unless
prescribed by the screening physician, serial physical examination or testing with chest radiographs or spirometry is neither necessary
nor required (287).
Training
HCWs should be provided annual training on multiple topics.
- Nature, extent, and hazards of TB disease in the health-care setting. This training can be conducted in conjunction
with other related training on infectious disease associated with airborne transmission (e.g., severe acute respiratory
syndrome [SARS]-coronavirus [CoV] and measles) and with serial TB screening.
- The risk assessment process and its relation to the respirator program.
- Signs and symbols used to demonstrate that respirators are required in an area.
- Reasons for using respirators.
- Environmental controls used to prevent the spread and reduce the concentration of infectious droplet nuclei.
- Reasons for selecting a particular respirator for a given hazard (see Selection of Respirators; and Respirator Options:
Special Circumstances).
- Operation, capabilities, and limitations of respirators.
- Respirator care (see Baseline Testing for M. tuberculosis
Infection After TST Within the Previous 12 Months).
- Cautions regarding facial hair and respirator use.
- Applicable federal, state, and local regulations regarding respirators, including assessment of employees' knowledge.
Trainees should be provided resources as an adjunct to the respiratoryprotection program.
- Opportunities to handle and wear a respirator until they are proficient (see Supplement, Fit Testing).
- Educational material for use as references.
- Instructions to refer all respirator problems immediately to the respirator program administrator.
Selection
Filtering facepiece respirators used for protection against
M. tuberculosis must be selected from those approved by
CDC/NIOSH under the provisions of 42 CFR 84 (http://www.cdc.gov/niosh/celintro.html). A listing of
CDC/NIOSH-approved disposable particulate respirators (filtering facepieces) is available at
http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part. If a health-care setting uses respirators for protection against other regulated hazards (e.g., formaldehyde
and ethylene oxide), then these potential exposures should be specifically addressed in the program. Combination product
surgical mask/N95 disposable respirators (respirator portion certified by CDC/NIOSH and surgical mask portion listed by FDA)
are available that provide both respiratory protection and bloodborne pathogen protection. Selection of respirators can be
chosen through consultation with respirator fit-testing experts, CDC, occupational health and infection-control
professional organizations, peer-reviewed research, respirator manufacturers, and advanced respirator training courses
(10,280--289).
Fit Testing
A fit test is used to determine which respirator fits the user adequately and to ensure that the user knows when the
respirator fits properly. After a risk assessment is conducted to validate the need for respiratory protection, perform fit testing during
the initial respiratoryprotection program training and periodically thereafter, in accordance with federal, state, and
local regulations.
Fit testing provides a method to determine which respirator model and size fits the wearer best and to confirm that
the wearer can properly fit the respirator. Periodic fit testing for respirators used in environments where a risk for
M. tuberculosis transmission exists can serve as an effective training tool in conjunction with the content included in employee training
and retraining. The frequency of periodic fit testing should be supplemented by the occurrence of 1) a risk for transmission of
M. tuberculosis, 2) a change in facial features of the wearer, 3) a medical condition that would affect respiratory function,
4) physical characteristics of respirator (despite the same model number), or 5) a change in the model or size of the
assigned respirator (281).
Inspection and Maintenance
Respirator maintenance should be an integral part of an overall respirator program. Maintenance applies both to
respirators with replaceable filters and to respirators that are classified as disposable but are reused. Manufacturer instructions
for inspecting, cleaning, maintaining, and using (or reuse) respirators should be followed to ensure that the respirator continues
to function properly (278).
When respirators are used for protection against noninfectious aerosols (e.g., wood dust) that might be present in the air
in heavy concentrations, the filter can become obstructed with airborne material. This obstruction in the filter material can
result in increased resistance, causing breathing to be
uncomfortable. In health-care settings in which respirators are used
for protection against biologic aerosols, the concentration of infectious particles in the air is probably low. Thus, the filter in
a respirator is unlikely to become obstructed with airborne material. In addition, no evidence exists to indicate that particles
that affect the filter material in a respirator are reaerosolized easily. Therefore, the filter material used in respirators in
health-care settings might remain functional for weeks. Because electrostatic filter media can degrade, the manufacturer should
be contacted for the product's established service life to confirm filter performance.
Respirators with replaceable filters are reusable, and a respirator classified as disposable can be reused by the same HCW
as long as it remains functional and is used in accordance with local infectioncontrol procedures. Respirators with
replaceable filters and filtering facepiece respirators can be reused by HCWs as long as they have been inspected before each use and
are within the specified service life of the manufacturer. If the filter material is physically damaged or soiled or if
the manufacturer's service life criterion has been exceeded, the filter (in respirators with replaceable filters) should be changed
or the disposable respirator should be discarded according to local regulations. Infectioncontrol personnel should
develop standard procedures for storing, reusing, and disposing of respirators that have been designated for disposal.
Evaluation
The respirator program must be evaluated periodically to ensure its continued effectiveness.
Cleaning, Disinfecting, and Sterilizing Patient-Care Equipment and Rooms
General
Medical instruments and equipment, including medical waste, used on patients who have TB disease are usually
not involved in the transmission of M. tuberculosis
(478--480). However, transmission of
M. tuberculosis and pseudo-outbreaks (e.g., contamination of clinical specimens) have been linked to inadequately disinfected bronchoscopes contaminated with
M. tuberculosis
(80,81,160,163,164,166). Guidelines for cleaning, disinfecting, and sterilizing flexible endoscopic
instruments have been published (481--485).
The rationale for cleaning, disinfecting, or sterilizing
patient-care instruments and equipment can be understood
more readily if medical devices, equipment, and surgical materials are divided into three general categories
(486). The categories are critical, semicritical, and noncritical and are based on the potential risk for infection if an item remains contaminated at
the time of use.
Critical Medical Instruments
Instruments that are introduced directly into the bloodstream or other normally sterile areas of the body (e.g.,
needles, surgical instruments, cardiac catheters, and implants) are critical medical instruments. These items should be sterile at the
time of use.
Semicritical Medical Instruments
Instruments that might come into contact with mucous membranes but do not ordinarily penetrate body surfaces
(e.g., noninvasive flexible and rigid fiberoptic endoscopes or bronchoscopes, endotracheal tubes, and anesthesia breathing
circuits) are semicritical medical instruments. Although sterilization is preferred for these instruments, high-level disinfection
that destroys vegetative microorganisms, the majority of fungal spores, mycobacteria (including tubercle bacilli), and
small nonlipid viruses can be used. Meticulous cleaning of such items before sterilization or high-level disinfection is
essential (481). When an automated washer is used to clean endoscopes and bronchoscopes, the washer must be compatible with
the instruments to be cleaned (481,487). High-level disinfection can be accomplished with either manual procedures alone or
use of an automated endoscope reprocessor with manual cleaning
(80,481). In all cases, manual cleaning is an essential
first-step in the process to remove debris from the instrument.
Noncritical Medical Instruments or Devices
Instruments or devices that either do not ordinarily touch the patient or touch only the patient's intact skin (e.g.,
crutches, bed boards, and blood pressure cuffs) are noncritical medical instruments. These items are not associated with transmission
of M. tuberculosis. When noncritical instruments or equipment are contaminated with blood or body substances, they should
be cleaned and then disinfected with a hospital-grade, Environmental Protection Agency (EPA)-registered germicide
disinfectant with a label claim for tuberculocidal activity (i.e., an intermediate-level disinfectant). Tuberculocidal activity is not
necessary for cleaning agents or low-level disinfectants that are used to clean or disinfect minimally soiled noncritical items
and environmental surfaces (e.g., floors, walls, tabletops, and surfaces with minimal hand contact).
Disinfection
The rationale for use of a disinfectant with tuberculocidal activity is to ensure that other potential pathogens with
less intrinsic resistance than that of mycobacteria are killed. A common misconception in the use of surface disinfectants in
health care relates to the underlying purpose of products labeled as tuberculocidal germicides. Such products will not interrupt
and prevent transmission of M. tuberculosis
in health-care settings, because TB is not acquired from environmental surfaces.
The tuberculocidal claim is used as a benchmark by which to measure germicidal potency. Because mycobacteria have the
highest intrinsic level of resistance among the vegetative bacteria, viruses, and fungi, any germicide with a tuberculocidal claim on
the label (i.e., an intermediate-level disinfectant) is considered capable of inactivating many pathogens, including much
less resistant organisms such as the bloodborne pathogens (e.g., hepatitis B virus, hepatitis C
virus, and HIV). Rather than the product's specific potency against mycobacteria, a germicide that can activate many pathogens is the basis for protocols
and regulations indicating the appropriateness of tuberculocidal chemicals for surface disinfection.
Policies of health-care settings should specify whether cleaning, disinfecting, or sterilizing an item is necessary to decrease
the risk for infection. Decisions regarding decontamination processes should be based on the intended use of the item, not on
the
diagnosis of the condition of the patient for whom the item is used. Selection of chemical disinfectants depends on
the intended use, the level of disinfection required, and the structure and material of the item to be disinfected.
The same cleaning procedures used in other rooms in the health-care setting should be used to clean AII rooms.
However, personnel should follow airborne precautions while cleaning these rooms when they are still in use. Personal
protective equipment is not necessary during the final cleaning of an AII room after a patient has been discharged if the room has
been ventilated for the appropriate amount of time (see Supplement, Environmental Controls; Table 2).
Frequently Asked Questions (FAQs)
The following are FAQs regarding TST, QFTG, BAMT, treatment for LTBI, risk assessment, environmental
controls, respiratory protection, and cough-inducing and
aerosol-generating procedures.
TST and QFT-G
- Does having more than one TST placed in 1 year pose any risk?
No risk exists for having TSTs placed multiple times
per year.
- Can repeated TSTs, by themselves, cause the TST
result to convert from negative to positive? No, the TST itself
does not cause false-positive results. Exposure to other mycobacteria or BCG vaccination can cause false-positive TST results.
- What defines a negative TST result? A TST result of 0 mm or a measurement below the defined cut point for each
criteria category is considered a negative TST result (Box 2).
- What defines a positive TST result? A TST result of any millimeter reading above or at the defined cut point for each
criteria category is considered a positive TST result (Box 2). The cut point (5 mm, 10 mm, and 15 mm) varies according to
the purpose of the test (e.g., infectioncontrol surveillance or medical and diagnostic evaluation, or contact investigation
versus baseline testing).
- What defines a false-negative result? A false-negative TST or QFTG result is one that is interpreted as negative for
a particular purpose (i.e., infectioncontrol surveillance versus medical and diagnostic evaluation) in a person who
is actually infected with M. tuberculosis. False-negative TST results might be caused by incorrect TST placement (too
deeply or too shallow), incorrect reading of the TST result, use of an incorrect antigen, or if the person being tested is
anergic (i.e., unable to respond to the TST because of an immunocompromising condition) or sick with TB disease.
- What defines a false-positive result? A false-positive TST or QFTG result is one that is interpreted as positive for
a particular purpose (i.e., infectioncontrol surveillance versus medical and diagnostic evaluation) in a person who
is actually not infected with M.
tuberculosis. False-positive TST results are more likely to occur in persons who have
been vaccinated with BCG or who are infected with NTM, also known as mycobacteria other than TB (MOTT). A
false-positive TST result might also be caused by incorrect reading of the TST result (reading erythema rather than
induration) or use of incorrect antigen (e.g., tetanus toxoid).
- Is placing a TST on a nursing mother safe? Yes, placing a TST on a nursing mother is safe.
- A pregnant HCW in a setting is reluctant to get a TST. Should she be encouraged to have the test administered?
Yes, placing a TST on a pregnant woman is safe. The HCW should be encouraged to have a TST or
offered BAMT. The HCW should receive education that 1) pregnancy is not contraindication to having a TST
administered and 2) skin testing does not affecting the fetus or the mother. Tens of thousands of pregnant women have received TST since the
test was developed, and no documented episodes of TST-related fetal harm have been reported. Guidelines issued by
ACOG emphasize that postponement of the application of a TST as indicated and postponement of the diagnosis of
infection with M. tuberculosis during pregnancy is unacceptable.
- A pregnant HCW in a setting has a positive TST result and is reluctant to get a chest radiograph. Should she
be encouraged to have the chest radiograph performed?
Pregnant women with positive TST results or who are suspected
of having TB disease should not be exempted from recommended medical evaluations and radiography. Shielding
consistent with safety guidelines should be used even during the first trimester of pregnancy.
- Are periodic chest radiographs recommended for HCWs (or staff or residents of LTCFs) who have positive TST
or BAMT results? No, persons with positive TST or BAMT results should receive one baseline chest radiograph to exclude
a diagnosis of TB disease. Further chest radiographs are not needed unless the patient has symptoms or signs of TB
disease or unless ordered by a physician for a specific diagnostic examination. Instead of participating in serial skin
testing, HCWs with positive TST results should receive a medical evaluation and a symptom screen. The frequency of
this medical evaluation should be determined by the risk assessment for the setting. HCWs who have a previously
positive TST result and who change jobs should carry documentation of the TST result and the results of the baseline
chest radiograph (and documentation of treatment history for LTBI or TB disease, if applicable) to their new employers.
- What is boosting? Boosting is a phenomenon in which a person has a negative TST (i.e., false-negative) result years
after infection with M. tuberculosis and then a positive subsequent TST result. The positive TST result is caused by a
boosted immune response of previous sensitivity rather than by a new infection (false-positive TST conversion). Two-step
testing reduces the likelihood of mistaking a boosted reaction for a new infection.
- What procedure should be followed for a newly hired HCW who had a documented negative TST result 3
months ago at their previous job? This person should receive one baseline TST upon hire (ideally before the HCW
begins assigned duties). The negative TST result from the 3 months preceding new employment (or a documented negative
TST result anytime within the previous 12 months) should be considered the first step of the baseline two-step TST. If
the HCW does not have documentation of any TST result, the HCW should be tested with baseline two-step TST (one
TST upon hire and one TST placed 1--3 weeks after the first TST result was read).
- Why are two-step TSTs important for the baseline (the beginning of an HCW's employment)?
If TST is used for TB screening (rather than BAMT), performing two-step TST at baseline minimizes the possibility that boosting will lead
to suspicion of transmission of M. tuberculosis
in the setting during a later contact investigation or during serial testing
(false-positive TST conversions). HCWs who do not have documentation of a positive TST result or who have not
been previously treated for LTBI or TB disease should receive baseline two-step TST.
- If a person does not return for a TST reading within 48--72 hours, when can a TST be placed on them again?
A TST can be administered again as soon as possible. If the second step of a two-step TST is not read within
48--72 hours, administer a third test as soon as possible (even if multiple months have elapsed), and ensure that the result is read
within 48--72 hours.
- Should a TST reading of >10 mm be accepted 7 days after the TST was placed?
If the TST was not read between 48--72 hours, another TST should be placed as soon as possible and read within 48--72 hours. However, certain studies
indicate that positive TST reactions might still be measurable 4--7 days after the TST was placed. If the TST reaction is read
as >15 mm 7 days after placement, the millimeter result can be recorded and considered to be a positive result.
- Do health-care settings or areas in the United States exist for which baseline two-step skin TST for newly
hired HCWs is not needed? Ideally, all newly hired HCWs who might share air space with patients should receive
baseline two-step TST (or one-step BAMT) before starting duties. In certain settings, a choice might be offered not to
perform baseline TST on HCWs who will never be in contact with or share air space with
patients who have TB disease, or who will never be in contact with clinical specimens (e.g., telephone operators in a separate building from patients).
- In our setting, workers are hired to provide health care in homes, and they are not medically trained. Two-step
skin testing is difficult because of the requirement to return for testing and reading multiple times. Can the
two-step TST be omitted? No, ideally, all HCWs who do not have a previously documented positive TST result or treated LTBI
or TB disease should receive two-step baseline skin testing in settings that have elected to use TST for screening. BAMT is
a single test procedure. Baseline testing for M. tuberculosis
infection will ensure that TB disease or LTBI is detected
before employment begins and treatment for LTBI or TB disease is offered, if indicated.
- When performing two-step skin testing, what should be done if the second-step TST is not placed in 1--3
weeks? Perform the second-step TST as soon as possible, even if several months have passed.
- Should gloves be worn when placing TST? Specific CDC recommendations do not exist regarding this topic. If your
local area indicates that universal precautions should be practiced with skin testing, the local areas should determine
what precautions should be followed in their setting.
- Is TST QC important? Yes, performing QC for HCWs during training and retraining of placing and reading TST
is important to avoid false-negative and false-positive TST results, and to ensure appropriate treatment decisions.
- If the longitudinal reading of the induration of the TST result is 12 mm and the horizontal reading is 8 mm,
what should be recorded? The correct TST reading should be recorded as 8 mm (not 12 mm or 8 x 12 mm). For purposes
of standardization, only record the millimeters of induration, which should be measured transversely (i.e., perpendicular),
to the long axis of the forearm. Erythema (redness) around the TST site should not be read as part of the TST
result. Consideration should be given to retesting if the selected area for placement was on or near a muscle margin, scar,
heavy hair, veins, or tattoos, which could be barriers to reading the TST
result, or consider offering a BAMT. BAMT results should be recorded in detail. The details should include date of blood draw, result in specific units, and the
laboratory interpretation (positive, negative, or indeterminate---and the concentration of cytokine measured, e.g.,
IFN-g).
- Should HCWs who report upon hire that they have had a positive TST result or have been previously treated
for LTBI or TB disease receive baseline two-step TST when beginning work at a new health-care setting?
Unless the HCW has documentation of a positive TST result or previously treated LTBI or TB disease, they should usually
receive baseline two-step testing before starting duties. If documentation is available of a positive TST result, that result can
be considered as the baseline TST result for the HCW at the new setting, and additional testing is not
needed. Recommendations for testing HCWs who transfer from one setting to another where the risk assessment might
be different are presented (see Use of Risk Classification to Determine Need for TB Screening and Frequency of
Screening HCWs).
- If an HCW has a baseline first-step TST result
between 0--9 mm, does a second-step TST need to be placed?
Yes, if the baseline first-step TST result is <10 mm, a second-step TST should be applied 1--3 weeks
after the first TST result was read. HCWs who are immunocompromised are still subject to the 10 mm cutoff for baseline two-step testing
for surveillance purposes but would be referred for medical evaluation for LTBI using the 5 mm cutoff.
- An HCW in a medium-risk setting who had a two-step baseline TST result of 8 mm is retested 1 year later for
serial TB screening and had a TST result of 16 mm. No known exposure to
M. tuberculosis had occurred. Although the TST is now >10 mm, a
>10 mm increase did not occur in the TST result to meet the criteria for a TST
conversion. How should this reading be interpreted?
The TST result needs to be interpreted from two perspectives:
1) administrative and 2) individual medical interpretation. Because an increase by
>10 mm did not occur, the result would not be classified as a TST conversion for administrative purposes. However, this HCW should be referred for a
medical evaluation. The following criteria are used to determine whether a TST result is positive or negative,
considering individual clinical grounds: 1) absolute measured induration (i.e.,
>5, >10, or >15 mm induration, depending on the
level of risk and purpose of testing); 2) the change in the size of the TST result; 3) time frame of the change; 4) risk
for exposure, if any; and 5) occurrence of other documented TST conversions in the setting. For HCWs at low risk for
LTBI, TST results of 10--14 mm can be considered negative from a clinical standpoint, and these HCWs should not have
repeat TST, because an additional increase in induration of
>10 mm will not be useful in determining the likelihood of LTBI.
- Are baseline two-step TST needed for HCWs who begin
jobs that involve limited contact with patients (e.g.,
medical records staff)? Yes, all HCWs who might share air space with patients should receive baseline two-step TST (or
one-time BAMT) before starting duties. However, in certain settings, a choice might be offered not to perform baseline TST
on HCWs who will never be in contact with or share air space with patients who have TB disease, or who will never be
in contact with clinical specimens (e.g., telephone operators in a separate building from patients).
- A setting conducts skin testing annually on the anniversary of each HCW's employment. Last year, multiple
TST conversions occurred in April; therefore, all HCWs received a TST during that month. In the
future, do all HCWs need to be tested annually in April?
No, after a contact investigation is performed, the best and preferred schedule
for annual TB screening is on the anniversary of the HCW's employment date or on their birthday (rather than testing
all HCWs at the same time each year), because it increases the opportunity for early recognition of
infectioncontrol problems that can lead to TST conversions.
- An HCW who has been vaccinated with BCG is being hired. She states that BCG will make her TST result
positive and that she should not have a TST. Should this HCW be exempted from baseline two-step TST?
Unless she has documentation of a positive TST result or previously treated LTBI or TB disease, she should receive baseline
two-step TST or one BAMT. Some persons who received BCG never have a positive TST result. For others, the positive
reaction wanes after 5 years. U.S. guidelines state that a positive TST result in a person who
received BCG should be interpreted as indicating LTBI.
- Does BCG affect TST results and interpretations? BCG is the most commonly used vaccine in the world. BCG
might cause a positive TST (i.e., false-positive) result initially; however, tuberculin reactivity caused by BCG
vaccination typically wanes after 5 years but can be boosted by subsequent TST. No reliable skin test method has been developed
to distinguish tuberculin reactions caused by vaccination with BCG from reactions caused by natural
mycobacterial infections, although TST reactions of >20 mm of induration are not usually caused by BCG.
- What steps should be taken when an HCW has had a recent BCG vaccination?
When should the TST be placed? A TST may be placed anytime after a BCG vaccination, but a positive TST result after a recent BCG vaccination can be
a false-positive result. QFTG should be used, because the assay test avoids cross reactivity with BCG.
- A hospital HCW has not had a TST in 18 months because she was on maternity leave and missed her annual
TST. She has been employed at the hospital for the previous 5 years. Is two-step testing necessary on her next skin
test date? No, two-step TSTs are needed only to establish a baseline for a specific setting for newly hired HCWs and
others who will receive serial TST (e.g., residents or staff of correctional facilities or LTCFs). The HCW should have a
single TST or BAMT upon returning to work and should then resume a routine testing schedule on the next normal
TST anniversary date.
- Should two-step testing be performed in a contact investigation for HCWs who have not had a TST within
the preceding 12 months? No, two-step testing should only be used for baseline TST screening and has no role in a
contact investigation. In a contact investigation, a follow-up TST should be placed 8--10 weeks after an initial negative TST
result is read.
- What length of time should a person who has had contact with someone with TB disease be included in a
contact investigation? This decision can best be made in consultation with the local TB program, which frequently has
experience responding to similar situations. A minimum exposure time has not been established, but the minimum length of
contact time with a person who has TB disease necessary for transmission will depend on multiple factors. Begin by estimating
the duration of the infectious period (see Supplement, Contact Investigations; and CDC self-training modules
[http://www.phppo.cdc.gov/phtn/tbmodules/modules6-9/m6/6-12.htm]). The highest priority for evaluation should be given
to 1) persons with a medical risk factor for TB disease (e.g., HIV infection or immunosuppressive therapy); 2) infants
and children <4 years; 3) household or congregate setting contacts; and 4) persons present during medical procedures
(e.g., bronchoscopies, sputum induction, or autopsies). In addition, offer TB screening to all persons named by the patient
as work or social contacts during the infectious period. Determining whether to broaden the investigation will depend
on whether evidence of transmission to any of the above contacts exists (positive TST or BAMT results or conversions),
the duration of the potential exposure, and the intensity of the exposure (e.g., in a poorly ventilated environment
versus outdoors). If the exposure was to pulmonary TB that was cavitary on chest radiograph or if the patient had positive
AFB sputum smear results, usually the minimum exposure duration for a person to be considered a contact would be
shorter. Nonetheless, infection with M. tuberculosis
requires some degree of prolonged or regular exposure (i.e., days to weeks,
not just a few hours).
- If an HCW in a setting has a latex allergy, should this person receive a TST?
A person with a latex allergy can receive a TST when latex-free products are used. Latex allergy can be a contraindication to skin testing if the
allergy is severe and the products used to perform the test (e.g., syringe plungers, PPD antigen bottle stopper, and gloves) contain latex.
Latex-free products are, however, usually available. If a person with a latex allergy does have a TST performed using products
or equipment that contain latex, interpretation of the TST results can be difficult, because the TST reaction might be
the result of the latex allergy, reaction to PPD, or a combination of both. Consider repeating the TST using
latex-free products or use BAMT.
- Should the TST site be covered with an adhesive bandage?
No, avoid covering the TST site with anything that might
interfere with reading the TST result (e.g., adhesive bandages, cream, ointment, lotion, liquids, and medication).
- When can a TST be placed if other vaccines are also being administered (e.g., measles, varicella, yellow
fever, and smallpox)? A TST should be administered
either on the same day as vaccination with live virus or
4--6 weeks later. Vaccines that might cause a
false-negative TST result are measles, varicella, yellow fever, smallpox, BCG, mumps,
rubella, oral polio, oral typhoid, and live-attenuated influenza.
- How frequently should persons in the general public receive TST?
Testing for LTBI in the general public is not
necessary unless the person is at risk for exposure to
M. tuberculosis (e.g., someone who had contact with a person with TB
disease) or at increased risk for progression to TB disease [e.g., someone infected with HIV]).
- Should we use a multiple puncture
(Tine®) skin test to perform a TST?
No, in the United States, the Mantoux method of skin testing is the preferred method
because it is more accurate than
Tine® skin tests. BAMT (currently QFTG) is
also now recommended as a test for M. tuberculosis
infection.
- What steps should be taken if an HCW has a baseline TST result of 16 mm and 1 year later the TST result was read as
0 mm? If documentation existed for the 16 mm result, administering another TST to the HCW subsequently was
not necessary. One or both of these TST results could be false results. The first result might have been documented as 16
mm, but perhaps 16 mm of erythema was measured and no induration was present. The second result of 0 mm might have
been caused by incorrect administration of the TST (i.e., too deeply or too
shallow), or was read and recorded incorrectly if it
was actually positive). In this instance, another TST should be placed, or a BAMT should be offered, or if TB disease is
suspected, a chest radiograph should be performed.
- What steps should be taken if the TST is administered intramuscularly instead of intradermally?
QC for administering TST is critical. If the TST is administered intramuscularly (too deeply), repeat the skin test immediately,
or offer BAMT.
- How are annual TST conversion rates for HCWs calculated?
A TST conversion is a change in the result of a test for
M. tuberculosis infection wherein the condition is interpreted as having progressed from uninfected to
infected. Annual TST conversion rates are calculated for a given year by dividing the number of test conversions among HCWs in the
setting that year (numerator) by the total number of HCWs who received tests in the setting that year (denominator)
multiplied by 100. By calculating annual TST conversion rates, yearto-year comparisons can be used to identify transmission of
M. tuberculosis that was not previously detected.
- Where can PPD be obtained? Local and state health departments can provide PPD antigen for TST without charge
to selected targeted testing and treatment programs. Purchase of the antigen and supplies is regulated by local and state
laws related to professional licensure.
- Where can millimeter rulers be obtained to measure TST results?
A TST training kit, which includes a TST training video, guide for facilitators, and a TST millimeter ruler is available free of charge from CDC
(https://www2.cdc.gov/nchstp_od/PIWeb/TBorderform.asp). In addition, check with your local or state health department and TST
antigen manufacturers.
- Where can materials be obtained for educating HCWs regarding TB?
A list of TB websites and resources is available (Appendix E). Local or state health departments should have additional materials and access to resources and might
be able to help develop a setting-specific TB education program.
- Where can self-reading TST cards be obtained that allow HCWs to report their own results? HCWs and patients should not be allowed to read and report their own TST results; therefore, self-reading cards for reporting TST results
are not recommended. All TST results should be read and recorded by a trained TST reader other than the person on
whom the TST was placed.
Treatment for LTBI
- Who should be treated for LTBI? Persons with LTBI who are at increased risk for developing TB disease should be
offered treatment for LTBI regardless of age, if they have no contraindication to the medicine.
- What are contraindications to treatment of LTBI?
Active hepatitis and ESLD are contraindications to the use of INH
for treatment of LTBI. Persons who have these conditions might be eligible for rifampin for 4 months for treatment of
LTBI. Because of the substantial and complex drug-drug interactions between rifamycins and HIV protease inhibitors (PI)
and nonnucleoside reverse transcriptase inhibitors (NNRTI), clinicians are encouraged to seek expert advice if the
concurrent use of these drugs is being considered in persons infected with HIV. Information regarding use of these drugs is
available at http://www.cdc.gov/nchstp/tb/tb_hiv_drugs/toc.htm.
- Do persons need to be in a specific age range to be eligible for treatment of LTBI?
No age restriction for eligibility of treatment for LTBI currently exists. Targeted TST programs should be conducted for persons at high risk, and
these programs are discouraged for persons or settings considered to be low risk. However, for infectioncontrol programs
that conduct TB screening that includes HCWs who are frequently at low risk, proper medical evaluation needs to
be conducted when an HCW with a positive TST result is identified. In this context, age might be a factor in the decision
to administer treatment, because older persons are at increased risk for
hepatic toxicity caused by INH.
- What is the preferred regimen for treatment of LTBI?
Nine months of daily INH is the preferred treatment regimen
for patients who have LTBI. The 6-month regimen of INH or the 4-month regimen of rifampin are
also acceptable alternatives.
- Why is the 2-month regimen of RZ generally not offered for treatment of LTBI?
Although the 2-month regimen of RZ was previously recommended as an option for the treatment of LTBI, reports of severe liver injury and death
prompted the American Thoracic Society and CDC to revise recommendations to indicate that this regimen should generally not
be offered for treatment of LTBI.
- Can sputum specimens collected over a 2-day period that are reported as negative for AFB be used to
exclude a diagnosis of TB disease? Yes, airborne precautions can be discontinued when infectious TB disease is considered
unlikely and either 1) another diagnosis is made that explains the clinical syndrome or 2) the patient has three negative
AFB sputum smear results (109--112). Each of the three consecutive sputum specimens should be collected 8--24 hours
apart (124), and at least one specimen should be an early morning specimen, because respiratory secretions pool
overnight. Generally, this method will allow patients with negative sputum smear results to be released from airborne precautions
in 2 days.
- When does an infectious TB patient become noninfectious?
Historically, health-care professionals have believed
that the effect of antituberculosis treatment to reduce infectiousness was virtually immediate; older texts state that patients
on antituberculosis treatment are not infectious. Surrogates that are used for noninfectiousness include conversion of
positive sputum AFB results to negative AFB results and clinical response to antituberculosis treatment (i.e., improvement
of symptoms and chest radiograph result).
Risk Assessment
- In certain health-care settings (e.g., outpatient clinics or emergency medical settings) where patients are
evaluated before a hospitalization during which TB disease is diagnosed, determining the number of TB patients who
were encountered can be difficult. How should the risk classification be assigned?
These situations underscore the importance of obtaining an accurate patient history, completing contact investigations for all persons with suspected
or confirmed TB disease, and ensuring effective communication to all settings in which persons with TB disease
are encountered before diagnosis. Collaboration between infectioncontrol personnel at the setting and the
TBcontrol program staff at the local health department can help with this estimation.
- At a pediatric hospital, the parents are normally with the child at the time of the TB diagnosis, and the parents
can be diagnosed with TB disease at the same time as the child. To determine the number of patients diagnosed at
the health-care setting, should the parents with TB disease who are visiting also be included in the total TB
patient count? Only patients with TB disease who were evaluated or treated in the health-care setting count, not visitors who
have TB (unless they were diagnosed at the same setting).
- In a 160-bed hospital, three HCWs have had TST conversions during a 2-month period, which is usually the number
of TST conversions detected in the hospital in 1 year. Should the setting be classified as potential ongoing
transmission? If the HCWs with TST conversions can be linked together in some way, either through a job type, location of work, or
DNA fingerprinting, then the classification of potential ongoing transmission might
apply to one group of HCWs or one part of the setting. Evidence of ongoing transmission in this setting appears to exist, and a problem evaluation should be
conducted to ascertain the reason for the TST conversions (see Problem Evaluation). Reasons could range from an undiagnosed case
of TB in the setting to incorrect placement or reading of TST. Early consultation with the local health department and
an expert in TB infection control might be helpful in identifying and resolving the problem.
- If a health-care setting has a risk classification of
potential ongoing transmission, how long should that
classification be applied? The classification of potential ongoing transmission should be assigned only on a temporary basis and
always warrants a problem evaluation (see Problem Evaluation). After resolution of problems, settings with a classification
of potential ongoing transmission should be reclassified as a medium-risk classification for at least 1 year.
Environmental Controls
- What is the difference between environmental controls and engineering controls ?
"Environmental controls" is a more inclusive term than "engineering controls". Examples of environmental controls are UVGI, HEPA filters and AII
rooms. Examples of engineering controls are local exhaust ventilation (e.g., booths, hoods, and tents) and general
ventilation (including directional airflow and negative pressure).
- Is an AII room the same as a negative-pressure isolation room?
"AII room" is an accepted term and is used in the
AIA guidelines that describe the purpose for and details
of ventilation of AII rooms. An AII room is a special
negative-pressure room for the specific purpose of isolating persons who might have suspected or confirmed infectious TB disease
from other parts of the setting. Not all negative-pressure rooms are AII rooms, because they might not have the required
air flow or differential pressure of an AII room.
- Our TB clinic only treats persons with LTBI. Do we need an AII room and a respiratoryprotection program?
Ideally, yes, because persons with LTBI are at risk for developing TB disease. TB clinics usually should have at least one AII
room and a respiratoryprotection program. An AII room and a respiratoryprotection program might not be needed if 1)
each person treated in the clinic will be adequately screened before admission and are
determined to not have TB disease, 2) a system exists to promptly detect and triage persons who have symptoms or signs of TB disease, and 3) no
cough-inducing procedures will ever be performed in the clinic.
- Can airborne precautions be discontinued for a
patient with suspected TB disease who has positive AFB
sputum smear results but has a negative NAA for
M. tuberculosis? Yes, if the NAA test result is negative and dual infection
with M. tuberculosis and another mycobacterial
species is not clinically suspected, the patient may be released from
airborne precautions. An NAA test is highly sensitive and specific for the identification of
M. tuberculosis when performed properly on a patient who has a positive AFB sputum smear result.
- During the winter months at a hospital, inadequate numbers of AII rooms are available for all patients
with suspected or confirmed infectious TB disease. Can only two negative sputum smear results be obtained for
AFB before releasing patients from airborne precautions?
In general, the criterion for the release of a patient
with suspected infectious TB disease from airborne precautions is that infectious TB disease is considered
unlikely and either 1) another diagnosis is made that
explains the clinical syndrome or 2) the patient has three negative AFB sputum smear results
(109--112). Each of the three consecutive sputum specimens should be collected 8--24 hours apart
(124), and at least one specimen should be an early morning specimen. Generally, this method will allow patients with negative sputum
smear results to be released from airborne precautions in 2 days. If the number of AII rooms in the setting is
inadequate, consider adding one or more AII rooms. Before undertaking this expense, however, ensure that the criteria for
placing patients in AII rooms are correct and that the available rooms are not being used for patients in whom
infectious TB disease is not suspected. In addition, the following intervals should be reviewed to identify any delays that could
be corrected and decrease time for patients in AII rooms: 1) time between admission and ordering of sputum specimens
for AFB examination, 2) time between ordering and collecting specimens, and 3) time between collection of specimens
and receipt of results from the laboratory.
- How many AII rooms are required in a 120-bed hospital?
For a hospital with 120 beds, a minimum of one AII room
is needed. Although no available data exist to quantify the number of rooms needed for a given number of cases of
suspected or confirmed TB disease, a reasonable choice is one additional AII room for every 200 patient-days of cases of
suspected or confirmed TB disease. The setting's risk assessment will help determine the number of AII rooms needed.
- Who is responsible for ensuring that negative pressure is achieved in AII rooms?
Ensuring that negative pressure is achieved in AII rooms is a function of the infectioncontrol program at each health-care setting. This responsibility
may be delegated to engineering, maintenance, or other appropriate staff to perform the actual negative pressure tests.
AII rooms should be checked for negative pressure before occupation by a patient with suspected or confirmed infectious
TB disease, and when in use by a person with TB disease, negative pressure should be checked daily with smoke tubes or
other visual checks.
- What is the difference between VAV and CAV? How do I determine which settings need them? VAV is variable air volume, and CAV is constant air volume. These terms refer to how the ventilation system is designed to deliver air to
and maintain temperature and relative humidity control within a room. CAV systems usually are best for AII rooms and
other negative-pressure rooms, because the negative-pressure differential is easier to maintain. VAV systems are
acceptable if provisions are made to maintain the minimum total and outside ACH and a negative pressure
>0.01 inch of water gauge relative to adjacent areas at all times.
- Why was the differential pressure requirement for an AII room increased from 0.001 inch of water gauge to
>0.01 inch of water gauge? In an ideal, controlled environment, 0.001 inches of water gauge has been demonstrated to
ensure negative pressure in AII rooms. However, AIA and other organizations have demonstrated that a minimum of 0.01
inches of water gauge is needed in certain installations to ensure that negative pressure is consistently achieved.
- How can a portable HEPA filter unit help control
TB? Portable HEPA filtration units recirculate room air, and
the HEPA filters effectively remove all particles from the air in the size range of droplet nuclei, resulting in a dilution of
the concentration of infectious particles in the room.
Respiratory Protection
- What is the difference between a CDC/NIOSH-certified
respirator and a surgical or procedure mask? Respirators
are designed to help reduce the wearer's (i.e., HCW's) exposure to airborne particles. The primary purpose of a surgical
or procedure mask is to help prevent biologic particles from being expelled into the air by the wearer (i.e., patient).
- How important is the fit of the respirator? This step is critical. The fit of a respirator is substantially important. If
a respirator does not fit tightly on the face, airborne hazards can penetrate or enter underneath the facepiece seal and
into the breathing zone. Before each use, the wearer of a respirator should perform a user-seal check on themselves to
minimize contaminant leakage into the facepiece (http://www.cdc.gov/niosh/topics/respirators).
- How do I perform a respirator user-seal check?
Performing a user-seal check (formerly called "fit check")
after redonning the respirator each time is critical to
ensure adequate respiratory protection. The seal checks for respirators are described
in the respirator user instructions and should be consulted before the respirator is used. The two types of user-seal
checks usually are positive-pressure and negative-pressure checks.
To check positive pressure seal after donning the respirator, the wearer should cover the surface of the respirator
with their hands or with a piece of household plastic film and exhale gently. If air is felt escaping around the facepiece,
the respirator should be repositioned, and the user-seal check should be performed again. If the wearer does not feel
air escaping around the facepiece, the positive pressure user-seal check was successful.
To check the negative pressure seal after donning the respirator, the wearer should gently inhale, which should create
a vacuum, causing the respirator to be drawn in toward the face. If the respirator is not drawn in toward the face or if
the wearer feels air leaking around the face seal, the respirator should be removed and examined for any defects (e.g., a
small hole or poor molding of the respirator to the face [especially around the nose area]). If no holes are found, the
respirator should be repositioned and readjusted, and a second attempt at negative pressure user-seal check should be made. If
the check is not successful, try a new respirator.
- Is performing a user-seal check (formerly called "fit check") on a respirator before each use always necessary?
Yes, performing a user-seal check on respirators before each use is essential to minimize contaminant leakage into the facepiece. Each respirator manufacturer has a recommended user-seal check procedure that should be followed by the user each
time the respirator is worn.
- What is a respirator fit test and who does fit testing?
A fit test is used to determine which respirator does or does not
fit the user adequately and to ensure that the user knows when the respirator fits properly. Fit testing must be performed by
a qualified health professional. Fit testing should be performed during the initial respiratoryprotection program
training and periodically thereafter, based on the risk assessment for the setting and in accordance with applicable federal, state,
or local regulations.
Periodic fit testing for respirators used in TB environments can serve as an effective training tool in conjunction
with the content included in employee training and retraining. The frequency of fit testing should be determined by a
change in the 1) risk for transmission of M.
tuberculosis, 2) facial features of the wearer, 3) medical condition that would
affect respiratory function, 4) physical characteristics of the respirator (despite the same model number), or 5) model or size
of the assigned respirator.
- What kind of respiratory protection should HCWs use when providing care to persons with suspected or
confirmed infectious TB disease in the home? The recommended respiratory protection for HCWs who provide care in the
homes of patients with suspected or confirmed infectious TB disease is at least an N95 respirator.
- What kind of respiratory protection should HCWs use when transporting patients with suspected or
confirmed infectious TB disease? The risk assessment for the setting should consider the potential for shared air. Drivers, HCWs and other staff who are transporting patients with suspected or confirmed infectious TB disease in an
enclosed vehicle should consider wearing an N95 disposable respirator. If the patient has symptoms or signs of infectious TB disease
(e.g., productive cough or positive AFB sputum smear result), the patient should wear a surgical or procedure mask, if
possible, during transport, in waiting areas, or when other persons are present. Patients who cannot tolerate masks because
of medical conditions should observe strict respiratory hygiene and cough etiquette procedures.
- What type of respiratory protection should be used in the operating room (OR) by HCWs with facial hair or
other factors that preclude proper fitting of an N95 respirator?
Will wearing a surgical or procedure mask underneath
a PAPR solve this problem? HCWs with facial hair should not wear negative pressure respirators (e.g., N95
disposable respirators that require a tight faceseal). In the OR, HCWs with facial hair who are caring for a person with suspected
or confirmed infectious TB disease should consult their infectioncontrol committee and respirator manufactures
regarding optimal respiratory protection and adequate infectioncontrol measures. The HCW in this case might wear a surgical
or procedure mask to protect the surgical field underneath a loose-fitting PAPR. However, the user cannot be assured
of proper operation unless the PAPR's manufacturer tested the PAPR over a surgical or procedure mask or N95
respirator. All respiratoryprotection equipment should be used in
accordance with the manufacturer's instructions.
- Should bacterial filters be used routinely on the breathing circuits of all ventilators and anesthesia equipment
on patients with suspected or confirmed infectious TB disease?
Yes, bacterial filters should be used routinely on
the exhalation breathing circuits of patients with suspected or confirmed infectious TB disease to prevent exhaled
air containing infectious droplet nuclei from contaminating the room air. Filters should be used on mechanical
ventilators and also on hand-held ventilating bags (i.e., manual resuscitators [e.g., ambu-bags®]). The bacterial filter should
be specified by the manufacturer to filter particles 0.3
µm in both the unloaded and the loaded states, with a filter
efficiency of >95% (i.e., filter penetration of <5%) at the maximum design flow rates of the ventilator.
- Who should not wear an N95 respirator? Any HCW who is restricted from using a respirator because of medical
reasons should not wear one nor should persons who cannot pass a fit test because of the presence of facial hair or other
condition that interferes with the seal of the respirator to the face.
- How long can I use my respirator for TB exposures before I discard it?
Disposable respirators can be functional for weeks to months and reused by the same HCW. Reuse is limited by hygiene, damage, and breathing resistance, and
manufacturer instructions should be considered.
- Should persons who perform maintenance on and replace filters on any ventilation system that is likely to
be contaminated with M. tuberculosis wear a respirator? Laboratory studies indicate that re-aerosolization of
viable mycobacteria from HEPA filters and N95 disposable respirator filter media is unlikely under normal conditions;
however, the risks associated with handling loaded HEPA filters in ventilation systems under field-use conditions have not
been evaluated. Therefore, persons performing maintenance and replacing filters on any ventilation system that is likely to
be contaminated with M. tuberculosis should wear a respirator (see Respiratory Protection) and adhere to
local recommendations for eye protection and gloves.
Cough-Inducing and Aerosol-Generating Procedures
- Should a bronchoscopic procedure be performed on a patient with TB disease?
If possible, bronchoscopic procedures should be avoided for patients with 1) a clinical syndrome consistent with infectious pulmonary or laryngeal TB
disease and 2) in persons with positive AFB sputum smear results, because bronchoscopic procedures substantially increase
the risk for transmission either through an airborne route or a contaminated bronchoscope. If the diagnosis of TB
is suspected, consideration should be given to empiric antituberculosis treatment, but a bronchoscopic procedure
might have the advantage of confirmation of the diagnosis with histologic specimens; collection of additional
specimens, including post bronchoscopy sputum that can increase the diagnostic yield and increase the opportunity to confirm
an alternate diagnosis. Microscopic examination of three consecutive sputum specimens obtained at least 8 hours apart
is recommended instead of bronchoscopy.
- For ORs without an AII room, postoperative recovery is usually in the OR suite.
Is this location acceptable? If the OR has an anteroom, this location is acceptable. Reversible flow rooms (OR or isolation) are not recommended by
CDC, AIA, or ASHRAE.
Acknowledgments
The authors acknowledge contributions from leaders of substantial medical, scientific, public health and labor organizations, and
other
experts in the fields of TB, HIV/AIDS, infection control, hospital epidemiology, microbiology, ventilation, industrial hygiene,
nursing, dental practice, and emergency medical services.
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Terms and Abbreviations Used in this Report
ACET Advisory Council for the Elimination of Tuberculosis
ACGIH American Conference of Governmental Industrial Hygienists
ACH Air changes per hour
ACOG American College of Obstetricians and Gynecologists
AERS Adverse event reporting system
AFB Acid-fast bacilli
AIA American Institute of Architects
AIDS Acquired immunodeficiency syndrome
AII Airborne infection isolation
ALA American Lung Association
ALT Alanine aminotransferase
ANSI American National Standards Institute
APF Assigned protection factor
APIC Association for Professionals in Infection Control and Epidemiology,
Inc.
ART Antiretroviral therapy
ASHRAE American Society of Heating, Refrigerating, and Air-Conditioning
Engineers, Inc.
AST Aspartate aminotransferase
ATS American Thoracic Society
BAMT Blood assay for Mycobacterium tuberculosis
BCG Bacille Calmette-Guérin
BIDR Blinded independent duplicate reading
BMBL Biosafety in Microbiological and Biomedical Laboratories
BSL Biosafety level
BSC Biological safety cabinet
CAV Constant air volume
CDC Centers for Disease Control and Prevention
CEL Certified equipment list
CFM Cubic feet per minute
CFR Code of Federal Regulations
CoV Coronavirus
CPL Compliance policy directive
CT Computed tomography
DHHS U.S. Department of Health and Human Services
DNA Deoxyribonucleic acid
DTBE Division of Tuberculosis Elimination
DOT Directly observed therapy
DTH Delayed-type hypersensitivity
ED Emergency department
EMS Emergency medical service
EPA Environmental Protection Agency
ESRD End-stage renal disease
ETL Electrical Testing Laboratories
FDA U.S. Food and Drug Administration
FGI Facility Guideline Institute
FPM Feet per minute
HAART Highly active antiretroviral therapy
HCW Health-care worker
HEPA High-efficiency particulate air
HIV Human immunodeficiency virus
HMO Health maintenance organization
HPLC High-pressure liquid chromatograph
HVAC Heating, ventilation, air conditioning
ICU Intensive care unit
IDSA Infectious Diseases Society of America
IFN-g Inteferon-gamma
IGRA Interferon gamma release assay
INH Isoniazid
IUATLD International Union Against Tuberculosis and Lung Disease
JCAHO Joint Commission on Accreditation of Healthcare Organizations
LTBI Latent tuberculosis infection
MDR TB Multidrug-resistant tuberculosis
MOTT Mycobacterium other than tuberculosis
NAA Nucleic acid amplification
NCID National Center for Infectious Diseases
NIAID National Institute of Allergy and Infectious Diseases
NIH National Institutes of Health
NIOSH National Institute for Occupational Safety and Health
NM Nanometer
NNRTI Nonnucleoside reverse transcriptase inhibitors
NPIN National Prevention Information Network
NTCA National Tuberculosis Controllers Association
NTM Nontuberculous mycobacteria
OR Operating room
OSHA Occupational Safety and Health Administration
PAPR Powered air-purifying respirator
PCP Pneumocystis pneumonia
PCR Polymerase chain reaction
PE Protective environment
PET Permissible exposure time
PI Protease inhibitor
PPD Purified protein derivative
PPE Personal protective equipment
QC Quality control
QFT QuantiFERON®-TB test
QFT-G QuantiFERON®- TB Gold test
QLFT Qualitative fit test
QNFT Quantitative fit test
REL Recommended exposure limit
RFLP Restriction fragment length polymorphism
RNA Ribonucleic acid
RZ Rifampin and pyrazinamide
SARS Severe acute respiratory syndrome
SGOT Serum glutamic-oxalacetic transaminase*
SGPT Serum glutamic-pyruvic transaminaseâ€
SWPF Simulated workplace protection factor
TB Tuberculosis
TNF-a Tumor necrosis factor-alpha
TU Tuberculin unit
TST Tuberculin skin test
UL Underwriters Laboratories
UV Ultraviolet
UVGI Ultraviolet germicidal irradiation
VAV Variable air volume
WHO World Health Organization
WPF Workplace protection factor
* Older term for AST.
Older term for ALT.
Glossary of Definitions
acid-fast bacilli (AFB) examination |
A laboratory test that involves microscopic
examination of a stained smear of a patient specimen (usually
sputum) to determine if mycobacteria are present. A presumptive
diagnosis of pulmonary tuberculosis (TB) can be made with a
positive AFB sputum smear result; however, approximately 50% of
patients with TB disease of the lungs have negative AFB sputum
smear results. The diagnosis of TB disease is usually not
confirmed until Mycobacterium tuberculosis is identified
in culture or by a positive nucleic acid amplification (NAA)
test result.
|
administrative controls |
Managerial measures that reduce the risk for exposure to persons who might have
TB disease. Examples include coordinating efforts with the local or state health
department; conducting a TB risk assessment for the setting; developing and instituting a written
TB infection-control plan to ensure prompt detection, airborne infection isolation
(AII), and treatment of persons with suspected or confirmed TB disease; and screening
and evaluating health-care workers (HCWs) who are at risk for TB disease or who might
be exposed to M. tuberculosis. |
aerosol |
Dispersions of particles in a gaseous medium (e.g., air). Droplet nuclei are an example
of particles that are expelled by a person with an infectious disease (e.g., by
coughing, sneezing, or singing). For M.
tuberculosis, the droplet nuclei are approximately 1--5
µm. Because of their small size, the droplet nuclei can remain suspended in the air
for substantial periods and can transmit M.
tuberculosis to other persons. |
air change rate |
Ratio of the airflow in volume units per hour to the volume of the space
under consideration in identical volume units, usually expressed in air changes per
hour (ACH).
|
air change rate (equivalent) |
Ratio of the volumetric air loss rate associated with an environmental control
(or combination of controls) (e.g., an air cleaner or ultraviolet germicidal
irradiation [UVGI] system) divided by the volume of the room where the control has been
applied. The equivalent air change rate is useful for describing the rate at which bioaerosols
are removed by means other than ventilation.
|
air change rate (mechanical) |
Ratio of the airflow to the space volume per unit time, usually expressed in air
changes per hour (ACH). |
air changes per hour (ACH)
|
Air change rate expressed as the number of air exchange units per hour.
|
airborne infection isolation (AII) precautions |
The isolation of patients infected with organisms spread through airborne droplet nuclei 1--5
µm in diameter. This isolation area receives substantial ACH
(>12 ACH for new construction since 2001 and
>6 ACH for construction before 2001) and is
under negative pressure (i.e., the direction of the air flow is from the outside adjacent
space [e.g., the corridor] into the room). The air in an AII room is preferably exhausted to
the outside, but can be recirculated if the return air is filtered through an high
efficiency particulate respirator (HEPA) filter. |
AII room |
A room designed to maintain AII. Formerly called negative pressure isolation room,
an AII room is a single-occupancy patient-care room used to isolate persons with
suspected or confirmed infectious TB disease. Environmental factors are controlled in AII
rooms to minimize the transmission of infectious agents that are usually spread from
person-to-person by droplet nuclei associated with coughing or aerosolization of
contaminated fluids. AII rooms should provide negative pressure in the room (so that air flows
under the door gap into the room), an air flow rate of 6--12 ACH, and direct exhaust of
air from the room to the outside of the building or recirculation of air through a
HEPA filter.
|
American Institute of Architects/Facility Guideline Institute (AIA/FGI)
|
A professional organization that develops standards for building design and construction, including ventilation parameters, and enforced by the Joint Commission on Accreditation of Healthcare Organizations.
|
American Society of Heating, Refrigerating, and Air-Conditioning
Engineers, Inc. (ASHRAE) |
A professional organization that develops guidelines for building ventilation.
|
aminotransaminases |
Also called transaminases. Used to assess for hepatotoxicity in persons
taking antituberculosis medications and include aspartate amino transferase (AST),
serum glutamic oxalacetic transaminase, formerly SGOT, and amino alanine
transferase, formerly ALT.
|
aminotransferases |
Also called transaminases. Used to assess for hepatotoxicity in persons
taking antituberculosis medications and include aspartate amino transferase (AST)
(formerly serum glutamic oxalacetic transaminase) and amino alanine transferase (ALT)
(formerly serum glutamic pyruvic transaminase).
|
anaphylactic shock |
An often severe and sometimes fatal systemic reaction upon a second exposure to
a specific antigen (as wasp venom or penicillin) after previous sensitization that
is characterized especially by respiratory symptoms, fainting, itching, and hives.
|
anemometer |
An instrument used to measure the velocity (speed) of air.
|
anergy |
A condition in which a person has a diminished ability to exhibit delayed
T-cell hypersensitivity to antigens because of a condition or situation resulting in
altered immune function. An inability to react to a skin test is called cutaneous anergy.
Skin tests for anergy (i.e., control antigens) have poor predictive value and are
not recommended.
|
anteroom |
Small room leading from a corridor into an AII room. An anteroom is separated
from both the AII room and the corridor by doors. An anteroom can act as an
airlock, preventing the escape of contaminants from the AII room into the corridor.
|
apical |
Relating to or located at the tip (an apex).
|
assigned protection factor (APF) |
The minimum anticipated protection provided by a properly worn and
functioning respirator or class of respirators.
|
asymptomatic |
Neither causing nor exhibiting signs or symptoms of disease.
|
Bacille Calmette-Guérin (BCG) |
A vaccine for TB named after the French scientists Calmette and Guérin used in
most countries where TB disease is endemic. The vaccine is effective in
preventing disseminated and meningeal TB disease in infants and young children. It may
have approximately 50% efficacy for preventing pulmonary TB disease in adults.
|
baseline TB screening |
Screening HCWs for LTBI and TB disease at the beginning of employment.
TB screening includes a symptom screen for all HCWs, and tuberculin skin tests (TSTs)
or blood assay for Mycobacterium tuberculosis
(BAMT) for those with previous negative test results for
M. tuberculosis infection. |
baseline TST or baseline BAMT |
The TST or BAMT is administered at the beginning of employment to newly
hired HCWs. If the TST method is used, for HCWs who have not had a
documented negative test result for M.
tuberculosis during the preceding 12 months, the baseline
TST result should be obtained by using the two-step method. BAMT baseline testing
does not need the two-step method. |
biological safety cabinet (BSC) |
A ventilated box that provides HCWs with a degree of protection against
hazardous aerosols that are generated within it. BSC is the principal device used to
contain infectious splashes or aerosols generated by multiple microbiology processes.
BSC provides physical barriers and directional airflow to carry hazards away from the
HCW. Maintenance is an essential part of ensuring proper BCS function.
|
Biosafety in Microbiological and Biomedical Laboratories (BMBL) |
A publication of the U.S. Public Health Service that describes the combinations of standard and special microbiology practices, safety equipment, and facilities
constituting biosafety levels (BSLs) 1--4, which are recommended for work with various
infectious agents in laboratory settings. The recommendations are advisory and intended
to provide a voluntary guide or code of practice. |
biosafety levels (BSLs) |
Four BSLs are described in Section III of BMBL that comprise combinations
of laboratory practices and techniques, safety equipment, and laboratory settings.
|
blinded independent duplicate reading (BIDR) |
Process in which two or more TST readers immediately measure the same TST result by standard procedures, without consulting or observing one
another's readings, and record results. BIDRs help ensure that TST readers continue to read
TST results correctly.
|
blood assay for Mycobacterium tuberculosis (BAMT) |
A general term to refer to recently developed in vitro diagnostic tests that assess for the presence of infection with
M. tuberculosis. This term includes, but is not limited to,
IFN-g release assays (IGRA). In the United States, the currently available test is
QuantiFERON®-TB Gold test (QFT-G).
|
BAMT converter |
A change from a negative to a positive BAMT result over a 2-year period.
|
boosting |
When nonspecific or remote sensitivity to tuberculin purified protein derivative
(PPD) in the skin test wanes or disappears over time, subsequent TSTs can restore
the sensitivity. This process is called boosting or the booster phenomenon. An initially
small TST reaction size is followed by a substantial reaction size on a later test, and
this increase in millimeters of induration can be confused with a conversion or a recent
M. tuberculosis infection. Two-step testing is used to distinguish new infections
from boosted reactions in infection-control surveillance
programs.
|
bronchoscopy |
A procedure for examining the lower respiratory tract in which the end of
the endoscopic instrument is inserted through the mouth or nose (or tracheostomy)
and into the respiratory tree. Bronchoscopy can be used to obtain diagnostic
specimens. Bronchoscopy also creates a high risk for
M. tuberculosis transmission to HCWs if it
is performed on an untreated patient who has TB disease (even if the patient has
negative AFB smear results) because it is a cough-inducing procedure.
|
case |
A particular instance of a disease (e.g., TB). A case is detected, documented,
and reported.
|
cavity (pulmonary) |
A hole in the lung parenchyma, usually not involving the pleural space. Although a
lung cavity can develop from multiple causes, and its appearance is similar regardless of
its cause, in pulmonary TB disease, cavitation results from the destruction of
pulmonary tissue by direct bacterial invasion and an immune interaction triggered by
M. tuberculosis. A TB cavity substantial enough to see with a normal chest radiograph
predicts infectiousness.
|
clinical examination |
A physical evaluation of the clinical status of a patient by a physician or
equivalent practitioner.
|
close contact (TB) |
A person who has shared the same air space in a household or other
enclosed environment for a prolonged period (days or weeks, not minutes or hours) with a
person with suspected or confirmed TB disease. Close contacts have also been referred to
as high-priority contacts because they have the highest risk for infection with
M. tuberculosis.
|
cluster (TB) |
A group of patients with LTBI or TB disease that are linked by epidemiologic,
location, or genotyping data. Two or more TST conversions within a short period can be a
cluster of TB disease and might suggest transmission within the setting. A genotyping cluster
is two or more cases with isolates that have an identical genotyping pattern.
|
combination product surgical mask/N95 disposable respirator |
Product certified by CDC's National Institute for Occupational Safety and Health (NIOSH) and cleared by the Food and Drug Administration (FDA) that provides both
respiratory protection and bloodborne pathogen protection.
|
constant air volume (CAV) |
A descriptor for an air-handling system which, as the name implies, supplies
and exhausts air at a constant flow rate. The flow rate does not change over time based
on temperature load or other parameters.
|
contact (TB) |
Refers to someone who was exposed to
M. tuberculosis infection by sharing air
space with an infectious TB patient.
|
contact investigation |
Procedures that occur when a case of infectious TB is identified, including
finding persons (contacts) exposed to the case, testing and evaluation of contacts to
identify LTBI or TB disease, and treatment of these persons, as indicated.
|
contagious |
Describes a characteristic of a disease that can be transmitted from one living being
to another through direct contact or indirect contact; communicable. The
agent responsible for the contagious character of a disease is also described as being
infectious; the usual culprits are microorganisms. |
contraindication |
Any condition, especially any condition of disease, which renders a certain line
of treatment improper or undesirable. |
conversion |
See TST conversion. |
conversion rate |
The percentage of a population with a converted test result (TST or BAMT) for
M. tuberculosis within a specified period. This is calculated by dividing the number
of conversions among eligible HCWs in the setting in a specified period (numerator)
by the number of HCWs who received tests in the setting over the same
period (denominator) multiplied by 100. |
culture |
Growth of microorganisms in the laboratory performed for detection and
identification in sputum or other body fluids and tissues. This test usually takes 2--4 weeks
for mycobacteria to grow (2--4 days for most other bacteria). |
cough etiquette |
See respiratory hygiene and cough ettiquette.
|
cross contamination |
When organisms from one sample are introduced into another sample, causing a
false-positive result.
|
delayed-type hypersensitivity (DTH) |
Cell-mediated inflammatory reaction to an antigen, which is recognized by the
immune system usually because of previous exposure to the same antigen or similar ones.
Cell-mediated reactions are contrasted with an antibody (or humoral) response.
DTH typically peaks at 48--72 hours after exposure to the antigen.
|
deoxyribonucleic acid |
DNA fingerprinting is a clinical laboratory technique used to distinguish
between different strains of M. tuberculosis and to help assess the likelihood of TB transmission. |
differential pressure |
A measurable difference in air pressure that creates a directional airflow
between adjacent compartmentalized spaces. |
directly observed therapy (DOT) |
Adherence-enhancing strategy in which an HCW or other trained person watches
a patient swallow each dose of medication. DOT is the standard care for all patients
with TB disease and is a preferred option for patients treated for LTBI.
|
disposable respirator |
A respirator designed to be used and then discarded; also known as a
filtering-facepiece respirator. Respirators should be discarded after excessive resistance, physical damage,
or hygiene considerations.
|
droplet nuclei |
Microscopic particles produced when a person coughs, sneezes, shouts, or sings.
These particles can remain suspended in the air for prolonged periods and can be carried
on normal air currents in a room and beyond to adjacent spaces or areas receiving
exhaust air.
|
drug-susceptibility test |
A laboratory determination to assess whether an
M. tuberculosis complex isolate is susceptible or resistant to antituberculosis drugs that are added to mycobacterial
growth medium or are detected genetically. The results predict whether a specific drug is
likely to be effective in treating TB disease caused by that isolate.
|
environmental control measures |
Physical or mechanical measures (as opposed to administrative control measures) used
to reduce the risk for transmission of M.
tuberculosis. Examples include ventilation, filtration, ultraviolet lamps, AII rooms, and local exhaust ventilation devices.
|
epidemiologic cluster |
A closely grouped series of cases in time or place.
|
erythema
|
Abnormal redness of the skin. Erythema can develop around a TST site but should
not be read as part of the TST result. |
expert TST trainer |
A designated instructor who has documented TST training experience. This
may include having received training on placing and reading multiple TST results.
|
exposed cohorts |
Groups of persons (e.g., family members, co-workers, friends, club, team or
choir members, persons in correctional facilities, or homeless shelter residents) who
have shared the same air space with the suspected patient with TB disease during
the infectious period. A person in the exposed cohort is a contact. See also contact and
close contact.
|
exposure |
The condition of being subjected to something (e.g., an infectious agent) that
could have an effect. A person exposed to M.
tuberculosis does not necessarily become
infected. See also transmission. |
exposure period |
The coincident period when a contact shared the same air space as the index TB
patient during the infectious period.
|
exposure site |
A location that the index patient visited during the infectious period (e.g., school,
bar, bus, or residence).
|
extrapulmonary TB |
TB disease in any part of the body other than the lungs (e.g., kidney, spine, or
lymph nodes). The presence of extrapulmonary disease does not exclude pulmonary TB disease.
|
false-negative TST or BAMT result |
A TST or BAMT result that is interpreted as negative in a person who is
actually infected with M. tuberculosis. |
false-positive TST or BAMT result |
A TST or BAMT result that is interpreted as positive in a person who is not
actually infected with M. tuberculosis. A false-positive TST result is more likely to occur
in persons who have been vaccinated with BCG or who are infected with
nontuberculous mycobacteria (NTM). |
facility |
A physical building or set of buildings.
|
filtering-facepiece respirator |
A type of air purifying respirator that uses a filter as an integral part of the facepiece
or with the entire facepiece composed of the filtering medium. |
fit check |
See user-seal check.
|
fit factor |
A quantitative estimate of the fit of a particular respirator to a specific person;
typically estimates the ratio of the concentration of a substance in ambient air to its
concentration inside the respirator when worn.
|
fit test |
The use of a protocol to qualitatively or quantitatively evaluate the fit of a respirator
on a person. See also QLFT and QNFT. |
flutter strips |
Physical indicators used to provide a continuous visual sign that a room is
under negative pressure. These simple and inexpensive devices are placed directly in the
door and can be useful in identifying a pressure differential problem.
|
genotype |
The DNA pattern of M.
tuberculosis used to discriminate among different strains. |
health-care--associated |
Broader term used instead of "nosocomial." |
health-care setting |
A place where health care is delivered. |
health-care workers (HCWs) |
All paid and unpaid persons working in health-care settings.
|
heating, ventilating, or air conditioning (HVAC) |
Mechanical systems that provide either collectively or individually heating, ventilating, or air conditioning for comfort within or associated with a building.
|
high efficiency particulate air (HEPA) filter |
A filter that is certified to remove >99.97% of particles 0.3
µm in size, including
M. tuberculosis--containing droplet nuclei; the filter can be either portable or
stationary. Use of HEPA filters in building ventilation systems requires expertise in installation
and maintenance.
|
high-pressure liquid chromatograph (HPLC) |
Laboratory method used to identify Mycobacterium species by analysis of species-specific
fatty acids called mycolic acids, which are present in the cell walls of mycobacteria.
|
human immunodeficiency virus (HIV) infection |
Infection with the virus that causes acquired immunodeficiency syndrome (AIDS). A person with both LTBI and HIV infection is at high risk for developing TB disease. |
hemoptysis |
The expectoration or coughing up of blood or blood-tinged sputum; one of
the symptoms of pulmonary TB disease. Hemoptysis can also be observed in
other pulmonary conditions (e.g., lung cancer).
|
hypersensitivity |
A state in which the body reacts with an exaggerated immune response to a
foreign substance. Hypersensitivity reactions are classified as immediate or delayed, types I
and IV, respectively. See also delayed-type hypersensitivity. |
immunocompromised and immunosuppressed |
Describes conditions in which at least part of the immune system is functioning at less than normal capacity. According to certain style experts, "immunocompromised" is
the broader term, and "immunosuppressed" is restricted to conditions with
iatrogenic causes, including treatments for another condition.
|
incentive |
A gift given to patients to encourage or acknowledge their adherence to treatment.
|
incidence |
The number of new events or cases of disease that develop during a specified period.
|
index case |
The first person with TB disease who is identified in a particular setting. This
person might be an indicator of a potential public health problem and is not necessarily
the source case. See also source case or patient. |
induration |
The firmness in the skin test reaction; produced by immune-cell infiltration in
response to the tuberculin antigen that was introduced into the skin. Induration
is measured transversely by palpation, and the result is
recorded in millimeters. The measurement is compared with
guidelines to determine whether the test result is classified as
positive or negative.
|
infection with M. tuberculosis |
In some persons who are exposed to and who inhale
M. tuberculosis bacteria, the bacteria are not promptly cleared by respiratory defense systems, and the bacteria multiply
and are spread throughout the body, thereby infecting the exposed person. In the majority
of persons who become infected, the body is able to fight the bacteria to stop the
bacteria from growing, further establishing a latent state. The bacteria are inactive, but
they remain alive in the body and can become active later. In other persons, the
infection with M. tuberculosis can progress to TB disease more promptly.
M. tuberculosis infection encompasses both latent TB infection and TB disease. See also latent TB infection
and reinfection.
|
infectious |
See contagious.
|
infectious droplet nuclei |
Droplet nuclei produced by an infectious TB patient that can carry tubercle bacteria
and be inhaled by others. Although usually produced from patients with pulmonary
TB through coughing, aerosol-generating procedures can also generate infectious
droplet nuclei.
|
infectious period
|
The period during which a person with TB disease might have transmitted
M. tuberculosis organisms to others. For patients with positive AFB sputum smear
results, the infectious period begins 3 months before the collection date of the first
positive smear result or the symptom onset date (whichever is earlier) and ends when the
patient is placed into AII or the date of collection for the first of consistently negative
smear results. For patients with negative AFB sputum smear results, the infectious
period extends from 1 month before the symptom onset date and ends when the patient
is placed into AII (whichever was earlier).
|
interferon-γ release assays (IGRA) |
A type of an ex vivo test that detects cell-mediated immune response to this cytokine.
In the United States, QFT-G is a currently available IGRA.
|
isoniazid (INH) |
A highly active antituberculosis chemotherapeutic agent that is a cornerstone
of treatment for TB disease and the cornerstone of treatment for LTBI. |
laryngeal TB |
A form of TB disease that involves the larynx and can be highly infectious.
|
latent TB infection (LTBI) |
Infection with
M. tuberculosis without symptoms or signs of disease have manifested.
See also infection with M. tuberculosis.
|
manometer |
An instrument used to measure pressure differentials (i.e., pressure inside an AII
room relative to the corridor of the room).
|
Mantoux method
|
A skin test performed by intradermally injecting 0.1 mL of PPD tuberculin
solution into the volar or dorsal surface of the forearm. This method is the recommended
method for TST.
|
mask
|
A device worn over the nose and mouth of a person with suspected or
confirmed infectious TB disease to prevent infectious particles from being released into room air.
|
mechanical ACH |
Air change rate based on only the mechanical ventilation flowrates.
|
medical evaluation |
An examination to diagnose TB disease or LTBI, to select treatment, and to
assess response to therapy. A medical evaluation can include medical history and TB
symptom screen, clinical or physical examination, screening and diagnostic tests (e.g., TSTs,
chest radiographs, bacteriologic examination, and HIV testing), counseling, and
treatment referrals.
|
meningeal |
TB A serious form of TB disease involving the meningies, the covering of the
brain. Meningeal TB can result in serious neurologic complications. |
miliary TB |
A serious form of TB disease sometimes referred to as
disseminated TB. A dangerous and difficult form to diagnose of
rapidly progressing TB disease that extends throughout the body.
Uniformly fatal if untreated; in certain instances, it is
diagnosed too late to save a life. Certain patients with this
condition have normal findings or ordinary infiltrates on the
chest radiograph |
mitogen |
A substance that stimulates the growth of certain white blood cells. Mitogen is used as
a positive control in BAMT tests.
|
multidrug-resistant tuberculosis (MDR TB) |
TB disease caused by M. tuberculosis organisms that are resistant to at least INH and rifampin.
|
mycobacteria other than tuberculosis (MOTT)
|
See NTM. |
Mycobacterium tuberculosis |
The namesake member organism of
M. tuberculosis complex and the most common causative infectious agent of TB disease in humans. In certain instances, the
species name refers to the entire M.
tuberculosis complex, which includes M.
bovis and M. african, M. microti, M. canetii, M. caprae,
and M. pinnipedii.
|
M. tuberculosis culture |
A laboratory test in which the organism is grown from a submitted specimen
(e.g., sputum) to determine the presence of M.
tuberculosis. In the absence of cross-contamination, a positive culture confirms the diagnosis of TB disease.
|
N95 disposable respirator |
An air-purifying, filtering-facepiece respirator that is
>95% efficient at removing 0.3
µm particles and is not resistant to oil. See also respirator.
|
negative pressure |
The difference in air-pressure between two areas. A room that is under negative
pressure has a lower pressure than adjacent areas, which keeps air from flowing out of the
room and into adjacent rooms or areas. Also used to describe a nonpowered respirator. See
also AII and AII room.
|
nontuberculous mycobacteria (NTM)
|
Refers to mycobacterium species other than those included as part of
M. tuberculosis complex.
Although valid from a laboratory perspective, the term can be misleading
because certain types of NTM cause disease with pathologic and clinical manifestations
similar to TB disease. Another term for NTM is mycobacterium other than
tuberculosis (MOTT). NTM are environmental mycobacteria.
|
nosocomial |
Acquired in a hospital. The broader term "health-care--associated" is used in this report.
|
nucleic acid amplification (NAA) |
Laboratory method used to target and amplify a single DNA or RNA sequence
usually for detecting and identifying a microorganism. The NAA tests for
M. tuberculosis complex are sensitive and specific and can accelerate the confirmation of pulmonary
TB disease.
|
periodic fit testing |
Repetition of fit testing performed in accordance with federal, state, and
local regulations. Additional fit testing should be used when 1) a new model of respirator
is used, 2) a physical characteristic of the user changes, or 3) when the user or
respiratory program administrator is uncertain that the HCW is obtaining an adequate fit. |
pleural effusion |
Abnormal accumulation of fluid between the lining of the lung and the chest
wall. Persons with TB pleural effusions might also have concurrent unsuspected pulmonary
or laryngeal TB disease. These patients should be considered contagious until infectious
TB disease is excluded. |
polymerase chain reaction (PCR) |
A system for in vitro amplification of DNA that can be used for diagnosis of infections.
|
positive predictive value of a TST |
The probability that a person with a positive TST result is actually infected with
M. tuberculosis. The positive predictive value is dependent on the prevalence of
infection with M. tuberculosis in the population being tested and on the sensitivity and
specificity of the test.
|
potential ongoing transmission |
A risk classification for TB screening, including testing for
M. tuberculosis infection when evidence of ongoing transmission of
M. tuberculosis is apparent in the setting. Testing might need to be performed every 8--10 weeks until lapses in infection
controls have been corrected, and no further evidence of ongoing transmission is apparent.
Use potential ongoing transmission as a temporary risk classification only. After
corrective steps are taken, reclassify the setting as medium risk. Maintaining the classification
of medium risk for at least 1 year is recommended.
|
powered air-purifying respirator (PAPR) |
A respirator equipped with a tight-fitting facepiece (rubber facepiece) or loose-fitting facepiece (hood or helmet), breathing tube, air-purifying filter, cartridge or canister,
and a fan. Air is drawn through the air-purifying element and pushed through the
breathing tube and into the facepiece, hood, or helmet by the fan. Loose-fitting PAPRs
(e.g., hoods or helmets) might be useful for persons with facial hair because they do
not require a tight seal with the face.
|
prevalence |
The proportion of persons in a population who have a disease at a specific time.
|
protection factor |
A general term for three specific terms: 1) APF, 2) SWPF, and 3) WPF. These terms
refer to different methods of defining adequacy of respirator fit. See also APF, SWPF,
and WPF.
|
pulmonary TB |
TB disease that occurs in the lung parenchyma, usually producing a cough that
lasts >3 weeks. |
purified protein derivative (PPD) tuberculin |
A material used in diagnostic tests for detecting infection with
M. tuberculosis. In the
United States, PPD solution is approved for administration as an intradermal
injection (5 TU per 0.1 mL), a diagnostic aid for LTBI (see TST). In addition, PPD
tuberculin was one of the antigens in the first-generation QFT.
|
qualitative fit test (QLFT) |
A pass-fail fit test to assess the adequacy of respirator fit that relies on the response of
the person to the test agent.
|
quality control (QC) |
A function to ensure that project tools and procedures are reviewed and
verified according to project standards.
|
QFT and QFT-G |
Types of BAMT that are in vitro cytokine assays that detects cell-mediated
immune response (see also DTH) to M.
tuberculosis in heparinized whole blood from venipuncture. This test requires only a single patient encounter, and the result can
be ready within 1 day. In 2005,
QuantiFERON®-TB was replaced by
QuantiFERON®-TB Gold (QFT-G), which has greater specificity because of antigen selection.
QFT-G appears to be capable of distinguishing between the sensitization caused by
M. tuberculosis infection and that caused by BCG vaccination.
|
quantitative fit test (QNFT) |
An assessment of the adequacy of respirator fit by numerically measuring the amount
of leakage into the respirator.
|
recirculation |
Ventilation in which all or the majority of the air exhausted from an area is returned
to the same area or other areas of the setting.
|
recommended exposure limit (REL)
|
The occupational exposure limit established by CDC/NIOSH. RELs are intended
to suggest levels of exposure to which the majority of HCWs can be exposed
without experiencing adverse health effects. |
reinfection |
A second infection that follows from a previous infection by the same causative
agent. Frequently used when referring to an episode of TB disease resulting from a
subsequent infection with M. tuberculosis and a different genotype. |
resistance |
The ability of certain strains of mycobacteria, including
M. tuberculosis, to grow and multiply in the presence of certain drugs that ordinarily kill or suppress them.
Such strains are referred to as drug-resistant strains and cause drug-resistant TB disease.
See also multidrug-resistant TB.
|
respirator |
A CDC/NIOSH-approved device worn to prevent inhalation of airborne contaminants.
|
respiratory hygiene and cough etiquette |
Procedures by which patients with suspected or confirmed infectious TB disease can minimize the spread of infectious droplet nuclei by decreasing the number of
infectious particles that are released into the environment. Patients with a cough should
be instructed to turn their heads away from persons and to cover their mouth and
nose with their hands or preferably a cloth or tissue when coughing or sneezing.
|
respiratory protection
|
The third level in the hierarchy of TB infection-control measures after
administrative and environmental controls is used because of the risk for exposure.
|
restriction fragment length polymorphism (RFLP) |
A technique by which organisms can be differentiated by analysis of patterns derived from cleavage of their DNA. The similarity of the patterns generated can be used
to differentiate strains from one another. See also genotype. |
reversion |
A subsequent TST or BAMT result that is substantially smaller than a previous
test; reversion has been observed to be more likely when the intervening time between
TSTs increases.
|
Rifampin |
A highly active antituberculosis chemotherapeutic agent that is a cornerstone
of treatment for TB disease.
|
screening (TB) |
Measures used to identify persons who have TB disease or LTBI. See also
symptom screen.
|
secondary (TB) case |
A new case of TB disease that is attributed to recent transmission as part of the
scenario under investigation. The period for "recent" is not defined but usually will be
briefer than 2 years. Technically, all cases are secondary, in that they originate from
other contagious cases. |
simulated workplace protection factor (SWPF) |
A surrogate measure of the workplace protection provided by a respirator.
|
smear (AFB smear)
|
A laboratory technique for preparing a specimen so that bacteria can be
visualized microscopically. Material from the specimen is spread onto a glass slide and
usually dried and stained. Specific smear, stain, and microscopy methods for mycobacteria
are designed to optimally detect members of this genus. The slide can
be scanned by light or fluorescent high-power microscopy. These methods require ongoing quality
assurance for prompt and reliable results. The results for sputum smears usually are reported
as numbers of AFB per high-powered microscopy field or as a graded result, from +1
to +4. The quantity of stained organisms predicts infectiousness. See also AFB.
|
source case or patient |
The person or the case that was the original source of infection for secondary cases
or contacts. The source case can be, but is not necessarily, the index case.
|
source case investigation |
An investigation to determine the source case could be conducted in at least
two circumstances: 1) when a health-care setting detects an unexplained cluster of TST conversions among HCWs or 2) when TB infection or disease is diagnosed in a
young child. The purposes of a source case investigation are to ascertain that the source case
has been diagnosed and treated, to prevent further M. tuberculosis
transmission, and to ensure that other contacts of that source
case are also evaluated and, if indicated, provided treatment.
|
source control |
A process for preventing or minimizing emission (e.g., aerosolized
M. tuberculosis) at the place of origin. Examples of source-control methods are booths in which a
patient coughs and produces sputum, BSCs in laboratories, and local exhaust ventilation.
|
spirometry |
A procedure used to measure time expired and the volume inspired, and from
these measurements, calculations can be made on the effectiveness of the lungs.
|
sputum |
Mucus containing secretions coughed up from inside the lungs. Tests of sputum
(e.g., smear and culture) can confirm pulmonary TB disease. Sputum is different from
saliva or nasal secretions, which are unsatisfactory specimens for detecting TB
disease. However, specimens suspected to be inadequate should still be processed
because positive culture results can still be obtained and might be the only
bacteriologic indication of disease.
|
sputum induction |
A method used to obtain sputum from a patient who is unable to cough up a
specimen spontaneously. The patient inhales a saline mist, which stimulates coughing from
deep inside the lungs.
|
supervised TST administration |
A procedure in which an expert TST trainer supervises a TST trainee who performs
all procedures on the procedural observation checklist for administering TSTs.
|
supervised TST reading |
A procedure in which an expert TST trainer supervises a TST trainee who performs
all procedures on the procedural observation checklist for reading TST results.
|
suspected TB |
A tentative diagnosis of TB that will be confirmed or excluded by subsequent
testing. Cases should not remain in this category for longer than 3 months.
|
symptomatic |
A term applied to a patient with health-related complaints (symptoms) that
might indicate the presence of disease. In certain instances, the term is applied to a
medical condition (e.g., symptomatic pulmonary TB).
|
symptom screen |
A procedure used during a clinical evaluation in which patients are asked if they
have experienced any departure from normal in function, appearance, or sensation related
to TB disease (e.g., cough).
|
targeted testing |
A strategy to focus testing for infection with
M. tuberculosis in persons at high risk for LTBI and for those at high risk for progression to TB disease if infected.
|
tuberculosis (TB) disease |
Condition caused by infection with a member of the
M. tuberculosis complex that has progressed to causing clinical (manifesting symptoms or signs) or subclinical (early
stage of disease in which signs or symptoms are not present, but other indications of
disease activity are present [see below]) illness. The bacteria can attack any part of the body,
but disease is most commonly found in the lungs (pulmonary TB). Pulmonary TB
disease can be infectious, whereas extrapulmonary disease (occurring at a body site outside
the lungs) is not infectious, except in rare circumstances. When the only clinical finding
is specific chest radiographic abnormalities, the condition is termed "inactive TB" and
can be differentiated from active TB disease, which is accompanied by symptoms or
other indications of disease activity (e.g., the ability to culture reproducing TB organisms
from respiratory secretions or specific chest radiographic finding).
|
TB case |
A particular episode of clinical TB disease. Refers only to the
disease, not to the person with the disease. According to local
laws and regulation, TB cases and suspect TB cases must be
reported to the local or state health department.
|
TB contact |
A person who has shared the same air space with a person who has TB disease for
a sufficient amount of time to allow possible transmission of
M. tuberculosis.
|
TB exposure incident |
A situation in which persons (e.g., HCWs, visitors, and inmates) have been exposed to
a person with suspected or confirmed infectious TB disease (or to air containing
M. tuberculosis), without the benefit of effective infection-control measures.
|
TB infection |
See LTBI. |
TB infection-control program |
A program designed to control transmission of
M. tuberculosis through early detection, isolation, and treatment of persons with infectious TB. A hierarchy of control
measures are used, including 1) administrative controls to reduce the risk for exposure to
persons with infectious TB disease and screening for HCWs for LTBI and TB disease,
2) environmental controls to prevent the spread and reduce the concentration of
infectious droplet nuclei in the air, and 3) respiratory protection in areas where the risk
for exposure to M. tuberculosis is high (e.g., AII rooms). A TB infection-control plan
should include surveillance of HCWs who have unprotected high-risk exposure to TB
patients or their environment of care.
|
TB screening |
An administrative control measure in which evaluation for LTBI and TB disease
are performed through initial and serial screening of HCWs, as indicated. Evaluation
might comprise TST, BAMT, chest radiograph, and symptom screening. See also
symptom screen.
|
TB screening program |
A plan that health-care settings should implement to provide information that is
critical in caring for HCWs and information and that facilitates detection of
M. tuberculosis transmission. The TB screening program comprises four major components: 1)
baseline testing for M. tuberculosis infection, 2) serial testing for
M. tuberculosis infection, 3) serial screening for signs or symptoms of TB disease, and 4) TB training and education. |
TB risk assessment |
An initial and ongoing evaluation of the risk for transmission of
M. tuberculosis in a particular health-care setting. To perform a risk assessment, the following factors
should be considered: the community rate of TB, number of TB patients encountered in
the setting, and the speed with which patients with TB disease are suspected, isolated,
and evaluated. The TB risk assessment determines the types of administrative
and environmental controls and respiratory protection needed for a setting.
|
transmission |
Any mode or mechanism by which an infectious agent is spread from a source
through the environment or to a person (or other living organism). In the context of
health-care--associated TB infection control, transmission is the airborne conveyance of
aerosolized M. tuberculosis contained in droplet nuclei from a person with TB disease, usually
from the respiratory tract, to another person, resulting
in infection.
|
treatment for LTBI |
Treatment that prevents the progression of infection into disease.
|
tuberculin skin test (TST) |
A diagnostic aid for finding
M. tuberculosis infection. A small dose of tuberculin
is injected just beneath the surface of the skin (in the United States by the
Mantoux method), and the area is examined for induration by palpation 48--72 hours after
the injection. The indurated margins should be read transverse (perpendicular) to the
long axis of the forearm. See also Mantoux method and PPD.
|
TST conversion |
A change in the result of a test for M. tuberculosis infection wherein the condition
is interpreted as having progressed from uninfected to infected. An increase of >10 mm
in induration during a maximum of 2 years is defined as a TST conversion for
the purposes of a contact investigation. A TST conversion is presumptive evidence of
new M. tuberculosis infection and poses an increased risk for progression to TB disease.
See also conversion.
|
tubercle bacilli |
M. tuberculosis organisms.
|
tuberculin |
A precipitate made from a sterile filtrate of
M. tuberculosis culture medium.
|
two-step TST
|
Procedure used for the baseline skin testing of persons who will receive serial TSTs
(e.g., HCWs and residents or staff of correctional facilities or long-term--care facilities)
to reduce the likelihood of mistaking a boosted reaction for a new infection. If an
initial TST result is classified as negative, a second step of a two-step TST should
be administered 1--3 weeks after the first TST result was read. If the second TST result
is positive, it probably represents a boosted reaction, indicating infection most
likely occurred in the past and not recently. If the second TST result is also negative,
the person is classified as not infected. Two-step skin testing has no place in
contact investigations or in other circumstances in which ongoing transmission of
M. tuberculosis is suspected.
|
tumor necrosis factor-alpha (TNF-α) |
A small molecule (called a cytokine) discovered in the blood of animals (and
humans) with tumors but which has subsequently been determined to be an essential
host mediator of infection and inflammation. TNF-a is released when humans are
exposed to bacterial products (e.g., lipopolysaccharide) or BCG. Drugs (agents) that
block human TNF-a have been demonstrated to increase the risk for progression to
TB disease in persons who are latently infected.
|
ulceration (TST) |
A break in the skin or mucosa with loss of surface tissue.
|
ultraviolet germicidal radiation (UVGI)
|
Use of ultraviolet germicidal irradiation to kill or inactivate microorganisms.
|
UVGI lamp |
An environmental control measure that includes a lamp that kills or
inactivates microorganisms by emitting ultraviolet germicidal irradiation, predominantly at
a wavelength of 254 nm (intermediate light waves between visible light and
radiographs). UVGI lamps can be used in ceiling or wall fixtures or within air ducts of
ventilation systems as an adjunct to other environmental control measures. |
user-seal check |
Formerly called "fit check." A procedure performed after every respirator is donned
to check for proper seal of the respirator.
|
variable air volume (VAV) |
VAV ventilation systems are designed to vary the quantity of air delivered to a
space while maintaining a constant supply air temperature to achieve the desired
temperature in the occupied space. Minimum levels are mechanical, and outside air is maintained.
|
vesiculation
|
An abnormal elevation of the outer layer of skin enclosing a watery liquid; blister.
|
wheal
|
A small bump that is produced when a TST is administered. The wheal disappears
in approximately 10 minutes after TST placement.
|
workplace protection factor (WPF) |
A measure of the protection provided in the workplace by a properly
functioning respirator when correctly worn and used.
|
Guidelines for Preventing the Transmission of
Mycobacterium tuberculosis in Health-Care Settings, 2005
TB Infection-Control Guidelines Work Group: Diane I. Bennett, MD, Michael F. Iademarco, MD, Paul A. Jensen, PhD, Lauren A. Lambert,
MPH, Beverly Metchock, DrPH, Renee Ridzon, MD, Division of Tuberculosis Elimination, National Center for HIV, STD and TB Prevention,
CDC (Currently with the Bill and Melinda Gates Foundation); Paul M. Arguin, MD, Denise M. Cardo, MD, Amy B. Curtis, PhD, Adelisa L. Panlilio,
MD, Patricia M. Simone, MD, Division of Global Migration and Quarantine, National Center for Infectious Diseases, CDC; Jennifer L. Cleveland,
DMD, Amy S. Collins, MPH, Division of Oral Health, National Center for Chronic Disease Prevention and Health Promotion, CDC; G. Scott Earnest,
PhD, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, CDC; Teri Palermo, Division of
Respiratory Disease Studies, National Institute for Occupational Safety and Health, CDC; Teresa A. Seitz, MPH, Division of Surveillance, Hazard Evaluations,
and Field Studies, National Institute for Occupational Safety and Health; Yona Hackl, MS, Occupational Health and Safety, Office of the Director,
CDC; Jonathan Y. Richmond, PhD (Retired), Office of Health and Safety, Office of the Director, CDC; John C. Ridderhof, DrPH, Division of Public
Health Partnerships, National Center for Health Marketing, CDC; Allison Greenspan, Office of the Director, National Center for Infectious Diseases, CDC.
External Contributors: James August, MPH, American Federation of State, County and Municipal Employees, Washington, DC; Scott Barnhart,
MD, Harborview Medical Center, Seattle, Washington; Joe Bick, MD, University of California, Davis, California; Henry Blumberg, MD, Emory
University, Atlanta, Georgia; Dorothy Dougherty, Occupational Safety and Health Administration, Washington, DC; Charles E. Dunn, Sr, Commercial
Lighting Design, Inc. (Lumalier), Memphis, Tennessee; Amanda L. Edens, MPH, Occupational Safety and Health Administration, Washington, DC, New
Jersey Medical School, Newark, New Jersey; Kevin Fennelly, MD, New Jersey Medical School, Newark, New Jersey; Victoria Fraser, MD,
Washington University School of Medicine, St. Louis, Missouri; Mary Gilchrist, PhD, University Hygienic Laboratory, Iowa City, Iowa; Robert J. Harrison,
MD, California Department of Health Services, Oakland, California; Denise Ingman, U.S. Department of Health and Human Services, Helena,
Montana; Pam Kellner, MPH, New York City Department of Health, New York, New York; James McAuley, MD, Rush-Presbyterian-St. Luke's Medical
Center, Chicago, Illinois; Roy McKay, PhD, University of Cincinnati, Cincinnati, Ohio; Dick Menzies, MD, McGill University, Montreal, Canada; Shelly
L. Miller, PhD, University of Colorado, Boulder, Colorado; Jose Montero, MD, New Hampshire Department of Health and Human Services,
Concord, New Hampshire; Edward Nardell, MD, Harvard Medical School, Boston, Massachusetts; Mark Nicas, PhD, University of California at
Berkeley, Berkeley, California; Paul S. Ninomura, Health Resources and Services Administration, Seattle, Washington; Tholief O'Flaherty, PhD, New York
City Department of Health, New York, New York; Nicholas Pavelchak, New York State Department of Health, Troy, New York; Jean Pottinger,
MA, University of Iowa, Iowa City, Iowa; Gina Pugliese, MS, Premier Safety Institute, Chicago, Illinois; Randall Reves, MD, Denver Public
Health Department, Denver, Colorado; Jane Siegel, MD, University of Texas, Dallas, Texas; Kent Sepkowitz, MD, Memorial Sloan-Kettering Cancer
Center, New York, New York; Andrew J. Streifel, MS, University of Minnesota, Minneapolis, Minnesota; Rachel L. Stricof, MPH, New York State
Department of Health, Albany, New York; Michael L. Tapper, MD, Lenox Hill Hospital, New York, New York; Robert Weinstein, MD, Healthcare Infection
Control Practices Advisory Committee; Sharon Welbel, MD, Cook County Hospital, Chicago, Illinois; Karen Worthington, MS, Occupational Safety
and Health Administration, Lambertville, New Jersey.
CDC Contributors: Heinz William Ahlers, JD, National Institute for Occupational Safety and Health, CDC, Pittsburgh, Pennsylvania;
Gabrielle Benenson, MPH, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Roland BerryAnn, National Institute for
Occupational Safety and Health, CDC, Pittsburgh, Pennsylvania; Regina Bess, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia;
Yvonne Boudreau, MD, National Institute for Occupational Safety and Health, CDC, Denver, Colorado; Kenneth G. Castro, MD, National Center for
HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; L. Casey Chosewood, MD, Office of Health and Safety, CDC, Atlanta, Georgia; Christopher
C. Coffey, PhD, National Institute for Occupational Safety and Health, CDC, Morgantown, West Virginia; Janet L. Collins, PhD, National Center
for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Maria Fraire, MPH, National Center for HIV, STD, and TB Prevention, CDC,
Atlanta, Georgia; Judy Gibson, MSN, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Robert C. Good, PhD (Retired),
National Center for Infectious Diseases, CDC, Atlanta, Georgia; Maryam Haddad, MSN, National Center for HIV, STD, and TB Prevention, CDC,
Atlanta, Georgia; Connie Henderson, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Kashef Ijaz, MD, National Center for
HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; William R. Jarvis, MD (Retired), National Center for Infectious Diseases, CDC, Atlanta,
Georgia; John A. Jereb, MD, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Margaret Kitt, MD, National Institute
for Occupational Safety and Health, CDC, Morgantown, West Virginia; Mark Lobato, MD, National Center for HIV, STD, and TB Prevention,
CDC, Atlanta, Georgia; Suzanne Marks, MPH, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Stephen B. Martin, Jr.,
National Institute for Occupational Safety and Health, CDC, Morgantown, West Virginia; Kenneth F. Martinez, MSEE, National Institute for
Occupational Safety and Health, CDC, Cincinnati, Ohio; Jerry Mazurek, MD, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; R.
Leroy Mickelsen, MS, National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio; Vincent Mortimer, MS (Retired), National
Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio; Glenda Newell, National Center for HIV, STD, and TB Prevention, CDC,
Atlanta, Georgia; Tanja Popovic, MD, Office of the Director, CDC, Atlanta, Georgia; Laurence D. Reed, MS, National Institute for Occupational Safety
and Health, CDC, Cincinnati, Ohio; Apavoo Rengasamy, PhD, National Institute for Occupational Safety and Health, CDC, Pittsburgh,
Pennsylvania; Millie P. Schafer, PhD, National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio; Philip Spradling, MD, National Center
for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; James W. Stephens, PhD, National Institute for Occupational Safety and Health,
CDC, Atlanta, GA; Carol M. Stephenson, PhD, National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio; Zachary Taylor,
MD, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Tonya Thrash, National Center for HIV, STD, and TB Prevention,
CDC, Atlanta, Georgia; Douglas B. Trout, MD, National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio; Andrew Vernon,
MD, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Gregory R. Wagner, MD, National Institute for Occupational Safety
and Health, CDC, Washington, DC; Wanda Walton, PhD, National Center for HIV, STD, and TB Prevention, CDC, Atlanta, Georgia; Angela M.
Weber, MS, National Center for Environmental Health, CDC, Atlanta, Georgia; Robbin S. Weyant, PhD, Office of Health and Safety, CDC, Atlanta,
Georgia; John J. Whalen, MS (Retired), National Institute for Occupational Safety and Health, CDC, Cincinnati, Ohio.
Table 1
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