| |
Fact Sheets
Targeted Tuberculin Testing and Interpreting
Tuberculin Skin Test Results
Last Updated: May 2005
Introduction
Targeted tuberculin testing is used to focus program activities,
provider practices, and financial resources on groups at the highest
risk for latent tuberculosis infection (LTBI). Once TB disease
has been ruled out, those who would benefit from treatment of
LTBI should be offered this option regardless of their age.
Every effort should be made to test only those persons at the
highest risk, interpret tuberculin skin test (TST) reactions accurately,
and ensure appropriate treatment and completion of the recommended
regimen.
Persons at Risk for Developing TB Disease
Generally, persons at high risk for developing TB disease fall
into two categories: those who have been recently infected, and
those with clinical conditions that increase the risk of progression
from LTBI to TB disease.
Recent infection should be suspected in the following:
- Close contacts of a person with infectious TB
- Persons who have immigrated from areas of the world with
high rates of TB
- Children < 5 years of age who have a positive TST
result
- Recent converters (those with an increase of 10 mm or more
in size of TST reaction within a 2-year period)
- Groups with high rates of M. tuberculosis transmission,
such as homeless persons, injection drug users, and persons
with HIV infection
- Persons who work or reside with people who are at high risk
for TB in facilities or institutions such as hospitals, homeless
shelters, correctional facilities, nursing homes, and residential
homes for those with HIV
Clinical conditions that increase the risk of progression from
LTBI to TB disease:
- HIV infection
- Radiographic evidence of prior TB
- Low body weight (> 10% below ideal)
- Silicosis
- Diabetes mellitus
- Chronic renal failure or being on hemodialysis
- Gastrectomy
- Jejunoileal bypass
- Solid organ transplant
- Head and neck cancer
- Prolonged use of immunosuppressive agents (e.g., prednisone,
TNF-α antagonists)
Criteria for Classifying Positive TST Reactions
Reaction of > 5 mm of induration is considered positive
in
- HIV-infected persons
- Recent contacts of infectious TB cases
- Persons with fibrotic changes on chest radiograph consistent
with prior TB
- Organ transplant recipients
- Persons who are immunosuppressed for other reasons (e.g.,
taking the equivalent of >15 mg/day of prednisone for 1 month
or more, taking TNF-α antagonists)
Reaction of > 10 mm of induration is considered
positive in
- Recent immigrants (within last 5 years) from high-prevalence
countries
- Injection drug users
- Residents or employees of high-risk congregate settings
- Mycobacteriology laboratory personnel
- Children < 4 years of age, or children or adolescents
exposed to adults at high risk
- Persons with clinical conditions previously mentioned
Reaction of > 15 mm of induration is considered positive
in
- Persons with no known risk factors for TB*
* Although skin testing programs should be conducted only
among high-risk groups, certain individuals may require TST for
employment or school attendance. An approach independent of risk
assessment is not recommended by CDC or the American Thoracic
Society.
Special Considerations
Questions often arise about the interpretation of TST results
in persons with a history of Bacille Calmette-Guérin (BCG) vaccine,
HIV infection, and recent contacts to an infectious TB case.
BCG vaccine is currently used in many parts of the world to protect
infants and children from severe TB disease, especially TB meningitis.
It does not confer lifelong immunity, and its significance in
persons receiving the TST causes confusion in the medical and
lay community.
- History of BCG vaccine is NOT a contraindication for tuberculin
testing
- TST reactivity caused by BCG vaccine generally wanes with
time
- If more than 5 years have elapsed since administration of
BCG vaccine, a positive TST reaction is most likely a result
of M. tuberculosis infection
Persons who are HIV infected have a much greater risk for progression
to TB disease if they have LTBI.
- Individuals with HIV infection may be unable to mount an
immune response to the TST and may have false-negative TST results
- Usefulness of anergy testing in TST-negative persons who
are HIV infected has not been demonstrated
Persons with a postive TST result who are contacts of an individual
with infectious TB should be treated regardless of age.
- Some TST-negative persons should also be considered for treatment
(i.e., young children, immunosuppressed)
- Repeat TST in 8–12 weeks if initial test result is negative.
A delayed-type hypersensitivity response to tuberculin is detected
2–12 weeks after infection
References
Additional Resources
Websites:
The following resources can be viewed and downloaded from the
CDC website at www.cdc.gov/tb.
Slide Set:
Fact Sheets:
Last Reviewed: 05/18/2008
Content Source: Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
|
| |
Back to Top of Page
If you would like to order any of the DTBE publications please visit the online order form.
You will need Adobe Acrobat™ Reader v5.0 or higher to read pages that are in PDF format. Download the Adobe Acrobat™ Reader.
If you have difficulty accessing any material on the DTBE Web site because of a disability, please contact us
in writing or via telephone and we will work with you to make the information available.
Division of Tuberculosis Elimination
Attn: Content Manager, DTBE Web site
Centers for Disease Control and Prevention
1600 Clifton Rd., NE Mailstop E-10
Atlanta, GA 30333
CDC-INFO at (1-800) 232-4636
TTY: 1 (888) 232-6348
E-mail: cdcinfo@cdc.gov
Home | Site Map
| Contact Us
Accessibility
| Privacy Policy Notice |
FOIA
| USA.gov
CDC Home |
Search |
Health Topics A-Z
Centers for Disease Control & Prevention
National Center for HIV/AIDS,
Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination
Please send comments/suggestions/requests to: CDCINFO@cdc.gov
|
