|
|
Report of an Expert Consultation on the Uses of Nucleic Acid
Amplification Tests for the Diagnosis of Tuberculosis
Return to Contents
General Recommendations of the Expert Panel:
- All U.S. clinicians and public health TB programs should
have access to molecular tests to aid in the diagnosis of TB. NAA testing for TB should become standard practice for TB
suspects.
- NAA testing should be performed on a respiratory specimen
from each patient with signs and symptoms of active pulmonary TB
disease for whom a diagnosis of TB is being considered (i.e., TB
suspect), but has not been established.
- NAA testing does not replace the need for AFB smear and
culture. All current guidelines and recommendations for
culture-based testing should remain in effect, especially
recommended turn around times for culture and DST.
- A single positive NAA test result can support the
diagnosis of TB in a patient for whom there is a reasonable
index of suspicion. This result should trigger reporting to
public health officials, initiation of treatment if not already
started, and intensified efforts to obtain an isolate for drug
susceptibility testing.
- In a patient with little suspicion of having active TB, a
single positive NAA test result should be viewed with suspicion
(i.e., a possible false-positive result) and interpreted in the
same way as a single culture-positive result, i.e., by
correlating the results with other diagnostic findings.
- A single negative NAA test result should never be used as
a definitive test to exclude TB, especially in suspects with a
moderate to high clinical suspicion of TB. Rather, the negative
NAA test result should be used as additional information to aid
in making clinical decisions to expedite a work-up for an
alternative diagnosis or to prevent unnecessary use of TB
treatment in suspects with a low clinical suspicion.
- Specimens may contain inhibitors. Testing for inhibitors
should be considered for specimens that are AFB-smear positive
and NAA test-negative. Each laboratory should establish the rate
of inhibition to determine if routine testing for inhibitors is
necessary. If inhibition testing is not performed on NAA
test-negative specimens, it should be noted on the laboratory
report.
- If the clinician is inexperienced with the diagnosis and
treatment TB, consultation with a TB expert should be obtained
with respect to the interpretation of NAA test results in the
context of other diagnostic evidence.
- It is recommended that the appropriate work group
consider amending the guidelines for ‘Controlling the
Transmission of TB in Health Care Settings 2005’ section on
‘Suspected TB Disease’ to: ‘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, 2) the patient has three negative AFB sputum
smear results,’ or 3) the patient has a sputum specimen that has
a negative NAA test result and two additional sputum specimens
that are AFB-smear negative. ‘Each of the three consecutive
sputum specimens should be collected in 8–24-hour intervals, 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.’
Note: this recommendation does not apply to patients with a
suspicion for TB that is high enough to start TB medication. For
these patients, release from isolation requires clinical
response to treatment, usually four to seven days of treatment
in addition to three negative specimens by sputum AFB smears or
NAA testing as outlined above.
- NAA testing should be treated as a priority test.
- Health care providers should be provided with clear
instructions for the collection of quality specimens and
encouraged to collect an adequate volume (5-10ml).
- The processed diagnostic specimen must be suspended in
sufficient volume to ensure adequate samples for NAA testing,
AFB-smear microscopy, and culture.
- The interval from specimen collection to the time that
the laboratory report is communicated to the treating clinician
must be as brief as possible. Laboratories and programs should
track this performance measure.
- Specimens must be delivered promptly to the laboratory
that does the NAA testing.
- Specimens must be tested promptly in the laboratory,
preferably on the day received (i.e., without introducing
significant delays by batching specimens).
- The results of NAA tests should be available within 48
hours of specimen collection.
- Laboratorians should treat an initial positive NAA test
result as a critical test value. They must immediately report
NAA test results to the health care provider and be available
for consultation as to appropriate test interpretation and
possible need for follow-up testing.
- Laboratorians should immediately report initial positive
NAA test results to public health authorities for earlier
interventions and possibly earlier engagement of a TB expert in
the management of the patient.
- For laboratories that do not have sufficient resources
for NAA testing or sufficient test volume for NAA testing
without adding delays from batching, specimens for NAA testing
should be referred promptly to laboratories that have
demonstrated proficiency in the test and can provide timely
results (e.g., within 24–48hrs).
- Laboratories performing NAA testing should participate in
a NAA proficiency testing program (e.g., WSLH PT [Wisconsin
State Laboratory of Hygiene Proficiency Testing], CAP [College
of American Pathologists], or other accredited program).
- The number and types of NAA tests, commercial sources,
FDA-approved tests, and validated ASR tests should be increased.
- Research is needed to improve specimen processing,
referral processes, testing algorithms, NAA test performance and
ease-of-use, utility for diagnosing extrapulmonary and pediatric
TB, and regulatory quality trials.
- The expert panel endorses the recommendations under
consideration in the proposed revision of the ‘Diagnostic
Standards and Classification of Tuberculosis in Adults and
Children’ supporting the routine use of molecular methods for
detection of drug resistance directly in AFB smear-positive
sputum sediments for TB patients who are suspected of having
drug-resistant disease or are from a region or population with a
high prevalence of drug resistance.
Last Modified: 11/25/2008
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
|
|
|