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*The FDA-approved NAA tests for TB have slightly less sensitivity than culture-isolation methods, and the 15% to 20% of U.S. TB cases that are reported with negative culture results may also have negative NAA test results. Thus, a negative NAA test result does not exclude the diagnosis of TB. | *The FDA-approved NAA tests for TB have slightly less sensitivity than culture-isolation methods, and the 15% to 20% of U.S. TB cases that are reported with negative culture results may also have negative NAA test results. Thus, a negative NAA test result does not exclude the diagnosis of TB. | ||
*Further research is needed before specific recommendations can be made on the use of NAA testing in the diagnosis of TB in children who cannot produce sputum and in the diagnosis of extrapulmonary TB, although there is much anecdotal evidence of the utility of such testing in individual cases. | *Further research is needed before specific recommendations can be made on the use of NAA testing in the diagnosis of TB in children who cannot produce sputum and in the diagnosis of extrapulmonary TB, although there is much anecdotal evidence of the utility of such testing in individual cases. | ||
==References== | ==References== | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Because of difficulties with the Tuberculin skin test, many laboratory methods of diagnosis are emerging [1] [2].
Other Diagnostic Studies
Adenosine Deaminase
In 2007, a systematic review of adenosine deaminase by the NHS Health Technology Assessment Programme concluded, "There is no evidence to support the use of ADA tests for the diagnosis of pulmonary TB. However, there is considerable evidence to support their use in pleural fluid samples for diagnosis of pleural TB, where sensitivity was very high, and to a slightly lesser extent for TB meningitis. In both pleural TB and TB meningitis, ADA tests had higher sensitivity than any other tests."[2]
Nucleic Acid Amplification Tests (NAAT) Adapted from CDC [3]
- This is a heterogeneous group of tests that use polymerase chain reaction (PCR) to detect mycobacterial nucleic acid.
- These test vary in which nucleic acid sequence they detect and vary in their accuracy.
- The two most common commercially available tests are the amplified mycobacterium tuberculosis direct test (MTD, Gen-Probe) and Amplicor (Roche Diagnostics). I
- n 2007, a systematic review of NAAT by the NHS Health Technology Assessment Programme concluded that "NAAT test accuracy to be far superior when applied to respiratory samples as opposed to other specimens. Although the results were not statistically significant, the AMTD test appears to perform better than other currently available commercial tests."[2]
- The CDC recommends that 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. .
- The FDA-approved NAA tests for TB have slightly less sensitivity than culture-isolation methods, and the 15% to 20% of U.S. TB cases that are reported with negative culture results may also have negative NAA test results. Thus, a negative NAA test result does not exclude the diagnosis of TB.
- Further research is needed before specific recommendations can be made on the use of NAA testing in the diagnosis of TB in children who cannot produce sputum and in the diagnosis of extrapulmonary TB, although there is much anecdotal evidence of the utility of such testing in individual cases.
References
- ↑ Drobniewski F, Caws M, Gibson A, Young D (2003). "Modern laboratory diagnosis of tuberculosis". Lancet Infect Dis. 3 (3): 141–7. PMID 12614730.
- ↑ 2.0 2.1 2.2 Dinnes J, Deeks J, Kunst H, Gibson A, Cummins E, Waugh N, Drobniewski F, Lalvani A (2007). "A systematic review of rapid diagnostic tests for the detection of tuberculosis infection". Health Technol Assess. 11 (3): 1–314. PMID 17266837.
- ↑ Template:Cite web: url=http://www.cdc.gov/tb/publications/guidelines/amplification tests/reccomendations.htm