Performance of Cobas TaqMan MTB for Detection of Mycobacterium tuberculosis Complex in Respiratory Specimens

Choi, Young Jin

Abstract

OBJECTIVE
Because tuberculosis is a major global health problem, rapid and accurate identification of Mycobacterium tuberculosis complex (MTBC) in clinical specimens is essential for the control of the spread of tuberculosis. One of real-time polymerase chain reaction assays for direct detection of MTBC, Cobas TaqMan MTB (Roche Diagnostics) assay has been widely used in clinical setting in Korea. The aim of study was to evaluate of the performance of Cobas TaqMan MTB assay in respiratory specimens.
METHODS
Total of 619 respiratory specimens (572 sputum specimens and 47 bronchoalveolar washing fluid specimens) was collected in August and September, 2011. All specimens were analyzed for the detection of MTBC by direct smear examination, mycobacterial culture, and Cobas TaqMan MTB assay.
RESULTS
When the culture method was used as the gold standard test for comparison, Cobas TaqMan MTB assay for detection of MTBC had a sensitivity and specificity of 80.9% (38/47) and 100% (572/572), respectively. Positive predictive value and negative predictive value of Cobas TaqMan MTB assay was 100% and 98.5%, respectively. The sensitivity of Cobas TaqMan MTB assay was 100% in AFB smear-positive samples and 59.1% in smear-negative samples.
CONCLUSION
Cobas TaqMan MTB assay has an excellent performance in smear-positive respiratory specimens. But performance of Cobas TaqMan MTB assay in smear-negative respiratory samples was not good. For detection of paucibacillary tuberculosis, conventional mycobacterial culture must not be replaced by Cobas TaqMan MTB assay.