| Clinical Utility of Polymerase Chain Reaction for the Differentiation of Nontuberculous Mycobacteria in Patients with Acid-fast Bacilli Smear-positive Specimens. |
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Jae Seung Lee, Hyun Shuk Ji, Sang Bum Hong, Yeon Mok Oh, Chae Man Lim, Sang Do Lee, Younsuck Koh, Woo Sung Kim, Dong Soon Kim, Won Dong Kim, Tae Sun Shim |
1Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea. shimts@amc.seoul.kr
2Department of Diagnostic Laboratory Medicine, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea. |
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| Abstract |
BACKGROUND
In Korea, polymerase chain reaction (PCR) test for M. tuberculosis has been used for the diagnosis of acid-fast bacilli (AFB) smear-negative tuberculosis in order to increase diagnostic sensitivity. However, there have been no data dealing with the clinical utility of PCR in AFB smear-positive patients to differentiate between M. tuberculosis and nontuberculous mycobacteria. METHOD: We retrospectively analyzed the PCR test results which have been performed in patients who had AFB smear-positive sputum but had ambiguous clinical manifestations of active tuberculosis. PCR test was done using AMPLICORa M. tuberculosis kit. The sensitivity, specificity, and positive and negative predictive values of the PCR test were calculated based on culture and final clinical diagnosis result. RESULTS: Fifty-six consecutive patients (62 PCR tests) were included in the study. Active tuberculosis was diagnosed in 23 patients (41.0%), while 9 patients had NTM infection (16.0%). The sensitivity, specificity, positive- and negative-predictive value of PCR test were 88.8%, 86.8%, 76.1% and 94.3%, respectively, according to the culture result. In comparison, they were 91.3%, 100%, 100%, 94.3%, respectively, according to the final clinical diagnosis. All 15 patients with NTM isolates, including 6 patients who had other lung diseases but expectorated NTM isolate, were negative for PCR test. CONCLUSION: Even though tuberculosis is still prevalent in Korea, PCR test is useful to differentiate between M. tuberculosis and NTM in patients with AFB-smear positive sputum but with ambiguous clinical manifestations of active tuberculosis. |
| Key Words:
AFB smear-positive, Mycobacterium tuberculosis, Nontuberculous mycobacterium (NTM), Polymerase chain reaction (PCR) |
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