PURPOSE: Microscpic examination of sputum smear for acid-fast bacilli(AFB) is the most important and rapid diagnostic test for pulmonary tuberculosis. However, the AFB observed on the smear may represent either M. tuberculosis or nontuberculous mycobacteria(NTM). There was a gradual increase in number of NTM isolation in patients who were suspected to have pulmonary tuberculosis in Korea. This study examined the clinical usefulness of PCR test for M. tuberculosis(TB-PCR) for the differentiation of pulmonary tuberculosis and NTM lung disease in patients with AFB smear-postive sputums.
METHODS: We retrospectively analyzed the results of TB-PCR test which have been performed in patients who had AFB smear positive sputum and positive culture for M.tuberculosis or NTM. from January 2005 to December 2006 in Seoul Veterans Hospital. TB-PCR test was done using AMPLICOR M.tuberculosis kit.
RESULTS: NTM were recovered from 28.2%(175/620) of the AFB smear positive sputum specimens and 27.6%(59/214) of the patients with AFB smear positive sputum with M. avium complex(MAC) being the predominant species isolated. 33 patients(55.9%) had MAC and 14 patients(23.7%) had M. abscessus. In the patients with pulmonary tuberculosis, 92.3% of the patients showed TB-PCR positive, and all the patients except one(98.3%) with NTM lung disease showed negative results on the TB-PCR test (p<0.001). In patients with AFB smear positive sputum, a positive result of TB-PCR test was able to predict pulmonary tuberculosis with 92.3% sensitivity, 98.3% specificity, 99.3% positive prective value and 82.6% negative predictive value.
CONCLUSION: The TB-PCR test for sputum specimens could be useful to differentiate between NTM lung disease and pulmonary tuberculosis in the patients with AFB smear positive sputum in Korea.
CLINICAL IMPLICATIONS: TB-PCR test is recommended to differentiate tuberculosis and NTM lung disease in patients with AFB smear positive sputum.
DISCLOSURE: Yong-Ho Roh, No Financial Disclosure Information; No Product/Research Disclosure Information