Fiberoptic bronchoscopy in the rapid diagnosis of unknown tuberculosis with the use of NAA tests

Background. NAA tests (nucleic acid amplified tests) directly enable rapid detection RNA or DNA of the Mycobacterium tuberculosis complex in clinical samples. The aim of this study was to estimate the diagnostic utility of fiberoptic bronchoscopy (FOB) in conjunction with the use of NAA tests in the rapid diagnosis of TB in sputum smear negative patients. Methods. Authors in a retrospective study reviewed the results of NAA tests obtained by examinations of bronchoalveolar lavage fluid (BAL) or bronchoaspirate (BA). During a period of 5 years (1995 to 1999), 2,349 BAL and BA specimens with NAA tests in two, 284 patients were examined. Results. The Amplicor and PCR (polymerase chain reaction) tests were used in 1,807 samples and the Mycobacterium tuberculosis direct test (MTDT, Gen-Probe) in 542. The NAA test was positive in 91 patients (3.8%), and culture positivity was verified in 77 of them. In the 14 patients with just the NAA test positivity the final diagnosis of TB was accepted in eight cases on the basis of clinical and radiological improvement after 2 months of therapy. In six cases the test was estimated to be a false positive, and there were 12 false negative cases (NAA test negative, culture positive). Sensitivity was 88.5%, specificity 99.3%, positive predictive value 84.8%, and negative predictive value 99.4%. Conclusions, The findings suggested that the identification of the Mycobacterium tuberculosis complex in bronchoalveolar lavage fluid or bronchoaspirate using NAA tests is a useful method for the rapid diagnosis of TB in patients with negative acid fast bacilli (AFB). Bronchoscopic examination can also exclude other pulmonary diseases.