Pleural fluid ADA, IgA-ELISA and PCR sensitivities for the diagnosis of pleural tuberculosis.

The diagnosis of pleural tuberculosis (pTB) is difficult, and more sensitive and specific techniques are needed. In the period August 1998 to November 2002, we evaluated 132 patients with a pleural effusion submitted to a thoracentesis and pleural biopsy in a tertiary care hospital in Rio de Janeiro, Brazil. Three tests were performed and compared in the pleural fluid: ADA activity measurement, IgA-ELISA for two combined specific Mycobacterium tuberculosis antigens, and polymerase chain reaction (PCR) for detection of M. tuberculosis DNA. Ninety-five patients (72%) were given a final diagnosis of pTB. Overall histopathologic sensitivity was 77%. The sensitivities of pleural fluid culture and AFB smear were 42% and 1%, respectively. Twenty-one (22%) additional patients had a clinical diagnosis of pTB. Median follow-up time of all TB patients after the completion of antituberculous treatment was 13 months. Sensitivities of ADA, IgA-ELISA and PCR were 91%, 78% and 82%, while specificities were 93%, 96% and 85%, respectively. Only ADA sensitivity was significantly higher than the histopathologic examination (McNemar chi2 test; p = 0.002) and also significantly higher than ELISA (p = 0.049), but not higher than PCR (p = 0.143). We conclude that the routine use of ADA activity measurement in pleural fluid can obviate the need for a pleural biopsy in the initial diagnostic approach to pleural effusions, while IgA-ELISA and PCR techniques, potentially more specific tests, need further refinement to improve their accuracy.

Detection of Mycobacterium tuberculosis by a polymerase chain reaction colorimetric dot-blot assay.

SETTING: A public health laboratory in a tuberculosis-endemic region in Brazil. OBJECTIVE: To evaluate the accuracy of a combined polymerase chain reaction (PCR) colorimetric dot-blot protocol for Mycobacterium tuberculosis detection in clinical samples in a public health laboratory. DESIGN: Eighty clinical samples (13 cerebrospinal fluid, 31 induced sputum, 17 expectorated sputum, eight bronchoalveolar lavage and 11 pleural fluid) were assayed with the developed protocol. The accuracy of polymerase chain reaction (PCR) dot-blot methodology was compared to PCR agarose gel electrophoresis (PCR-AG) using as a gold standard the bacteriological result (culture and biochemical identification) combined with clinical follow-up. One internal region of the IS6110 repetitive element of the M. tuberculosis complex was selected for amplification and the amplified product transferred to nylon membranes to be detected by biotinylated DNA probe. RESULTS: Overall sensitivity and specificity obtained were respectively 90% and 97% for PCR-AG and 95% and 97% for the PCR dot-blot. Among the 56 respiratory specimens, the sensitivity and specificity results for PCR-AG were respectively 88% and 95%, and for PCR dot-blot they were 94% and 95%. Among the 24 non-respiratory specimens the sensitivity and specificity results were respectively 83% and 100% for PCR-AG, and 100% and 100% for the PCR dot-blot protocol. CONCLUSION: The results demonstrated that the PCR dot-blot assay may be helpful in the diagnosis of tuberculosis, and feasible even in resource-poor countries.