The diagnosis of tuberculosis may depend on examination of the sputum, examination ofthe pleural fluid for Mycobacterium tuberculosis, and histopathological examination ofthe parietal pleura, still in many cases, there is no conclusive prooffor the diagnosis. The present study aimed at evaluating the role ofthe polymerase chain reaction (peR) in the diagnosis ofdifferent forms of tuberculosis from different tissue samples and bu.fJY coat of the peripheral blood. This study included 37 patients, divided into three groups. Group 1 included 20 patients with active tuberculosis sputum smear and/or cliiture positive for acid fast bacilli. Group JJ included 13 patients with unilateral tuberculous pleural effusion with highly positive tuberculin test and exudative lymphocytic pleural effusion. The diagnosis was confirmed by culture ofthe pleural fluid on L.J. media. also by histopathological examination for caseating tuberculous granuloma ofthe parietal pleural biopsy. Group lJJ included 4 patients with right side transudative pleural effusion secondary to congestive heartfailure. Sputum peR was positive in /8 out of20 patients in group / but negative in all cases ofgroup /l and l/l (sensitivity 90.9% and specificity 100%). Pleural fluid peR was positive in 10 patients out of13 cases in group /l but negative in group l/l (sensitivity 81.2% and specificity 100%). Peripheral blood peR was negative in all patients ofthe three groups (sensitivity zero% and specificity 100%). From this study it can be concluded that peR is a
useful, sensitive, specific and rapid technique for the diagnosis oftuberculosis from the tissue samples ofthe affected organ and not from the peripheral blood.