Evaluation of polymerase chain reaction for rapid diagnosis of clinically suspected tuberculous pleurisy

Abstract

Pleural effusion is one of the commonest presentations of tuberculosis, the clinical manifestations being typically abrupt resembling bacterial pneumonia. Since delayed hypersensitivity is the underlying immune response, bacterial load is very low. Owing to these facts, tuberculous pleurisy as an extra-pulmonary disease poses a diagnostic dilemma. The conventional bacteriological methods rarely detect Mycobacterium tuberculosis in pleural fluid and are of limited use in diagnosis of tuberculous pleurisy. We evaluated the efficacy of polymerase chain reaction (PCR) in the diagnosis of tuberculous pleurisy by targeting the gene segment coding for MPB64 protein specific forMycobacterium tuberculosis. Based on the clinical criteria, 82 patients with lymphocytic exudative pleural effusion were included in the study. Patients were analyzed in two groups; one group consisting of 48 patients of tubercular pleural effusion confimed by various diagnostic procedures and another group of 34 patients comprising of non-tubercular pleural effusion. There were no false positive results by PCR and the specificity worked out to be 100%. Twenty two patients tested positive for Mantoux with a sensitivity of 45%. ZN-staining for AFB was found in samples from 15 patients (20% sensitivity). ADA was positive for 28 patients with a sensitivity of 53%. PCR was positive for 32/48 patients (67% sensitivity). Thus, PCR was found to be more sensitive than any other conventional method in diagnosis of clinically suspected tubercular pleurisy.