Diagnostic approaches in patients with tuberculous pleural effusion

The conventional bacteriologic methods used for diagnosing pleural tuberculosis are less sensitive and time consuming. The objective of this study was to develop nonbacteriologic methods and to assess their potential utilities for the rapid diagnosis, especially in smear/culture-negative patients. One hundred forty patients with pleural effusion were investigated for tuberculous etiology by bacteriologic methods. Mycobacterium tuberculosis in the pleural fluid specimens was isolated in 11 patients. To establish a tuberculous etiology in the remaining 129 patients, we performed the following assays: a) estimation of tuberculosis-associated glycolipid antigen (TBGL) by a modified indirect enzyme-linked immunosorbent assay (ELISA), b) an immunocytochemical method for the demonstration of TBGL antigen in the Cytospin smears, and c) detection of mycobacterial DNA by polymerase chain reaction (PCR). Estimation of TBGL antigen by ELISA showed 100% specificity and overall 85.5% sensitivity. Immunocytochemistry could be applied only in those samples with adequate number of macrophages. PCR carried sensitivity and specificity of 87% and 93%, respectively. Estimation of TBGL antigen in pleural fluid specimens by ELISA has a definite role in establishing tuberculous etiology, particularly in those patients in whom bacteriologic methods did not demonstrate M. tuberculosis and also in those in whom a distinction between tuberculous and nontuberculous etiology was not possible based on the clinical and radiologic features of the thorax.