Evaluation of Polymerase Chain Reaction and Pleural Fluid Adenosine Deaminase Levels for the Diagnosis of Tuberculous Pleural Effusion

BACKGROUND We wanted to evaluate the performance of Polymerase Chain Reaction (PCR) and pleural Adenosine Deaminase (ADA) levels for the diagnosis of tuberculous pleural effusion (TPE) as compared to the composite reference standard (CRS) based on clinical findings, smear microscopy, culture, cytology, site specific computerized tomography scan and response to anti-tuberculosis therapy. METHODS A total of 134 pleural fluid samples obtained as a part of routine diagnostic workup from patients suspected of TPE were subjected to real time PCR and determination of pleural ADA levels. Test results of PCR and ADA were compared with CRS. Sensitivity, specificity, positive predictive value, negative predictive value were determined using Statistical Package for the Social Sciences, Version 16. RESULTS 60 patients (44.77%) were found to be positive by both PCR and ADA, 22 (16.41%) patients were positive by ADA alone and 9 (6.71%) patients were positive by PCR alone; whereas, 43 (32.08%) patients were negative by both the assays. The overall sensitivity of TB PCR and pleural ADA was found to be 87.34% and 88.61% respectively. Whereas the specificity of PCR and pleural ADA levels for TPE detection was found to be 100 % and 80% respectively. CONCLUSIONS Although we observed almost similar sensitivity of PCR and ADA for diagnosis of TPE, the specificity of PCR was much higher than ADA. PCR and pleural ADA are promising tools in diagnostic workup of TPE. A significant association of TPE with young age males and diabetic patients was observed which remains a concern and signifies the need of further elaborate studies.