The diagnostic efficacy of polymerase chain reaction and adenosine deaminase in tubercular effusion

The aim of this study was to evaluate the efficacy of combination of adenosine deaminase and polymerase chain reaction in the diagnosis of tubercular effusions. This study was conducted in the department of General Medicine and Cardiovascular and thoracic surgery SKIMS for a period of two years between November 2008 to November 2010. A total of 57 patients presenting with pleural effusion during these two years were included in this study. Patient’s criteria: In order to be included in this study, patients had to present with clinical manifestations suggestive of tuberculosis, i.e., the presence of productive cough, low-grade fever, night sweats, weight loss and chest pain, especially if these symptoms last ≥ 4 weeks. If the patients presented with less than two of these symptoms and especially if the clinical manifestations were of < 4 weeks in duration, they were excluded from the study. The combination of both ADA and PCR with a positive result by either of the two methods increased the sensitivity over both the tests. When used in combination, both ADA and PCR picked up 38 out of the 39 diagnosed pleural tuberculosis patients increasing the sensitivity to 97.4% at the cost of specificity (50%). Pleural biopsy was performed in 37 of the 57 studied patients. Out of the 39 patients with pleural tuberculosis, pleural biopsy was performed in 21 patients. Histological findings suggestive of tuberculosis were found in six patients. In our study the sensitivity of pleural biopsy was only 28.6% and a specificity of 100%. The combination of ADA and PCR improved the sensitivity to 97.4% which was much higher than pleural biopsy (28.6%), PCR (51.3%) and even ADA (89.7%) but at the cost of specificity which dropped to 50%. Comparison of sensitivity and specificity of this combination to ADA and PCR and to the “gold standard” pleural biopsy supports the feasibility of using the PCR of pleural fluid together with determination of ADA activity as the first diagnostic approach in circumstances in which pleural tuberculosis is suspected and access to procedures such as needle biopsy of pleura is limited.