Diagnostic value of the ratio of pleural fluid adenosine deaminase activity to serum adenosine deaminase activity in children with tuberculosis and non tuberculosis pleural effusion

Adenosine deaminase (ADA) activity was assayed in pleural fluid and serum of 78 subjects with pleural effusion. 48 of them had tuberculosis (TB) pleural effusion and the remaining 30 had pleural effusions due to non TB respiratory diseases. It is a retrospective study conducted in the biochemistry department, Niloufer hospital, Hyderabad. Serum and pleural fluid ADA activities were assayed spectrophotometrically by the method of guisti and gallant. The aim is to evaluate the value of (ADA) concentration in the pleural effusions for differentiating TB pleural effusions from non TB pleural effusions. The mean pleural ADA (99.78±75.80), serum ADA (79.19±59.17), and pleural fluid/serum ADA ratio(1.26±0.21) are significantly higher in TB pleural effusion cases as compared to non TB pleural effusion cases (The mean pleural ADA 23.10±11.92, Serum ADA 21.69±8.98, Pleural fluid/serum ADA ratio 1.07±0.47) respectively. Using the cutoff value 1.26 the ratio of pleural fluid/serum ADA was found to have a sensitivity of 40% and specificity of 81.25% for the diagnosis of tuberculosis in children. From this study it is concluded that ratio of pleural fluid ADA to serum ADA is a useful tool to diagnose tuberculous pleural effusion cases in children.