Role of serum and pleural adenosine deaminase activity compared to pleural fluid analysis in patients with pleural effusion of various etiology

Abstract

Background: Numerous tests are available for determining the cause of exudate, but all these tests lack sensitivity and specificity, and they are not generally available. Adenosine deaminase (ADA) activity in pleural or peritoneal fluid is simple and useful investigation in diagnosis of exudate effusion, particularly in differentiating tuberculous from nontuberculous exudative effusion. Objectives: To estimate the diagnostic utility of pleural and peritoneal fluid ADA/serum ADA ratio, in the diagnosis of tubercular pleural effusion. Materials and Methods: A hospital-based cross-sectional diagnostic evaluation study was carried out among 50 patients with pleural effusions selected to assay ADA activity in pleural fluid and serum along with pleural fluid analysis. Effusions were classified into transudative and exudative after careful evaluation of all biochemical parameters of pleural fluid. Cutoff value for pleural ADA was taken as 60 U/L and for pleural/serum ADA was taken as 2.5. Results: Forty-three patients had exudative effusions among which 38 were tubercular and five were nontubercular, seven cases were transudative. Mean pleural ADA levels in tuberculous group (80.31 ± 24.84 U/L) were higher (P < 0.01) than nontubercular group (23.00 ± 5.22 U/L). Serum ADA levels in tubercular group (27.23 ± 7.32 U/L) were significantly higher (P < 0.0l) as compared to nontubercular group (14.95 ± 7.04 U/L). Serum ADA levels in tubercular group (27.23 ± 7.32 U/L) were also significantly higher as compared to the control group of healthy individuals (13.00 ± 2.75 U/L). Pleural ADA cutoff at 60 U/L gave a sensitivity and specificity of 81% and 100%, respectively, whereas pleural serum ADA ratio at a cutoff of 2.5 gave a sensitivity and specificity of 71% and 81%, respectively. Conclusion: The measurement of ADA in tubercular pleural effusion is not only relevant, but also of a high diagnostic value when other clinical and laboratory tests are either negative or inconclusive.