Diagnostic value of pleural fluid adenosine deaminase activity in tuberculosis pleurisy

Diagnosis of tuberculosis pleurisies is difficult because of its nonspecific clinical presentation and insufficient traditional diagnostic methods. We investigated the use of adenosine deaminase (ADA) activity in tuberculosis pleurisies. A number of 85 patients were analyzed with exudative pleural effusions. Using the ROC curve, we determined the optimal cutoff for TB pleurisy. A number of 58 exudative samples were nontuberculous (non-TB) and 27 were tuberculosis (TB). There was statistically significant difference (p<0.0001) between the means of pleural fluid ADA levels among the TB and non-TB populations. The prevalence of TB pleurisy in the studied population was 31%. Using the cutoff point equal to 35 for diagnosing TB effusions the sensitivity and specificity 70.3% and 91.3%, respectively. The positive predictive value (PPV) was 79.1% and the negative predictive value (NPV) was 86.8%. A pleural fluid ADA value <19 IU/L suggests that a tuberculosis effusion is highly unlikely. Pleural fluid total ADA assay is a sensitive and specific test suitable for rapid diagnosis of TB pleurisy.