Background: Pleural fluid adenosine deaminase (ADAPF) is a diagnostic test for diagnosing the early tuberculous pleuritis (TBP). However, cutoff values vary widely in many studies.
Objective: To determine the optimal diagnostic value of ADAPF.
Material and Method: A prospective study was performed between August 2012 and August 2014. One hundred seventyeight patients with pleural effusions; 29 TBPs, 63 malignant pleural effusions (MPEs), 40 parapneumonic effusions (PARAEs), 18 transudates, 5 empyemas, 19 other exudates, and 4 unknown causes, were investigated.
Results: Mean + SD of ADAPF was 60.0+25.6 U/L with TBPs, 15.6+11.1 U/L with MPEs, 15.8+9.9 U/L with PARAEs,
6.6+5.7 U/L with transudates, 13.8+7.7 U/L with empyemas, 14.5+7.1 U/L with other exudates, and 17.8+4.6 U/L with
unknown causes. The area under the ROC curve was 0.983 (95% CI: 0.969-0.998) for the best ADAPF cutoff value of 33.5 U/L, with 93.1% sensitivity, 94.6 % specificity, 77.1% positive predictive value, and 98.6% negative predictive. ADAPF level <30.5 U/L suggests that a TBP is highly unlikely.
Conclusion: Pleural fluid ADA assay is a helpful diagnostic tool with high sensitivity and specificity for the rapid diagnosis of TBP.

Keywords: Adenosine deaminase, Tuberculous pleuritis, Pleural fluid