A Study of Pleural Fluid Adenosine Deaminase Levels in Tubercular and Other Exudative Pleural Effusions

Tuberculosis is among the commonest causes of pleural effusion in India. Adenosine Deaminase (ADA) level in pleural fluid is chemical biomarker that can be employed as a rapid screening tool for tuberculosis. A prospective study was designed to evaluate the importance of pleural fluid ADA level in the diagnosis of tubercular pleural effusion and differentiating it from other causes of exudative pleural effusion. A total of 232 cases of pleural effusion were evaluated, of which 169 (72.85%) were found to be exudative pleural effusion. There were 76 (45%) cases of TB, 32 (19%) of malignancy and 50 (29.6%) of parapneumonic effusion whereas 11 (6.5%) cases belong to other causes or remained undiagnosed. Median ± SD value of ADAfor tubercular pleural effusion, malignant pleural effusion and parapneumonic effusion were 62.37 ± 22.63, 24.12 ± 10.88, and 34.55 ± 20.45 U/l respectively. Our study showed that 68 of 76 cases (89.5%) of patients with tubercular pleural effusion had ADA ≥ 40 U/l while only 3 (9.3%) out of 32 cases of malignant pleural effusion had ADA ≥ 40 U/l. Pleural fluid ADA ≥ 40 U/L yielded 89.47% sensitivity, 72.04% specificity, positive predictive value was 72.34% and a negative predictive value was 89.33% for diagnosis of TB. Pleural fluid ADAcan be utilized for differentiating TB effusions from those of non-tubercular etiology. Moreover it can obviate the need for pleural biopsy.