Adenosine Deaminase as a Diagnostic Aid to Ascertain Tuberculous Etiology of Pleural Effusions

Aim: To determine the sensitivity and specificity of pleural fluid ADA for the diagnosis of tuberculous pleural effusion taking the cut off value of ADA as ≥ 40 mg/dl. Methods: It was a prospective, analytical study comprised of 220 patients having pleural effusion. Sputum smear examination and sputum culture for mycobacterium tuberculosis, pleural fluid examination for protein, glucose, cell count, malignant cells, Gram’s stain, AFB, pleural fluid culture for mycobacterium tuberculosis and other relevant investigations were performed. ADA was measured in pleural fluid by colorimetric method of Guisti and Galanti. Results: Tuberculosis was the final clinical diagnosis in 164 (74.5%) patients having pleural effusion out of which 161 (98.2%) patients had ADA level ≥ 40 IU/L and only 3 (1.8%) had ADA level < 40 IU/L. None of the patients of pleural effusion with other than tuberculous etiology except 3 patients of parapneumonic effusions had ADA level ≥ 40 IU/L. The cut off value of 40 IU/L for pleural fluid ADA level was found to have 98.17% sensitivity and 94.64% specificity. Conclusion: Pleural fluid adenosine deaminase level >40% is a sensitive and specific marker of tubercular etiology in cases of pleural effusion. Keyword: Tuberculosis, pleural effusion, adenosine deaminase