Diagnostic Role of Adenosine Deaminase level in Exudative Lymphocytic Pleural Effusions

Abstract

Background: Exudative lymphocytic pleural effusion is common problem and tissue diagnosis is gold standard for the diagnosis but it is invasive procedure with complications. Raised ADA levels are observed in tuberculous effusion but definite cut off levels is lacking for our population.Aims and Objectives:To determine the diagnostic accuracy of pleural fluidADAwhile comparing with closed pleural biopsy.Study Design: It was a Cross-sectional (validation) study conducted inPulmonology Department, SIMS/ Services Hospital Lahore, from December15, 2013 to October 22, 2015.Materials & Methods: It is a prospective, non-randomized study performed inpulmonology Department, Services Hospital Lahore. 108 patients withlymphocytic exudative pleural Effusion were enrolled in the study. ADA levelswere measured using commercially available ADA kit DIAZYME (Diazymelaboratories Poway, CA 92064, USA) on pleural fluid obtained by thoracocentesis and pleural biopsy specimen was taken by close pleural biopsy fromeach enrolled patient after informed consent.Results: Out of 108 patients 75 (69.4%) were males and 33 (30.6%) were females. Mean age was 45.21 +17.85 SD years. 69 (63.8%) cases were diagnosed as having Tuberculosis by pleural biopsy and/or AFB culture, 36 (33.33%) cases were diagnosed as malignant and 3 (2.7%) cases wereinconclusive. In biopsy proven tuberculous pleural effusion (n=69), ADA levelranged from 30-128 IU/L with mean pleural fluid ADA level of 55.93 +14.12 IU/L and 68 patients had >40 IU/L. In non TB pleural effusion (NTPE) (n=39), ADA level ranged from 10-45 IU/L with mean pleural fluid ADA level of 21.35+12.65 IU/L. Only three patients had raised ADA levels >40. Taking pleuralbiopsy as gold standard and taking ADA level > 40 IU/L as cut off value, thesensitivity and specificity of pleural fluid ADA level in the diagnosis of TPE were95.77% and 92.31%, respectively. Positive predictive value was 91.89%,negative predictive value was 97.29% and overall Diagnostic accuracy was96.29%.Conclusion:ADA level in pleural fluid can be used as a diagnostic test in theworkup for tuberculosis pleural effusion with sensitivity and specificitycomparable to histopathology and/or culture for acid fast bacilli in pleuralbiopsy specimen.