Comparative Evaluation of Pleural Fluid Adenos-ine Deaminase (Ada) Versus Lactate Dehydroge-nase/Adenosine Deaminase (Ldh/Ada) Ratio for Distinguishing Tubercular From Non-Tubercular Pleural Effusions

Introduction: Pleural effusion is a frequently encountered clinical condition with varied aetiologies, including tuberculosis, malignancy, and bacterial infections.While pleural fluid adenosine deaminase (ADA) is a commonly used marker for diagnosing tuberculous pleural effusion (TPE), its diagnostic specificity may be limited in cases with elevated ADA levels.The lactate dehydrogenase to adenosine deaminase (LDH/ ADA) ratio in pleural fluid has recently emerged as a promising marker for differentiating TPE from non-tuberculous pleural effusion (NTPE). Materials and Methods:This retrospective study included 80 patients with pleural effusion and pleural fluid ADA 40 IU/L who underwent diagnostic thoracentesis at a tertiary care centre.Patients were categorised into TPE and NTPE groups based on microbiological, cytological, and clinical response criteria.Demographic, clinical, and pleural fluid biochemical data including LDH and ADA were analysed.Results: Of the 80 patients, 40 had TPE and 40 had NTPE.The median LDH/ADA ratio was significantly lower in TPE (5.46) than in NTPE (39.82).A cutoff of 13.9 for the LDH/ADA ratio showed 76.5% sensitivity and 91.2% specificity for diagnosing TPE (AUC: 0.87). Conclusion:The pleural fluid LDH/ADA ratio is a reliable and superior diagnostic tool compared to ADA alone in distinguishing TPE from NTPE in patients with elevated ADA.It offers enhanced specificity and can aid clinical decision-making in TB-endemic settings.