To assess diagnostic utility of pleural fluid adenosine deaminase (ADA), interferon gamma (IFN), lymphocyte/neutrophil ratio (L/N) and its combination in differentiating tubercular and non-tubercular exudative pleural effusion

Background: One of the common extrapulmonary manifestation of tuberculosis (TB) is pleural effusion. The conventional culture suffers from lack of sensitivity. Many pleural fluid markers have been evaluated but none has been proved to be ideal in diagnosing tubercular pleural effusion. We have studied Adenosine deaminase (ADA), Interferon gamma (IFN), lymphocyte/neutrophil (L/N) ratio and their combination for diagnosis of tubercular pleural effusion. Methodology: All consecutive patients with pleural effusion were subjected to thoracentesis and segregated into transudative and exudative using Light`s criteria. Patients with exudative pleural effusion were enrolled and divided into two groups. Group-I comprised of patients with tubercular etiology, Group-II- non-tubercular etiology. 45 patients were selected for each group. ADA, IFN, L/N ratio in pleural fluid of these patients were measured. The sensitivity, specificity and predictive values were calculated. Results: The sensitivity, specificity, positive predictive value, negative predictive value of ADA, IFN, L/N ratio were 88.89%, 99.85%, 86.96%, 99.87%; 97.78%, 97.78%, 97.78%, 97.78%; 88.89%,17.78%, 51.95%, 61.54%  respectively. Combination of ADA, IFN, L/N ratio provided the highest specificity that is 100%. Conclusions: Pleural fluid ADA, IFN were found to be useful in differentiating tubercular from non-tubercular patients. Combination of ADA, IFN, L/N was found to be most beneficial. Keywords: ADA; sExtrapulmonary tuberculosis; Pleural effusion.