Diagnostic Value of Adenosine Deaminase Level for the Differential Diagnosis of Tuberculosis and Malignancy in Exudative Lymphocytic Pleurisy

Objective: To evaluate the diagnostic performance of adenosine deaminase (ADA) levels in patients with exudative lymphocytic pleurisy for the differential diagnosis of tuberculous pleurisy (TBP) and malignant pleural effusion (MPE). Methods: Data on patients with exudative lymphocytic pleurisy were retrospectively analyzed. The study population comprised 54 patients. Thirty-seven were diagnosed with TBP and 17 were diagnosed with MPE. Results: Significant differences were determined in terms of age and ADA, total protein, albumin, and LDH levels between the TBP and MPE groups. The optimal cut-off value of ADA levels was 35.1 U/L for diagnosing TBP. Sensitivity and specificity were 92% and 100%, respectively. Logistic regression analysis was performed to assess independent variables associated with TBP. Independent predictive factors in the model were ADA (OR: 1.21, 95% CI: 1.06-1.39, p=0.006)], and (OR: 0.92, 95% CI: 0.84-1.00, p=0.052)]. The AUC value by the regression equation was 0.979 (p<0.001). When patients were categorized according to age (<50 ve >= 50), two different cut-off values (> 13.51 and > 35.1) for each age range were found in all, but one, TBP patients. Conclusion: ADA levels are useful for the diagnosis of TBP in cases where pleural biopsy cannot be performed or that are inconclusive in making a diagnosis of TBP. In this group, reducing the conventional cut-off value and/or performing an age-based approach seems to improve the diagnostic performance of ADA levels.