Diagnostic Accuracy of Pleural Fluid Soluble Interleukin 2 Receptor in Patients with Tuberculous Pleural Effusion

Background: Pleural tuberculosis occurs in 4% of newly diagnosed cases of tuberculosis. T-cells have an important role on the immunity against mycobacterial infections and as a result, the level of soluble interleukin 2 receptors (SIL-2R) as a marker of T-cell activation is elevated in patients with tuberculous pleural effusion.

Materialss and Methods: In this cross sectional study, the diagnostic accuracy of SIL-2R level was assessed in separating tuberculous from non- tuberculous effusions in Zahedan, Iran. From 112 patients fulfilled entrance criteria for exudative pleural effusion, 88 patients were included and underwent diagnostic procedures to identify the origin of pleural effusion. The SIL-2R was evaluated at various cut-off levels by nonparametric receiver operating characteristic (ROC) curve, and values affording greatest diagnostic accuracy were selected.

Results: SIL-2R level in TB group was 9147±3573 while this level in non-TB group was 2724±1326 and the difference was statistically significant (p=0.001). The cut-off point in our study was 4200 U/ml and the area under curve was 0.930 with 95% CI: 0.881–0.979 (p=0.001). The sensitivity and specificity for this level is 86 and 89%.

Conclusion: Several factors lead to the variation in the level and cut-off point of SIL-2R in different regions. Our cut-off point was lower than other studies. The level of SIL-2R in patients with tuberculosis is significantly higher than parapneumonic effusions. We suggest that measuring the SIL-2R level in pleural fluid of tuberculous patients is a useful diagnostic tool in diagnosing tuberculous pleural effusion.