Accuracy of interleukin-27 in diagnosing tuberculous pleural effusion: Age should be considered

Background Tuberculous pleural effusion (TPE) diagnosis still faces many difficulties and challenges. Some studies have shown that pleural interleukin -27 (IL-27) had a diagnostic potential for TPE. However, their findings are not always consistent. This study aimed to investigate the diagnostic accuracy of pleural IL-27 for TPE. Methods We prospectively enrolled 211 patients with undiagnosed pleural effusion. Effusion Mycobacterium tuberculosis (Mtb) culture, Ziehl-Neelsen staining, biopsy, and response to antituberculosis therapy were used to define TPE. The pleural IL-27 levels were determined by enzyme-linked immunosorbent assay (ELISA). A receiver operating characteristic curve (ROC) with the area under the curve (AUC) was used to evaluate the diagnostic accuracy of IL-27 for TPE. In addition, we investigated the influence of age on the diagnostic performance of IL-27 by resampling patients with different upper age limits in the inclusion criteria. Results Among the 211 enrolled participants, 33 were TPE and 178 were non-TPE. The mean concentration of IL-27 in TPE patients was significantly higher than that of non-TPE patients. The AUC of IL-27 was 0.76 (95 %CI: 0.67-0.86). At the threshold of 500 pg/mL, the sensitivity and specificity of IL-27 were 0.26 (95 %CI: 0.20-0.33) and 0.91 (95 %CI:0.76-0.97), respectively. The AUC of IL-27 is 0.84 in patients with an upper age limit of 70. Still, it decreased to 0.76 in patients with an upper age limit of 75. Conclusion Age can affect the diagnostic performance of IL-27 for TPE.