A novel biomarker for pleural effusion diagnosis: Interleukin-36 gamma in pleural fluid

Background: Numerous studies have described the critical importance of interleukin (IL) -36 gamma in host defense against lung infections, but it is unknown whether it plays a role in infectious pleural effusion (IPE). This study aimed to examine the levels of IL-36 gamma in pleural effusions of different etiologies and evaluate the diagnostic accuracy of IL-36 gamma in the differential diagnosis of IPE. Methods: A total of 112 individuals was enrolled in this research. IL-36 gamma levels in pleural fluids of all 112 patients were measured by enzyme-linked immunosorbent assay (ELISA). We also characterized these markers' diagnostic values across various groups. Results: Patients with tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) had exhibited markedly higher IL-36 gamma levels in their pleural fluid than the malignant pleural effusion (MPE) and transudative effusion patients. Furthermore, the IL-36 gamma concentrations in TPE patients were evidently higher than in uncomplicated parapneumonic effusion (UPPE) patients but significantly lower than in complicated parapneumonic effusion (CPPE)/empyema patients. Pleural fluid IL-36 gamma is a useful marker to differentiate TPE from UPPE, at a cut-off value for 657.5 pg/ml (area under the curve = 0.904, p < 0.0001) with 70.0% sensitivity and 95.7% specificity. Conclusions: The elevated IL-36 gamma in pleural effusion may be used as a novel biomarker for infectious pleural effusion diagnosis, particularly in patients with CPPE/empyema, and is a potentially promising biomarker to differentiate between TPE and UPPE.