A novel biomarker for pleural effusion diagnosis: Interleukin‐36γ in pleural fluid

BACKGROUND: Numerous studies have described the critical importance of interleukin (IL) ‐36γ 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‐36γ in pleural effusions of different etiologies and evaluate the diagnostic accuracy of IL‐36γ in the differential diagnosis of IPE. METHODS: A total of 112 individuals was enrolled in this research. IL‐36γ 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‐36γ levels in their pleural fluid than the malignant pleural effusion (MPE) and transudative effusion patients. Furthermore, the IL‐36γ 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‐36γ 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‐36γ 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.