IL-33 levels differentiate tuberculous pleurisy from malignant pleural effusions

Tuberculous pleural effusions (TPEs) and malignant pleural effusions (MPEs) are difficult to differentiate between in certain clinical situations. Interleukin (IL)-33 is a cytokine that participates in inflammatory responses and may have a role in pleural effusions. The present study aimed to investigate the concentrations and potential differential significance of IL-33 in patients with TPE and MPE. IL-33 levels in pleural effusion and serum samples were detected using sandwich enzyme-linked immunosorbent assay in 23 patients with TPE and 21 patients with MPE. The concentration of IL-33 (mean ± standard deviation) in the TPE patients (22.962±0.976 ng/l) was significantly higher than that in the MPE patients (12.603±5.153 ng/l; P<0.001; z=−4.572); however, there was no significant difference in the serum level of IL-33 in the patients with TPE compared with those with MPE (P>0.05). The concentration of IL-33 in the pleural effusions was positively correlated with that in the serum samples in each group (TPE: r=0.563, P=0.05; MPE: r=0.535, P<0.05). The cut-off value of pleural IL-33 for TPE was 19.86 ng/l, which yielded a sensitivity of 0.869, a specificity of 0.905 and an area under the corresponding receiver operating characteristic curve of 0.903. The present study identified that the level of pleural IL-33 is significantly increased in TPEs and may serve as a novel biomarker to differentiate between patients with TPE and MPE.