Abstract:

Objective: To investigate the expression levels of interleukin-33 (IL-33) and soluble ST2(sST2) in the pleural effusion and the corresponding peripheral blood of the patients with malignant pleural effusion (MPE) and tuberculous pleural effusion(TPE),and to clarify their significances.Methods: A total of 72 patients with pleural effusion were selected (42 cases of MPE,30 cases of TPE).The expression levels of IL-33 and sST2 in the pleural effusion and peripheral blood were measured by ELISA.Another 38 healthy controls were selected as healthy control group.The expression levels of IL-33 and sST2 in the pleural effusion and peripheral blood were compared between MPE,TPE patients, and healthy people.The correlation between the expression levels of IL-33 and sST2 in the pleural effusion and serum of the patients in two groups were analyzed. The IL-33 level and the ratio of sST2/IL-33 were obtained using receiver operating characteristic curve (ROC) to identify the cut-off values of MPE and TPE and the corresponding sensitivity and specificity.Results: There was no statistical significance in the expression levels of serum IL-33 and sST2 between MPE and TPE (P>0.05),but they were higher than those in healthy control group (P<0.01).The expression level of IL-33 in pleural effusion of the TPE patients was higher than that in the corresponding serum (P<0.01),but the expression level of IL-33 in pleural effusion of the MPE patients was significantly lower than that in the corresponding serum (P<0.05).The expression level of IL-33 in pleural effusion of the TPE patients was significantly higher than that of the MPE patients(P<0.05).The expression level of sST2 in pleural effusion of the MPE patients was higher than that of the TPE patients (P<0.01). The expression levels of IL-33 in pleural effusion in MPF (r_MPF=0.930 4) and TPE(r_TPF=0.990 7) patients were positively correlated with those in corresponding serum; the expression level of sST2 in pleural effusion of the MPE patients was positively correlated with sST2 level in the corresponding serum (r=0.934 5),but there was no correlation in the TPF patients.The cut-off value of IL-33 expression level in pleural effusion for the differential diagnosis of TPE and MPE was 17.08 ng·L^-1,with the corresponding sensitivity of 96.7% and the specificity of 92.9%,respectively.The cut-off value of sST2/IL-33 ratio in pleural effusion for the differential diagnosis of TPE and MPE was 15.06,with the corresponding sensitivity of 96.8% and the specificity of 95.5%,respectively.Conclusion: IL-33 and sST2 are likely to participate in the inflammatory response of pleurisy of TPE and MPE in different degrees.The montoring of expression level of IL-33 in pleural effusion and the ratio of IL-33/sST2 may be a new method for the differential diagnosis of MPE and non-MPE with better clinical application value.

Key words: pleural effusion, soluble ST2, carcino-embryonic antigen, interleukin-33