Circulating Interleukin-37 Levels in Rheumatoid Arthritis and Systemic Lupus Erythematosus and Their Correlations With Disease Activity: A Meta-analysis

Abstract

Objective. To assess the circulating levels of interleukin (IL)-37 in rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), and determine a correlation between plasma/serum IL-37 levels and disease activity. Methods. We performed a meta-analysis comparing plasma/serum IL-37 level between patients with RA or SLE and controls, and examined correlation coefficients between circulating IL-37 levels and disease activity. Results. A total of 14 publications included 711 patients with RA and 394 controls, 522 patients with SLE and 259 controls. In the RA group, the IL-37 level was significantly higher than in the control group (standardized mean difference [SMD]=1.222, 95% confidence interval [CI]=0.722∼1.711, p<0.001). Subgroup analysis by sample size showed a significantly higher IL-37 level in RA group of large (n>90) and small sample numbers (n≤90) (SMD=0.994, 95% CI=0.323∼1.666, p<0.001; SMD=1.617, 95% CI=1.328∼1.906, p<0.001). In addition, IL-37 level in SLE group was significantly higher than in control group (SMD=1.096, 95% CI=0.635∼1.558, p<0.001). A strong association between circulating IL-37-level and RA activity based on Disease activity Score 28 was shown (correlation coefficients=0.547, 95% CI=0.355∼0.695, p<0.001). Meta-analysis of the coefficients for correlation indicated a positive correlation between the circulating level of IL-37 and SLE activity based on Systemic Lupus Erythematosus Disease Activity Index (coefficients for correlation<0.588, 95 % CI=0.270∼0.806, p=0.003). Conclusion. Our meta-analysis showed that circulating IL-37 levels are higher in RA and SLE patients, and there is a positive correlation between IL-37 and disease activity in RA and SLE.