Early reduction of serum interleukin-6 levels as a predictor of clinical remission in systemic juvenile idiopathic arthritis

Background: Interleukin (IL)-6 is the main proinflammatory cytokine in systemic juvenile idiopathic arthritis (SJIA). Objective: To determine if serial changes in serum IL-6 levels can predict outcomes of SJIA patients. Methods: This was a retrospective cohort study. Medical records of patients aged 2–19 years with active SJIA between January 2012 and February 2014 were reviewed. Baseline characteristics were recorded at enrollment. Serum IL-6 levels were measured at enrollment and at 2–4 weeks, 6–8 weeks, 3 months, and 6 months thereafter. Treatment response and clinical remission were assessed after 2 years of follow-up. Results: Of the 35 patients with active SJIA, 16 were in remission at the end of the study. IL-6 levels in the remission group returned to normal within 6 months, whereas they remained persistently high in the non-remission group. At the 3-month follow-up, patients were assigned to groups A and B based on reductions in serum IL-6 levels of > 50% and ≤ 50%, respectively. At the end of the study, more patients in group A (72.2%) than in group B (17.6%) achieved clinical remission (p < 0.05). After multivariate analysis, a > 50% reduction in serum IL-6 levels at the 3-month follow-up visit was a predictor of clinical remission at 2 years (odds ratio 22.74, 95% confidence intervals 2.16–239.85, p < 0.01). Conclusions: An early reduction in serum IL-6 levels is significantly associated with clinical remission at 2 years in SJIA patients. Monitoring of serial changes in serum IL-6 levels is beneficial for predicting clinical remission.