Methods. We prospectively collected patient and disease characteristics from patients with JIA who started biological therapy. Adverse events were collected during the follow-up period. Predictors of response at 1 year and drug retention rates were assessed at 4 years of treatment for the first biologic agent.Results. A total of 812 JIA patients [65% females, mean age at JIA onset 6.9 years (s.d. 4.7)], 227 rec...