The first of PRINTO’s achieved goals was to define a core set of outcome measures and a definition of improvement to be used in clinical trials in children with juvenile arthritis (JA). This project was developed under the leadership of the US-based Pediatric Rheumatology Collaborative Study Group (PRCSG). Following publication of the definition of improvement (Giannini EH, Ruperto N, et al) it was subsequently adopted by the US Food and Drug Administration (FDA) as primary outcome for all clinical trials involving children with JIA and recently also by the European Medicines Agency (EMEA). This definition is now officially recognized as American College of Rheumatology (ACR) paediatric 30 definition of improvement