Outcome measures in paediatric rheumatology: the contribution of the Paediatric Rheumatology INternational Trials Organisation and the Pediatric Rheumatology Collaborative Study Group

Over the past 30 years, the Paediatric Rheumatology INternational Trials Organisation (PRINTO), in active collaboration with the Pediatric Rheumatology Collaborative Study Group (PRCSG), has played a central role in transforming paediatric rheumatology into a methodologically rigorous and internationally coordinated and harmonised discipline. The development of standardised and validated outcome measures has allowed to compare different therapeutic strategies, quantify drug efficacy and design rigorous randomised clinical trials to establish evidence-based treatment strategies in paediatric rheumatology. In juvenile idiopathic arthritis (JIA), the development of a core set of outcome measures used to calculate the JIA/American College of Rheumatology (ACR) 30 criteria for improvement represented a milestone in 1997, establishing for the first time standardised response measures for use in clinical trials. This achievement was followed by the development of criteria for inactive disease and clinical remission, and the validation of the Juvenile Arthritis Disease Activity Score (JADAS) for disease activity. Applying a similar methodological approach, development and prospective validation has occurred also in juvenile dermatomyositis and childhood-onset systemic lupus erythematosus with core sets of outcome measures, response and remission criteria, also comprising physician and patient/parent-reported outcomes. Additionally, in hereditary recurrent fevers, the Auto-Inflammatory Diseases Activity Index (AIDAI) provided a validated tool for the patient/parents’ daily assessment of disease activity. The continuous involvement of families and patient-research partners also has led to the cross-cultural adaptation and validation of tools for assessing functional ability and quality of life in more than 30 languages. This effort was later extended to the Juvenile Arthritis Multidimensional Assessment Report (JAMAR), which is now available in over 50 languages worldwide. The involvement of family associations, health professionals worldwide, and of the Paediatric Rheumatology European Society (PReS), has been finally central to the development of the PRINTO/PReS website for families of paediatric and young adult patients with rheumatic diseases. These achievements reflect a systematic endeavour to standardise outcome assessment and finally improve research methodology and children care. This review summarises the main outcome measures developed and validated by PRINTO, often in collaboration with the PRCSG, in its 30-year history (1996–2026).