Research definitions of flare in non-systemic juvenile idiopathic arthritis: An OMERACT scoping review

To summarize the flare definitions used in non-systemic juvenile idiopathic arthritis (JIA) clinical research.

A scoping review of seven databases (PubMed, Medline, Embase, Web of Science, Cumulative Index of Nursing and Allied Health Literature, Allied and Complementary Medicine and World Health Organization Global Index Medicus) was performed on 30 June 2024 and updated on 30 November 2025. Peer-reviewed clinical research publications using "flare" as an outcome for patients, of any age, with non-systemic JIA were included.

Of the 3812 records identified, 139 articles were analyzed, consisting of 19 interventional trials and 120 observational studies. Flare is increasingly reported as an outcome, with 49% of articles published within the last five years (n = 67/139). Researchers have used 13 distinct approaches to measure "flare", generating 39 different interpretations, due to varying measurement thresholds. This inconsistency stems from competing perspectives on whether flare represents: the presence or recurrence of active disease, change in disease activity scores, patient/parent-report, physician assessment, medication modification, or a combination of these factors. Most operationalized flare definitions were based on the American College of Rheumatology Core Response Variables (CRV) (27%, n = 37/139), and the Wallace Criteria (24%, n = 33/139). However, measurement threshold variability yielded nine different interpretations of flare using the CRV approach. Disease activity scores were uncommonly used to define flare (9%, n = 12/139). Aside from measuring the patient global assessment of overall wellbeing in the CRV and Juvenile Arthritis Disease Activity Score (JADAS), only 4% (n = 5/139) of articles identified flare using patient or caregiver assessment.

In JIA clinical research, "flare" is a common, but inconsistently defined, outcome. The lack of standardized outcome reporting creates barriers in analyzing and communicating research findings. Development of an internationally recognized flare outcome in JIA research would improve shared decision making between healthcare professionals, patients, and caregivers.