To establish the cut-off values for inactive disease, as well as low disease activity (LDA), moderate disease activity (MDA) and high disease activity (HDA) in non-systemic JIA based on the Juvenile Arthritis Disease Activity Score (JADAS) and assessed with the 10-joint JADAS (JADAS10) and clinical JADAS10 (cJADAS10).
In a multicentre cross-sectional study consisting of ∼20% of all patients with JIA in Finland (n = 509), we obtained data on their most recent registered visits between January 2013 and January 2014. We calculated the JADAS10 and cJADAS10 and established the cut-off values of both of these scores using two different receiver operating characteristics-based statistical methods.
Of the 509 patients studied, 65.8% were females and 53.8% had polyarticular disease. The most suitable method for determining cut-off values was the Youden index. In oligoarticular patients, a JADAS10 score of 0-0.5 represented inactive disease, 0.6-2.7 LDA and ≥2.8 MDA. In polyarticular disease, a JADAS10 score of 0-0.7 represented inactive disease, 0.8-3.9 LDA and ≥4.0 MDA. The cut-off values for HDA were not possible to establish because only two visits fulfilled HDA criteria.
We established cut-off values for LDA and MDA. A reliable definition for HDA will require more patients. In the clinical setting, both the cJADAS10 and JADAS10 serve equally well both for research and quality control purposes. In the future, uniform clinical disease activity levels should be established. We also suggest revising and validating the criteria for HDA. Valid and robust cut-off values for disease activity levels can guide both clinicians and researchers and equip them for quality control.