Trajectories of Physical Function in Canadian Children With Juvenile Idiopathic Arthritis.

Abstract

We describe trajectories of physical function in children newly diagnosed with juvenile idiopathic arthritis (JIA) and identify trajectories with persisting functional impairments and associated baseline characteristics. We included patients enrolled in the Canadian Alliance of Pediatric Rheumatology Investigators (CAPRI) Registry between 2017 and 2024 whose parents provided Kids Disability Screen (KDS) scores from at least two visits (from 0 = no disability to 10 = severe disability). Analyses included descriptive statistics, locally weighted scatterplot smoothing, Kaplan-Meier plots of time to KDS = 0, latent class trajectory analysis (LCTA), and classification trees to predict trajectories with persisting impairments. We included 940 patients providing 7,351 KDS scores starting at a median 6 days after diagnosis up to 7 years. Baseline KDS scores were highest for rheumatoid factor-positive polyarthritis (mean 4.9, SD 3.1) and lowest for psoriatic arthritis (mean 2.4, SD 2.5), and mean scores improved within the first year in all JIA categories. Median time to KDS = 0 was 36 weeks (from 13 weeks for systemic arthritis to 73 weeks for undifferentiated arthritis). LCTA identified five trajectories: one with little measurable impairment (38% of patients), two with impairments resolving in one to two years (24%), and two with persisting mild impairments (38%). A baseline KDS ≥1.5 had a sensitivity of 0.79 and specificity of 0.48 to detect persisting mild impairment trajectories. There were no trajectories with persisting moderate or severe impairments. Most children with JIA in this cohort had mild to moderate functional impairments at diagnosis that resolved in one to two years, but one in three followed trajectories with mild persisting impairments.