Predictors of Disease Activity in Juvenile Idiopathic Arthritis at 12 and 24 Months After Diagnosis

Identification of characteristics associated with risk of active disease in Juvenile Idiopathic Arthritis (JIA) could inform treatment strategies early in the disease state. This study evaluates JIA disease activity outcomes and patient characteristics associated with active disease at 12- and 24-months post diagnosis from a single large US center. Methods: Disease activity status at 12- and 24-months after diagnosis was assessed retrospectively from 2004 – 2018 and categorized as “active” or “inactive” disease based on a modification of the Wallace criteria. The prevalence of disease activity was examined in relation to clinical and demographic characteristics identified at the time of JIA diagnosis and 3 months later. Patients without follow up at either 12 or 24 months were not included in the main analysis for this time point. The primary analysis cohort was separated into three time of diagnosis cohorts which align with availability of novel biologic DMARD medications, and prevalence of active disease was examined for clinical and demographic characteristics of interest with particular attention to the most contemporary cohort (1/1/014 – 12/31/2018). A sensitivity analysis included patients on whom follow-up information was not available, with the presumption of these patients likely had inactive disease. Results: A total of 1151 JIA subjects were included, with 38% having oligoarticular disease. At 12 months, a 40-50% higher prevalence of active disease was noted in children five years and older, when compared to those less than five years old. Additionally, those with active disease 3 months after diagnosis had a higher prevalence of active disease at 12 months than those who were inactive at 3 months (relative prevalence (RP) 1.48 (95% CI 1.22, 1.78)). Relative to children with monoarticular involvement, those with polyarticular RF-negative (RP 1.22 (95% CI 1.01, 1.38)), psoriatic arthritis (RP 1.34 (95% CI 1.06, 1.68)), or enthesitis related arthritis (ERA) (RP 1.23 (95% CI 0.99, 1.53) had a higher prevalence of active disease. At 24 months, a higher prevalence of active disease was seen in children 10 years or older compared to those under five years (RP 1.5 (95% CI 1.19, 1.88)), in children with polyarticular RF-, psoriatic arthritis, and ERA (though to a lesser extent than at 12 months), and in those with active disease at 3 months (RP 1.28 (95% CI 1.02, 1.59)). The prevalence of active disease was 25% smaller in the most recent time period than in the earliest period (RP=0.75 (95% CI 0.62, 0.92), but the predictors of disease activity at 12 and 24 months after diagnosis were broadly similar over time. Conclusion: In this large center, real world cohort, JIA patient characteristics associated with active disease at 12 and 24 months included older age at diagnosis, polyarticular RF-, psoriatic arthritis, or ERA categories, and the presence of active disease at 3 months after diagnosis. Overall, the modest associations demonstrated are broadly in agreement with those seen in earlier studies, but offer little guidance for patient management. Further work is needed to identify predictors of active disease during the 1-2 years following a diagnosis of JIA.