O29. PREVALENCE AND COURSE OF LOWER LIMB DISEASE ACTIVITY AND WALKING DISABILITY IN THE FIRST 5 YEARS OF JUVENILE IDIOPATHIC ARTHRITIS

Abstract

Background: Lower limb synovitis is common in juvenile idiopathic arthritis (JIA). Cross-sectional studies suggest that along with synovitis, walking difficulties are also present; however there are no longitudinal studies reporting their prevalence rates from disease onset and change over time. Therefore, the aim of this study was to determine the prevalence of lower limb synovitis and walking disability and its course from first presentation of JIA (baseline) over 5 years. Methods: The Childhood Arthritis Prospective Study (CAPS) is a longitudinal study of children under 16 years of age who were recruited with a new JIA diagnosis. CAPS data collected include demographics and core outcome variables at baseline, 6 months and yearly thereafter. Synovitis was determined using active joint counts recorded at the hip, knee, ankle, subtalar, inter-tarsal (range 0-2), metatarsophalangeal (MTP) and interphalangeal (IP) joints (range 0-5), and dichotomized as present (1 or more) or absent (0). Walking disability was measured using the Childhood Health Assessment Questionnaire (CHAQ) walking subscale (range 0-3) and dichotomized as present (1 or more) or absent (0). The prevalence of lower limb synovitis and walking disability are expressed as percentages of participants. Change over time from baseline is expressed as percentages of participants with new or stable active synovitis and walking disability. Results: Data were available for 1,394 participants (median age 7.6 years, 64% female), dropping to 543 at 5 years. Baseline knee and ankle synovitis prevalence was 70% and 30% respectively, decreasing to approximately 15-20% and 10-15% after 1 year; of which 2.4% and 3.2% were new, and 12.9% and 5.7% were stable cases with active synovitis (Table 1). Baseline hip and foot synovitis prevalence was less than 12%, decreasing to less than 5% after 1 year; of which ≤1% or less were new or stable active cases. At least mild walking disability was present in 52% at baseline, stabilizing at 25-30% after 1 year. Conclusion: Prevalence rates for knee and ankle joint synovitis and walking disability are initially high and then stabilize. Persistent walking disability affects a significant proportion of children with JIA after 1 year despite low prevalence rates of lower limb synovitis. (Table Presented).