Musculoskeletal Ultrasound and the Assessment of Disease Activity in Juvenile Idiopathic Arthritis

Objective To determine the frequency of subclinical synovitis on musculoskeletal ultrasonography (MSUS) in juvenile idiopathic arthritis (JIA) and correlate patient‐ and provider‐reported outcome measures with MSUS synovitis. Method JIA patients with an active joint count (AJC) of >4 underwent a 42‐joint MSUS performed at baseline and 3 months. B‐mode and power Doppler images were obtained and scored (range 0–3) for each of the 42 joints. Outcomes evaluated included physician global assessment of disease activity (PhGA), patient global assessment of disease activity (PtGA), patient pain, Childhood Health Assessment Questionnaire (C‐HAQ), and AJC. Subclinical synovitis was defined as synovitis detected by MSUS only. Generalized estimation equations were used to test the relationship between clinical arthritis (positive/negative) and subclinical synovitis (positive/negative). Spearman's correlation coefficients (rs) were calculated to determine the association between MSUS synovitis and patient‐ and physician‐reported outcomes. Results In 30 patients, subclinical synovitis was detected in 30% of joints. Clinical arthritis of the fingers, wrists, and knee joints was significantly associated with MSUS synovitis in these joints. PtGA and the C‐HAQ had a moderate (rs = 0.44, P = 0.014) to weak (rs = 0.37, P = 0.045) correlation with MSUS synovitis. There was a statistically significant strong correlation between MSUS synovitis and PhGA (rs = 0.61, P = 0.001), but a weak correlation with AJC (rs = 0.37, P = 0.048) at the follow‐up visit. Conclusion Subclinical synovitis was commonly observed in this cohort of JIA patients. The fair‐to‐moderate correlation of MSUS synovitis with patient‐ and provider‐reported outcomes suggests that MSUS assesses a different, possibly more objective, domain not determined by traditional JIA outcome measurements.