Musculoskeletal Ultrasound in Childhood Arthritis Limited Examination: A Comprehensive, Reliable, Time-Efficient Assessment of Synovitis.

Abstract

To develop and initially validate a comprehensive pediatric musculoskeletal ultrasound (MSUS) joint-specific scoring system, and to determine the minimum number of joints needed to identify active disease. A semiquantitative scoring system was developed by consensus and initially validated by interrater reliability using intraclass correlation coefficients (ICCs). Subsequently, newly diagnosed juvenile idiopathic arthritis patients with an active joint count of >4 had a 42-joint MSUS performed at baseline and 3 months using this protocol. A minimum set of joints needed to identify all patients with synovitis on MSUS was obtained through a data reduction process. Spearman's correlation (rs ) was calculated to determine the association between MSUS findings and clinical Juvenile Arthritis Disease Activity Score in 10 joints (cJADAS10). Standardized response means (SMRs) were used to assess change over time. The final joint-specific scoring system revealed an excellent interrater reliability (ICC 0.81-0.96) for all joints. Thirty patients were enrolled. Scanning 5 joints bilaterally (wrists, second and third metacarpophalangeal joints, knees and ankles) captured 100% of children with B-mode synovitis and had moderate correlation with the cJADAS10 at baseline (rs =0.45). Mean ultrasound scores at baseline and follow-up were 28.3 and 22.3, with an SRM of 0.69 (P=0.002) for 42 joints, and 36 and 27.7, with an SRM of 0.76 (P=0.003) for the reduced joints, respectively. A limited MSUS examination called musculoskeletal ultrasound in childhood arthritis limited examination (MUSICAL) captures all patients with active synovitis, and our new joint-specific scoring system is highly reliable and sensitive to change.