The MUSICAL pediatric ultrasound examination – a comprehensive, reliable, time efficient assessment of synovitis

Objective To develop and initially validate a comprehensive pediatric musculoskeletal ultrasound (MSUS) joint-specific scoring system. To determine the minimum number of joints needed to identify active disease. Methods A semiquantitative scoring system was developed by consensus and initially validated by inter-rater reliability using intraclass correlation coefficients (ICC). Subsequently, newly diagnosed Juvenile Idiopathic Arthritis (JIA) patients with an active joint count >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-10 (cJADAS-10). Standardized response means (SMR) were used to assess change over time. Results The final joint-specific scoring system revealed an excellent inter-rater reliability (ICC = 0.81-0.96) for all joints. Thirty patients were enrolled. Scanning 5 joints bilaterally: wrists, 2nd and 3rd MCPs, knees and ankles captured 100% of children with B-mode synovitis and had moderate correlation with cJADAS-10 at baseline (rs=0.45). Mean ultrasound scores at baseline and follow-up were 28.3 and 22.3 with SRM of 0.69 (p=0.002) for 42 joints and 36 and 27.7 with SRM of 0.76 (p=0.003) for the reduced joints, respectively. Conclusion A limited MSUS examination called MUSICAL (Musculoskeletal UltraSound In Childhood Arthritis Limited-examination) captures all patients with active synovitis and our new joint specific scoring system is highly reliable and sensitive to change.