Objective: To propose a reduced joint power Doppler US (PDUS) assessment and provide preliminary evidence of its validity, feasibility, reliability and sensitivity to change compared with a comprehensive (i.e. 44 joints) PDUS assessment in evaluating synovitis in JIA.
Methods: This multicentre study included 42 children with active JIA with ≥4 clinically involved joints requiring modified therapy. At each visit, clinical and PDUS assessments were performed blinded. Each joint was scored for greyscale (GS) synovitis and power Doppler signal according to a 4-point semiquantitative scale with calculation of US composite indices and US composite joint counts. A process of data reduction based on the frequency of US joint involvement was performed to obtain a reduced PDUS assessment. The relationship between the comprehensive and the reduced PDUS assessments was investigated by Spearman's coefficient at all visits, as well as the relationship between changes in the two PDUS assessments during follow-up. In addition, the metric properties of the comprehensive and the reduced PDUS assessments were tested.
Results: The 10-joint PDUS assessment, including bilateral knee, ankle, wrist, elbow and the second MCP joints, detected 100% of children with GS synovitis and power Doppler signal. The two PDUS assessments were highly correlated at all visits. The reduced model had a higher responsiveness than the comprehensive model. Intraobserver and interobserver agreement was good for both US findings.
Conclusion: The 10-joint PDUS assessment is valid and feasible for assessment of synovitis in JIA in clinical practice.
Keywords: Doppler; diagnostic imaging; inflammation; juvenile idiopathic arthritis; synovium; ultrasonography; validity.