Reliability of the novel 7-joint ultrasound score: results from an inter- and intraobserver study performed by rheumatologists

Abstract

Objective: To assess the inter- and intraobserver reliability of 26 rheumatologists when performing the 7-joint ultrasound score (US7).

Methods: Six patients with rheumatoid arthritis were examined by 26 sonographers in 12 rater groups who performed the US7 score. The US7 score includes the clinically dominant wrist, the second and third metacarpophalangeal (MCP) and proximal interphalangeal joints, and the second and fifth metatarsophalangeal (MTP) joints, which were evaluated for synovitis, tenosynovitis/paratenonitis, and erosions from the dorsal side and palmar/plantar aspects by gray-scale and power Doppler (PD) ultrasound. Additional lateral scans were performed at the MCP2 and MTP5 joints. All of the groups repeated the examination in 4 patients in order to calculate the intraobserver reliability. The results of one group that included 2 expert sonographers were considered as the reference standard. Kappa values, median agreement rates (interobserver), and P values (intraobserver evaluation) were calculated.

Results: The median overall kappa value for detecting synovitis was 0.51, for tenosynovitis/paratenonitis was 0.57, and for erosions was 0.45. In detail, the best interobserver results were found for the detection of erosions in the MTP2 joint from the plantar aspect (κ = 1; median agreement rate 89.4%) and for PD signal detection in the palmar wrist region (κ = 0.79; median agreement rate 78.8%). Good agreement was found for detecting erosions in the MCP2 joint from the radial side (κ = 0.67; median agreement rate 77.3%).

Conclusion: The inter- and intraobserver reliability of the US7 score shows moderate to substantial kappa values and good agreements. Therefore, this ultrasound score has the potential to be an important imaging tool, including multicenter analysis to assess structural changes.