A Semiquantitative Ultrasound Scoring System to Assess Cartilage in RA

Ultrasound is a reliable tool for the evaluation of metacarpophalangeal (MCP) joint cartilage changes in patients with rheumatoid arthritis (RA), and research supports further development of a new semiquantitative ultrasound scoring system for the evaluation of cartilage involvement in RA, according to a study published in Rheumatology.

For this study, an Outcome Measures in Rheumatology Ultrasound Working Group (OMERACT USWG) task force with 34 rheumatology experts from 17 countries performed a systematic review of published literature on ultrasound assessment of cartilage in RA, developed a new semiquantitative US scoring system agreed upon using a Delphi survey on cartilage changes, and then tested the scoring system with a web-based exercise and patient exercise. The web-based exercise asked OMERACT USWG task force members to score a dataset of static images of MCP joints in RA patients and healthy control participants, all anonymized and containing duplicate images. Then 12 task force members conducted a reliability exercise using the same ultrasound to score MCP cartilage and proximal interphalangeal joints of 6 patients with RA. Prevalence of lesions and percentage agreement were calculated, as weighted kappa assessed intrareader reliability and Light’s kappa assessed interreader reliability.

A 3-grade semiquantitative scoring system was formulated with grade 0 as normal cartilage, grade 1 as minimal change (focal thinning or incomplete loss of cartilage), and grade 2 as severe change (diffuse thinning or complete loss of cartilage). In the web-based exercise, the kappa values for intrareader reliability were 0.87 (95% CI, 0.83-0.92), and the kappa values for interreader reliability were 0.64 (95% CI, 0.63-0.64). In the patient-based exercise, kappa values for intrareader reliability were 0.78 (95% CI, 0.74-0.82) for the standardized MCP joint scan, 0.83 (95% CI, 0.80-0.86) for the dynamic MCP joint scan, and 0.66 (95% CI, 0.60-0.71) for the proximal interphalangeal (PIP) joints. Interreader reliability kappa values were 0.44 (95% CI, 0.38-0.51) for the standardized MCP joint scan, 0.48 (95% CI, 0.41-0.54) for the dynamic MCP joint scan, and 0.17 (95% CI, 0.13-0.21) for the PIP joints.

Study investigators conclude, “Based on the present study, the OMERACT USWG recommends the use of the presently described semiquantitative [musculoskeletal ultrasound] score for assessing cartilage pathology in the MCP joints of patients with RA. Further testing of this scoring system in the MCP joints of other RA cohorts in addition to joints where cartilage can be visualized (eg, knee, metatarsophalangeal, tibiotalar, etc.) and assessment of sensitivity of change in longitudinal studies is required before the scoring system can be recommended as an outcome measure to be used in clinical trials.”

This study was supported by an unrestricted grant from UCB Pharma GmbH.

Reference
Mandl P, Studenic P, Filippucci E, et al. Development of semiquantitative ultrasound scoring system to assess cartilage in rheumatoid arthritis [published online April 26, 2019]. Rheumatology (Oxford). doi: 10.1093/rheumatology/kez153