EULAR-OMERACT consensus-based scoring system for synovitis 10 years later: a validated tool for routine care and clinical trials

Assessing the presence and degree of synovitis is the cornerstone of managing patients with arthritis. Ultrasound has been shown to be a valuable tool for this in routine care, and several scoring systems have been developed over time. Although there is an overall good validity across several different semi-quantitative scoring systems, they lack reliability when applied in the same patient cohort, emphasising the need for a consensus-based scoring system. A European Alliance of Associations for Rheumatology (EULAR) and Outcome Measures in Rheumatology (OMERACT) collaboration developed, almost 10 years ago, the consensus-based EULAR-OMERACT scoring system, which has subsequently been validated. It has face and content validity as it makes sense and allows to visualise all components constituting the synovitis complex. It has discriminant validity as it is sensitive to change during treatment, can discriminate between active treatment and placebo in clinical trials and has a moderate-to-excellent inter-observer and intra-observer reliability. It has construct validity by showing a parallel improvement in ultrasound sum scores and Disease Activity Score 28 and joint assessment, respectively. It has criterion validity with a predictive validity for biological disease-modifying antirheumatic drug (bDMARD) discontinuation and for flares while tapering bDMARDs. In addition, a correlation between the scoring system and histological inflammation was established. Finally, the EULAR-OMERACT scoring system is feasible, as a 24-joint assessment can be performed in 20 min. In conclusion, the EULAR-OMERACT scoring system is a valid scoring system that also fulfils the OMERACT 2.1 filter for instrument selection.