Correlation and agreement between physical and ultrasound examination after a training session dedicated to the standardization of synovitis assessment in rheumatoid arthritis patients

Objectives Assessing disease activity in rheumatoid arthritis (RA) patients requires comprehensive quantification of tender and swollen joints. We aimed to evaluate the correlation and agreement between rheumatologists after a training session dedicated to the standardization of synovitis assessment and compare its performance with a reference imaging modality such as musculoskeletal ultrasonography (MSUS). Methods In this cross-sectional study, a total of 28 and 10 joints in RA patients were evaluated by physical examination and ultrasound (US), respectively. After participating in a training session, individual joint assessment for tenderness and swelling was performed by three rheumatologists. MSUS examination was performed separately by an experimented radiologist in a standardized manner, evaluating findings according to the Outcome Measures in Rheumatology Clinical Trial (OMERACT) guidelines. Results A total of 80 RA patients were included, with a mean Disease Activity Score based on 28 joints (DAS28)-ESR of 4.02. The interobserver overall agreement and concordance rate in a total of 2240 joints assessed was 81.7% (k = 0.449, p < 0.0001) for tender joints and 66% (k = 0.227, p < 0.0001) for swollen joints. The overall concordance rate was fair (Fleiss' kappa = 0.21, p = 0.027) with an overall agreement of 67.18% yet, more joints were found to be swollen by the US assessment, compared to the physical examination (43% vs 39%). Conclusion In our study population, joint tenderness showed better interobserver agreement, correlation, and concordance rate than joint swelling. When comparing the US assessment to the physical examination, a fair overall concordance rate supports the need for the implementation of training sessions dedicated to standardization in rheumatology clinics.