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

Abstract

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.