Limited discriminatory value of RAMRIS findings between RA and hand osteoarthritis: a cross-sectional MRI study.

To evaluate the capacity of the RA MRI Score (RAMRIS) in distinguishing rheumatoid arthritis (RA) and hand osteoarthritis (HOA). Patients with RA and HOA were retrospectively matched in pairs. Inflammatory and degenerative changes in MRI scans of the hands were quantified and compared using RAMRIS, focusing on bone marrow edema (BME), erosion, synovitis, and tenosynovitis. CRP, ESR, and autoantibodies (RF and ACPA) and clinical scores (DAS-28, FFbH, and pain level), smoking status, and medication use were assessed additionally. Overall, 100 RA and 100 HOA patients with confirmed diagnosis were included. Age, pain severity, and functional impairment did not differ between groups. RAMRIS revealed significantly higher synovitis subscores in RA compared to HOA (p<0.001), while no significant differences were found for BME (p = 0.076), erosion (p = 0.366), or tenosynovitis (p = 0.129). Higher RAMRIS scores were observed at the level of individual joints in RA. The mean erosion-subscore was found to be higher in RA males than in RA females, though this was not observed in all joints. In HOA, men exhibited a mean erosion score that was higher than that of women. Smoking status had limited association with RAMRIS findings, but RA non-smokers exhibited greater inflammatory burden than HOA non-smokers in multiple joints. RA exhibited significantly higher synovitis subscores, indicative of active inflammation and leading to overall higher RAMRIS scores, compared to HOA. However, HOA demonstrated high RAMRIS scores for synovitis, tenosynovitis, erosions, and BME. MRI may assist in distinguishing RA from HOA; however, its interpretation must be integrated into the clinical context.