MRI of rheumatoid arthritis: Comparing the outcome measures in rheumatology clinical trials (OMERACT) scoring and volume of synovitis for the assessment of biologic therapy

The outcome measures in rheumatology clinical trials (OMERACT) scores are the most mature quantitation system for rheumatoid arthritis (RA) on magnetic resonance imaging (MRI). Direct measuring techniques of synovial volume have been reported with good reproducibility, although few reports have demonstrated the changes of these measures in response to treatment. To assess these clinical responses, we evaluated the correlation of the changes of clinical activity score 28-joints disease activity score (DAS28-CRP) with the changes of OMERACT scores and with synovial volume measurements. Eight RA patients who were treated by biologic agents were examined with MRI of the dominant affected wrist and finger joints before and one year after the treatment. The total OMERACT score was reduced from 48.0 to 41.3, and synovial volume was reduced from 15.4 to 8.8 milliliters. Positive correlations were seen between the changes of DAS28-CRP and the changes of OMERACT synovitis score (r = 0.27), OMERACT total score (r = 0.43) and synovial volume (r = 0.30). Limited to synovium assessment, synovial volume showed a better correlation with DAS28-CRP than the OMERACT synovitis score. On the other hand, the OMERACT total score showed a higher correlation with DAS28-CRP than synovial volume, probably because the OMERACT total score includes scores for bone erosion and bone edema as well.