A modification of the Omeract RA MRI score for erosions for use with an extremity MRI system with reduced field of view.

OBJECTIVES To develop and test the reliability of a modified version of the OMERACT rheumatoid arthritis magnetic resonance imaging score (RAMRIS) for erosions using extremity MRI (eMRI) with reduced field of view (RAMRIS-RV). METHODS Using a MagneVu 0.2 T machine, the preliminary RAMRIS-RV assessed erosions in metacarpophalangeal (MCP) joints 2-3, bases of metacarpal (MC) 2-5, and all wrist bones excluding base MC 1, pisiform and trapezium. T1 weighted images of >/=500 MCP and wrist bony sites from a mixed severity RA and control cohort were evaluated. An inter-reader reliability study evaluating 300 wrist and 160 MCP bony sites was then performed. RESULTS Mean per cent exact (and close) agreement results were as follows: MCP proximal sites 83.5 (96.2), MCP distal 54.4 (77.2), bases MC 2-4 85.2 (96.7), carpal bones 79.0 (92.1), distal radius/ulna 66.4 (87.8). The base of MCP 5 was visualised in </=50% cases (13/25) and was removed from the final RAMRIS-RV. CONCLUSIONS The RAMRIS-RV is a practical tool that can be used with eMRI with a reduced field of view. This study shows excellent inter-reader reliability for erosion assessment, albeit in a reduced number of bony sites.