OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Studies. Exercise 3: an international multicenter reliability study using the RA-MRI Score.

We examined inter-reader agreement of the revised OMERACT 5 Rheumatoid Arthritis MRI Score (RAMRIS v3). Magnetic resonance (MR) images of 10 sets of metacarpophalangeal (MCP) joints 2-5 and 8 sets of rheumatoid arthritis (RA) wrists [1.5 T, coronal and axial T1 and T2 spin-echo, +/- fat saturation (FS), +/- intravenous gadolinium (Gd)] were scored for (1) synovitis using a global score (0-3) and a direct measurement of synovial thickness (mm) and (2) three bone lesions: erosions, defects and edema, (score 0-10 by the volume of the lesion as a proportion of the "assessed bone volume" by 10% increments). Six readers from 5 multinational centers performed all scoring. Three statistical methods were used to analyze the data: (1) single-measure fixed effects intraclass correlations (sICC) and average-measure fixed effects ICC (avICC), (2) percentage exact and close agreement, and (3) the smallest detectable difference (SDD). The sICC were moderate to good (between 0.60 and 0.91) for half of the joint sites for the 2 synovitis scoring methods, and for bone erosions and bone edema. After adjusting for 6 readers, the avICC was very good to excellent (0.80-0.98) for two-thirds of the joint sites by lesion, excluding bone defects that performed relatively poorly, primarily because few readers scored these lesions. The aggregated scores with the best reliability were those with a wide range of scores, high ICC, low SDD, and low percentage SDD (< 33%). The metacarpophalangeal (MCP) bone erosion (sICC 0.58, avICC 0.89, %SDD +/- 27), wrist bone erosion scores (0.72, 0.94, +/- 31%), the wrist synovitis global (0.74, 0.94, +/- 32%), and synovial maximal thickness (0.6, 0.94, +/- 32%) met these conditions. MCP joint synovitis global (0.76, 0.95, +/-35%), MCP joint bone edema (0.63, 0.91, +/- 34%), and wrist bone edema (0.78, 0.95, +/- 38%) performed marginally less well. Bone defects performed poorly (MCP joint 0.18, 0.46, +/- 56%; wrist 0.06, 0.24, +/- 55%). The revised OMERACT 5 RAMRIS has acceptable inter-reader reliability for measures of disease activity (synovitis global and bone edema scores) and damage (bone erosion score). Whether the score is sensitive to change will be determined by its performance in longitudinal and intervention studies.