Iterative Development and Reliability of the OMERACT Hand Osteoarthritis MRI Scoring System

Objective. To develop and test the interreader reliability of the OMERACT Hand Osteoarthritis Magnetic Resonance Scoring System (HOAMRIS) for assessment of structural and inflammatory hand OA features in the interphalangeal joints. Methods. The HOAMRIS was developed through an iterative process. Selection of features and their scaling was agreed upon through consensus by members of the OMERACT Magnetic Resonance Imaging (MRI) Task Force, using the Oslo Hand Osteoarthritis (OA) MRI Score system as a template. Two reliability exercises were performed, in which 6 and 4 readers participated, respectively. After the first exercise, an atlas was developed and used in the second exercise to facilitate reading. In each exercise, readers independently scored 8 MRI scans from the Oslo Hand OA cohort (coronal/axial short-tau inversion recovery and coronal/axial/sagittal T1-weighted fat-suppressed pre-/post-Gadolinium images). Interreader reliability was assessed by intraclass correlation coefficients (ICC), percentage exact and close agreement (PEA/PCA). Results. The preliminary OMERACT HOAMRIS included assessment of synovitis, erosive damage, cysts, osteophytes, cartilage space loss, malalignment, and bone marrow lesions (BML), of which all were scored on a 0-3 scale for normal, mild, moderate, and severe (increments of 0.5 for synovitis, erosive damage, and BML). In the first exercise, most features showed good to very good ICC values (0.64-0.94), except synovitis (0.34). In the second exercise using the atlas, the ICC values were > 0.74 for all MRI features, and the PEA/PCA values were higher than in the first exercise. Conclusion. A preliminary HOAMRIS with good to very good interreader reliability was developed. Longitudinal studies are needed to assess its sensitivity to change.