Testing an OMERACT MRI scoring system for peripheral psoriatic arthritis in cross-sectional and longitudinal settings.

OBJECTIVE Magnetic resonance imaging (MRI) is increasingly used to measure articular inflammation and damage in patients with psoriatic arthritis (PsA). We evaluated the reliability of a new OMERACT PsA MRI scoring system, PsAMRIS, in PsA fingers. METHODS In 2 separate studies, MRI scans were obtained from patients with clinical evidence of synovitis or dactylitis of the fingers. For the first cross-sectional study, images were obtained at one timepoint. For the second longitudinal study, images were obtained at 2 timepoints, 6 weeks apart. Scans were scored using PsAMRIS in an international multireader setting, for synovitis, tenosynovitis, periarticular inflammation, bone edema, bone erosions, and bone proliferation. RESULTS Global status scores from both datasets revealed moderate to high reliability for scoring most features, although reliability was poor for periarticular inflammation in the cross-sectional study. Change scores that reflected inflammatory activity also exhibited moderate to good reliability in the longitudinal exercise, despite there being very little absolute change in MRI synovitis or tenosynovitis observed in this dataset. At the distal interphalangeal joints, reliability for change scores was acceptable only for synovitis and tenosynovitis. CONCLUSION Further development and testing of the PsAMRIS is planned to improve its performance as a clinical and research tool to identify and measure pathology in peripheral joint PsA.