Validation of the OMERACT Psoriatic Arthritis Magnetic Resonance Imaging Score (PsAMRIS) for the Hand and Foot in a Randomized Placebo-controlled Trial.

Objective: To assess changes following treatment and the reliability and responsiveness to change of the Outcome Measures in Rheumatology (OMERACT) Psoriatic Arthritis Magnetic Resonance Imaging Score (PsAMRIS) in a randomized controlled trial.

Methods: Forty patients with PsA randomized to either placebo or abatacept (ABA) had MRI of either 1 hand (n = 20) or 1 foot (n = 20) at baseline and after 6 months. Images were scored blindly twice by 3 independent readers according to the PsAMRIS (for synovitis, tenosynovitis, periarticular inflammation, bone edema, bone erosion, and bone proliferation).

Results: Inflammatory features improved numerically but statistically nonsignificantly in the ABA group but not the placebo group. Baseline intrareader intraclass correlation coefficients (ICC) were good (≥ 0.50) to very good (≥ 0.80) for all features in both hand and foot. Baseline interreader ICC were good (ICC 0.72-0.96) for all features, except periarticular inflammation and bone proliferation in the hand and tenosynovitis in the foot (ICC 0.25-0.44). Intrareader and interreader ICC for change scores varied. Guyatt's responsiveness index (GRI) was high for inflammatory features in the hand and metatarsophalangeal joints (GRI -0.67 to -3.13; bone edema not calculable). Minimal change and low prevalence resulted in low ICC and GRI for bone damage.

Conclusion: PsAMRIS showed overall good intrareader agreement in the hand and foot, and inflammatory feature scores were responsive to change, suggesting that PsAMRIS may be a valid tool for MRI assessment of hands and feet in PsA clinical trials.