The OMERACT Psoriatic Arthritis Magnetic Resonance Imaging Score (PsAMRIS) is reliable and sensitive to change: results from an OMERACT workshop.

Objective: The aim of this multireader exercise was to assess the reliability and sensitivity to change of the psoriatic arthritis magnetic resonance imaging score (PsAMRIS) in PsA patients followed for 1 year.

Methods: MRI was acquired from 12 patients with PsA before initiation of treatment and after 12 months. MR images were scored according to PsAMRIS (for synovitis, tenosynovitis, periarticular inflammation, bone marrow edema, bone erosion, and bone proliferation) under standardized conditions, in unknown chronological order. Intraobserver/interobserver reliability was examined by intraclass correlation coefficients (ICC) and sensitivity to change by standardized response means (SRM).

Results: The interobserver reliability of PsAMRIS was high for synovitis, tenosynovitis, periarticular inflammation, and bone edema status and change scores (interobserver ICC 0.87-0.97). The intraobserver reliability was moderate to high (ICC 0.60-0.98) for status and change scores, except for change in periarticular inflammation (ICC 0.33). PsAMRIS sensitivity to change was moderate for synovitis, tenosynovitis, and periarticular inflammation (SRM 0.5-0.8), while poor (SRM 0.1-0.3) for bone marrow edema, erosion, and bone proliferation. Rare occurrence and minimal change contributed to poor SRM and change-score ICC for bone parameters.

Conclusion: This multireader exercise, performed under standardized conditions, confirmed PsAMRIS to have high interobserver and intraobserver reliability for hand PsA. Measures of inflammation were sensitive to change, implying that PsAMRIS may be a valuable tool for monitoring change in inflammation during PsA clinical trials.