Is a simplified version of PsAMRIS (sPsAMRIS) a potential tool for therapy monitoring in established psoriatic arthritis?

Background: To evaluate whether a simplified version of the psoriatic arthritis magnetic resonance imaging score (PsAMRIS), sPsAMRIS, is a potential tool for therapy monitoring in psoriatic arthritis (PsA). Methods: Seventeen patients with PsA, according to CASPAR classification criteria, with inadequate methotrexate response received anti-TNF treatment and were assessed by 3T MRI of the clinically dominant hand at baseline and after 6 months. Scoring was according to PsAMRIS. Items were reduced based on standard response mean (SRM), resulting in a simplified PsAMRIS (sPsAMRIS), which was compared to PsAMRIS by calculation of the total SRM and relative efficiency (RE) after bootstrapping. Results: The PsAMRIS subscore of MCP3, 4, and PIP4 resulted in the highest SRM (–0.07 each) and were, therefore, included in sPsAMRIS. sPsAMRIS had a higher SRM compared to PsAMRIS (–0.13 vs. –0.02) and a higher RE (29.46). PsAMRIS and sPsAMRIS were highly correlated at baseline (r=0.75, p