Impact of clinical domains other than arthritis on composite outcomes in psoriatic arthritis: comparison of treatment effects in the SEAM-PsA trial

OBJECTIVE: We used the Study of Etanercept And Methotrexate in Combination or as Monotherapy in Subjects with Psoriatic Arthritis (SEAM-PsA) data set to examine the impact of presence of enthesitis, dactylitis, nail disease and/or psoriasis on treatment response in patients with early psoriatic arthritis (PsA). METHODS: This post hoc analysis evaluated the effect of baseline Spondyloarthritis Research Consortium of Canada (SPARCC) Enthesitis Index (EI), Leeds Enthesitis Index (LEI), Leeds Dactylitis Index (LDI), modified Nail Psoriasis Severity Index (mNAPSI) scores and body surface area (BSA) on composite outcomes of minimal disease activity (MDA) responses, Psoriatic Arthritis Disease Activity Score (PASDAS) low disease activity (LDA), PASDAS changes and Good Responses and Disease Activity Index for Psoriatic Arthritis (DAPSA) scores at Week 24. RESULTS: Overall, 851 patients completed the SEAM-PsA trial and were included in the analysis. Baseline enthesitis (SPARCC EI>0 vs SPARCC EI=0 or LEI>0 vs LEI=0) was not associated with improved outcomes. Baseline dactylitis (LDI>0 vs LDI=0) was positively associated with improved MDA (OR: 1.4, p=0.0457), PASDAS LDA (OR: 1.8, p=0.0014) and Good Responses (OR: 1.6, p=0.0101) and greater reductions in PASDAS (estimate: –0.9, p<0.0001) and DAPSA scores (estimate: –3.8, p=0.0155) at Week 24. Similarly, baseline nail disease (mNAPSI >1 vs mNAPSI≤1) was positively associated with improved MDA (OR: 1.8, p=0.0233) and PASDAS LDA (OR: 1.8, p=0.0168) responses and greater reduction in PASDAS (estimate: –0.7, p=0.0005) at Week 24. CONCLUSIONS: Results from our analysis suggest that presence of dactylitis and nail disease, but not enthesitis, are associated with improved outcomes in patients with early PsA who were treated with methotrexate and/or etanercept.