Psoriatic arthritis: improvement in outcomes but persistent sex difference - 5-year follow-up study of a Norwegian outpatient clinic population.

Objective: This study aimed to explore long-term changes in disease activity and remission rates, and potential sex-related differences in these outcomes, in psoriatic arthritis (PsA) patients treated in an outpatient clinic.

Method: This prospective longitudinal cohort study included 114 patients. The Disease Activity Index for Psoriatic Arthritis (DAPSA), clinical DAPSA (cDAPSA), 28-joint Disease Activity Score (DAS28), Simplified and Clinical Disease Activity Indices (SDAI, CDAI), Boolean remission for PsA, and minimal and very low disease activities (MDA, VLDA) were assessed. For group characteristics, parametric statistics and linear regression were used.

Results: At 5 year follow-up, improvement was noted for multiple measures reflecting disease activity and patient-reported outcomes. Statistically significant increases in remission rates were observed using DAS28 (+21.2%), CDAI (+9.7%), and cDAPSA (+7.6%), but not SDAI, DAPSA, Boolean remission, MDA, or VLDA. During the study period, the proportion of patients treated with biological disease-modifying anti-rheumatic drugs (bDMARDs) increased from 37.7% to 48.3% (p = 0.007). At baseline, women reported higher pain and fatigue, and had higher tender joint counts, DAPSA, cDAPSA, SDAI, CDAI, and DAS28 than men. Despite higher mean baseline C-reactive protein, men more often achieved remission, regardless of the definition applied. A higher proportion of men than women was treated with bDMARDs (baseline: 46.6% vs 28.6%; follow-up: 58.6% vs 33.9%).

Conclusion: This study adds evidence supporting recent improvements in PsA outcomes. Women had higher disease activity and were less likely to achieve remission than men. Despite progress in achieving remission goals, there is still room for improvement in therapeutic approaches for PsA patients.