Prevalence of Psoriatic Arthritis in Patients with Moderate-to-Severe Psoriasis in the Era of Biologics and Small Molecule Therapies

Objectives: To estimate the prevalence of psoriatic arthritis (PsA) and associated factors in patients with moderate-to-severe psoriasis. Methods: Retrospective, single-center study of a cohort of psoriasis patients in standard follow-up in a dermatology department from July 2008 to January 2024. Patients ≥18 years with moderate-to-severe psoriasis were included and classified into three groups according to the treatment received: group 1, biologics or small molecules with or without conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs); group 2, only csDMARDS; and group 3, non-pharmacological treatments. Demographic and clinical variables were collected. The prevalence of PsA was estimated with its 95% confidence interval (CI). The cumulative incidence of PsA was analyzed across groups, and logistic regression models were built. Results: The study population comprised 308 patients (67.2%, 22.7%, 10% in groups 1, 2, and 3, respectively). Differences between the groups were observed in severity of psoriasis, weight, smoking status, and dyslipidemia (p < 0.05). The prevalence of PsA was 11.7% (95% CI, 8.1–15.3), with most patients in group 1. This group had a higher risk of PsA following diagnosis of psoriasis or initiation of treatment. Belonging to groups 2 and 3 had a smaller effect than belonging to group 1 in the development of PsA; nail involvement and obstructive sleep apnea (OSA) were associated with development of PsA (p < 0.05). Conclusions: The prevalence estimate was lower than previous estimates, probably owing to the increased use of biologics. Nail involvement and OSA were associated with PsA.