Incidence of arthritis in a prospective cohort of psoriasis patients.

Objective: Epidemiologic studies about the incidence of psoriatic arthritis (PsA) are limited to a few population-based studies. There are limited data regarding the incidence of PsA in patients with psoriasis. We aimed to determine the incidence of PsA among a prospective cohort of psoriasis patients.

Methods: The setting is a prospective longitudinal cohort study of psoriasis patients without arthritis. The patients are assessed annually by a rheumatologist in order to detect the onset of arthritis. We summarize the results of 4 years of followup and report the cumulative incidence of PsA from the time of entry to the study that was estimated using an event per person-years analysis and a nonparametric analysis.

Results: Three hundred thirteen psoriasis patients that had at least 1 year of followup were included in the analysis. The annual incidence rate was found to be 1.87 (95% confidence interval 0.71-3.03) PsA cases per 100 psoriasis patients.

Conclusion: The incidence rate of PsA in patients with psoriasis may be higher than previously reported, particularly among patients with moderate to severe psoriasis.