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