Previous estimates on the incidence of psoriatic arthritis among patients with psoriasis may not accurately reflect the prevalence of disease, according to recently published research that noted patients with uveitis, nail pitting and low levels of education may have a higher risk for developing psoriatic arthritis.
Researchers studied data from 464 patients who participated in the Toronto Psoriasis Cohort and had a dermatologist-confirmed diagnosis of psoriasis. All patients were evaluated for inflammatory arthritis, enthesitis and spondylitis. Patients were excluded at baseline if they had any articular involvement. Participants were evaluated annually, and suspected cases of psoriatic arthritis (PsA) were confirmed by at least two rheumatologists from a PsA research team following review of clinical, laboratory and imaging details.
During the 8-year follow-up, 51 patients developed confirmed PsA and nine had suspected PsA based on high scores on a questionnaire. A total of 1,880.9 person-years of follow-up were available for the remaining 404 patients who did not develop PsA.
Including only confirmed cases of PsA, the annual incidence rate was 2.7 cases per 100 patients with psoriasis and 3.2 per 100 when both suspected and confirmed cases were included.
Patients with nail pitting had a relative risk (RR) of 2.21 for developing PsA, and an RR of 3.86 was identified in patients with severe psoriasis compared with an RR of 1.35 for patients with moderate psoriasis. A low level of education was associated with a higher risk of PsA than patients with college education, and the use of retinoid medications was associated with an RR of 2.8. Adjusted Cox regression models produced similar results. – by Shirley Pulawski
: Eder’s work was supported by the Krembil Foundation and a Canadian Institutes of Health Research (CIHR) fellowship award. The Psoriatic Arthritis Program is funded in part by the Arthritis Society, CIHR and the Krembil Foundation.