To estimate the incidence of psoriatic arthritis (PsA) in patients with psoriasis who had received a continuous treatment with biological disease-modifying antirheumatic drugs (bDMARDs) compared with phototherapy.
A retrospective non-randomised study involving patients with moderate-to-severe plaque psoriasis, who were prescribed at least 5 years of bDMARDs or at least three narrow-band ultraviolet light B (nb-UVB) phototherapy courses, and did not have a diagnosis of PsA at enrolment. Development of PsA in each patient was assessed by a rheumatologist according to the Classification for Psoriatic Arthritis criteria. The annual and cumulative incidence rate of PsA was estimated by using an event per person-years analysis. Cox proportional hazards models were undertaken to assess the hazard risk (HR) of PsA after adjustment for confounders.
A total of 464 psoriatic patients (bDMARDs, n=234 and nb-UVB, n=230) were followed between January 2012 and September 2020 (corresponding to 1584 and 1478 person year of follow-up for the two groups, respectively). The annual incidence rate of PsA was 1.20 cases (95% CI 0.77 to 1.89) versus 2.17 cases (95% CI 1.53 to 3.06) per 100 patients/year in the bDMARDs versus phototherapy group, respectively (HR 0.29, 0.12-0.70; p=0.006). The variables independently associated with higher risk of PsA were older age (adjusted HR 1.04, 1.02-1.07), nail psoriasis (adjusted HR 3.15, 1.63-6.06) and psoriasis duration >10 years (adjusted HR 2.02, 1.09-3.76); notably, bDMARDs treatment was associated with a lower risk of incident PsA (adjusted HR 0.27, 0.11-0.66).
bDMARDs treatment may delay or reduce the risk of incident PsA in patients with moderate-to-severe chronic plaque psoriasis.