Does biologic therapy impact the development of PsA among patients with psoriasis?

Objective To examine the association of biologic therapy use for psoriasis with incident psoriatic arthritis (PsA) diagnosis. Methods A retrospective cohort study was conducted in the OptumInsights Electronic Health Record Database between 2006 and 2017 among patients with psoriasis between the ages of 16 and 90 initiating a therapy for psoriasis (oral, biologic or phototherapy). The incidence of PsA was calculated within each therapy group. Multivariable Cox models were used to calculate the HR for biologic versus oral or phototherapy using biologics as a time-varying exposure and next in a propensity score-matched cohort. Results Among 1 93 709 patients with psoriasis without PsA, 14 569 biologic and 20 321 cumulative oral therapy and phototherapy initiations were identified. Mean age was lower among biologic initiators compared with oral/phototherapy initiators (45.9 vs 49.8). The incidence of PsA regardless of therapy exposure was 9.75 per 1000 person-years compared with 77.26 among biologic users, 61.99 among oral therapy users, 26.11 among phototherapy users and 5.85 among those without a prescription for one of the target therapies. Using a multivariable adjustment approach with time-varying exposure, adjusted HR (95% CI) for biologic users was 4.48 (4.23 to 4.75) compared with oral or phototherapy users. After propensity score matching, the HR (95% CI) was 2.14 (2.00 to 2.28). Conclusions In this retrospective cohort study, biologic use was associated with the development of PsA among patients with psoriasis. This may be related to confounding by indication and protopathic bias. Prospective studies are needed to address this important question.