Systemic psoriasis therapy shows high between-country variation: a sign of unwarranted variation? Cross-sectional analysis of baseline data from the PSONET registries

BACKGROUND: Several national prospective registries of psoriatic patients treated with systemic therapies are running, with the aim of describing the population treated, safety and effectiveness of these treatments, especially biologics. Psonet is an initiative to pool data from these registries. OBJECTIVES: To describe psoriasis therapy in Psonet countries, using baseline data of patients included in these registries. METHODS: We collected data from Psocare (Italy), Dermbio (Denmark), Biobadaderm (Spain), Clalit Health Services (Israel), Australasian Psoriasis Registry, Psobest (Germany), and AMC Medical Center Registry (Netherlands). We described previous use of drugs at the time that patients started a new classic systemic drug or any biologic drug. RESULTS: Data from 20,232 patients was pooled in our analysis (9,668 treated with biologics, 10,564 with other systemic therapies). At a given time in the life course of psoriasis, we have shown large between country heterogeneity on the previous use of systemic drugs for psoriasis and relevant rates of use of biologic drugs in potentially off-label use (first line use and use in psoriasis forms different from plaque psoriasis). Variability in therapy is larger than variability in available patient characteristics likely to influence therapy. CONCLUSIONS: We have shown the presence of large heterogeneity on the use of systemic drugs for psoriasis in participating countries, including differences in patient access to biologics amongst the participating countries. This might be an indicator of unwarranted clinical variation in some countries: a marker of inefficient or less safe use of systemic drugs for psoriasis, and requires further study