BACKGROUND: Patients with moderate-to-severe psoriasis are candidates for systemic treatment, but it is unknown how many receive such therapy at a national level in Denmark.

OBJECTIVES: We aimed to determine the prevalence of conventional systemic therapy use in patients with moderate-to-severe psoriasis, and further, to investigate the time to discontinuation of conventional systemic therapy and initiation of biological therapy among bio-naïve patients.

METHOD: This registry-based study identified a cohort of patients with psoriasis in Denmark. We estimated the prevalence of moderate-to-severe psoriasis at a national level using registry data. Inverse probability weighting was used to mitigate the potential selection bias in the prevalence-estimate of moderate-to-severe psoriasis.

RESULTS: Of patients with psoriasis in Denmark, 10.9% were estimated to have moderate-to-severe psoriasis of whom 62.3% received either conventional systemic or biological therapy meaning 37.7% who were considered candidates for systemic therapy did not receive any systemic treatment. The study demonstrated that time on conventional systemic therapy for patients with moderate-to-severe psoriasis was shorter today than previous (median time of 3.0 years in 1985-1994 vs. 0.6 years in 2014-2018), more patients initiated biologic therapy as second-line therapy with 69.5% in 2010-2013 and 71.2% in 2014-2018 and the median time from initiation of systemic therapy to initiation of biological therapy decreased from 13.3 years in 2010-2013 to 1.9 years in 2014-2018.

CONCLUSION: This study found that nearly 37.7% of the patients with moderate-to-severe psoriasis do not receive systemic treatment even though they would qualify for this. Further, for patients treated with conventional systemics, the drug survival decreased during the observation period.