Treatment and referral patterns for psoriasis in United Kingdom primary care: a retrospective cohort study

BACKGROUND: In the UK, referrals to specialists are initiated by general practitioners (GPs). Study objectives were to estimate the incidence of diagnosed psoriasis in the UK and identify factors associated with GP referrals to dermatologists. METHODS: Newly diagnosed patients with psoriasis were identified in The Health Improvement Network (THIN) database between 01 July 2007-31 Oct 2009. Incidence of diagnosed psoriasis was calculated using the number of new psoriasis patients in 2008 and the mid-year total patient count for THIN in 2008. A nested case-control design and conditional logistic regression were used to identify factors associated with referral. RESULTS: Incidence rate of diagnosed adult psoriasis in 2008 was 28/10,000 person-years. Referral rate to dermatologists was 18.1 (17.3-18.9) per 100 person-years. In the referred cohort (N=1,950), 61% were referred within 30 days of diagnosis and their median time to referral was 0 days from diagnosis. For those referred after 30 days (39%, median time to referral: 5.6 months), an increase in the number of GP visits prior to referral increased the likelihood of referral (OR=1.87 95% CI:1.73-2.01). A prescription of topical agents such as vitamin D3 analogues 30 days before referral increased the likelihood of being referred (OR=4.67 95% CI: 2.78-7.84), as did corticosteroids (OR=2.45 95% CI: 1.45-4.07) and tar products (OR=1.95 95% CI: 1.02-3.75). CONCLUSIONS: Estimates of the incidence of diagnosed adult psoriasis, referral rates to dermatologists, and characteristics of referred patients may assist in understanding the burden on the UK healthcare system and managing this population in primary and secondary care.