PMS18 Cost-Utility Evaluation Comparing Disease Progression in Moderate Versus Severe Psoriasis in Adults in the United Kingdom

Abstract

Delayed systemic treatment of psoriasis (PSO) is common and increases the risk of disease progression. This cost-utility model investigated the impact of baseline PSO severity on patients’ health outcomes and cost to the UK NHS. A Markov model (35-year time horizon, 1-month cycles) estimated progression from PSO towards psoriatic arthritis (PsA), PsA+comorbid hypertension, low disease levels or death, in 1,000 patients. Output from two model runs, covering either moderate PSO (Psoriasis Area Severity Index [PASI]>10–≤20) or severe PSO (PASI>20), were compared. Transition probabilities were estimated using published risk ratios, treatment guidelines and effectiveness data, and death registration data, tailored to PSO severity. Transition to the low disease health state required a PASI75 response. Cumulative direct costs and quality-adjusted life years (QALYs) were modelled with an annual discount rate of 3.5%. Costs and utility weights were sourced from the literature and inflated to 2019 values. A probabilistic sensitivity analysis (PSA) explored the impact of uncertainty in each model’s parameters on the variation of final utilities and costs across 1,000 patients. Patients with severe PSO at baseline had higher cumulative costs/patient than moderate PSO patients after 5 (£21,717 vs £16,176), 10 (£39,422 vs £29,625) and 35 (£89,489 vs £66,864) years; this was driven by differences in low disease levels (35 year: 25.0% vs 32.9%) rather than treatment costs. Severe PSO patients also had fewer QALYs compared with moderate PSO patients after 5 (3.02 vs 4.06), 10 (5.54 vs 7.43) and 35 (12.52 vs 16.77) years. The PSA showed no correlation (R2=0.0019) between cumulative QALYs and costs for moderate PSO vs a negative correlation (R2=-0.7389) for severe PSO; i.e. more severe disease states (lower QALYs) correlated to higher costs. Treating PSO patients appropriately, early in their disease journey, could provide improved long-term health outcomes and offset and reduce future costs to the NHS.