Treatment pathways and economic analysis of treatment for severe psoriasis
Psoriasis is a chronic skin disease that affects up to 2% of the UK population. The clinical presentation ranges from mild disease to extensive, severe disease that causes considerable discomfort and distress. Severe disease usually requires photochemotherapy or systemic treatment. Information about the effectiveness, safety and costs of the different treatments is required to enable dermatologists to formulate evidence-based treatment guidelines. Systematic reviews of the four main treatment modalities for moderate-severe psoriasis (cyclosporin, methotrexate, systemic retinoids and photochemotherapy) were performed. Randomised controlled trials were located systematically by electronic searching, hand searching and personal communications. Data on trial characteristics and outcomes were extracted and tabulated. Where possible data were pooled to give summary effect sizes as odds ratios, rate differences or numbers needed to treat (NNTs). Firm RCf evidence of efficacy was found for cyclosporin, oral ret.inoids, particularly in combination with PUV A, phototherapy, photochemotherapy and for combinations of topical calcipotriol or steroids with phototherapy. The corresponding NNTs were low, indicating high levels of efficacy. RCI' evidence of efficacy is lacking for methotrexate. Two observational studies of patients attending the Psoriasis Specialty Clinic were performed. The first was a crosssectional study that used data in existing disease assessment docwnentation to identify the characteristics of a group of 256 patients. The second was a longitudinal study that followed the treatment pathways of 166 patients in the first group. These studies confirmed that this group of patients and their treatments were comparable with those described in the literature. An economic analysis was performed, using a previously published decisionanalytic model, to compare four treatment strategies for severe psoriasis from the health service perspective. The results (cost-effectiveness ratios) showed that methotrexate was the most cost-effective primary treatment followed by cyc1osporin, acitretin and PUV A. The rank order was not sensitive to changes in response rates. Modifications to the decision analytic model are proposed including a wider array of pathways and an allowance for adverse effects of treatment. Future analyses should include narrowband UVB alone as a primary treatment.