Cost-Effectiveness Analysis of Topical Calcipotriol versus Short- Contact Dithranol

Objective: To examine the relative cost effectiveness of topical calcipotriol and short-contact dithranol in the treatment of mild to moderate plaque psoriasis.

Design and setting: This was a modelling study from the perspective of the UK National Health Service as payer.

Methods: The interventions were compared using 2 decision-analytic models: one using a short term horizon (12 weeks) and the other using a longer term horizon (up to 1 year). Clinical success of treatment and relapse rates were obtained from the results of randomised controlled trials.

Main outcome measures and results: The outcome measure used was the degree of improvement in psoriasis as judged by the patient. In the short term comparison, calcipotriol was the most effective treatment (60.8% success), but it was also the most expensive (£96.03; 2000 values). The incremental cost per success was £577.50 using a 12-week course of calcipotriol compared with short-contact dithranol. Over the long term horizon, first-line treatment with calcipotriol still had the highest expected cost per successful treatment (£164.91), but the incremental cost using this strategy was £38.66 compared with short-contact dithranol. In terms of cost per successful day’s treatment (i.e. the cost for a day in which the patient reported a marked improvement or cleared lesions), the cost of each additional successful day’s treatment was £19.93 when using calcipotriol as first line treatment rather than short-contact dithranol.

Conclusion: The combination of differences in drug acquisition costs and relapse rates can lead to large differences in the comparative cost effectiveness of topical treatments for plaque psoriasis. From the perspective of the prescriber, the results of this analysis suggest that selecting short-contact dithranol as first-line treatment was the most cost-effective strategy.