Willingness-To-Pay and Time-Trade-Off: Useful Utilities in Patients with Psoriasis vulgaris?

Abstract

Background: For cost-utility-analyses in pharmaco-economic research, it is necessary to additionally assess quality-of-life (QoL) parameters for content validation of the utilities. Utilities such as ‘willingness-to-pay’ and ‘time-trade-off’ bear several advantages in comparison to questionnaires of QoL: utilities are more practicable and provide data that are easier to use for pharmaco-economic evaluations. Objective: Development of suitable questions for assessing both ‘willingness-to-pay’ and ‘time-trade-off’ and evaluation of correlation with a standardized QoL questionnaire. Methods: Both assessments were employed in a survey on patients suffering from psoriasis vulgaris pre and post treatment with synchronous balneo-phototherapy. Simultaneously the Psoriasis Disability Index (PDI) for evaluation of quality-of-life was used. Results: Data of 105 patients could be annualized. Com-pared to the assessments pre treatment, mean reduction of PDI was 25.5% (29 pre treatment, 21.6 post treatment), mean reduction in willingness-to-pay was 22.5% (proportion of monthly income in %: 16 pre to 12.4 post treatment) and mean reduction in time-trade-off 1% (percentage of hours per day: 3.4 pre to 3.3 post treatment). While willing-ness- to-pay is highly correlated with the PDI (p < 0.05), time-trade- off does not seem to be a valid parameter for assessment of utilities over time in this target population. Conclusion: The results indicate that the principle of willingness- to-pay bears high potential for use in dermatological indications, especially in pharmaco-economic evaluations.