Using conjoint analysis and choice experiments to estimate QALY values: issues to consider.

There is increasing interest in using ranking tasks, discrete choice experiments and best-worst scaling studies to estimate QALY values for use in cost-utility analysis. The research frontier in choice modelling is moving rapidly, with a number of issues being explored across several disciplines. These issues include the estimation of discount factors, proper modelling of the variance scale factor and the estimation of individual-level utility functions. Some of these issues are particularly acute when discrete choice tasks are used to facilitate extra-welfarist analyses that rely on population-based values. There are also potential problems in implementing such tasks that have received little interest in the non-health discrete choice literature because they are specific to the QALY framework. This article details these issues and offers recommendations on the conduct of 21st century QALY valuation exercises that propose to use any tasks that rely on discrete choices.