Exploring differences between TTO and DCE in the valuation of health states

Abstract

There is recent interest in using Discrete Choice Experiments (DCEs) to derive health state utility values and results can differ from Time Trade Off (TTO). Clearly DCE is 'choice-based' whereas TTO is generally considered to be a 'matching' task. We explore whether procedural adaptations to the TTO -which make the method more closely resemble a DCE -makes TTO and choice converge. In particular, we test whether making the matching procedure in TTO less 'transparent' to the respondent reduces disparities between TTO and DCE. We designed an interactive survey that was hosted on the internet and 2022 interviews were achieved in the UK in a representative sample of the population. We found a marked divergence between TTO and DCE, but this was not related to the 'transparency' of the TTO procedure. We conclude that a difference in the error structure between TTO and choice and that factors other than differences in utility are affecting choices is driving the divergence. The latter has fundamental implications for the way choice data are analysed and interpreted.