Assessing the Direct Impact of Death on Discrete Choice Experiment Utilities

Background

The dead state can affect the value sets derived from discrete choice experiments (DCEs). Our aim was to empirically assess the direct impact of the immediate death state on health utilities using discrete choice experiment with time (DCE_TTO).

Methods

A sample of the general population in Quebec, Canada, completed two approaches: DCE_TTO followed by a best-worst scaling with time (BWS_TTO) (hereafter referred to as DCE_BWS), versus DCE_TTO followed by the dominated option and the immediate death state (hereafter referred to as DCE_DOD), both designed with the SF-6Dv2. In DCE_BWS, all participants first completed 10 DCE_TTO choices (i.e., option A vs B), followed by 3 BWS_TTO. In DCE_DOD, the same participants first completed the same 10 DCE_TTO choices, followed by a repeated choice between the dominated option (i.e., A or B) and the immediate death state. A conditional logit model was used to estimate value sets. The performance of models was assessed using goodness of fit using Bayesian information criterion, parameters’ logical consistency, and levels’ significance. The direct impact of the death state on DCE latent utilities was evaluated by examining the magnitude of coefficients, assessing the agreement among the value sets estimated by DCE_TTO with DCE_BWS and with DCE_DOD using Bland-Altman plots, the proportion of worst-than-dead (WTD) health states, and analyzing the range of estimated values.

Results

From 398 participants, a total of 348 participants were included for final analysis. The number of parameters with illogical consistency and non-significant coefficients was lower in DCE_BWS. The observed consistency in the relative importance of dimensions across all approaches suggests a stable and reliable ranking. The utility range for DCE_DOD (− 0.921 to 1) was narrower than for DCE_TTO (− 1.578 to 1) and DCE_BWS (− 1.150 to 1). The DCE_DOD estimated a lower percentage of WTD health states (20.01 %) compared to DCE_TTO (47.19 %) and DCE_BWS (33.73 %). The agreement between DCE_TTO and DCE_BWS was slightly stronger than between DCE_TTO and DCE_DOD, and the mean utility values were higher in DCE_DOD than in DCE_BWS.

Conclusions

The inclusion of the immediate death state directly within DCE increased utility values. This increase was higher when the immediate death was included in a sequence within a DCE_TTO (i.e., DCE_DOD) than when it was included in a continuum of DCE_TTO (i.e., DCE_BWS). The use of DCE_DOD was potentially better suited to incorporate the dead state into a DCE.