An exploration of the non-iterative time trade off method to value health states

Time Trade-Off (TTO) usually relies on “iteration”, which is susceptible to bias. Discrete Choice Experiment with duration (or DCETTO) is free of such bias, but respondents find this cognitively more challenging. This paper explores non-iterative TTO with or without lead time: NI(LT)TTO. In NI(LT)TTO respondents see a series of independent pairwise choices without iteration (similar to DCETTO), but one of the two scenarios always involves full health for a shorter duration (similar to TTO). We compare three different “Types” of NI(LT)TTO relative to DCETTO. Each Type is presented in two “Modes”: (a) verbally tabulated (as in a DCE); and (b) with visual aids (as in a TTO). The study has eight survey variants, each with 12 experimental choice tasks and a 13th task with a logically determined answer. Data on the 12 experimental choices from an online survey of 6,618 respondents are modelled, by variant, using conditional logistic regressions. The results indicate that NI(LT)TTO is feasible, but some relatively mild states appear to have implausibly low predicted values, and the range of predicted values is much narrower than in DCETTO. The presentation of NI(LT)TTO tasks needs further improvement.