Discrete Choice Experiment with Duration Versus Time Trade-off: a Comparison of Test-retest Reliability of Health Utility Elicitation Approaches in SF-6Dv2 Valuation

Objectives: To evaluate and compare the test-retest reliability of discrete choice experiments with duration (DCE) and time trade-off (TTO) in the Chinese SF-6Dv2 valuation study.

Methods: During face-to-face interviews, a representative sample of the Chinese general population completed 8 TTO tasks and 10 DCE tasks. Retest interviews were conducted after two weeks. For both DCE and TTO, the consistency of raw responses between the two tests was firstly evaluated at the individual level. Regressions were conducted to investigate the association between the test-retest reliability and the respondents' characteristics and the severity of health states. Consistency was then analyzed at the aggregate level by comparing the rank order of the coefficients of dimensions.

Results: In total, 162 respondents (51.9% male; range 18-80 years) completed the two tests. The intraclass correlations coefficient 0.958 for TTO, with identical values accounting for 59.3% of observations. 76.4% of choices were identical for DCE, with a Kappa statistic of 0.528. Respondents' characteristics had no significant impact while the severity of health states valued in TTO and DCE tasks had a significant impact on the test-retest reliability. Both approaches produced relatively stable rank order of dimensions in constrained model estimations between test and retest data.

Conclusions: Individual responses of both approaches are relatively stable over time. The rank orders of dimensions in model estimations between test and retest for TTO and DCE are also consistent. The differences of utility estimation between the two tests for DCE need to be further investigated based on a larger sample size.