Feasibility, reliability, and validity of three health-state valuation methods using multiple-outcome vignettes on moderate-risk pregnancy at term

Abstract

Objectives: Preference-based health-state valuation methods such as discrete choice experiment (DCE) are claimed to be superior than attitude-based valuation methods like visual analogue scale (VAS) and time trade-off (TTO). We compared VAS, TTO, and DCE in terms of feasibility, reliability, and validity using vignettes depicting moderate-risk pregnancy at term. Methods: People from the community (n = 97) participated in both a panel session and an individual home assignment. Each participant valuated 46 vignettes with VAS, TTO, and DCE. Each vignette consisted of five attributes: maternal health antepartum, time between diagnosis and delivery, process of delivery, maternal outcome, and neonatal outcome. The questionnaire included Feasibility, which we evaluated by questionnaire. Test-retest reliability and interobserver consistency were assessed by intraclass correlation (ICC), and variance consistency by generalization theory. Convergent validity was determined with ICC and Cohen's kappa; construct validity was determined with linear regression, multinomial logit modeling, and Kendall's Tau-b correlation (θ). Results: The DCE was reported as most feasible (DCE: 87% vs. VAS: 69% vs. TTO: 42%). Test-retest reliability was high overall and equal (VAS: ICC = 0.77; TTO: ICC = 0.79; DCE: κ = 0.78). The VAS had the highest interobserver reliability (ICC = 0.73). Convergent validity between VAS and DCE was high (κ = 0.79) and there was sufficient construct validity between VAS and DCE (θ = 0.68). The TTO yielded less optimal results. Generally, neonatal and maternal outcomes weighed most, whereas process outcomes weighed least in moderate-risk pregnancy at term. Conclusions: In our context of multidimensional health states with complex trade-offs, DCE was superior to TTO and performed equal to VAS, with DCE displaying slightly higher user feasibility. © 2009, International Society for Pharmacoeconomics and Outcomes Research (ISPOR).