FEASIBILITY, RELIABILITY, AND VALIDITY OF THREE HEALTH-STATE RATING METHODS USING MULTIPLE-OUTCOME VIGNETTES ON MODERATE-RISK PREGNANCY AT TERM

PURPOSE Preference-based health state rating methods such as discrete choice experiment (DCE) are claimed to be superior over attitude-based 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. Feasibility was evaluated by questionnaire. Test-retest reliability and inter-observer consistency were assessed by intraclass correlation (ICC), and variance consistency by generalization theory (G-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 (τ).

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 inter-observer 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 (τ =0.68). The TTO yielded less optimal results. Generally, neonatal and maternal outcomes weighed most, while process outcomes weighed least in moderate-risk pregnancy at term.

CONCLUSION DCE was superior to TTO and performed equal to VAS, with DCE displaying slightly higher user feasibility.