Purpose: In measuring preference for multistate health profiles, past literature showed that the Quality-Adjusted Life Year (QALY) model, in which QALYs for each health state in the profiles are evaluated independently and all are combined to produce the overall QALYs, violates a key required assumption, additive independence. Moreover, several studies have shown that the preferences for entire health profiles are potentially impacted by many factors such as trend, rate of change, peak and final intensity, spreading of outcomes, and timing of events within the multistate health profile. In this study, we aimed at investigating the relationship between two consecutive health states and exploring and understanding how the preference for a future health state is dependent upon the current health state.

Methods: Using the VAS method, ninety-two subjects evaluated a set of hypothetical health scenarios described in EQ-5D system on a visual analog scale. Each health scenario was composed of two consecutive health states: the current health state and the following (future) health state. Three factors of interests were: (1) direction of change from current to future health states (improving vs. declining), (2) amplitude of change (small vs. large), and (3) current health state duration (1 year vs. 10 years). A full 23 factorial design (three factors with 2 levels each) with three replications at three different levels of future health states was designed and employed, which yielded a total of 24 health scenarios for each subjects.

Results: Main effects and their interactions on the preference score for the future health state were found significant. Moreover, when current health state was at nearly perfect level, scores for the deteriorated future health state were significantly lower than when being assessed independently. Also, when current health state was at a low level, scores for the improved future health state were significantly higher than when being assessed independently.

Conclusions: Preference for a future health state was found to be strongly dependent on the level of current health state. The nature and extent of the impact of the current health state characteristics in assessing preference for a future health state also depend on the level of the future health state itself. The results have strong implications for cost-effectiveness studies.