Do they just know more, or do they also have different preferences? An exploratory analysis of the effects of self-reporting serious health problems on health state valuation.

BACKGROUND: Health state valuation is often conducted by people valuing either only their own health state (experience-based valuation) or several stylised states (hypothetical valuation). The approach used can affect the elicited values, but it is not clear whether this is caused by different understandings of the states (an "information mechanism") and/or by different opinions of the states (a "preference mechanism"). Justifying privileging the valuations of those with the relevant health state experience solely because they are better informed is insufficient when their opinions differ. This study proposes a new framework to examine the effect of having health problems on health state valuation by distinguishing "within-dimensional" effects (which can be due to better information or due to differences in opinion) and "cross-dimensional" effects (which must be due to differences in opinion). METHODS: Secondary data from the UK that valued EQ-5D-5L using Discrete Choice Experiments with duration (DCETTO) are remodelled controlling for whether a respondent self-reports serious (viz., severe or extreme) problems in "pain or discomfort" (PD) or "anxiety or depression" (AD). The main analysis uses respondents who have serious PD or serious AD alongside matched respondents who do not, and assumes constant proportional time trade-off. RESULTS: Self-reporting serious PD or serious AD problems has no within-dimensional effect on health state preferences. However, self-reporting serious AD problems has negative cross-dimensional effects on the utility of having any problem in PD, which suggests that the preference mechanism is present. A similar pattern holds when all available (unmatched) data are used and when constant proportional time trade-off is relaxed. CONCLUSIONS: Findings consistent with the preference mechanism indicate that those with serious health problems may have different opinions on the value of health states compared to the rest of the population, which has normative implications for the debate on which values to use.