Conclusion This section has considered the performance of different elicitation techniques and the distinctive aspects of value implicitly conveyed by each one. Comparing methods for eliciting health state preferences directly may be less relevant for guiding CEA in regulatory analysis, however, than is comparing the specific HRQL instruments, or generic indexes, presented later in this chapter. The choice among alternative preference elicitation techniques is embedded in the choice of generic index, because each index relies on a valuation survey that employed a particular elicitation method. If health state values are elicited directly in new surveys, however, the researcher must choose a preference elicitation method.
In the previous section we relied on the QALY as the construct for which different preference elicitation methods are applied. This section further considers the QALY and several other HALY constructs, in light of their suitability for regulatory CEA.
As noted in Chapter 1, the QALY was the first HALY metric, developed about 30 years ago as an outcome measure for CEA. It was designed to facilitate the maximization, in accordance with individual preferences for health, of aggregate health benefits for a given level of resources invested.
QALYs can be interpreted in different ways. When initially developed, the QALY was simply an index with an intuitive meaning, corresponding to the equivalent number of years in full health. More formally, QALYs can be thought of as an index for which relative values are calculated using utility theory or as a measure of economic utility (Gafni, 2004).
Pliskin and colleagues (1980) first proposed an underlying utility model for QALYs. This model applies to individual decision makers who are presumed to maximize expected utility when outcomes are uncertain. The authors derived the behavioral assumptions about preferences for health states and longevity that would be consistent with QALYs as a utility function, in situations where health status is constant over the life span. As described in the previous section, the SG and TTO are commonly used to determine the value of a particular health state that will last the rest of one’s life in terms of the risk of death or the loss of life expectancy that the individual is willing to accept in order to achieve optimal health.
The behavioral assumptions of the utility-theoretical model are as follows: