QALYs versus HYEs (healthy year equivalents): a reply to Gafni, Birch and Mehrez

QALYs versus HYEs--what's right and what's wrong. A review of the controversy

The paper uses an axiomatic approach to the description of individual preferences for health status sequences to resolve the major issues at state in the recent controversy over QALYs versus HYEs. While the HYE accounts for an individual's time preference for health, QALY scores based on the time trade-off method will generally differ from the number of HYEs. HYEs do not represent preferences for health under risk unless the utility function for reference flows of health is linear. Collapsing the two-step HYE assessment procedure into a single step entails a loss of information as regards the utility of a health status sequence. Although the procedure does represent preferences for health, it fails to supply a description in terms of HYEs in the case of risk. As a remedy, a modified HYE approach is proposed.

Where are we now in British health economics?

Health economics took off in 1970 or thereabouts, just after the take-off date for the economics of education. Although early health economics made use of human capital theory as did the economics of education, it soon took a different route inspired by Arrow's work on medical insurance. The economics of education failed to live up to its promising start in the 1960s and gradually ran out of steam. The economics of health, however, has made steady theoretical and empirical progress since 1970, principally in coming to grips with the implications of supplier-induced demand and the difficulties of evaluating health care outcomes. Some of the best work on British health economics has been in the area of normative welfare economics, defining more precisely what is meant by equity in the delivery of health care and measuring the degree of success in achieving equity. Recent efforts to reform the NHS by the introduction of 'quasi markets' have improved the quantity and quality of health care in Britain. In short, British health economics has been characterised by the use of Pigovian piecemeal rather than Paretian global welfare economics, retaining a distinctive style that sets it apart from American health economics.

HYE (healthy years equivalent) and TTO (time trade-off): what is the difference?

This paper demonstrates that the HYE (healthy-years-equivalent) procedure not only has nothing more to offer than the TTO (time trade-off) method, but that it introduces a systematic bias that is not present using TTO. Diagrams are used to illustrate that the HYE yields health status values, not utilities as its creators suggest, and to show that the HYE and TTO techniques are theoretically identical. Then, empirical evidence concerning the standard gamble/certainty equivalence disparity noted elsewhere in the literature is shown to indicate that HYE responses are likely to contain systematic biases that will lead to HYE estimates exceeding TTO values.

Standard gamble, time trade-off and rating scale: experimental results on the ranking properties of QALYs

This paper compares the relative performance of quality adjusted life years (QALYs) based on quality weights elicited by rating scale (RS), time trade-off (TTO) and standard gamble (SG). The standard against which relative performance is assessed is individual preference elicited by direct ranking. The correlation between predicted and direct ranking is significantly higher for TTO-QALYs than for RS-QALYs and SG-QALYs. This holds both based on mean Spearman rank correlation coefficients calculated per individual and based on two social choice rules: the method of majority voting and the Borda rule. Undiscounted TTO-QALYs are more consistent with direct ranking than discounted TTO-QALYs.