The role of the Euroqol instrument in QALY calculations

The EuroQol measure of health-related quality of life (HRQoL) has many purposes other than the calculation of QALYs, but it is upon that particular use that this paper concentrates. For that purpose a simple generic measure yielding a single index score for each health state is required. The development of any HRQOL measure requires some key strategic simplifications to be made. In the case of the EuroQol measure these are that a profile of health states can be divided into separate time segments, and that the value of being in any one state is independent of the states which precede or succeed it. Further simplification is required to keep the range of dimensions of HRQOL manageable. When it comes to the number of levels within a dimension, discrimination requires a large number, but practicability requires a small number. The EuroQol Group wished from the outset to generate a measure which reflected the valuations of the general public, rather than the views of health care professionals. Thus the valuation process was as important as the descriptive content. For this purpose the instrument had to be capable of being used to elicit valuations in a postal questionnaire. This dictated the use of a rating scale in the form of a “thermometer” as the basic method. But more recent interview-based work has used the time-trade-off method as well. The contribution of the EuroQol instrument to the measure of HRQoL is: 1) as a simple way to generate descriptive data; 2) as a simple way to elicit people’s own rating of their current health states; 3) as a preference based generic index of health benefits (for use alongside more detailed condition-specific or treatment-specific measures).