Assumptions of the QALY procedure

The Quality Adjusted Life Year (QALY) has been proposed as a useful index for those managing the provision of health care because it enables the decision-maker to compare the 'value' of different health care programmes and in a way which, potentially at least, reflects social preferences about the appropriate pattern of provision. The index depends on a combination of a measure of morbidity and the risk of mortality. Methodological debate has tended to concentrate on the technicalities of producing a scale of health; and philosophical argument has concentrated on the ethics of interpersonal comparison. There is little recognition of the fragility of the theoretical assumptions underpinning the proposed combination of morbidity and risk of mortality. The context in which the proposed indices are being developed is examined in Section 2. Whilst most working in the field of health measurement eschew over-simplification, it is clear that the application of micro-economics to management is greatly facilitated if a single index can be agreed. The various approaches to combining morbidity and mortality are described in Section 3. The crucial assumptions concern the measurement and valuation of morbidity; the procedures used for scaling morbidity with mortality; and the role of risk. The nature of the valuations involved are examined in Section 4. It seems unlikely that they could ever be widely acceptable; the combination with death and perfect health poses particular problems; and aggregation across individuals compounds the problem. There are also several technical difficulties of scaling and of allowing for risk which have been discussed elsewhere and so are only considered briefly in Section 5 of this paper. The paper concludes by emphasising the importance of measuring outcomes but doubting the utility of pursuing the chimera of a global index given the wide variety of different kinds of assumptions involved.