Valuing health-related quality of life. A review of health state valuation techniques.

Given the growing need to value health-related quality of life, a review of the literature relating to health state valuation techniques was undertaken to appraise the current theoretical and empirical evidence available to inform on the techniques, to identify consensus, identify disagreement and identify important areas for future research. A systematic search of the literature was conducted, covering standard gamble (SG), time trade-off (TTO), visual analogue scale (VAS), magnitude estimation (ME) and person trade-off (PTO) techniques. The basic concepts of practicality, reliability, theoretical validity and empirical validity formed the criteria for reviewing the performance of valuation techniques. In terms of practicality and reliability, we found little evidence relating to ME and PTO. SG, TTO and VAS have been shown to be practical on a range of populations. There is little difference between the reliability of SG, TTO and VAS, and present evidence does not offer a basis to differentiate between them. When considering the theoretical basis of techniques, we conclude that choice-based methods (i.e. SG, TTO and PTO) are best placed to reflect the strength of preference for health, with the choice between these techniques depending on the study characteristics and the perspective employed. Empirical evidence relating to the theoretical perspective of the techniques has shown that there are problems with all techniques in terms of descriptive validity.