Putting the quality into quality-adjusted life years.

Over recent decades, a great deal of effort has been devoted towards developing instruments that can be used to elicit health state values. All of these instruments are conceptually very different from one another and all suffer from serious inherent biases. In this paper I outline the conceptual foundations and empirical limitations of the three principal health state value elicitation instruments. Given that the conceptual parameters internalized within an instrument influence the elicited health state values, I argue that it is necessary to attain a broad agreement on what the appropriate parameters ought to be. When the appropriate conceptual parameters have been identified we will be in a position to develop the methodology of a single standardized instrument.