The role of a pre-scored multi-attribute health classification measure in validating condition-specific health state descriptions

It is common to find specially constructed condition-specific health state descriptions used as the basis for benefit assessment in cost-utility analysis. For this approach to be valid it is necessary to have valid descriptors of health states. Yet the evidence demonstrating descriptive validity has been neglected in economic evaluation. This paper reports on the validity, reliability and feasibility of obtaining values from specially constructed condition-specific descriptions of breast cancer screening by mapping these descriptions into a pre-scored multi-attribute health classification measure (the EuroQol instrument) and comparing the values obtained with those derived from a time trade-off exercise. In doing so, it highlights the importance of descriptive validity in explaining why different valuation methods produce different results. Four descriptions typically associated with ex post true negative, false positive, true positive and false negative breast screening results were considered. Copyright (C) 1999 John Wiley & Sons, Ltd.