Weighting must wait: incorporating equity concerns into cost-effectiveness analysis may take longer than expected.

Current practice in economic evaluation is to assign equal social value to a unit of health improvement ('a QALY is a QALY is a QALY'). Alternative equity positions are typically considered separately from efficiency. One proposal seeks to integrate these two sets of societal concerns by attaching equity weights to QALYs. To date, research in pursuit of this goal has focussed on candidate equity criteria and methods for estimating such weights. It has implicitly been assumed that should legitimate, valid and reliable equity weights become available, it would be a straightforward task to incorporate them as a separate simple calculation after estimating cost per un-weighted QALY. This article suggests that, in many situations, these simple approaches to incorporating equity weights will not appropriately reflect the preferences on which the weights are based and that the appropriate incorporation of equity weights in cost-effectiveness analyses will be technically challenging. In addition to the technical challenges, there are a number of issues that arise in the movement from implicit to explicit consideration of equity. Whilst equity weights can, conceptually, be incorporated in economic evaluation, there are a number of challenges to be addressed before the results of such analyses can be considered robust and a fit basis for resource allocation decisions.