Health Opportunity Costs : Assessing the Implications of Uncertainty Using Elicitation Methods with Experts

Well-established methods of economic evaluation are used in many countries to inform decisions about the funding of new medical interventions. To guide such decisions, it is important to consider what health gains would be expected from the same level of investment elsewhere in the health care system. Recent research in the UK has evaluated the evidence available and the methods required to estimate the health effects of changes in health care expenditure within the National Health Service. Due to the absence of sufficiently broad-ranging data, assumptions were required to estimate health effects in terms of a broader measure of health (quality adjusted life-years), which is more relevant for policy. These assumptions constitute important sources of uncertainty. This work presents an application of the structured elicitation of the judgements of key individuals about these uncertain quantities. This paper describes the design and conduct of the exercise, including: the quantities elicited; the individual (rather than consensus) approach used; how uncertainty in knowledge was elicited (mode and bounds of an 80% credible interval); and methods to generate group estimates. It also reports on a successful application involving 28 clinical experts and 25 individuals with policy responsibilities. Whilst, as expected, most experts found replying to the questions challenging, they were able to express their beliefs quantitatively. Consistently across the uncertainties elicited, experts’ judgements suggest the QALY impacts of changes in expenditure from earlier work using assumptions are likely to have been underestimated and the ‘central’ estimate of health opportunity cost from that work (£12,936 per QALY) to have been over-estimated.