Health opportunity costs: assessing the implications of uncertainty using elicitation methods with experts

SUMMARY

1. Well-established methods of economic evaluation are used in many countries to inform decisions about new medical interventions warranting health system funding. To guide such decisions, it is important to consider what health gains the same level of investment would achieve elsewhere in the system, which can be termed health opportunity costs.

2. Recent research in the UK has evaluated the evidence available and the methods required to estimate the expected health opportunity costs within the National Health Service. Due to the absence of sufficiently broad-ranging data, assumptions were required to estimate health opportunity costs 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.

3. This work presents a protocol for the structured elicitation of the judgements of key individuals about these uncertain quantities. In summary, the protocol defines, among other design and conduct features: 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.

4. This work also reports on a successful application involving 28 clinical experts and 25 policy-related individuals, which demonstrated the feasibility of the protocol.

5. Whilst, as expected, most experts found replying to the questions challenging, they were able to comfortably express their beliefs quantitatively.

6. Consistently across the uncertainties elicited, experts’ judgements suggest the QALY impact of changes in expenditure are likely to be underestimated when using the assumptions which underpin the ‘central’ estimate of £12,936 per QALY reported in the abovementioned research.