Introduction: Purchasers of health services need up to date information on cost-effectiveness of interventions, in order to choose between and prioritise spending. Economic evaluation has not yet developed a formal methodology for reviewing and summing up evidence from primary economic research. This paper discusses the problems of reviewing the available information using two different examples, which highlight different issues that affect the possibility of summarising evidence.

Discussion: We first present a systematic review of the literature on influenza vaccination. This exercise has tested alternative methods for adjusting prices to take account of differences in currency and time periods. We compare conversion of costs to current US$ using the US Retail Price Index and exchange rate data, with price adjustments based on the theoretically more correct health specific Inflation Index and Purchasing Power Parity (PPP) data. An alternative approach is to express the results of the review in terms of quantities of resources used, rather than prices. Our second example, of the economics of surfactant treatment for RDS, based on a Cochrane Review of effectiveness, illustrates this approach. Such an approach is constrained by the available data, but could be more generally useful in that it allows direct comparison of underlying technologies, and calculations of costs using locally relevant valuations. These two exercises have highlighted many of the problems that arise in generalising from economics studies. Both methods need to be developed further if they are to be useful to decision makers.