Background: The substitution of primary for secondary care is progressing at a fast pace, yet there has been little evaluation of the appropriateness of such a fundamental change in health service organization. The aim of this paper is to raise some issues for discussion about the contribution of economics to future research on the substitution of primary for secondary care. Given the central role general practitioners (GPs) will play in a "primary care led' National Health Service, the paper concentrates on the replacement of secondary care by GP-based services.
Methods: The existing empirical evidence relevant to the replacement of secondary care by GP-based services is summarized. From this, issues for further research from an economic perspective are identified and discussed.
Results: The evidence comprises studies examining the efficiency or cost-effectiveness of substituting GP-based care for secondary care and studies examining the effects of incentives on the mixture and range of services provided. Cost-effectiveness evidence is scarce and inconclusive. The evidence on incentives suggests that new services are being provided in local areas which need them least. Several avenues of further research are suggested. As well as more economic evaluation, future research should concentrate on developing methods to elicit patients' and communities' preferences for GP-based care versus secondary care. Research into incentives should concentrate on assessing those factors, beyond practice characteristics, that influence GP's decisions about whether to provide services and how much to provide. This would help to design more appropriate incentives for GPs.
Conclusions: The appropriate balance between primary and secondary care is unknown. The transfer of services from secondary care to general practice (and other primary care providers) should be based on empirical evidence on cost-effectiveness, as should the incentives given to GPs. Although the research agenda is challenging, it is necessary in ensuring that a "primary care led' health system is the right way forward for the NHS.