Use of national clinical databases for informing and for evaluating health care policies.

Policy-makers and analysts could make use of national clinical databases either to inform or to evaluate meso-level (organisation and delivery of health care) and macro-level (national) policies. Reviewing the use of 15 of the best established databases in England, we identify and describe four published examples of each use. These show that policy-makers can either make use of the data itself or of research based on the database. For evaluating policies, the major advantages are the huge sample sizes available, the generalisability of the data, its immediate availability and historic information. The principal methodological challenges involve the need for risk adjustment and time-series analysis. Given their usefulness in the policy arena, there are several reasons why national clinical databases have not been used more, some due to a lack of 'push' by their custodians and some to the lack of 'pull' by policy-makers. Greater exploitation of these valuable resources would be facilitated by policy-makers' and custodians' increased awareness, minimisation of legal restrictions on data use, improvements in the quality of databases and a library of examples of applications to policy.