Routinely collected data in national and regional databases--an under-used resource.

Regional and national databases of routinely collected data contain large quantities of health information, usually covering whole populations and often spanning prolonged time periods. Using routine data involves identifying useful sources, assessing the quality of the data and deciding whether what is available is 'fit for purpose'. As long as adequate care is taken, these data may be used in a number of different ways beyond their traditional uses for population health assessments and health service planning.