Patterns of family doctor decision making in practice context. What are the implications for medical practice variation and social disparities?

Medical practice variation and social disparities in health are pervasive features of health care systems. But what impact might everyday clinical decision making have in shaping such aggregate patterns, and could this in turn be influenced by the immediate environment in which family doctors practise? We investigate this by studying inter-practitioner variation in clinical activity across four payment types in New Zealand, a “gatekeeper” primary care system. We do this for four measures of clinical activity by patient ethnic and socio-economic status in a 2001/2002 representative sample of 9272 encounters at 185 family practices. Initial analysis showed little variation in clinical activity either by patient status or by practice type. However, with the application of multi-level statistical techniques it was evident that, while there was still little systematic difference in practitioner activity rates by patient status, inter-practitioner variation was greater for patients of ethnic minority background and from socio-economically deprived areas. Furthermore, this variability was particularly marked in fee-for-service practice settings. Thus, to the extent that family doctor decision-making behaviour within practice context helps shape aggregate patterns of medical practice variation and social disparity, treatment differences are likely associated not with the level of service but with its variability.