The ambiguous relationship between practice variation and appropriateness of care: an agenda for further research.

The analysis of variation in the use of health care services, and particularly of practice variation, has been the subject of renewed interest because of the view that the inappropriate use of procedures could be a major cause of these differences. In this article, recent literature is reviewed and the results of personal research are described on both the variation in care provision and on appropriateness assessment. In the few studies which have focussed on both subjects no evidence has yet been found to suggest that practice variation is to be explained by differences in appropriateness rates. However, there are still many methodological pitfalls in both variation analyses (statistical problems) and appropriateness assessment (reliability of the judgement), implying that this conclusion is far from definitive. More research should therefore be conducted on methodological questions of variation analysis and appropriateness assessment. Furthermore in variation analysis the relative contribution of all potential determinants has to be studied on the various levels of care provision. Finally, to study the relationship between practice variation and appropriateness of care, the clinical problem and not the procedure should be the starting point.