Evaluating the effects of GP remuneration: problems and prospects.

General practice reform is occurring in a number of countries. Little is known, however, of the effects of remunerating general practitioners on the costs and outcomes of care. Valuable lessons can be learned for the scope and design of future research, however, from the existing literature on the effects of general practioner (GP) remuneration. The objectives of this paper are to highlight some of the problems and pitfalls that should be avoided in any further research on the effects of GP remuneration and to identify the main issues for future research. Eighteen studies of the effects of GP remuneration have been reviewed, with a focus on the methods used. Eight studies addressed the effect of changes in the level of remuneration, three evaluated the effect of special payments and bonuses and seven assessed the effects of different remuneration systems. Although there are often practical constraints on the choice of study design, crude 'before and after' analyses and the use of aggregate data should be avoided in favour of prospective evaluations using consultation-based data. The studies reviewed did not evaluate the effects of remuneration on patient welfare and were characterised by the omission of major confounding variables and an inability to generalise to other settings. These issues present a considerable challenge to researchers, GPs and policy makers.