Reducing systematic bias in studies of general practitioners: the use of a medical peer in the recruitment of general practitioners in research.

Reducing systematic bias in any group of study participants should be a priority of any researcher. This can be achieved by ensuring the sampling framework is adequate and by increasing response rates. Response rates in studies of general practitioners have to date tended to be low. Generalization of results to the wider population of GPs is therefore reduced. This paper systematically examines those factors which can reduce bias, recognising accurate identification of the target population, gaining good access to respondents, and maximising response rates as crucial factors. The importance of a medical peer in recruitment is examined. Applying these factors to a study situation, three different recruitment strategies were tested. As the strategy improved, there was an incremental improvement in the response rate (44%, 67%, 78%). These results indicate that by specifically addressing strategies which facilitate access to the target population, and increase the legitimacy and credibility of the study, significant improvements in response rates can be achieved.