Effect of mailed feedback on drug prescribing profiles in general practice: a seven-year longitudinal study in Storstrøm County, Denmark

BACKGROUND: Whether written feedback on drug prescribing in general practice affects prescribing habits is controversial. Most short-term studies showed no effect. However, the issue has not been tested in long-term studies involving the local general practitioner community. AIMS OF THE STUDY: To assess whether prescribing levels in general practice are affected by long-term, unsolicited, systematically repeated, mailed feedback. METHODS: Each of the 94 general practices in Storstrøm County, Denmark, received semi-annual, mailed feedback about their prescribing volumes and costs within 13 major drug groups, in relation to the levels for all the other 93 practices over a 7-year period in a project initiated by the local general practitioner association. Data on the number of defined daily doses (DDDs) prescribed per 1000 listed patients in each practice per 6-months, and practice characteristics, were obtained from the Pharmaceutical Database at the County Health Department. RESULTS: There was a large variation in drug prescribing volume between practices, but little within-practice variation over time. After adjustments for the influence of practice size and other potential outcome-affecting variables, there was no evidence of a general change of prescribing volume over time, no change among practices with a high or a low prescribing level, and no significant change within the various drug groups. CONCLUSIONS: We found no significant effects on prescribing levels of mailed feedback, even when repeated semi-annually during 7 years and initiated by the local general practitioner community.