OBJECTIVE: To evaluate the impact of feedback on the prescribing of antibiotics supplementary to clinical guidelines in the treatment of respiratory tract infections.

DESIGN: Randomised, controlled trial with GPs allocated to one of two groups. The first group received clinical guidelines on the treatment of respiratory tract infections plus postal feedback with aggregated data on their prescribing patterns for antibiotics. The second group served as controls for the first group and received the guidelines only.

SETTING: 299 GPs representing 181 practices with 455,843 listed patients in the County of Funen, Denmark.

MAIN OUTCOME MEASURES: Effects on GP prescribing patterns were measured by means of a prescription database and followed for a period of 2 years with 2 outcome measures: 1) the antibiotic prescription rate and 2) the fraction of prescriptions for narrow-spectrum antibiotics.

RESULTS: The addition of feedback had no impact on GP prescribing patterns.

CONCLUSION: Postal disseminated prescriber feedback in addition to a clinical guideline on the diagnosis and treatment of respiratory tract infections does not influence GP prescribing patterns. Interventions aimed at improving performance in general practice should go beyond just giving GPs information on whether they are living up to standards.