Background: Public agencies responsible for implementing health care policies often adapt and disseminate clinical practice guidelines, but the effectiveness of mass dissemination of guidelines is unknown.
Aim: To study the effects of guideline dissemination on physicians' prescribing practices for the treatment of stable angina pectoris.
Design: Randomized controlled trial.
Methods: A sample of 3293 Quebec physicians were randomly assigned to receive a one-page summary of clinical practice guidelines on the treatment of stable angina (in February 1999), to receive the summary and a reminder (in February and March 1999, respectively), or to receive no intervention (controls). The prescribing profiles of participants, as well as sociodemographic characteristics of the physicians and their patients, were examined for June-December 1999.
Results: The intervention had no effect on prescription rates of beta-blockers, antiplatelet agents, or hypolipaemic drugs. Compared to 1997 data for the same physicians, there was an overall 10% increase in appropriate prescription rates, irrespective of the intervention.
Discussion: In-house production and dissemination of clinical practice guidelines may not improve physicians' practice patterns if there is pre-existing substantial scientific consensus on the issue.