Evaluation of the effectiveness of guidelines, audit and feedback: improving the use of intravenous thrombolysis in patients with suspected acute myocardial infarction.

OBJECTIVE: To determine the effectiveness of medical audit as a means of improving the use of intravenous thrombolytics in patients with suspected acute myocardial infarction.
DESIGN: Time-series analyses of observations in four study hospitals conducting repeated audits and feedback compared to a control hospital.
SETTING: Five district general hospitals in North West Thames Region between April 1991 and July 1992.
SUBJECTS: 2593 patients admitted as emergencies with a suspected acute myocardial infarction. MAIN OUTCOME MEASURES: Proportion of eligible cases receiving intravenous thrombolytic therapy observed in each audit and proportion of patients in whom this therapy was used appropriately.
RESULTS: In the baseline audits, the proportions of eligible cases receiving thrombolytic therapy in the four study hospitals were 94%, 60%, 58% and 57%, and 53% in the control hospital. After three further audits in each study hospital over the subsequent year, the observed proportions had changed to 88% (to 6%), 92% (+32%), 95% (+37%), and 7796 (+20%). Meanwhile the proportion in the control hospital rose to 68% (+15%). The trend over time was significant in the second and third hospitals but not in the other two study hospitals or the control hospital. Reclassification of those cases in which the reliability of the diagnosis was poor altered the extent but not the direction of observed trends. Generally, the appropriateness of use of thrombolytic therapy increased with increasing treatment rates. There was a suggestion, however, that continued auditing in the presence of high treatment rates may have led to a reduction in appropriateness.
CONCLUSIONS: medical audit can be an effective means of improving the use of intravenous thrombolytics. It is possible that over auditing may result in greater inappropriate use.