Spillover From an Intervention on Antibiotic Prescribing for Family Physicians

Importance: Antibiotic audit and feedback is effective at reducing antibiotic prescribing in primary care. Objective: To evaluate the spillover of an audit-and-feedback intervention originally targeted at patients aged 65 years or older on a broader population of all age groups. Design, Setting, and Participants: This is a post hoc secondary analysis of a randomized clinical trial that was conducted among primary care physicians in Ontario, Canada. Physicians were randomized in a 4:1 allocation, with a peer comparison feedback letter sent in January 2022. Physicians in the control group received no letter. The randomized clinical trial was conducted from January 2021 to December 2022, and this analysis was performed from March to June 2024. Exposure: A mailed antibiotic prescribing feedback letter, with peer comparison. Main Outcomes and Measures: The primary outcome was the total number of antibiotic prescriptions by physicians at 12 months after the intervention for patients of all ages. This analysis was conducted utilizing a different administrative data source than the original trial; this source contained antibiotic prescription counts for all patient age groups. Data were analyzed with Poisson regression models, adjusted for baseline prescribing and stratified by patient age and sex. Results: Overall, 4964 of 5097 randomized physicians (97.4%) were included in this analysis. There were 3967 (74.5%) in the intervention group and 997 (25.5%) in the control group; 2766 physicians (55.7%) were male, and 2549 (51.3%) had been in practice for 25 years or more. The intervention group showed a reduction in antibiotic prescriptions at 12 months after intervention compared with the control group (adjusted rate ratio [aRR], 0.93; 95% CI, 0.93-0.94). Significant reductions were seen across all age and sex groups and for antibiotics typically used for respiratory infections. Additionally, the proportion of prescriptions exceeding 7 days decreased significantly in the intervention group (aRR, 0.82; 95% CI, 0.82-0.83). Conclusions and Relevance: In this post hoc secondary analysis of a randomized clinical trial of peer comparison antibiotic audit and feedback for physicians with data from patients aged 65 and older, the intervention group had a reduction in antibiotic prescriptions across all patient ages. These findings suggest that routinely collected administrative data can be effectively used for implementing and evaluating antibiotic audit and feedback, even when limited to older patients. Trial Registration: ClinicalTrials.gov Identifier: NCT04594200.