Mailed Audit and Feedback for Antibiotic Prescribing in Primary Care.

Importance: Inappropriate antimicrobial use is a major but modifiable contributor to antimicrobial costs and harms. To address this global threat, many countries have implemented national stewardship programs. However, the cost-effectiveness of such programs targeting primary care physicians remains unknown. Objective: To determine the economic value of an antibiotic audit and feedback (A&F) program from a Canadian public payer perspective. Design, Setting, and Participants: This economic evaluation used data from a randomized clinical trial of primary care physicians in Ontario, Canada, in which a mailed A&F intervention reduced antibiotic prescribing among patients 65 years and older. Trial data were linked with administrative databases to estimate the program costs and savings from reduced antibiotic use, adverse events, and undertreatment harms. A decision model was developed to calculate monetary costs and benefits. Data were collected from January 1 to July 1, 2022, and were analyzed from March 1 to April 1, 2025. All costs are reported in 2024 Canadian dollars. Intervention: A mailed A&F letter sent to primary care physicians with their antibiotic prescribing rate compared with their peers, with additional messaging about the harms of unnecessary antibiotics. Main Outcomes and Measures: Net costs and benefits, return on investment (ROI), and probability of achieving a positive ROI (>1). Uncertainty was explored using probabilistic analysis with 5000 simulations and deterministic sensitivity analyses. Results: The study included 4879 primary care physicians, of whom 2711 (55.6%) were male, with a mean (SD) of 25.0 (13.3) years since medical school graduation. The program cost was $5.50 per physician and generated $43.03 in savings. The ROI was $8.82 (95% uncertainty interval, $1.32-$22.56) per dollar invested. The probability that the antibiotic A&F program provided an ROI greater than 1 was 93.2%. Scaling the program to all primary care physicians in Ontario would further improve the estimated ROI. Results were robust across sensitivity analyses. Conclusions and Relevance: In this economic evaluation of a mailed antibiotic A&F intervention, the intervention was associated with substantial economic and clinical value. These findings support A&F as a scalable, low-cost component of antimicrobial stewardship programs and highlight its potential to optimize prescribing and reduce antimicrobial resistance.