• Mark T McIntyre, Sudipta Saha, Andrew M Morris, Lauren Lapointe-Shaw, Terence Tang, Adina Weinerman, Michael Fralick, Arnav Agarwal, Amol Verma, and Fahad Razak.
• Sinai Health (McIntyre, Fralick), Toronto, Ont.; Leslie Dan Faculty of Pharmacy (McIntyre), University of Toronto; Li Ka Shing Knowledge Institute (Saha, Verma, Razak), St. Michael's Hospital, Toronto, Ont.; Department of Social and Behavioral Sciences (Saha), Harvard T.H. Chan School of Public Health, Boston, Mass.; Department of Medicine (Morris, Lapointe-Shaw, Weinerman, Fralick, Verma, Razak), University of Toronto; Department of Medicine (Morris), Mount Sinai Hospital and University Health Network; Department of Medicine (Lapointe-Shaw), University Health Network, Toronto, Ont.; Trillium Health Partners (Tang), Mississauga, Ont.; Department of Medicine (Weinerman), Sunnybrook Health Sciences Centre; Division of General Internal Medicine (Agarwal); Department of Medicine (Agarwal), McMaster University, Hamilton, Ont. mark.mcintyre@sinaihealth.ca.
• CMAJ. 2023 Aug 21; 195 (32): E1065E1074E1065-E1074.

BackgroundVariability in antimicrobial prescribing may indicate an opportunity for improvement in antimicrobial use. We sought to measure physician-level antimicrobial prescribing in adult general medical wards, assess the contribution of patient-level factors to antimicrobial prescribing and evaluate the association between antimicrobial prescribing and clinical outcomes.MethodsUsing the General Medicine Inpatient Initiative (GEMINI) database, we conducted a retrospective cohort study of physician-level volume and spectrum of antimicrobial prescribing in adult general medical wards in 4 academic teaching hospitals in Toronto, Ontario, between April 2010 and December 2019. We stratified physicians into quartiles by hospital site based on volume of antimicrobial prescribing (days of therapy per 100 patient-days and antimicrobial-free days) and antibacterial spectrum (modified spectrum score). The modified spectrum score assigns a value to each antibacterial agent based on the breadth of coverage. We assessed patient-level differences among physician quartiles using age, sex, Laboratory-based Acute Physiology Score, discharge diagnosis and Charlson Comorbidity Index. We evaluated the association of clinical outcomes (in-hospital 30-day mortality, length of stay, intensive care unit [ICU] transfer and hospital readmission) with antimicrobial volume and spectrum using multilevel modelling.ResultsThe cohort consisted of 124 physicians responsible for 124 158 hospital admissions. The median physician-level volume of antimicrobial prescribing was 56.1 (interquartile range 51.7-67.5) days of therapy per 100 patient-days. We did not find any differences in baseline patient characteristics by physician prescribing quartile. The difference in mean prescribing between quartile 4 and quartile 1 was 15.8 days of therapy per 100 patient-days (95% confidence interval [CI] 9.6-22.0), representing 30% higher antimicrobial prescribing in the fourth quartile than the first quartile. Patient in-hospital deaths, length of stay, ICU transfer and hospital readmission did not differ by physician quartile. In-hospital mortality was higher among patients cared for by prescribers with higher modified spectrum scores (odds ratio 1.13, 95% CI 1.04-1.24).InterpretationWe found that physician-level variability in antimicrobial prescribing was not associated with differences in patient characteristics or outcomes in academic general medicine wards. These findings provide support for considering the lowest quartile of physician antimicrobial prescribing within each hospital as a target for antimicrobial stewardship.© 2023 CMA Impact Inc. or its licensors.

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