Evaluation of β-Lactam Allergy Delabelling and Antimicrobial Stewardship in Island Health.

Abstract

Background: Penicillin allergies are commonly reported in hospital settings, yet most are inaccurate and lead to unnecessary use of broad-spectrum antibiotics, which in turn contributes to antimicrobial resistance, adverse effects, and increased health care costs. In 2023, a provincial initiative was launched in British Columbia to promote standardized delabelling of penicillin allergies across health authorities. Island Health participated by implementing a structured process led by antimicrobial stewardship (AMS) pharmacists.

Objectives: To compare β-lactam allergy delabelling at AMS-supported and non-AMS-supported sites within Island Health and to describe trends by allergy type, year, and individual hospital site.

Methods: This retrospective multicentre observational study involved patients at least 18 years of age who underwent delabelling of a documented β-lactam allergy between January 1, 2017, and September 30, 2024. The primary outcome was the number of allergy delabellings at AMS-supported and non-AMS-supported sites. Secondary outcomes were delabelling counts by reported allergy type, year of delabelling, and individual hospital site. Data were extracted from electronic health records and analyzed using descriptive statistics. Counts were stratified by AMS status, allergy type, year, and site, and were standardized per 100 acute care beds.

Results: A total of 1039 β-lactam allergy delabellings were identified, with 928 (89.3%) occurring at AMS-supported sites. With standardization, delabelling counts were 62.8 per 100 beds at AMS-supported sites and 40.7 per 100 beds at non-AMS-supported sites.

Conclusions: Although causal relationships could not be confirmed, AMS-supported sites had a greater number of β-lactam allergy delabellings. These findings may reflect the impact of structured implementation and institutional support, potentially informing future efforts to integrate penicillin allergy delabelling processes into hospital-based AMS pharmacist programs.