Characterizing β-lactam allergy prevalence among patients receiving infectious disease specialty care within a large US healthcare system in Washington.

Background: Unverified drug allergies pose a significant barrier to successful antimicrobial stewardship efforts. Most delabelling efforts to date have occurred within an inpatient setting or through outpatient evaluations with an allergy specialist; limited data exist examining β-lactam allergies and delabelling efforts among diverse and underserved populations. Strategies are needed to better identify priority populations for allergy delabelling efforts and the highest-yield opportunities for intervention. Objectives: We aimed to evaluate the prevalence of penicillin allergy labels (PALs) or cephalosporin allergy labels (CALs) among patients receiving infectious diseases (ID) specialty care across multiple academic and community-based settings and to characterize reported reactions and referral patterns to allergy specialists. Methods: We conducted a cross-sectional, retrospective cohort study of patients with PAL or CAL receiving care within seven outpatient specialty ID clinics and five inpatient ID consultation services within a large health system between 1 April 2021 and 31 December 2024. Patients: Inclusion criteria for this study were patients >18 years old with a PAL or CAL listed in the electronic health record who received care at one of the above described clinics during the study time frame. Results: Among 4951 patients with a reported PAL or CAL, most were male (56%; Conclusions: High rates of penicillin and cephalosporin allergy labels, the majority of which reflect low-risk reactions, demonstrate a real ongoing need for innovative strategies to maximize delabelling efforts for patients with unverified drug allergies and infectious care needs.