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

Abstract 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%; n = 2754), non-Hispanic (86%; n = 4242) and white race (53%; n = 2623), with a mean age of 48.2 years. PAL and CAL rates were 7.6%–16.7% and 1.1%–5.3%, respectively, in outpatient ID clinics, and 8.8%–15.5% and 3.9%–6.1%, respectively, on inpatient ID consultation services. Of a total of 5965 PAL and 1506 CAL reported entries, most were consistent with hypersensitivity reactions (62.9% and 63.8%, respectively). There were 41.6% of patients with a PAL and 47.7% of patients with a CAL who reported isolated cutaneous symptoms only (flushing, itching, rash or urticaria). Few patients were referred to allergy specialists (7.8%) and ultimately delabelled. 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.