Evaluation of a pharmacist-led penicillin allergy testing service in a community health system

Abstract

Background: Roughly 10% of the U.S. population has a documented penicillin (PCN) allergy. Among these individuals, over 95% are able to tolerate PCNs. The inability to use PCNs can result in suboptimal outcomes. In August 2019, Lawrence Memorial Hospital Health System implemented a pharmacist-led PCN allergy testing service to assist with delabeling PCN allergies and increase access to this class of antibiotics.

Objectives: The primary objective was to describe the number of patients who underwent PCN allergy testing and were delabeled from PCN allergy. A secondary objective was to report the number of patients who received and tolerated PCN antibiotics after being delabeled from PCN allergy.

Methods: This retrospective chart review was conducted during the initial 17 months of a pharmacist-led PCN allergy testing service. Eligible patients with a history of an immunoglobulin E (IgE)-mediated reaction underwent a 3-step test that consisted of a scratch test, an intradermal test, and an oral challenge. Eligible patients who did not have a history of IgE-mediated reaction underwent a 2-step graded oral challenge. Descriptive statistics were used for data analysis.

Results: Between August 2019 and January 2022, 70 patients underwent testing, and 66 patients were delabeled from PCN allergy. Four patients who underwent the 3-step test developed reactions of mild to moderate severity. All patients who underwent the graded oral challenge were delabeled from PCN allergy. The rate of PCN allergy was 5.7%, whereas the rate of type I IgE-mediated reaction was 1.4%. All 23 patients who received an antibiotic from the PCN class after a negative allergy test tolerated the PCN antibiotic without an incident.

Conclusion: PCN allergy testing is an effective way to delabel PCN allergies from most patients presenting with a PCN allergy history. Skin testing followed by an oral challenge or a graded oral challenge alone are safe methods for conducting PCN allergy testing in the primary care setting.