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

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.

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.

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.

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.

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.