35% of Evaluated Patients De-Labeled in Penicillin Allergy Study

A multidisciplinary quality improvement initiative at an ambulatory care clinic led to a 35% reduction in inaccurate penicillin (PCN) allergy labels, according to data presented by Cadhan McFadden, PharmD, PGY-2 infectious diseases pharmacy resident at St. Joseph’s Health Hospital and Wegmans School of Pharmacy at St John Fisher University, during MAD-ID 2025.

The project focused on adult patients with documented PCN-related allergies seen in the clinic between October 2023 and October 2024. Out of 719 patients screened, 151 (21%) received comprehensive allergy evaluations. Among them, 53 (35%) were successfully de-labeled, 49 through pharmacist-led allergy interviews and 4 via supervised oral amoxicillin (AMX) challenges.

“This work supports the utility of PEN-FAST scoring and interdisciplinary collaboration to safely re-evaluate low-risk antibiotic allergies in ambulatory settings,” said McFadden.

Patients were risk-stratified using the PEN-FAST scoring tool. Those scoring under 3 were considered eligible for an oral AMX 250 mg challenge administered in clinic. Among 48 low-risk individuals, 34 (71%) consented to the challenge, but only 4 completed it. Each was monitored on-site for one hour and contacted a week later to assess for delayed reactions, none were reported.

Despite being cleared for PCN use, few patients ultimately received PCN-based antibiotics post-de-labeling. Only 4 patients (3%) had prescriptions within three months, and just 1 patient (.7%) within six months. McFadden noted that the intervention's benefits may be longer-term.

“I definitely think the impact after the de-label kind of comes within the future with more penicillins being able to be prescribed,” he explained. “Our biggest goal is to try to get more providers and the patient to feel comfortable using penicillin antibiotics.”

Achieving patient buy-in for oral challenges was another key hurdle, McFadden shared. Many patients believed their allergy was permanent. “I think the biggest challenge that we faced was the thought that once you have a penicillin allergy, it can't necessarily go away,” he said. “A lot of patients believe that... they can't take any type of penicillins in the future. So we really tried very hard with patients to talk them through the options... to make them feel more comfortable with trying it, and hopefully being able to de-label for the future.”

One barrier extended beyond the clinic: persistent allergy documentation across external systems. Even when de-labeled in the electronic health record (EHR), 26% of patients still had a penicillin allergy listed in the local health information exchange (HIE) at the 3-month follow-up.

“That’s a problem we actually face,” McFadden noted. “After we de-labeled these patients, our local health information exchange still had those allergies present... it kind of defeats what we’ve been trying to do.”

He emphasized that the team is now working toward a more unified process for allergy de-labeling across health systems. “Hopefully our goal is—we're going to try and have, like, a uniform way to de-label the patient's penicillin allergy throughout all networks, not only our hospital but other hospitals as well.”

The patient cohort had a median age of 52 years. Most were female (70%), identified as White (62%) or African American (29%), and more than half (52%) were covered by Medicaid. The study found no significant demographic differences between patients who accepted or declined the oral challenge.

The initiative reflects recommendations from the 2022 Drug Allergy Practice Parameter from the American Academy of Allergy, Asthma & Immunology, which endorses proactive de-labeling of low-risk PCN allergies, especially in outpatient settings.

Reference

McFadden C, Avery L, Farley S, Muniz T, Cipriano G. Decreasing Inaccurate Penicillin Allergies in an Ambulatory Care Clinic Using a Multidisciplinary Approach. Abstract 19. MAD-ID Meeting. May 28–31, 2025. Orlando, FL.