# P-2015. Applying PEN-FAST in Clinical Practice: Using the PEN-FAST Decision Tool to Guide Penicillin Allergy Challenges in Hospitalized Patients

## TL;DR

This study shows that using the PEN-FAST tool helps safely remove incorrect penicillin allergy labels in hospitalized patients, improving antibiotic choices.

## Contribution

A pharmacist-led protocol using the PEN-FAST score successfully de-labeled penicillin allergies in hospitalized patients with minimal adverse reactions.

## Key findings

- 76.9% of patients had their penicillin allergy label removed after testing.
- Only 3.4% of patients with PEN-FAST scores of 1 or 2 had a mild reaction during testing.
- No adverse reactions occurred in patients with PEN-FAST scores of 0 or 3.

## Abstract

Penicillin allergies are frequently documented without reevaluation, often resulting in fewer antibiotic options and increased use of broad-spectrum agents. Recent evidence supports direct oral challenges for patients identified as low risk utilizing the PEN-FAST clinical decision tool. The PEN-FAST score was incorporated into a pharmacist-led penicillin allergy testing protocol to identify patients eligible for de-labeling. The purpose of this study was to assess the rate of penicillin allergy de-labeling and the incidence of adverse reactions following testing.

This was a retrospective study of adults hospitalized at a 550-bed academic medical center with a reported penicillin allergy who had allergy testing performed between January 1st, 2019 and August 1st, 2024. Allergy testing included direct oral, 2-step oral, IV, 2-step IV, and skin testing. Variables collected include patient demographics, index penicillin allergy history, PEN-FAST score, type of allergy test performed, outcomes of the allergy test, rescue medications administered within 24 hours of allergy test, and change in allergy label.

Of 52 patients who had allergy testing, 40 (76.9%) had the allergy removed from their Electronic Health Record. A comment in the EHR stating the challenge was tolerated occurred in 10 (19.2%) patients. A penicillin allergy was re-added in 3 patients (5.8%) despite no new reactions post-challenge, and 1 patient (1.9%) retained their allergy label despite tolerating the challenge. The most common allergy test was the 2-step oral challenge (46.2%), followed by direct oral (34.6%), skin test (15.4%), and IV or 2-step IV challenge (1.9% each). Of the 13 patients with a PEN-FAST score of 3, none had a reaction. Of the 29 patients with a PEN-FAST score of 1 or 2, one (3.4%) had a reaction, reported as dyspnea and skin eruption after receiving a 10% test dose of amoxicillin and managed without significant harm. Of the 10 patients with a PEN-FAST score of 0, none had a reaction.

Among hospitalized patients, a pharmacist-led protocol for low risk penicillin allergies resulted in the safe de-labeling of a substantial proportion of allergies. The PEN-FAST score proved to be a valuable tool in identifying low risk patients appropriate for allergy challenges.

All Authors: No reported disclosures