Feasibility and impact of pharmacist-led penicillin allergy delabelling using the PEN-FAST scoring tool in a Canadian tertiary care hospital

Background: Penicillins are the most frequently prescribed antibiotics for a broad range of infections. In North America, up to 15% of hospitalized patients report a penicillin allergy, but research has shown that 98% of these patients can tolerate penicillins. Removing inaccurate allergy labels is an essential component of antimicrobial stewardship. While allergy delabelling used to be complex or require an allergist referral, the emergence of new tools, such as the PEN-FAST score, facilitates direct delabeling of low-risk patients. Objectives: The primary objective of this study was to trial the use of the PEN-FAST scoring tool at a major tertiary care center in Canada. Secondary objectives included measuring the pharmacy workload associated with the delabeling process. Methods: A prospective pilot study was implemented at a Canadian tertiary care hospital to identify new patients with a penicillin allergy label, perform a review of their medical history, obtain a PEN-FAST score, and if applicable, implement an oral challenge with amoxicillin. Results: Most of the 155 screened patients were delabeled based on their medical history. Twenty-nine patients were eligible for an oral challenge, and three challenges were conducted. Conclusion: PEN-FAST scoring in combination with direct oral challenge is a practical tool that can be prospectively implemented by pharmacists.