PEN-FAST penicillin allergy clinical decision rule

Stratifies the risk that a reported penicillin allergy is a true allergy, to identify low-risk patients for direct oral challenge / delabeling.

Evidence tier: Validated instrument.

Formula / logic

PEN-FAST score (0-5): Five years or less since reaction = 2; Anaphylaxis/angioedema OR Severe cutaneous adverse reaction = 2; Treatment required for the reaction = 1. Risk of positive penicillin allergy testing: 0 = <1%; 1-2 = ~5%; 3 = ~20%; 4-5 = ~50%. Score <3 identifies low-risk patients.

Interpretation

A PEN-FAST score <3 had a high negative predictive value for true penicillin allergy in the derivation/validation cohorts, supporting direct oral challenge without prior skin testing in appropriate low-risk patients.

Evidence & citations

  1. Trubiano JA, Vogrin S, Chua KYL, et al. Development and Validation of a Penicillin Allergy Clinical Decision Rule. JAMA Intern Med. 2020;180(5):745-752. PMID 32176248

Clinician decision support. Verify against the cited source. Not a substitute for clinical judgment. 100% on-device; no patient data is stored or transmitted.