BACKGROUND: Although penicillin allergy is frequently reported, the majority of labeled patients do not have confirmed hypersensitivity upon formal evaluation. The PEN-FAST clinical decision rule was developed to identify adults at low risk of true penicillin allergy; however, evidence supporting its performance in children remains limited. OBJECTIVE: To evaluate the diagnostic performance of the PEN-FAST score in a pediatric population with reported penicillin allergy. METHODS: We performed a retrospective cohort study including children younger than 18 years with a documented penicillin allergy label who underwent allergy evaluation at a tertiary referral center between January 2012 and February 2023. Children with suspected severe cutaneous adverse reactions (SCARs) or insufficient information to calculate the PEN-FAST score were excluded. Diagnostic evaluation included skin testing and/or drug provocation testing (DPT). Diagnostic performance of the PEN-FAST score was assessed by calculating sensitivity, specificity, predictive values, and the area under the receiver operating characteristic curve (AUC). RESULTS: Among 267 children included in the analysis, 19 (7.1%) had confirmed penicillin allergy. Using the original PEN-FAST cutoff of ≥ 3, the AUC was 0.62 (95%CI, 0.51-0.73), with sensitivity of 68.4%, specificity of 55.7%, positive predictive value of 10.6%, and negative predictive value of 95.8%. Exploratory analyses using alternative PEN-FAST score representations showed only minimal differences in discrimination. CONCLUSIONS: In this pediatric cohort, the PEN-FAST score demonstrated limited accuracy in distinguishing true penicillin allergy. These findings suggest that the adult-derived decision rule may require further refinement before routine application in children.
Yuenyongviwat et al. (2026) studied this question.