A Retrospective Critical Analysis and Risk Stratification of Penicillin Allergy Delabeling in a UK Specialist Regional Allergy Service

BACKGROUND: A spurious label of penicillin allergy (Pen-A) negatively impacts on antibiotic stewardship and health care costs. Recent studies have proposed a guideline-steered direct penicillin challenge without undertaking allergy tests when true allergy is unlikely. OBJECTIVE: To critically analyze Pen-A clinical presentation, perform risk stratification, and determine clinical predictors for true allergy. METHOD: Data were extracted retrospectively from clinical and electronic patient records. RESULTS: A total of 231 patients (M=82; F=149; mean age 51.22 [standard deviation +/- 18.07] years) were analyzed. Based on clinical history, patients were categorized as likely type I hypersensitivity reaction (HSR) (n=27), likely type IV HSR (n=65), indeterminate (n=111), and HSR unlikely (n=28). Based on an index reaction and comorbidities, patients were classified into low risk (n=143) and high risk (n=78). Pen-A was excluded in 74% of patients assessed having likely type I HSR, 91% with likely type IV HSR, 93% of indeterminate, and 100% of HSR unlikely patients. The negative predictive value for successful delabeling in the low risk group was 94% (odds ratio [OR] [2.9; P=.02). Predictors for true Pen-A were history of anaphylaxis (OR=30.6; P<.001), hospitalization (OR=7; P <.001), pound 5 years since the index reaction (OR=3; P=.04). CONCLUSIONS: Systematic clinical characterization and risk stratification has an important role in Pen-A delabeling. These data provide proof of concept for a guideline-based selection of patients labeled with Pen-A for a direct penicillin challenge. Patients in the low risk group seem suitable for this intervention, although a rigorous prospective evaluation is needed in a multicenter study. (C) 2019 American Academy of Allergy, Asthma & Immunology