A Retrospective Critical Analysis and Risk Stratification of Penicillin Allergy De-labelling in a UK Specialist Regional Allergy Service.

BACKGROUND A spurious label of penicillin allergy (Pen-A) negatively impacts on antibiotic stewardship and healthcare costs. Recent studies have proposed a guideline-steered direct penicillin challenge without undertaking allergy tests when 'true allergy' is unlikely. OBJECTIVE Critically analyse Pen-A clinical presentation, perform risk stratification and determine clinical predictors for 'true allergy'. METHOD Retrospective data extraction from clinical and electronic patient records. RESULTS 231 patients (M= 82; F=149; mean age 51.22 (SD ± 18.07 years) were analysed. Based on clinical history, patients were categorised as likely type I hypersensitivity [HSR] (n=27), likely type IV HSR (n=65), indeterminate (n=111) and HSR unlikely (n=28). Based on index reaction and co-morbidities, 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. Negative predictive value for successful de-labelling in the 'low risk' group was 94% (odds ratio [OR] - 2.9; p= 0.02). Predictors for 'true Pen-A' were history of anaphylaxis (OR - 30.6; p < 0.001), hospitalization (OR - 7; p