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Retrospective Review of Beta Lactam Allergy Prevalence in a Referral Population
Saturday, March 5, 2016
South Exhibit Hall H (Convention Center)
Andrew Wakeman, BSc(Hon), Alexander Singer, MB BaO BCh, CCFP, Elissa Michele Abrams, MD, FRCPC, Thomas V. Gerstner, MD, FRCPC
Rationale: It has been estimated that 8% of the general population are labelled as beta lactam allergic.  Avoidance of beta lactam antibiotics in hospital correlates with higher rates of antibiotic resistant infection, patient morbidity and higher costs of treatment.

Methods: A cross-sectional retrospective chart review of all evaluations for beta lactam allergy by a community allergy clinic from June 2010 to July 2015.

Results: Our sample includes 311 referred patients with a recent history of a reaction to a beta lactam antibiotic. Mean age was 11.6 (SD 17.3); 49.5% of patients were male.  Evaluation was based on reaction history, intradermal testing in those with histories that were vague or suggestive of an IgE mediated hypersensitivity, and/or oral beta lactam challenge.  There were only 1/107 positive intradermal tests, and 6/297 positive oral challenges. Following the consultations, only 0.64% were considered to be at increased risk of future IgE mediated reactions.  A further 2.3% were considered to be at increased risk of serious delayed-type III and IV reactions (serum sickness and Stevens-Johnson).  3.9% were advised they could avoid beta lactams to prevent future mild delayed reactions.  Overall, 93% of those evaluated were determined not to require avoidance of beta lactams after evaluation. 

Conclusions: Patients with documented beta lactam allergy were rarely allergic upon evaluation.  This study supports more aggressive interventions to identify incorrectly documented or invalid cases of beta lactam allergy leading to erroneous avoidance.