Type of Proposal
Schulich School of Medicine Windsor
Dr. Joel Liem
24-3-2015 11:00 AM
24-3-2015 11:50 AM
Importance of the Project
Verifying a penicillin allergy is important because it reduces patient exposure to other antibiotics that are associated with increased patient morbidity and healthcare costs. In fact, a penicillin allergy is associated with increased hospital use and infections with C. difficile, MRSA and VRE. It may be helpful to identify characteristics associated with a true penicillin allergy and to develop a protocol that verifies all patient-reported penicillin allergies.
Existing State of Knowledge
About 10% of people claim to have a penicillin allergy. However, patient reporting is an unreliable source of predicting a true allergy and only 10-20% of people continue to have a positive skin test. In the current literature, most patients with negative skin tests can tolerate oral doses of penicillin and only 1.2% of patients experience IgE-mediated reactions. It will be important to verify these findings within our community population, as well as identify characteristics typical of true penicillin allergies.
The aim of this study is to report the validity of self-reported penicillin allergies in patients presenting to an allergy clinic in Windsor as determined by the results of subsequent skin testing, intradermal testing and 5-day oral dose challenges of penicillin; and to report any patient trends associated with penicillin allergy.
This study is a retrospective chart review of 281 patients who presented to an allergy clinic for penicillin allergy assessment. Data was collected from patients who received skin testing, intradermal testing and 5-day oral dose challenges of penicillin from April 2011 to December 2014. Data collected includes: demographics (patient age, sex, date of birth, ethnicity); history of asthma; known allergies; family history of penicillin allergies; medical comorbidities; details on the previous penicillin allergic reaction (age, dose, route, indications for use, symptoms, treatment); any repeated exposure to penicillin; reason for allergy test; results of skin test, intradermal and 5-day oral challenge; and symptoms experienced in relation to the allergy tests. This study is associated with low risk ethics as all patient identifying information will be undisclosed.
8.5% (24/281) of self-reported penicillin allergies are true allergic reactions as determined by a positive skin test, intradermal testing or 5-day oral challenge. As much as 4 of the 24 reactions were skin test or intradermal positive. 7 reacted within 6 hours of ingestion of the first dose of oral challenge. In total, 45.8% (11/24) of true penicillin allergies can be categorized as an IgE-mediated reaction within the first 6 hours. 54.2% (13/24) of true penicillin allergies can be categorized as a delayed-type reaction with a rash occuring 24 hours after initial ingestion. All of the true penicillin allergies had skin reactions. Severe cardiac and pulmonary symptoms were only seen in people with immediate IgE-mediated reactions within the first 6 hours of oral ingestion. Of the oral challenges, the reactions included 1 person with gastrointestinal manifestations, 1 person with hypertension, and 1 person with difficulty breathing.
In our community population, of those reporting a penicillin allergy, only 8.5% were proven to be allergic. Of these, the majority had a delayed reaction to penicillin, which typically only involved a rash. Cardiopulmonary symptoms were only associated with immediate IgE-mediated reactions within the first 6 hours. Penicillin allergy testing is important, as it can be helpful in developing a protocol that verifies all patient-reported penicillin allergies. This can help reduce patient morbidity associated with increased hospital stay and antibiotic-resistant infections.
Validity of Self-Reported Penicillin Allergies in a Community Population