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Risk-stratification to optimise penicillin allergy testing

Published online: October 8, 2019

Allergy against penicillins is commonly self-reported in the community, but the majority of patients actually tolerate penicillins and related antibiotics when undergoing allergy testing. Most commonly, assessment includes penicillin skin testing followed by supervised administration of oral penicillin (“challenges”) to distinguish patients who can tolerate penicillin from those who are truly allergic. Recent evidence suggests that patients who – based on their initial penicillin reaction – are unlikely to have a true or severe allergy, can safely undergo a supervised penicillin challenge without skin testing. However, there has been no consensus on how to select these lower risk patients for penicillin challenges.

In The Journal of Allergy and Clinical Immunology: In Practice, Stevenson, Trevenen et al performed a multi-centre Australian study to statistically determine the optimal definition of a “low risk” penicillin allergy history. Outcome data were retrospectively collected for patients undergoing penicillin allergy testing (skin test and/or oral penicillin challenge) across seven Australian outpatient drug allergy clinics. Statistical modelling was performed with 8 low risk definitions, to determine an optimal low risk definition.

Four-hundred and forty-seven subjects were analysed, with a mean age 45.3 years, and 63.8% female. A history of benign penicillin-associated rash, occurring more than 1 year prior to the drug allergy assessment, was the optimal low risk definition. Of the 244/447 (54.6%) patients who met this low risk definition, 97.1% tolerated oral penicillin. The low risk patients who did not tolerate a penicillin challenge had mild reactions, with no episodes of anaphylaxis. Of 203 patients designated higher risk, 54 (26.6%) had their allergy confirmed by skin test (n=45) or challenge (n=9), suggesting that skin testing remains useful in this sub-group. This simple risk-based penicillin testing strategy could potentially be utilised by non-allergists, leading to more efficient penicillin allergy testing services with major clinical and health economic benefits.

The Journal of Allergy and Clinical Immunology: In Practice is an official scientific journal of the AAAAI, focusing on practical information for the practicing clinician.

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