Published Online: January 13, 2015
Allergy to penicillin is a commonly reported problem, with 10-20% of the population labelled as penicillin allergic. However, only some 10% of those with this label are truly penicillin allergic, and as the label of being penicillin allergic may be associated with worse health outcomes and increased economic costs, effective strategies to de-label individuals who are not truly allergic to penicillin are important. Prick and intradermal skin testing with specific penicillin reagents including benzylpenicillin, PPL (major determinant of penicillin) and minor determinant mixture (MDM) has proven safe and efficacious when applied to large populations. Yet despite negative test results, some patients continue to avoid the use of penicillin.
In a recent article published in The Journal of Allergy and Clinical Immunology: In Practice, Bourke et al. evaluated the application of established penicillin allergy testing protocols in a cohort of adult patients in a tertiary hospital system in Australia. Patients labelled as being allergic to penicillin (or another beta-lactam antibiotic) underwent skin testing, followed by oral drug challenge if appropriate. Following completion of the test each patient was given a recommendation for future antibiotic tolerance. Patient compliance with these recommendations was assessed by a follow-up telephone survey.
A total of 401 consecutively tested patients were included. In total, 51 patients (12.7%) had positive skin testing to one or more reagents. Positive skin testing to a selective antibiotic only, such as amoxicillin, was observed in 22 patients (43%). History of an immediate reaction (within 1 hour of dosing) and/or testing within 6 months of the reaction was associated with a significantly higher rate of positive skin testing. Overall, 89.9% of patients were de-labelled, with a recommendation for either selective or unrestricted beta-lactam use. In patients with a history of a non-immediate reaction, >95% were skin test negative and able to tolerate at least one antibiotic in the penicillin (beta-lactam) family.
However, the initial follow-up survey found that only 68% of patients were accurately following the recommendation given following testing. A second group of patients were surveyed after changes were made to the way that the recommendations were communicated to patients and their primary care physicians. In this group the compliance rate increased to 85%.
The authors conclude that current testing methods are safe and reliable, but that consistent, timely and clear communication of recommendations following testing may increase the uptake of testing results and their application to clinical practice. Risk stratification to determine the appropriate testing strategy is suggested, with modified testing protocols in low risk patients warranting further study.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.