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The changing landscape of penicillin skin testing

Published online: January 29, 2020

The prevalence of patient reported penicillin allergy has been estimated to be around 10%. However, many self-reported penicillin allergies are not true IgE-mediated hypersensitivities and clinically significant penicillin hypersensitivity is <5% and possibly as low as 1%. Penicillin skin testing (PST) is a method to help clarify a true IgE-mediated allergy. There have been previous reports that penicillin allergy is decreasing over time, but this has not been studied for over a decade.

PST consists of both major and minor determinants to indicate a possible hypersensitivity reaction. The major determinant (benzylpenicillin polylysine) is given that term because it detects the greatest number of penicillin allergic patients when skin testing is administered. The minor determinants (penicilloate and penicillin G potassium) help increase the sensitivity of detecting penicillin allergy on skin testing.  The aminopenicillins, amoxicillin or ampicillin, are also agents that can be used in PST. Amoxicillin self-reported allergy is increasing and has been reported to be as high as 65% of patients with penicillin allergy. There has been no recent data to assess whether benzylpenicillin polylysine is currently the most commonly found determinant to be positive on PST. Therefore, we conducted this study to determine whether the positive rates of the various PST components are changing in frequency, to help determine the key components of the PST, and whether the overall rate of PST is changing.

Voelker et al performed a retrospective chart review of over 30,000 patients undergoing PST at Mayo Clinic Rochester. The results of their findings will be published in The Journal of Allergy and Clinical Immunology: In Practice. The study consisted of reviewing all PST that occurred at Mayo Clinic Rochester from 2001-2017. A total of 30,883 skin tests were performed and used for data analysis. Data was divided into four cohorts based on time in order to determine the changing PST pattern. The cohorts were divided as follows: Cohort 1:2001-2005, Cohort 2: 2006-2010, Cohort 3: 2011-2015, and Cohort 4: 2016-2017.

The authors found that 1% (329 of 30,883 patients with a history penicillin allergy) were positive on PST. The study also showed that the positive PST is decreasing over time and the majority of the PST was positive to the intradermal skin testing (94%) compared to the prick skin testing.  Although the positive rate of the major determinant (benzylpenicillin polylysine) has been stable, the minor determinants and amoxicillin positive skin test positive rate has increased from 2001-2017.  

In summary, the positive PST is decreasing, and the majority will be positive to the intradermal PST. Moreover, the minor determinants and amoxicillin components of the PST play an important role in PST and evaluation of patients with a history of penicillin allergy.  

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

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