Abstract
BackgroundA history of penicillin allergy in patients is common, but only 10–15 % are truly allergic. While the gold standard for diagnosing penicillin allergy is challenge, it is not recommended that this be done without first carrying out diagnostic skin testing. This is carried out with the major determinant benzylpenicilloyl (PPL) and the minor determinant mixture (MDM), consisting of penilloate, penicilloate and Penicillin G. However, since availability of the MDM is limited, Penicillin G alone has been used.MethodsA retrospective chart review was carried out on patients tested for penicillin allergy in the Clinical Immunology and Allergy Clinic at the Health Sciences Centre, Winnipeg, Canada between 2005 and 2013. A total of 521 patients charts were reviewed, of whom 240 had skin testing, ImmunoCap® for IgE to Penicillin G and V and had oral challenges with penicillin, amoxicillin or cloxacillin.Results17/240 (7.5 %) were skin test positive, 8 to PPL, 4 to MDM and 5 to Penicillin G. One was also positive on ImmunoCap® testing. Three patients had negative skin tests but weakly positive ImmunoCap®. 222 patients with negative skin tests and serological tests were challenged. Of these, 12 patients reacted to challenge. Three of the challenges were equivocal. Of the nine patients with definite positive challenges, three were tested with Penicillin G and six with MDM. Therefore the false negative rates for testing were 2.3 % with PPL and Penicillin G and 6.97 % for PPL and MDM. The difference was not significant (p = 0.0856).ConclusionsIn this group of patients with a history of penicillin allergy tested with the major determinant of benzyl penicillin and either MDM or Penicillin G, there was no difference in the rate of false negative testing, based on oral penicillin challenges. Therefore, Penicillin G can be safely used as an alternative to MDM in diagnosing penicillin allergy.
Highlights
A history of penicillin allergy in patients is common, but only 10–15 % are truly allergic
The major determinant Benzylpenicilloyl is the metabolized form of penicillin used in the form of benzyl penicilloyl-polylysine (PPL) for skin testing [12, 13]
Seventy-six patients did not have complete skin tests and serology. 205 patients did not return for challenge after negative skin tests and serology
Summary
A history of penicillin allergy in patients is common, but only 10–15 % are truly allergic. While the gold standard for diagnosing penicillin allergy is challenge, it is not recommended that this be done without first carrying out diagnostic skin testing. This is carried out with the major determinant benzylpenicilloyl (PPL) and the minor determinant mixture (MDM), consisting of penilloate, penicilloate and Penicillin G. North America has had limited access to both PPL and MDM Using both major and minor determinants is considered the first line method for diagnostic skin testing for Beta-lactam immediate hypersensitivity [12, 14]. The usefulness of testing with the complete battery of minor determinants has been questioned [18, 19]
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