How Many Patients With History of Penicillin Allergy Are Truly Allergic?

Information sourced from NEJM Journal Watch:

Very Few Patients with Penicillin Allergy Histories Are Truly Allergic

David J. Amrol, MD reviewing Macy E and Ngor EW. J Allergy Clin Immunol Prac 2013 May.

Penicillin allergy testing can safely exclude IgE-mediated penicillin allergy.

Almost 8% of the U.S. population claims to be allergic to penicillin, but only a small proportion of these patients are truly allergic. Penicillin skin testing is the only way to identify IgE-mediated allergy (an immediate hypersensitivity reaction mediated by preformed IgE bound to the surface of mast cells and basophils). Penicilloyl-poly-lysine (Pre-Pen), the major determinant of penicillin allergy, has been available commercially since 2009, but clinicians rarely order skin testing. Some physicians are concerned that Pre-Pen testing is inadequate without also testing for minor determinants (penicilloate and penilloate), which are not readily available.

From 2010 to 2012, 500 patients with histories of penicillin allergy (based on diagnoses recorded in their records) were skin tested in a California allergy department using penicilloyl-poly-lysine and fresh penicillin G. Negative tests were followed by 1-hour observed oral challenges with amoxicillin. Four patients reacted to one of the two skin-test agents, and another four exhibited positive objective symptoms after oral challenges. None of these reactions [were] life threatening or required epinephrine.

COMMENT

In this study, fewer than 1 in 50 patients with penicillin allergy histories were truly allergic. We should stop accepting penicillin allergy history as a reason for lifelong avoidance. All drug reactions should be documented carefully. Patients with severe delayed reactions such as Stevens Johnson syndrome, drug reaction with eosinophilia and systemic symptoms (DRESS), or hemolytic anemia should never be challenged or tested; those with mild delayed reactions probably can undergo oral challenges. For those with potential IgE-mediated reactions (i.e., hives, edema, or other symptoms of anaphylaxis occurring within 1–2 hours), penicillin testing followed by oral challenge is safe and effective. Penicillin is the only antibiotic for which such testing is available.

Dr. Amrol is an Associate Professor of Clinical Internal Medicine and Director of the Division of Allergy and Immunology at the University of South Carolina School of Medicine in Columbia.

CITATION:

Macy E and Ngor EW. Safely diagnosing clinically significant penicillin allergy using only penicilloyl-poly-lysine, penicillin, and oral amoxicillin. J Allergy Clin Immunol Prac 2013 May; 1:258. [J Allergy Clin Immunol Prac article abstract]

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