Penicillin Skin Test Kit Demonstrates High Negative Predictive Value

A comprehensive penicillin skin test kit demonstrated very high negative predictive value in evaluating penicillin allergy, according to a study published in The Journal of Allergy and Clinical Immunology: In Practice.

In this prospective, multicenter, open-label study, investigators examined penicillin skin testing using the Penicillin Skin Test Kit (ClinicalTrials.gov Identifier: NCT01818336). Participants were aged ≥18 years and had a history of penicillin allergy (n=455), or were part of the control group and did not have a history of penicillin allergy (n=26). The Penicillin Skin Test Kit was composed of penicilloyl-polylysine, Pre-Pen^® (PPL), a tripartite minor determinant mixture (MDM) consisting of penicillin G, penicilloate and penilloate lyophilized powder (each 10 mmol/L), and amoxicillin sodium powder (20 mg/mL), each delivered via puncture (epicutaneous) skin testing on the inner volar aspects of the forearm, along with histamine and saline controls. Development of a wheal >4 mm in its longest diameter, 15 to 20 minutes after application determined a positive response. If the puncture test was positive, intradermal skin testing was not performed using that particular allergen; if the test was negative, intradermal testing was performed by injecting an amount sufficient to raise a small intradermal bleb of about 3 mm in diameter. A positive response was defined as a ≥3 mm increase in wheal size compared with the negative saline control, and a negative response was defined as no increase in wheal size compared with the negative saline control site.

Of the participants with a history of penicillin allergy, 63 (13.8%) had ≥1 positive tests. A total of 30 participants (47.6%) in this group reacted to a single reagent, and of these, MDM was positive in 80%. A total of 4 out of the 63 participants reacted to amoxicillin alone. In this group, 23.8% reacted to all 3 skin reagents. Seven of the skin testing participants had an adverse event: 2 were participants with strongly positive puncture skin tests, 1 involved a skin test site rash delayed 5 hours after application, and 4 were deemed to be non-immunoglobulin E-dependent local skin test site reactions.

A key limitation of this study was that pediatric patients were excluded from participating.

The researchers indicated that the Penicillin Skin Test Kit is an improvement over skin test reagents presently available in the United States. A high percentage of skin-test-positive participants, only positive to MDM, contrasts with findings of previous studies, which is likely related to the inclusion requirement of a convincing history of penicillin allergy. An FDA-approved penicillin skin testing kit represents an unmet need in the United States and elsewhere.

Disclosure: AllerQuest, LLC, funded this study. AllerQuest was involved in study design, analysis and interpretation of the data, in the writing of the report, and in the decision to submit the article for publication. Several authors acknowledge conflicts of interest. Please see reference for full list of disclosures.

Reference

Solensky R, Jacobs J, Lester M, et al. Penicillin allergy evaluation: A prospective, multicenter, open label evaluation of a comprehensive penicillin skin test kit [published online March 13, 2019]. J Allergy Clin Immunol Pract. doi:10.1016/j.jaip.2019.02.040