Skin tests used to predict allergies to amoxicillin not reliable

A new study has shown that a skin test is ineffective for diagnosing suspected allergy to amoxicillin in children presenting with a rash during antibiotic treatment, and that a graded oral provocation challenge is an effective diagnostic tool.

“Our study suggests that skin tests are essentially useless as diagnostic tests, and that we should go directly to the graded provocation test that is highly sensitive and specific,” Dr. Moshe Ben-Shoshan, a pediatric allergist and the study’s senior author, said in a McGill University Health Centre press release.

In the study, 818 children with a suspected history of allergy to penicillin were given a graded provocation challenge, receiving 10% of an oral dose of amoxicillin, and after 20 minutes, the remaining 90% of the dose, and observed for one hour. Of the 17 children who had immediate reactions to the antibiotic, a follow-up skin test was positive in only one child. If the skin test was an appropriate measure, it should have been positive in all 17, the authors noted. The graded provocation challenge had a negative predictive value of 89.1% and a positive predictive value of 100%.

The study, published in the April issue of JAMA Pediatrics, involved AllerGen investigator Dr. Ben-Shoshan, a pediatric allergist at the Montreal Children’s Hospital and an assistant professor of Pediatrics at McGill University, AllerGen collaborator Dr. Andrew O’Keefe, an allergist from St. John’s, Newfoundland, as well as several AllerGen trainees.

Read the CBC and Montreal Gazette coverage.