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Antibiotic allergies less prevalent than once believed

BOSTON — An overwhelming majority of individuals who believe they are allergic to cephalosporins and who are referred to seek confirmatory testing, are ultimately determined not to be allergic, according to study findings presented at the ACAAI Annual Scientific Meeting.

“We all know cephalosporin allergy labels are common, but we can typically [dispel the label] after [testing for] them,” Cosby Stone, MD, MPH, a research fellow in the allergy, pulmonary, and critical care medicine division at Vanderbilt University Medical Center, said during his presentation.

Eight percent of people in the United States believe they are allergic to cephalosporins, according to Stone.

“But, we don’t really have specific and validated testing strategies for cephalosporin allergy,” he said. “This is a problem we have with both immediate and delayed cephalosporin allergies.”

Stone cited how the field has attempted in vitro studies in the past, but the results did not translate well clinically.

“I think we are prone to thinking of penicillin allergy and cephalosporin allergy, as being something where [a patient] is allergic to [the] backbone of [a] molecule,” he said.

Stone and colleagues conducted a retrospective case series of 315 patients who received skin testing using a standardized protocol for a label of penicillin and/or cephalosporin allergy.

Intradermal testing to additional cephalosporins was combined with oral or intramuscular challenges if patients were believed to have strong histories of allergies.

Eight patients (2.5%) tested for a label of penicillin or cephalosporin allergy had positive results.

Four patients were skin test positive for immediate hypersensitivity to cefazolin and one to ceftriaxone/cefepime based on shared respective R1 side chains. Patients with immediate reactions after skin testing were able to tolerate cephalosporins and penicillins with non-shared R1 side chains as demonstrated by negative skin testing and ingestion challenges.

The participants did not experience any systemic reactions to skin testing or any subsequent challenges, Stone said.

There were multiple limitations with the study, according to Stone.

“Not all skin test negative patients were willing to do multiple oral challenges within the same day,” he said. “They either were bored, tired, hungry or wanted to go home.”

Additionally, patients that were identified as skin test-positive did not want to undergo further challenges.

Another limitation, according to Stone, was that patients with a history of severe reactions were not further challenged even if their skin test was negative.

“Similar to penicillin, most patients who get referred to us with a label of cephalosporin allergy, are not allergic and we can safely evaluate them,” he said. “We think that allergists’ knowledge of cephalosporin side chain families is going to be a crucial element of managing cephalosporin allergies going forward.” – by Ryan McDonald

Reference:

Stone C, et al. OR002. Presented at: the ACAAI Annual Scientific Meeting; Oct. 26-30, 2017; Boston, MA.

Disclosures: Stone reports no relevant financial disclosures.