Comparing Skin and Serum Testing to Direct Challenge Outcomes in Children With ß-Lactam Allergies.

ABSTRACT

BACKGROUND: There is a scarcity of prospective studies investigating the relative roles of skin prick and intradermal testing, serum specific IgE, and extended oral challenges in diagnosing children with reported ß-lactam allergies. OBJECTIVE: To determine the sensitivity and specificity of skin testing and serum specific IgE in children with ß-lactam allergies, with immediate and nonimmediate historic reactions. METHODS: Four hundred children with parent-reported ß-lactam allergies were recruited into an open-label prospective study. Detailed allergy histories were collected. Those with medically observed and documented histories of anaphylaxis, requiring epinephrine, or severe cutaneous adverse reactions were excluded. In total, 380 children underwent all testing modalities and a direct provocation test. Each child was followed up for a minimum of 3 years. RESULTS: True allergy in children was uncommon; 8.3% reacted to the direct provocation challenge or the 5-day extended oral provocation challenge. Children reporting cephalosporin allergy or a reaction within 1 year were more likely to react to direct provocation testing. The sensitivity, specificity, and positive predictive value of skin testing were 12.5%, 98.8%, and 20.0% for direct challenge outcomes, 4.76%, 99.0%, and 25.0% for extended challenge outcomes, and 6.9%, 99.0%, and 40.0% for both challenges combined, respectively. Follow-up investigations revealed that 5.7% of children had a mild repeat reaction and 2.7% continued to avoid the culprit despite successful delabeling. The relabeling rate for children readmitted to hospital was 15%, with the relabeing being unfounded. CONCLUSIONS: Genuine ß-lactam allergies were rare, with over 90% of children effectively delabeled. Skin and serum specific IgE testing did not aid the diagnosis of ß-lactam antibiotic allergy in children, regardless of medical history. Extended oral challenges proved valuable in confirming allergies and boosted parental confidence.