Introduction of peanuts in younger siblings of children with peanut allergy: a prospective, double-blinded assessment of risk, of diagnostic tests, and an analysis of patient preferences.

BACKGROUND: The prevalence of peanut allergy in younger siblings of children with peanut allergy has been reported between 7% and 8.5%, but the anaphylactic risk at the time of introduction is currently unknown, which limits our ability to best counsel parents on this issue.

OBJECTIVE: To determine the risk of anaphylaxis and working parameters of allergy testing in this context.

METHODS: One hundred and fifty-four peanut-naïve younger siblings of peanut-allergic children underwent double-blinded skin testing, followed by parent-led peanut introduction. Questionnaires were dispensed to parents to investigate preferences with regard to peanut introduction in this subgroup.

RESULTS: Eight participants (5.2%) presented unequivocal IgE-mediated reactions to peanut upon introduction, including five anaphylaxes. These participants were significantly older compared to the rest of the cohort (median 4.0 vs 1.9 years, P = 0.04). The negative predictive value of skin prick test with peanut extract and peanut butter and of specific IgE was 99%, 100%, and 100%, respectively. Six peanut-tolerant participants had positive peanut allergy tests. The option of introducing at home without prior skin testing was associated with high levels of anxiety (median 8.4 on 10-point Likert scale) when compared to supervised introduction (median 3.8, P < 0.0001) or home introduction after negative skin test (median 4.3, P < 0.0001).

CONCLUSIONS: There is an increased risk of anaphylaxis upon peanut introduction in siblings of children with peanut allergy, and parents are reluctant to introduce at home without testing. Allergy testing prior to introduction is negative in over 90% of cases and carries a high negative predictive value.