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

Abstract

The purpose of the Finding the Risk of Anaphylaxis and Testing Rational In youngEr Siblings (FRATRIES) study was to determine the risk of anaphylaxis, the predictive values of peanut allergy tests, and parents’ preferences in the context of peanut introduction in the younger siblings of peanut-allergic children.The study cohort included 154 peanut-naïve children (median age of 23 months) who each had an older sibling with a diagnosis of peanut allergy. Participants were recruited in Canada through advertising in allergy clinics and through local food allergy web-based communities. Reference cohorts included parents of (1) peanut-naïve children from nonallergy pediatric clinics and (2) peanut-allergic children.This was a prospective cohort study. Peanut-naïve younger siblings underwent double-blind skin prick testing (SPT) followed by parent-led peanut introduction. At least 2 g of peanut protein was ingested to consider the introduction complete. Subjects were observed in a clinic for 2 hours. A phone call 24 hours later inquired about delayed reactions. Parents were then advised to introduce peanut in the younger child’s diet at least once a week. A phone follow-up occurred 1 year later. Questionnaires were dispensed prior to and up to a year after peanut introduction to investigate parental preferences with regard to peanut introduction in this subgroup.Eight participants (5.2%) had an unequivocal IgE-mediated reaction upon peanut introduction, including 5 with anaphylaxis. Peanut-allergic participants were significantly older than the rest of the cohort (median age of 4.0 vs 1.9 years, P = .04). The negative predictive values of SPT with peanut extract, peanut butter, and peanut-specific IgE were 99%, 100%, and 100%, respectively. The absolute positive predictive values of peanut extract SPT, peanut butter SPT, and specific IgE were 88%, 72%, and 62%, respectively. Peanut introduction at home without supervision was associated with high levels of parental anxiety in parents with a previously peanut-allergic child (median of 8.4 on a 10-point Likert scale), compared with introduction under supervision without testing (median of 3.8, P < .001) and home introduction after negative testing (median of 4.3, P < .001). If a provider recommended home peanut introduction without prior testing, 82% of parents would keep avoiding the food.Siblings of children with peanut allergy have an increased risk of anaphylaxis upon peanut introduction, with a potentially higher risk for older children who delayed introduction. Parents with a previously peanut-allergic child have significant anxiety regarding introducing peanut without prior skin testing or without supervision.This study supports previous studies showing that younger siblings of peanut-allergic children have a higher rate of peanut allergy. Recent NIAID guidelines for the prevention of peanut allergy recommend early introduction of peanut for high-risk children but do not make specific recommendations for siblings without other risk factors. In our practice, we do specifically recommend early and consistent peanut introduction in younger siblings of peanut-allergic patients, usually with prior testing. As highlighted in this study, parental anxiety regarding a possible reaction in the younger sibling, as well as the peanut-allergic child, is likely to impact home peanut introduction unless it is done with some level of medical supervision.