Rising prevalence of allergy to peanut in children: Data from 2 sequential cohorts

The predictive value of a positive prick skin test to peanut in atopic, peanut-naïve children

BACKGROUND

Although allergy testing before food ingestion is generally not recommended, many peanut-naive children undergo prick skin tests (PSTs) to peanut because of atopy. Children with positive PSTs are generally advised to avoid peanuts either indefinitely or until a definitive diagnosis is made through challenge.

OBJECTIVE

To describe peanut challenges in atopic, peanut-naive children with PST to peanuts > or = 3 mm and the PST properties in this population.

METHODS

Between 1994 and 2001, 47 patients were identified who had a positive peanut PST, no previous peanut ingestion, and had undergone a peanut challenge.

RESULTS

Forty-nine percent of the challenges were positive. The mean of the largest wheal diameter (95% confidence interval [CI]) of the PST in children having a negative and positive challenge was 6.3 mm (CI, 5.3 to 7.3) and 10.3 mm (CI, 8.9 to 11.8), respectively. At a PST cutoff of > or = 5 mm, the sensitivity and negative predictive value (95% CI) was 100% (85.2 to 100) and 100% (29.2 to 100), whereas the specificity and positive predictive value (95% CI) was 12.5% (2.7 to 32.4) and 52.3% (36.7 to 67.5), respectively.

CONCLUSIONS

We show that 49% of atopic, peanut-naïve children sensitized to peanut developed allergic symptoms during oral provocation with peanut. Although the sensitivity of the PST at > or = 5 mm for the detection of peanut allergy in this study was 100%, our small sample size limits the applicability of this value. Further investigation is needed to determine whether children with wheal diameters of 3 or 4 mm, perhaps coupled with low peanut-specific IgE, could undergo less resource-intensive, accelerated challenges.

Food allergy: an overview

Food allergy affects between 5% and 7.5% of children and between 1% and 2% of adults. The greater prevalence of food allergy in children reflects both the increased predisposition of children to develop food allergies and the development of immunologic tolerance to certain foods over time. Immunoglobulin (Ig) E-mediated food allergies can be classified as those that persist indefinitely and those that are predominantly transient. Although there is overlap between the two groups, certain foods are more likely than others to be tolerated in late childhood and adulthood. The diagnosis of food allergy rests with the detection of food-specific IgE in the context of a convincing history of type I hypersensitivity-mediated symptoms after ingestion of the suspected food or by eliciting IgE-mediated symptoms after controlled administration of the suspected food. Presently, the only available treatment of food allergies is dietary vigilance and administration of self-injectable epinephrine.

9. Food allergy

Food allergies affect as many as 6% of young children, most of whom "outgrow" the sensitivity, and about 2% of the general population. Although any food may provoke a reaction, relatively few foods are responsible for the vast majority of food allergic reactions: milk, egg, peanuts, tree nuts, fish, and shellfish. Many of these food allergens have been characterized at a molecular level, which has increased our understanding of the immunopathogenesis of many responses and may soon lead to novel immunotherapeutic approaches. Food allergic reactions are responsible for a variety of symptoms involving the skin, gastrointestinal tract, and respiratory tract and may be due to IgE-mediated and non-IgE-mediated mechanisms. A systematic approach including history, laboratory studies, elimination diets, and often food challenges will lead to the correct diagnosis. Currently, management of food allergies consists of educating the patient to avoid ingesting the responsible allergen and to initiate therapy in case of an unintended ingestion.