Basophil Activation Test Can Limit Need For Oral Food Challenges In Nut, Seed Allergies

In children with one or more nut allergies who have undergone skin prick and specific IgE testing, the basophil activation test (BAT) can reduce the number of oral food challenges needed to clarify which other nuts, if any, the child is allergic to, researchers report.

The potential benefit of fewer oral food challenges (OFCs) is substantial, Dr. Alexandra F. Santos of the School of Immunology and Microbial Sciences, King's College London, told Reuters Health by email. OFCs "can result in allergic reactions of any severity, thus they need to be performed in a setting that has resources and a clinical team trained and able to treat allergic reactions, including anaphylaxis."

She added that an OFC "takes a few hours and requires frequent observations by a clinical team used and trained to interpret the outcomes of OFC. As a result, it is quite expensive, too."

The report notes that avoiding nuts and seeds can damage the quality of life and mental health of allergic children and their families, yet the "majority of children with nut or seed allergies can tolerate other nuts in their diet," they add.

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In previously reported findings from this study, Dr. Santos said, "60% of children had one or more peanut/tree nut/sesame seed allergies; however, on average children were able to introduce nine nuts in the diet out of the 11 nuts they were tested for." The downside is that determining this can require multiple OFCs.

This sub-study was part of Pronuts, a prospective, multicenter study that began in 2012 and enrolled individuals ages 6 months to 16 years, each with at least one nut or seed allergy (most commonly to peanut), at pediatric allergy centers in London and Geneva.

In this sub-study, 90 participants (median age, 5 years) were evaluated for possible allergies to cashew, hazelnut, almond, peanut and sesame seed. For each potential allergen, participants were classified as sensitized allergic, sensitized non-allergic, and non-sensitized non-allergic.

BAT to cashew, hazelnut, almond, sesame, peanut and peanut components Ara h 1, Ara h 2, and Ara h 6 showed a higher proportion of activated basophils - significantly higher for the vast majority of allergen concentrations - in participants who were allergic compared to those who were not.

"Using BAT as a second step in the diagnostic process, following equivocal skin prick test and IgE to extracts and components, reduced the number of total OFCs by 5-15% and of positive OFC by 33-75% (except for hazelnut) with 0% false-negatives and a diagnostic accuracy of 96-100%," the researchers report in The Journal of Allergy and Clinical Immunology: In Practice.

One benefit of reducing OFCs for allergy diagnosis, Dr. Santos said, is that this could facilitate using OFC for other indications, such as "to reassure patients that contact with or presence of a food in the same room does not trigger anaphylaxis."

Dr. Julie Wang, a clinical researcher in the Jaffe Food Allergy Institute at Mount Sinai, in New York City, told Reuters Health by email, "Diagnosing food allergies can be difficult because results of current allergy skin tests and blood tests are not 100% reliable markers for clinical allergy. The gold standard for a food allergy diagnosis is food challenges: medically supervised procedures that take multiple hours, are resource-intensive, and carry the risk of potentially severe allergic reactions."

BAT, she continued, might "increase the accuracy of food allergy diagnosis and reduce the need for food challenges for patients with suspected nut/sesame allergy."

Dr. Arnon Elizur, director of the Institute of Allergy, Immunology and Pediatric Pulmonology at Shamir Medical Center, in Tzrifin, Israel, said BAT could represent "more of the systemic picture of allergic reactivity" than skin prick and IgE testing, making BAT complementary to them.

Based on these findings, he told Reuters Health by email, "the optimal utilization of BAT is for patients with equivocal results from other allergic tests."

Neither Dr. Wang nor Dr. Elizur was involved in the study.

The study did not have commercial funding, but BAT kits were provided by the manufacturer. Dr. Santos disclosed personal fees and research support from the company.

—Scott Baltic

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