Those affected by peanut allergy might have heard about basophil activation tests (BATs), a potentially accurate tool for diagnosing food allergy. The skin prick test (SPT), and the IgE blood tests (sIgE) currently used for diagnosing allergies are helpful, but they indicate only a sensitization to food allergens. Sensitized individuals may or may not have, or develop a food allergy. Eliminating foods from a child’s diet based on SPT or sIgE outcomes can negatively affect childhood nutrition, and might contribute to the onset of a food allergy.
BAT: Basophil Activation Test
BAT, in clinical trials, more accurately diagnoses an allergy than SPTs or sIgE. Basophils are large white blood cells. They bind IgE antibodies and release histamine when activated by allergens. Using BAT, an individual’s blood cells are exposed to suspected food allergens and later examined for allergen-activated proteins.
Although basophil testing is not yet stable enough for general use, the test performs – in clinical trials – with nearly the same accuracy as an oral food challenge:
- In a study involving 11 children, BAT predicted the results of oral food challenges 91 percent of the time (in 30 of 33 tests).
- In one case study, a five-year-old with moderately severe eczema underwent sIgE testing. Based on the results, the child was put on an elimination diet for wheat, peanut, oat, soy, egg, rice, sesame, and tree nuts. The child’s subsequent BAT outcomes matched the boy’s food challenge results, which revealed he could safely eat soy, milk, wheat, and several types of tree nuts—foods that had also yielded positive SPTs.
Because a time-consuming oral food challenge is the only definitive food allergy test currently available, having a blood test that performs equally well, or nearly so, would be a diagnostic blessing for doctors and patients.
BAT and Peanut Allergy
Oral food challenges involve giving individuals incremental doses of a suspected food allergen in a safe, controlled environment. Beyond the risk for a reaction, some allergy clinics have difficulty responding to the increased demand for food challenges, creating an over-reliance on SPT and sIgE for peanut, and other allergy diagnoses.
In earlier testing, reported in The Journal of Allergy and Clinical Immunology, BATs diagnosed peanut allergy or tolerance with 97 percent accuracy. The BATs were performed with 104 children, 43 with peanut allergy, and 61 with peanut tolerance, in conjunction with other allergy tests.
According to the researchers their results suggest that BAT could be used in suspected peanut allergy cases when conventional testing proves inconclusive, and before referring a patient for an oral food challenge. If this suggestion becomes an approved reality, it will streamline peanut allergy diagnosis.