The combination of Ara h 2-sIgE and basophil activation test could be an alternative to oral food challenge in cases of suspected peanut allergy

Background: Most children with peanut sensitisation do not have a clinical peanut allergy (PA). Oral food challenge (OFC) is then necessary to diagnose PA and assess the reactive dose of the allergen. However, OFC is laborious to perform, expensive and stressful. We evaluated whether in vitro tests, such as basophil activation test (BAT), allergen-specific IgE (sIgE) and their combination, could be used to replace OFC for the diagnosis of PA in children.

Methods: Ninety-one patients aged 6 months to 18 years with suspected PA were prospectively recruited. These patients then underwent an OFC to assess PA. Whole peanut-sIgE, Ara h 2-sIgE, Ara h 8-sIgE and %CD63⁺ basophils (CCR3⁺ /SCC^low ) to peanut measured by BAT were investigated for PA diagnosis.

Results: Forty-one patients had a positive peanut OFC, and the remaining 50 were only sensitised. All patients with Ara h 2-sIgE >7 kU_A /L were allergic to peanut. A threshold of 6% for activated basophils yielded a sensitivity of 95% and a specificity of 54%. All patients with Ara h 2-sIgE ≤7 kU_A /L and BAT ≤6% (n = 22) had a negative OFC except for one who presented an oral syndrome due to PR-10 sensitisation.

Conclusions: We have shown that Ara h 2-sIgE >7 kUA/L is a discriminating threshold for the diagnosis of PA. Furthermore, when Ara h 2-sIgE ≤7 kUA/L and BAT ≤6%, patients do not need to adjust their diet and, thus, do not need an OFC.