Ara h 2-Specific IgE Is Superior to Whole Peanut Extract-Based Serology or Skin Prick Test for Diagnosis of Peanut Allergy in Infancy

Abstract

Screening of high-risk infants for peanut allergy before introduction has been recommended, but the optimal approach for screening is not clear. This study sought to compare the diagnostic test characteristics of the peanut skin-prick test (SPT), peanut-specific immunoglobulin E (sIgE), and sIgE with that of peanut components in a population of infants at a higher risk of peanut allergy before known peanut exposure.In the study, the researchers included 321 infants aged 4 to 11 months with no history of peanut ingestion, testing, or reaction and at least 1 of the following risk factors for the development of peanut allergy: having moderate to severe eczema, another food allergy, and/or a first-degree relative with peanut allergy.The infants underwent a peanut SPT and, depending on the SPT wheal size, a graded oral peanut challenge or an observed feeding with a full serving of peanut was performed. Additional testing included peanut-sIgE and component-IgE testing. Receiver-operator characteristic areas under the curve (AUCs) were compared, and diagnostic sensitivity and specificity were calculated.The median age of the participants was 7.2 months, and 58% were boys. A total of 37 (11%) were found to have peanut allergy. Overall, Ara h 2–sIgE at a cutoff point of 0.1 kUa/L best discriminated between allergic and nonallergic (AUC: 0.96; sensitivity: 94%; specificity: 98%), compared with peanut-sIgE at 0.1 kUa/L (AUC: 0.89; sensitivity: 100%; specificity: 78%) or 0.35 kUa/L (AUC: 0.91; sensitivity: 97%; specificity: 86%), or SPT at wheal size 3 mm (AUC: 0.90; sensitivity: 92%; specificity: 88%) or 8 mm (AUC: 0.87; sensitivity: 73%; specificity: 99%). Ara h 1–sIgE and Ara h 3–sIgE did not add to the prediction of peanut allergy, when included in a model with Ara h 2–sIgE, and Ara h 8–sIgE discriminated poorly (AUC: 0.51).Measurement of only Ara h 2–sIgE should be considered if screening of high-risk infants is performed before peanut introduction.As described in the accompanying article above, screening for peanut allergy before introduction does appear have value in those infants at the highest risk. This study clearly reveals that each of the available test methods are useful but that the serological test for the peanut component Ara h 2 has the greatest diagnostic value.