Diagnostic Value of Antigen-Specific Immunoglobulin E Immunoassays against Ara h 2 and Ara h 8 Peanut Components in Child Food Allergy

Abstract

Background: Peanut allergy is one of the most severe food allergies in children. The diagnostic gold standard is the oral food challenge (OFC). However, OFC has inherent risks and is time consuming. The measurement of specific immunoglobulin E (sIgE) to peanut components in blood detects peanut sensitization, but the decision point predicting allergy is still unclear. The aim of this study was to determine the diagnostic value of these tests for the evaluation of child peanut allergy. Methods: In this retrospective study, 81 children were referred for peanut allergy. The diagnosis of peanut allergy was based on the clinical context and a positive OFC. Levels of sIgE against whole peanuts or peanut components (Ara h 2 and Ara h 8) were determined by immunoassay. Results: The Ara h 2 sIgE assay has the best negative predictive value (0.93) and positive predictive value (1) at a cutoff of 0.1 kU/l. Ara h 2 sIgE titers can predict the risk of anaphylaxis (<0.44 kU/l, low risk; >14 kU/l, high risk). The Ara h 8 sIgE assay is not able to discriminate peanut-allergic patients but can be used to evaluate possible cross-reactions to birch pollen with a low risk of anaphylaxis. The best diagnostic strategy is to first determine the Ara h 2 sIgE level and, if negative, evaluate Ara h 8 sIgE. Conclusions: We propose an algorithm for a better use of peanut component sIgE immunoassays that should improve their diagnostic value and avoid unnecessary OFC.

International consensus (ICON) on: clinical consequences of mite hypersensitivity, a global problem

“…Using component-specific diagnosis, it was shown that allergic rhinitis to birch pollen in adolescence can be predicted by IgE reactivity to pathogenesis-related class 10 proteins in early childhood [181] and that sensitization to Fel d 1 and Can f 1 in childhood were associated with symptoms to cat and dog in adolescence [182]. Likewise, high Ara h 2 IgE titers were shown to be associated with peanut-induced anaphylaxis [183]. In the case of mite allergy, CRD with the MeDALL chip indicated that IgE responses to mites were initiated by Der p 1, Der p 2 or Der p 23 and increased in prevalence along the first decade of life [184].…”

Detection of the Peanut Allergens Ara h 2 and Ara h 6 in Human Breast Milk: Development of 2 Sensitive and Specific Sandwich ELISA Assays

“…Therefore, it is of increasing importance to focus on potential marker allergens to understand the mechanistic processes. Currently, the storage protein Ara h 2 is acknowledged as the most relevant marker allergen, associated with severe, sometimes fatal reactions [9,10,11,12]. Likewise, Ara h 6 is considered to predict peanut allergy with similar accuracy as both proteins belong to the 2S albumins with 59% sequence homology [13,14,15].…”

Recent Advances in Clinical Allergy and Immunology

“…It should be considered that OFC tests bear the risk of severe allergic reactions, for which a history of anaphylactic reactions and older age are considered risk factors [52]. Since serum IgE levels to Ara h 2 have both high negative and positive predictive values, the number of OFC needed in suspected peanut allergy can be reduced [53]. In peanut-allergic patients from China, Ara h 9, a nonspecific lipid transfer protein, was identified as a major allergen [54].…”