Predicting reactivity threshold in children with anaphylaxis to peanut

Abstract

Background

Peanut allergy necessitates dietary restrictions, preferably individualised by determining reactivity threshold through an oral food challenge (OFC). However, risk of systemic reactions often precludes OFC in children with severe peanut allergy.

Objective

We aimed to determine if clinical and/or immunological characteristics were associated with reactivity threshold in children with anaphylaxis to peanut and secondarily, to investigate if these characteristics were associated with severity of the allergic reaction during OFC.

Methods

A double-blind placebo controlled food challenge (DBPCFC) with peanut was performed in 96 5-15-year-old children with a history of severe allergic reactions to peanut and/or sensitisation to peanut (skin prick test (SPT) ≥ 3 mm or specific immunoglobulin E (s-IgE) ≥ 0.35 kUA/L). Investigations preceding the DBPCFC included a structured interview, SPT, lung function measurements, serological immunology assessment (IgE, IgG and IgG₄), basophil activation test (BAT) and conjunctival allergen provocation test (CAPT). International standards were used to define anaphylaxis and grade the allergic reaction during OFC.

Results

During DBPCFC, all 96 children (median age 9.3, range 5.1, 15.2) reacted with anaphylaxis (moderate objective symptoms from at least two organ systems). Basophil activation (CD63+ basophils ≥ 15%), peanut SPT and the ratio of peanut s-IgE/total IgE were significantly associated to reactivity threshold and lowest observed adverse events level (LOAEL) (all p < 0.04). Basophil activation best predicted very low threshold level (< 3 mg of peanut protein), with an optimal cut-off of 75.8% giving a 93.5% negative predictive value. None of the characteristics were significantly associated with the severity of allergic reaction.

Conclusion and Clinical Relevance

In children with anaphylaxis to peanut, basophil activation, peanut SPT and the ratio of peanut s-IgE/total Ig-E were associated with reactivity threshold and LOAEL, but not with allergy reaction severity.

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