Absence of serum IgE antibodies indicates non-type 2 disease in young asthmatics

Abstract

Background

Atopic asthma is associated with elevated type-2 biomarkers such as fraction of exhaled nitric oxide (FeNO) and blood eosinophil (B-Eos) count. However, increased type-2 markers have also been reported in traditionally-defined non-atopic asthma.

Objective

To determine a clinically useful level of IgE sensitisation for ruling out type-2 asthma.

Methods

Asthmatics (N = 408; age 10-35 years) were analysed using the multi-allergen tests Phadiatop and fx5 (ImmunoCAP). Subjects were grouped based on IgE-antibody concentrations: ≥ 0.35 kU_A/L for at least one test (n=326) or < 0.35 kU_A/L for both tests (n=82). Τhe latter group was subsequently divided into two groups: IgE 0.10-0.34 kU_A/L (n=34) and IgE < 0.10 kU_A/L (n=48). The relationships between type-2 biomarkers, and inadequate asthma control (ACT < 20), reduced lung function (FEV₁ < 80%), recent asthma attacks, and airway hyperresponsiveness (AHR) to methacholine were determined.

Results

In univariate analyses, at least one type-2 marker related to each asthma outcome in subjects with IgE ≥ 0.35 kU_A/L. In subjects with IgE 0.10-0.34 kU_A/L, elevated FeNO related to reduced lung function (p=0.008) and B-Eos to AHR (p = 0.03). No associations were found in subjects with IgE < 0.10 kU_A/L. In multivariate analysis, a relationship between FeNO and reduced lung function remained in subjects with IgE < 0.35 kU_A/L (p = 0.03).

Conclusion and clinical relevance

Clinically relevant elevation of type-2 biomarkers was seen in young asthmatics with IgE antibodies < 0.35 kU_A/L, but not those with IgE < 0.10 kU_A/L. It seems possible to define non-type 2 asthma through sensitive IgE-antibody measurement.

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