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Overlap of allergic, eosinophilic and type 2 inflammatory subtypes in moderate‐to‐severe asthma
Author(s) -
Chen Meng,
Shepard Kirk,
Yang Ming,
Raut Pranil,
Pazwash Hooman,
Holweg Cecile T.J.,
Choo Eugene
Publication year - 2021
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1111/cea.13790
Subject(s) - asthma , medicine , eosinophilic , immunology , eosinophil , exhaled nitric oxide , population , allergy , pathology , spirometry , environmental health
Background Current biologic therapies target allergic, eosinophilic or type 2 inflammation phenotypic asthma. However, frequency and degree of overlap among these subtypes is unclear. Objective To characterize overlap among allergic, eosinophilic and type 2 asthma phenotypes. Methods Post hoc analyses of baseline data were performed in two adult populations: (a) not selected for any asthma subtype (N = 935) and (b) selected for allergic asthma (N = 1049). Degree of overlap was examined using commonly accepted phenotypic definitions to guide treatment for allergic asthma (skin prick–positive and/or positive serum–specific immunoglobulin E > 0.35 kU/L) and eosinophilic asthma (blood eosinophil high count ≥ 300 cells/µL; low cut‐off ≥ 150 cells/µL). Consistent with previous studies, fractional exhaled nitric oxide high level of ≥ 35 ppb and low cut‐off of ≥ 25 ppb were selected as local markers of type 2 inflammation and to prevent overlap with the systemic eosinophilic asthma definition. Results In the non‐subtype–selected population, 78.0% had allergic asthma; of these, 39.5% had eosinophilic asthma and 29.5% had type 2 asthma. Within patients with eosinophilic asthma (40.6% of total), 75.8% had allergic asthma and 41.3% had type 2 asthma. Within patients with type 2 asthma (28.3% of total), 81.1% had allergic asthma and 59.2% had eosinophilic asthma. In the allergic asthma–selected population, 38.3% had eosinophilic asthma and 29.2% had type 2 asthma. Within patients with eosinophilic asthma, 46.3% had type 2 asthma. Within patients with type 2 asthma, 60.8% had eosinophilic asthma. Overlaps among subtypes increased at low cut‐off values. Conclusions and clinical relevance In this post hoc analysis in adults with moderate‐to‐severe asthma, allergic asthma was the most prevalent phenotype, followed by eosinophilic and type 2 asthma. Despite observed overlaps, a considerable proportion of patients had only a predominantly allergic subtype. Understanding the degree of overlap across phenotypes will help patient management and guide treatment options.