Children with severe persistent asthma have disparate peripheral blood and lower airway eosinophil levels

Guideline-based therapy of severe asthma in children is based primarily on data from adult studies, however, and the dynamics of exacerbations, lung function, and response to medication differ between children and adults.2 Advancing our understanding of asthma endotyping in children can improve our ability to predict response to asthma treatment, particularly to biologics that target specific endotypes.1 Characterizing asthma as eosinophilic or neutrophilic is one way to endotype asthma.1 Marked by high levels of eosinophils in peripheral blood, eosinophilic asthma is the most common endotype found among severe asthmatics and is thought to be more corticosteroid responsive.1 In contrast, neutrophilic asthma is marked by elevated peripheral blood neutrophils (>7000 cells/μL in patients aged 6-12 years, or >8000 cells/μL for those 12 years and older) and is commonly corticosteroid nonresponsive.3,4 Although elevated peripheral blood levels of eosinophils and neutrophils have both been associated with severe asthma,5 the direct role of these circulating eosinophils and neutrophils on airway inflammation remains poorly understood.6 In theory, circulating levels of eosinophils and neutrophils could reflect their levels in the lungs, but this has not been well investigated in children with severe asthma. Reflecting these discordant measures, there was poor agreement (Cohen's kappa, −0.03; P = .86) and no evidence for association (odds ratio, 0.86; 95% confidence interval, 0.10-6.35; Fisher's exact test P = 1) between peripheral blood eosinophil category (high vs normal) and BAL eosinophil percentage category (high vs normal). Characteristic Mean ± SD or n (%) Age (y) 12.8 ± 4.4 Sex (female) 11 (44%) Age at asthma diagnosis (y) 3.7 ± 4.3 Emergency department visits for asthma in the past year 4.3 ± 5.0 Hospitalization for asthma in the past year 2.6 ± 4.3 Symptoms (d/wk) 5.0 ± 2.3 Nighttime awakenings (d/wk) 2.1 ± 2.7 Short-acting β-agonist (SABA) use (d/wk) 6.5 ± 6.7 Asthma Control Test score 12.4 ± 4.7 Race Caucasian 6 (24%) African American 9 (36%) Asian 2 (8%) Other 8 (32%) Medications before bronchoscopy∗ SABA 25 (100%) Inhaled corticosteroid (ICS) only 6 (24%) ICS + long-acting β-agonist (LABA) 15 (60%) Leukotriene receptor antagonist 16 (64%) Allergic rhinitis 16 (64%) Eczema 13 (52%) Table I Baseline characteristics of children with severe persistent asthma who underwent bronchoscopic evaluation (N = 25)