Association Between Blood Eosinophils and Neutrophils With Clinical Features in Adult-Onset Asthma

Asthma is a disease that can be separated into different phenotypes and endotypes based on the clinical characteristics and the molecular mechanisms of the condition, respectively.

To assess the association between blood eosinophil and neutrophil counts with clinical and molecular features in patients with adult-onset asthma.

Blood eosinophil and neutrophil counts were measured from 203 patients who took part in the Seinäjoki Adult Asthma Study and attended the 12-year follow-up visit. The patients were then divided into four groups (paucigranulocytic [n = 108], neutrophilic [n = 60], eosinophilic [n = 21], and mixed granulocytic [n = 14]), according to eosinophil and neutrophil levels. The cutoff values used to define the groups were 0.30 × 10⁹ · L^-1 for blood eosinophils and 4.4 × 10⁹ · L^-1 for blood neutrophils.

The neutrophilic group had highest body mass index. It was dispensed the highest doses of inhaled corticosteroids during the 12-year follow-up and made the most unplanned respiratory visits. The neutrophilic, eosinophilic, and mixed granulocytic groups had more severe asthma compared with the paucigranulocytic group. The neutrophilic and eosinophilic groups were associated with higher dispensed antibiotics. The eosinophilic group had more nasal polyps, more suspected sinusitis, a greater decline in lung function, and increased levels of periostin, FeNO, and IgE. The neutrophilic group had increased high-sensitivity C-reactive protein, matrix metalloproteinase-9, IL-6, leptin, and soluble urokinase plasminogen activator receptor levels. The mixed granulocytic group showed increased resistin levels together with the neutrophilic group.

In addition to blood eosinophils, the blood neutrophil count reflects underlying inflammatory patterns and indicates important differences in asthma clinical features and outcomes.