Changes in the cellular composition of induced sputum in patients with asthma-COPD overlap

<b>Background:</b> Mechanisms of asthma-COPD overlap among patients with persistent airflow limitation and large bronchodilator reversibility are undefined. We aimed to determine the role of the neutrophilic component of bronchial inflammation in the genesis of irreversible airway obstruction in asthma patients. <b>Methods:</b> 51 subjects with mild-to-moderate persistent asthma (mean age 42,6±0,9 years) were divided into 2 groups: the 1st group – 19 patients with postbronchodilator FEV₁/FVC&lt;0,7 and the 2nd group – 21 patients with FEV₁/FVC˃0,7. We have examined cytological microslides of induced sputum (IS) and done the cytochemical analysis of myeloperoxidase (MPO) activity in eosinophilic and neutrophilic leucocytes using Graham-Knoll method. The level of asthma control has been estimated using Asthma Control Test (ACT). <b>Results:</b> The patients of the 1st group in comparison with the 2nd group had the increased neutrophil content (39.8±4.4 vs. 26.8±4.3%; р&lt;0.05) and decreased lymphocyte content (3.0±0.4 vs. 4.6±0.7%; р&lt;0.05) in IS. A tendency to MPO increase (102.5±15.0 vs. 78.0±8.4 pixels; р˃0.05) was noted. Patients of the 1st group had worse asthma control (14.8±1.0 vs. 18.9±1.1 ACT points; р&lt;0.001). Negative correlation of neutrophil content in IS with postbronchodilator FVC (r=-0.59; р&lt;0.01) and positive with MPO (r=0.75; р&lt;0.01) have been found out. The level of asthma control correlated negatively with neutrophil content in IS (r=-0.69; р&lt;0.05). Such relationships were not revealed in the 2nd group. <b>Conclusion:</b> The neutrophilization of bronchial inflammation in patients with mild-to-moderate asthma are associated with the formation of an irreversible component of airway obstruction.