Association between Eosinophilic Airway Inflammation and Persistent Airflow Limitation

Objective. We aimed to evaluate the association between eosinophilic inflammation in induced sputum and pulmonary function and persistent airflow limitation in children. Methods. A total of 92 asthmatic children and 72 controls were enrolled in this study. Eosinophil count (%) and eosinophil cationic protein (ECP) levels were measured in induced sputum. We performed spirometry and a methacholine challenge test, and measured total eosinophil count, total serum IgE, and serum ECP in all subjects. Results. Asthmatic children had significantly higher levels of sputum eosinophils (9% vs. 0%; P < 0.001) and sputum ECP (2.3 +/- 0.7 vs. 1.6 +/- 0.6 log mu g/L, p < .001) than controls. Sputum ECP levels showed a significant negative correlation with post-bronchodilator (post-BD) FEV1 (r = -0.307; p = .001) and post-BD FEV1/FVC (r = -0.286; p = .002), whereas sputum eosinophils showed no correlation with post-BD FEV1 and post-BD FEV1/FVC. However, no significant differences in sputum ECP and sputum eosinophil counts were observed in asthmatic children with and without persistent airflow limitation. Conclusions. Our findings suggest that sputum eosinophilic inflammation, especially ECP, is associated with pulmonary function and persistent airflow limitation, which is manifested by low post-BD FEV1/FVC.