522 Association between Eosinophilic Airway Inflammation and Persistent Airflow Limitation in Asthmatic Children

BACKGROUND: Eosinophilic airway inflammation contributes to persistent airflow limitation in adults with severe asthma. 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 control children were enrolled in this study. Eosinophil count (%) and eosinophil cationic protein (ECP) levels were measured in induced sputum. We performed spirometry and methacholine challenge test while measuring total eosinophil count, total serum IgE, and serum ECP in all subjects. Subjects with persistent airflow limitation were defined as the patients with postBD FEV1/FVC below the lower limit of controls, which is subtraction of 2 standard deviation from the mean ratio. RESULTS: Asthmatic children had significantly higher levels of sputum eosinophils (18.1 ± 21.5 vs 0.5 ± 1.3%, P < 0.001) and sputum ECP (2.3 ± 0.7 vs 1.6 ± 0.6 log ug/L, P < 0.001) compared to controls. No differences in sputum eosinophils and ECP among 4 asthmatic groups divided by the degree of persistent airflow limitation. Sputum ECP level had statistically significant inverse correlation with postbronchodilator (postBD) FEV1 (r = –0.307, P = 0.001) and postBD FEV1/FVC (r = –0.286, P = 0.002), whereas sputum eosinophils didn't show any correlation with postBD FEV1 and postBD FEV1/FVC. CONCLUSIONS: Our findings suggest that sputum eosinophilic inflammation, especially ECP, is associated with pulmonary function and persistent airflow limitation, which is manifested by low postBD FEV1 and postBD FEV1/FVC.