Significance of Eosinophils and Eosinophil Cationic Protein in Induced Sputum in Childhood Asthma

Jung, Seung Hee; Song, Do Young; Kang, Im Ju

Abstract

PURPOSE
Airway eosinophilic inflammation is a characteristic feature of asthma. Sputum analysis can be used as a non-invasive tool to assess severity of the airway inflammation. This study was performed to compare relationships between sputum eosinophils to other parameters of airway inflammation and to evaluate the clinical utility of sputum eosinophils and ECP in childhood asthma.
METHODS
A total of 40 asthmatic children over 6 years of age were divided into two groups : Group A of 15 current symptomatic subjects and Group B of 25 stable asymptomatic subjects with history of asthma for 2 weeks. Eosinophils in induced sputum were compared with the severity of asthma symptom, pulmonary function, bronchial hyperresponsiveness by methacholine, sputum ECP, blood eosinophils and serum ECP.
RESULTS
1) Asthmatics had a significantly higher proportion of sputum eosinophils than the control subjects (15.2+/-17.8% VS 3.8+/-4.5%, P<0.01). Group A had a significantly higher proportion of sputum eosinophils than group B (22.9+/-21.7% VS 11.2+/-14.8%, P<0.05). 2) Sputum eosinophils were correlated with symptom scores in asthmatics (r=0.76, P<0.01), inversely correlated with FEV1 in group A (r=-0.65, P<0.01) and with LogPC20 in group B (r=-0.45, P<0.05). 3) Sputum eosinophils were correlated with sputum ECP for group A; r=0.77 (P<0.01) and for group B; r=0.39 (P<0.05) but not correlated with serum ECP. 4) Sputum eosinophils were correlated with blood eosinophils in group A (r=0.67, P<0.05), but not in group B.
CONCLUSION
This study suggests that the proportion of eosinophils and the level of ECP in induced sputum may be sensitive and accurate means of assessing the airway inflammation in childhood asthma, and their relationships with blood eosinophils or serum ECP are to be studied further.