Evidence for eosinophil activation in bronchiectasis unrelated to cystic fibrosis and bronchopulmonary aspergillosis: discrepancy between blood eosinophil counts and serum eosinophil cationic protein levels

Abstract

BACKGROUND Increased serum levels of eosinophil cationic protein (ECP) have been detected in adolescent patients with cystic fibrosis. However, ECP concentrations in adult patients with bronchiectasis unrelated to cystic fibrosis have not been studied.

METHODS Eosinophil numbers and serum concentrations of ECP were determined in 14 patients with known or newly diagnosed bronchiectasis and compared with age and sex matched patients with allergic bronchial asthma, chronic obstructive pulmonary disease (COPD), and controls in whom bronchiectasis or obstructive pulmonary disease could be excluded.

RESULTS Serum ECP levels were significantly raised both in patients with bronchiectasis (median (range) 22.5 μg/l (7–85)) and allergic asthma (35.0 μg/l (7–128)) compared with the sex and age matched subjects suffering from COPD (6.7 μg/l (1.5–28); p<0.006) and non-obstructive normal controls (7.5 μg/l (3.5–19); p<0.003). In contrast, significantly increased peripheral eosinophil numbers were observed in patients with bronchial asthma (305 × 10⁶/l; p<0.01) but not in those with bronchiectasis (10² × 10⁶/l), COPD (117 × 10⁶/l), and healthy controls (101 × 10⁶/l).

CONCLUSIONS The discrepancy between eosinophil counts and eosinophil numbers in patients with bronchiectasis suggests that serum ECP levels may be more relevant in assessing local eosinophil involvement than blood eosinophil numbers.