Assessment of serum myeloperoxidase in children with bronchial asthma

Background: The role of neutrophils and myeloperoxidase (MPO) – assumed to be a marker of neutrophil activation – in bronchial asthma is still unclear, and the literature is controversial. Methods: To investigate the participation of neutrophils and their products in childhood asthma, we assessed neutrophil counts and serum MPO in 175 children with bronchial asthma. Ninety of them were asymptomatic, and 85 of them were symptomatic within the last 2 weeks before examination. Bacterial infection of the lower respiratory tract (LRTI) was present in 34 and viral infection in 49 patients. As controls, 45 patients with cystic fibrosis, 23 patients with bacterial LRTI, and 87 healthy children were recruited. Results: Median neutrophil counts (3135 cells/μl) and serum MPO levels (352 μg/l) were not different in children with bronchial asthma from healthy controls (2220 cells/μl and 401 μg/l, respectively), whereas in patients with cystic fibrosis and bacterial LRTI, neutrophil counts and MPO levels were increased. Asthmatic children with bacterial infection had significantly higher serum MPO and neutrophil counts then asthmatic children with viral infection or without infection. In addition, a significant correlation was found between serum MPO and neutrophil counts and C‐reactive protein (CRP), and between neutrophil counts and CRP, but no relationship was detected for serum MPO and disease activity or lung function. Conclusions: Our data indicate that serum MPO – a marker of neutrophil activation – does not contribute to the assessment of the inflammatory process in childhood asthma. In addition, measurement of serum MPO appears not to be useful in assessing the participation of the neutrophil in asthmatic children. However, assessment of MPO may be useful to distinguish between bacterial and viral infection. Abbreviations. BAL: bronchoalveolar lavage; CF: cystic fibrosis; CRP: C‐reactive protein; ECP: eosinophil cationic protein; EPX: eosinophil protein X; LRTI: lower respiratory tract infection; MPO: myeloperoxidase.