Blood eosinophil counts rarely reflect airway eosinophilia in children with severe asthma

Background The inflammatory phenotypes of severe asthma in adults may be reflected in peripheral blood. If this were true in children with severe therapy-resistant asthma (STRA), invasive tests could be avoided. At the moment there is no conclusive evidence in children. Methods All patients underwent blood tests, exhaled nitric oxide (FeNO), sputum induction, bronchoalveolar lavage (BAL) and endobronchial biopsy (EB). Results Sixty-three (71.6%) patients had a normal blood profile and only 1/88 had a combined blood eosinophilia and neutrophilia. 76/88 (86%) had normal blood eosinophils, but of these, 84% had airway eosinophilia in either BAL (n=43;66%) or EB (n=41;79%). In children with STRA blood eosinophilia was associated with airway eosinophilia. However, normal blood eosinophil levels did not exclude airway eosinophilic inflammation. Conclusions Peripheral blood counts are not reliable in characterising airway inflammation in severe asthmatic children exposed to high dose steroid therapy, therefore bronchoscopy with BAL should be considered.