Risk of hospitalised bronchiectasis exacerbation based on blood eosinophil counts

SETTING: There has been growing recognition on the importance of phenotyping of airway diseases. The eosinophilic phenotype was proposed in bronchiectasis; however, there has not been any evidence on its association with the risk of hospitalised bronchiectasis exacerbations. OBJECTIVE: To investigate the association between baseline blood eosinophil count (BEC) and bronchiectasis exacerbations requiring hospitalisation with validation by an independent cohort. DESIGN: This was a retrospective cohort study. RESULTS: Over a 24-month period, 37/318 (11.6%) study participants experienced an exacerbation requiring hospitalisation. The mean baseline serum eosinophil was 135 ± 92 cells/µL in those who had exacerbations, and 188 ± 161 cells/µL in those who did not. A serum eosinophil level of 250 cells/µL at stable state was the most significant cut-off for predicting hospitalised bronchiectasis exacerbation, which was validated by the independent cohort. CONCLUSIONS: Patients with BEC below 250 cells/µL at stable state are at increased risk of having hospitalised bronchiectasis exacerbations.