Risk of hospitalised bronchiectasis exacerbation based on blood eosinophil counts.

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. To investigate the association between baseline blood eosinophil count (BEC) and bronchiectasis exacerbations requiring hospitalisation with validation by an independent cohort. This was a retrospective cohort study. 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. Patients with BEC below 250 cells/µL at stable state are at increased risk of having hospitalised bronchiectasis exacerbations.