Oh YM, et al. - Researchers explored the prognostic role of blood eosinophil count in COPD patients, focusing on the associated factors and mortality based on blood eosinophil count in these patients. From 16 hospitals of the Korean Obstructive Lung Disease cohort (n=395) and COPD in Dusty Area cohort (n=234) of Kangwon University Hospital, they recruited COPD patients for this investigation. On the basis of blood eosinophil count, the two merged cohorts were divided into high (≥5%), middle (2%–5%), and low (<2%) groups. An independent association of emphysema severity with low blood eosinophil count was observed in patients with COPD, while increased blood eosinophil count was observed in relation to longer survival period, though it was not proven in the multivariate analysis.