Clinical Research Progress of Peripheral Blood Eosinophils in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) accounts for one of the major health and economic burdens worldwide. As a heterogeneous disease, the underlying inflammatory pattern of COPD differs from the previously thought neutrophil-dominated inflammation, with eosinophilic inflammation occupying approximately one third of stable COPD. Although the eosinophil (EOS) threshold associated with clinical relevance in patients with COPD is currently debated, eosinophil count can be used as a biomarker to guide treatment and to assess the risk of acute exacerbations of COPD, the efficacy of inhaled corticosteroids, and clinical outcomes. The purpose of this review is to describe the biological characteristics of eosinophils and the related research progress as clinical biomarkers.