Blood Eosinophils: A Biomarker of Response to Extrafine Beclomethasone/Formoterol in Chronic Obstructive Pulmonary Disease

To the Editor: Chronic obstructive pulmonary disease (COPD) is a heterogeneous condition (1). The identification of COPD phenotypes may allow stratified treatment approaches that modulate discrete disease mechanisms. Peripheral blood eosinophilia is both a common and repeatable finding in COPD (2). In addition, the presence of a blood/sputum eosinophilia is associated with a significant proportion of COPD exacerbations (3, 4) and a favorable...