Serial blood eosinophils and clinical outcome in patients with chronic obstructive pulmonary disease

Abstract Background Blood eosinophils have been suggested as a potential biomarker in chronic obstructive pulmonary disease (COPD), and their stability over time has been investigated in a few studies. However, the association between the stability of blood eosinophils and long-term clinical outcomes in COPD patients has yet to be fully elucidated. This study aimed to evaluate the stability of blood eosinophils and its association with clinical outcomes in COPD patients. Methods In total, 299 COPD patients from the Korean Obstructive Lung Disease cohort with at least two blood eosinophil measurements were included. Patients were stratified according to a cut-off of 300 cells/μL, and the association between eosinophil changes and all-cause mortality was analysed. The annual decline in forced expiratory volume in 1 s (FEV1), serial changes in St George’s Respiratory Questionnaire score (SGRQ), and exacerbations during follow-up were compared among eosinophil groups. Results Patients were stratified into three groups according to the blood eosinophil cut-off: persistently