Blood eosinophil count variability in chronic obstructive pulmonary disease and severe asthma

Background: Blood eosinophils are essential biomarkers that vary substantially over time in patients with COPD and asthma. However, no study has identified the changes and effects in the changes of the blood eosinophil counts over time in both diseases. This study aimed to demonstrate blood eosinophil variability in patients with COPD and severe asthma based on these backgrounds. Methods: A total of 172 patients with COPD from the Hokkaido COPD cohort study and 96 patients with severe asthma from the Hokkaido Severe Asthma Cohort Study, whose blood eosinophil counts were measured annually over a 3-year period, were analyzed. The factors contributing to consistently high or low blood eosinophil counts were examined in each cohort. The stability of the eosinophil classification (<150, 150-299, similar to 300 cells/mL) was compared based on the number of asthma-like features in patients with COPD and the smoking status in patients with severe asthma. Results: Among all the patients, the most stable range of baseline blood eosinophil counts differed between the two diseases, with <150 cells/mL in COPD and similar to 300 cells/mL in severe asthma. In COPD, the number of asthma-like features (bronchodilator reversibility, blood eosinophilia, and atopy) affects the blood eosinophil count variation patterns. In severe asthma, smoking status did not affect the blood eosinophil count variation patterns. Conclusions: We identified variations in the blood eosinophil counts and their contributing factors in patients with COPD and severe asthma. (C) 2022 Japanese Society of Allergology. Published by Elsevier B.V.