Benefits and Risks of Inhaled Corticosteroid Treatment in Patients with Chronic Obstructive Pulmonary Disease Classified by Blood Eosinophil Counts

Background Chronic obstructive pulmonary disease (COPD) typically includes neutrophilic airway inflammation and eosinophilic inflammation in some cases. Inhaled corticosteroid (ICS) suppresses eosinophilic inflammation of the airway and reduces acute exacerbation (AE). The present study investigated the relationship between ICS and AE in patients with COPD classified by blood eosinophil counts. Methods Overall, 244 patients with COPD were retrospectively evaluated between 2014 and 2017 and classified into two groups based on blood eosinophil counts (≥ 300/μL and < 300/μL). These patients were then reclassified into subgroups of those with and without ICS. Differences in the characteristics and incidence of AE and pneumonia with AE in each subgroup were evaluated retrospectively. Results All patients with ICS used 320 μg budesonide twice daily. In the group with blood eosinophil counts ≥ 300/μL, patients with ICS had a significantly lower incidence of AE than those without ICS ( P = 0.023). Meanwhile, no significant differences were observed in incidence of AE in the group with blood eosinophil counts < 300/μL. In the group with blood eosinophil counts < 300/μL, patients with ICS had a higher incidence of pneumonia with AE ( P = 0.009). Conversely, no significant differences were observed in the group with blood eosinophil counts ≥ 300/μL. Conclusions ICS significantly reduced AE in COPD patients with blood eosinophil counts ≥ 300/μL. Meanwhile, ICS significantly increased pneumonia rate in patients with blood eosinophil count < 300/μL. Blood eosinophil count may be a useful indicator to identify the benefits and risks of ICS in COPD.