Background: The blood eosinophil count (BEC) is an effective biomarker for predicting inhaled corticosteroid responsiveness in patients with chronic obstructive pulmonary disease (COPD).
Methods: A 12-month prospective observational study was conducted in patients with COPD. BEC was measured at enrolment, and after 6 and 12 months. Patients were classified into three groups according to their baseline BEC: <100, 100 - 299, and ≥300 cells/µL. We aimed to describe the patterns of blood eosinophil stability in patients with stable COPD and compare the exacerbation rates and other clinical outcomes at 6 and 12 months.
Results: A total of 252 patients with COPD were included. The <100, 100 - 299, and ≥ 300 cells/μL groups consisted of 14.7, 38.9, and 46.4% of patients, respectively. BEC stability was highest (85%) in the ≥300 cells/μL group for both durations. The lowest stability was observed in the <100 cells/μL group at 57 and 46% after 6 and 12 months, respectively. The persistent ≥ 300 cells/μL group had a higher incidence of moderate-to-severe exacerbation (IRR 2.44, 95% confidence interval (CI): 1.13-5.27, p value 0.023, as well as severe exacerbation (IRR 2.19, 95%CI: 1.39-3.45, p value 0.001). Other patient-reported outcomes did not differ significantly between groups.
Conclusion: Blood eosinophil levels had good stability in patients with COPD with BEC ≥300 cells/µL and was associated with a high risk of exacerbation in the persistent ≥300 cells/μL group. The variability of BEC was higher in patients with COPD with BEC <300 cells/µL.
Keywords: blood eosinophil levels; chronic obstructive pulmonary disease; exacerbation; stability; variability.
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