Blood Eosinophil Count Stability and Clinical Outcomes in Patients With Chronic Obstructive Pulmonary Disease in a High Endemic Area of Parasitic Infection: A Prospective Study.

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 enrollment, and after 6 and 12 months. Patients were classified into 3 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 (incidence rate ratio [IRR] 2.44, 95% confidence interval [CI]: 1.13-5.27, value 0.023), as well as severe exacerbation (IRR 2.19, 95%CI: 1.39-3.45, 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 a 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 a BEC <300 cells/µL.