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/<mu>L. 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/mu L groups consisted of 14.7%, 38.9%, and 46.4% of patients, respectively. BEC stability was highest (85%) in the >= 300 cells/mu L group for both durations. The lowest stability was observed in the <100 cells/mu L group at 57% and 46% after 6 and 12 months, respectively. The persistent >= 300 cells/mu L group had a higher incidence of moderate- to- severe exacerbation (incidence rate ratio [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 a BEC >= 300 cells/mu L and was associated with a high risk of exacerbation in the persistent >= 300 cells/mu L group. The variability of BEC was higher in patients with COPD with a BEC<300 cells/<mu>L.