The Correlation of Peripheral Eosinophilia With the Severity and Exacerbation in Chronic Obstructive Pulmonary Disease Patients

Background: Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous disorder characterized by persistent airflow limitation and diverse inflammatory phenotypes. The eosinophilic phenotype has gained attention because of its potential association with exacerbation risk, disease severity, and corticosteroid responsiveness. Aim: This study evaluated the relationship between peripheral blood eosinophil counts and markers of disease severity, including spirometric indices, GOLD stage, and recent exacerbation frequency, among patients with COPD. Methods: A cross-sectional analytical study was conducted on 100 patients aged ≥40 years with confirmed COPD (post-bronchodilator FEV1/FVC <0.70) attending outpatient clinics at Mirjan Medical City, Babylon, Iraq. Peripheral blood eosinophil counts were measured and patients were categorized into two groups: <300 cells/µL and ≥300 cells/µL. Pulmonary function was assessed using spirometry. Associations between eosinophil levels and FEV1% predicted, GOLD stage, and exacerbations in the preceding six months were analyzed using Spearman’s rank correlation. Results: The median eosinophil count was 247.5 cells/µL. Patients with eosinophil counts ≥300 cells/µL demonstrated significantly lower median FEV1% predicted (48% vs. 75%; p<0.001) and post-bronchodilator FEV1 (55% vs. 79%; p<0.001). Eosinophil counts increased progressively across GOLD stages, from 62.5 cells/µL in stage 1 to 805 cells/µL in stage 4. Significant negative correlations were observed between eosinophil counts and lung function parameters, while positive correlations were identified with GOLD stage (ρ=0.623, p<0.001) and exacerbation frequency (ρ=0.490, p<0.001). Conclusion: Elevated peripheral eosinophil counts are strongly associated with greater airflow limitation, advanced disease severity, and increased exacerbation burden in COPD, supporting their role as an accessible biomarker for high-risk phenotyping.