Correlation of Serum Eosinophil Count with Severity and Treatment Response in COPD

Abstract

Background
Chronic obstructive pulmonary disease (COPD) is a heterogeneous respiratory disorder characterized by persistent airflow limitation, chronic inflammation, and variable response to therapy. Blood eosinophil count has emerged as an important biomarker for identifying eosinophilic COPD phenotype and predicting response to corticosteroid-based treatment. The present study was conducted to evaluate the correlation between serum eosinophil count, COPD severity, and treatment response among patients with COPD.

Methods
This prospective observational study included 110 patients diagnosed with COPD. All patients underwent detailed clinical evaluation, spirometry, and peripheral blood eosinophil estimation. COPD severity was assessed according to GOLD criteria, along with symptom assessment using standardized clinical parameters. Patients were followed after initiation of standard COPD therapy, and treatment response was evaluated based on changes in lung function, symptom scores, and exacerbation frequency. The association between serum eosinophil count and clinical outcomes was analyzed using appropriate statistical methods.

Results
The mean age of study participants was 61.8 ± 8.7 years, with male predominance (89.1%). The mean serum eosinophil count was 238.6 ± 156.4 cells/µL, and 31.8% of patients had eosinophil levels >300 cells/µL. Serum eosinophil count showed a significant correlation with FEV₁ (r=0.34, p<0.001) and symptom severity assessed by CAT score (r=-0.29, p=0.002). Patients with eosinophilic COPD demonstrated higher FEV₁ values and fewer exacerbations compared with non-eosinophilic patients. Following treatment, significant improvement was observed in FEV₁, CAT score, mMRC score, and exacerbation frequency, with greater clinical improvement among patients with higher eosinophil levels.

Conclusion
Serum eosinophil count serves as a valuable biomarker for COPD phenotyping and prediction of treatment response. Incorporation of eosinophil assessment into routine COPD evaluation may facilitate personalized therapy selection and improve clinical outcomes.