Impact of Eosinophil Levels on Disease Progression and Clinical Outcomes in Chronic Obstructive Pulmonary Disease (COPD) Patients: A Retrospective Study.

Objective: The role of total eosinophil count (EOS) in chronic obstructive pulmonary disease (COPD) remains debated, with studies suggesting both positive and negative impacts on disease progression. This retrospective study aimed to investigate the relationship between stable-state blood EOS levels and clinical outcomes, including hospitalizations, emergency room (ER) visits, and pneumonia, in COPD patients. Methods: Data from 398 COPD patients were analyzed, focusing on blood EOS counts and percentages acquired during stable periods. Patients were categorized based on EOS thresholds of 150 cells/μL and 2%. The number of hospitalizations, ER visits, and pneumonia diagnoses in the preceding year was retrieved from hospital records and patient reports. Results: Patients with EOS levels below 150 cells/μL or 2% showed a significantly higher number of hospitalizations. Additionally, patients with EOS percentages below 2% had higher COPD Assessment Test and Modified Medical Research Council scores, indicating greater symptom burden and dyspnea. Logistic regression analysis confirmed that a lower EOS percentage was an independent predictor of increased hospitalizations, similar to its association with lower FEV1% and more than two ER visits. Conclusions: This study suggests that low blood EOS counts are associated with increased hospitalizations and worse clinical outcomes in COPD patients. This finding highlights the importance of considering EOS levels as a potential biomarker for disease severity and may lead to personalized treatment strategies. Further prospective studies are needed to validate these findings and elucidate the underlying mechanisms.