Eosinophil counts in first COPD hospitalizations: a comparison of health service utilization

Purpose: Current evidence suggests that a higher blood eosinophil cell count at admission for acute exacerbation of COPD (AECOPD) is associated with a favorable response to systemic steroids. However, the impact of blood eosinophil counts at admission on post-hospitalization outcomes is still unclear. The main objective of this study is to investigate readmission outcomes associated with blood eosinophilia following severe COPD exacerbation in patients with infrequent COPD hospitalizations. Patients and methods: This is an observational cohort study design. We retrospectively analyzed data of patients with a first hospitalization within 5 years for COPD exacerbation between April 2006 and March 2013. Patients were stratified into the eosinophilic group if the blood eosinophil count on admission was ≥200 cells/µL and/or ≥2% of the total white blood cell (WBC) count. The primary outcome was 1-year COPD-related readmission. Secondary outcomes included 1-year all-cause mortality, 1-year all-cause readmission, length of stay, time to COPD-related readmission, and number of 1-year COPD-associated emergency department (ED) and ambulatory visits. Results: A total of 479 patients were included. Of whom, 173 were stratified into the eosinophilic group. Higher blood eosinophil cell count was associated with an increased risk of 1-year COPD-related readmission (OR, 1.83 [95% CI, 1.16-2.89]; P<0.01), a shorter time to first COPD-related readmission (HR, 1.64 [95% CI, 1.14-2.36]; P<0.01), and an increased number of 1-year COPD-related ED visits (incidence rate ratio, 1.78 [95% CI, 1.21-2.61]; P<0.01). All-cause mortality, all-cause readmission, length of stay, and number of ambulatory visits did not differ between groups. Conclusion: Higher blood eosinophil cell count at admission for a COPD exacerbation is associated with increased COPD readmission rates in patients with infrequent COPD hospitalizations.