Blood Eosinophil Count and Hospital Readmission in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Matthew J Hegewald,^1,2 Benjamin D Horne,^3,4 Frank Trudo,⁵ James L Kreindler,⁵ Yen Chung,⁵ Susan Rea,⁶ Denitza P Blagev<sup>1,2

1</sup>Pulmonary and Critical Care Medicine Division, Intermountain Medical Center, Murray, UT, USA; ²Pulmonary and Critical Care Medicine, University of Utah, Salt Lake City, UT, USA; ³Intermountain Heart Institute at Intermountain Healthcare, Salt Lake City, UT, USA; ⁴Division of Cardiovascular Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA; ⁵Health Economics Outcomes Research, AstraZeneca, Wilmington, DE, USA; ⁶Enterprise Analytics, Intermountain Healthcare, Salt Lake City, UT, USA

Correspondence: Matthew J Hegewald
Pulmonary and Critical Care Medicine Division, Intermountain Medical Center, 5121 S Cottonwood Street, Murray, UT 84107, USA
Tel +1-801-507-4870
Fax +1-801-507-4792
Email matt.hegewald@imail.org

Purpose: This retrospective, observational cohort study investigated the association of blood eosinophil counts within 1 week of hospitalization for acute exacerbation of COPD (AECOPD) with subsequent risk of all-cause and COPD-related readmission from a large integrated health system.
Patients and Methods: Electronic medical records were extracted for index hospitalization for AECOPD at all Intermountain Healthcare hospitals. The primary outcome was the relationship of blood eosinophil count to 30-day all-cause readmission; secondary outcomes were 60-day, 90-day, and 12-month all-cause readmission, COPD-related readmission, and empiric derivation of the eosinophil count with the highest area under the curve (AUC) for predicting 30-day all-cause readmission.
Results: Of 2445 included patients, 1935 (79%) had a blood eosinophil count < 300 cells/μL and 510 (21%) had a count ≥ 300 cells/μL. Using a 300-cells/μL threshold, there was no significant difference between high and low eosinophil groups in 30-day (odds ratio [OR]=1.05, 95% confidence interval [CI]=0.75– 1.47) or 60-day (OR=1.15, 95% CI=0.88– 1.51) all-cause readmissions. However, patients with greater (versus lesser) eosinophil counts had increased 90-day and 12-month all-cause readmissions (OR=1.35, 95% CI=1.06– 1.72, and OR=1.32, 95% CI=1.07– 1.62). COPD-related readmission rates were significantly greater for patients with greater (versus lesser) eosinophil counts at 30, 60, and 90 days and 12 months (OR range=1.52– 1.97). A total of 70 cells/μL had the most discriminatory power to predict 30-day all-cause readmission (highest AUC).
Conclusion: Eosinophil counts in patients with COPD were not associated with a difference in 30-day all-cause readmissions. However, greater eosinophil counts were associated with increased risk of all-cause readmission at 90 days and 12 months and COPD-related readmission at 30, 60, and 90 days and 12 months. Patients with eosinophils < 70 cells/μL had the lowest risk for 30-day all-cause readmission. Blood eosinophils in patients hospitalized with AECOPD may be a useful biomarker for the risk of hospital readmission.

Keywords: AECOPD, phenotype, biomarkers, eosinophils, electronic medical records