Greater eosinophil counts at first COPD hospitalization are associated with more readmissions and fewer deaths

Abstract

Purpose

The impacts of high blood eosinophil count (HBEC) at admission for COPD exacerbation on posthospitalization outcomes are still unclear. Previous studies have focused on its associations with first readmission rates; yet, its impacts on longitudinal outcomes such as subsequent readmissions still have to be explored. The main objective of this study is to investigate outcomes associated with HBEC following a first hospitalization for COPD exacerbation.

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 HBEC group if the blood eosinophil count at admission was ≥200 cells/µL and/or ≥2% of the total white blood cells. With information on exact dates of subsequent hospitalizations and death, we modeled readmissions and death as states in a multi-state Markov model and estimated transition probabilities to the next states. Sensitivity analyses were performed by varying thresholds for the definition of HBEC (≥300 cells/µL and/or ≥3%).

Results

A total of 479 patients were included, of which 173 had HBEC. The transition probabilities for a first readmission was 74% (95% CI, 66%–83%) for patients with HBEC vs 70% (95% CI, 63%–77%) for patients with normal blood eosinophil count (NBEC). The transition probabilities for a second readmission were 91% (95% CI, 84%–100%) for HBEC patients in contrast with 83% (95% CI, 74%–92%) for NBEC patients. Meanwhile, transition probability for death was lower in patients with HBEC. The differences enlarged in sensitivity analyses with higher cutoff.

Conclusion

Greater blood eosinophil cell counts during a first hospitalization for COPD predict increased susceptibility to up to two readmissions. These patients may however have a lower risk of death.

Keywords:

• COPD
• blood eosinophil cell count
• exacerbations
• readmissions
• death
• multi-state Markov model
• transition probability
• observational cohort study
• clinical data
• administrative data

Supplementary material

Figure S1 Observed snapshot percentages of patients in the six states, from day 0 to 12 months with an interval of 30 days. Snapshots are taken at each exact point in time. HBEC patients (defined as ≥400 cells/µL and/or ≥4% of the WBC count) are compared to NBEC patients.

Abbreviations: HBEC, high blood eosinophil count; NBEC, normal blood eosinophil count; WBC, white blood cell.

Acknowledgments

This study was conducted with funding support from Astra-Zeneca Canada Inc. The sponsor had no role in the design of the study, the collection and analysis of the data, or the preparation of the manuscript. Dr Li thanks Xinjiang University for the funding (116/62008056). Drs Vanasse, Poder, and Larivée are members of the Fonds de Recherche Québec – Santé (FRQS)-funded Centre de recherche du CHUS.

Disclosure

AV and TGP report grants from AstraZeneca Canada Inc., during the conduct of the study; PL reports grants and personal fees from AstraZeneca, Boehringer Ingelheim, and Novartis, grants from Sanofi, and personal fees from Merck, outside the submitted work. The other authors report no conflicts of interest in this work.