High Blood Eosinophil Count at Stable State is Not Associated with Airway Microbiota Distinct Profile in COPD

Purpose: The heterogeneity of clinical features in COPD at stable state has been associated with airway microbiota. Blood eosinophil count (BEC) represents a biomarker for a pejorative evolution of COPD, including exacerbations and accelerated FEV₁ decline. We aimed to analyse the associations between BEC and airway microbiota in COPD at stable state.
Patients and Methods: Adult COPD patients at stable state (RINNOPARI cohort) were included and characterised for clinical, functional, biological and morphological features. BEC at inclusion defined 2 groups of patients with low BEC < 300/mm³ and high BEC ≥ 300/mm³. Sputa were collected and an extended microbiological culture was performed for the identification of viable airway microbiota.
Results: Fifty-nine subjects were included. When compared with the low BEC (n=40, 67.8%), the high BEC group (n=19, 32.2%) had more frequent exacerbations (p< 0.001) and more pronounced cough and sputum (p< 0.05). The global composition, the number of bacteria per sample and the α-diversity of the microbiota did not differ between groups, as well as the predominant phyla (Firmicutes), or the gender repartition.
Conclusion: In our study, high BEC in COPD at stable state was associated with a clinical phenotype including frequent exacerbation, but no distinct profile of viable airway microbiota compared with low BEC.

Keywords: COPD, eosinophil, sputum, microbiota