Late Breaking Abstract - Lack of stability of blood eosinophil counts in patients with COPD

Background: Blood eosinophils (B-eos) have been suggested as a useful biomarker to guide treatment decisions. GOLD 2019 suggests using ICS and a bronchodilator combination therapy as a first-line option for patients who have frequent exacerbations and with B-eos counts of 300 cells/µL or more. However, data is controversial regarding stability of B-Eos level in individual patients. We aimed to describe stability over time of B-eos count in patients diagnosed with COPD. Methods: This observational, retrospective, longitudinal cohort, database Auria Biobank study included Finnish patients with confirmed COPD-diagnosis, aged ≥ 40, and with a smoking history. Patients with a history of asthma were excluded. The patients must be clinically stable and have at least two B-Eos count measurements post-COPD diagnosis separated by a minimum of 6 months and maximum of 24 months. A pre-specified B-eos cut-off of 300 cells/µL was used to stratify the subjects into respective groups. Results: The number of patients matching the inclusion criteria was 176. According to the serial B-eos count in 2-year follow-up 13 (7.4%), 86 (48.9%) and 77 (43.8%) patients were persistently high (all count ≥ 300 cells/µL), persistently low (all counts < 300 cells/µL) and variable (oscillating above and below) eosinophilic, respectively. Conclusion: In this carefully characterized COPD cohort, a single B-eos value was insufficient because B-Eos levels varied significantly and the stability of B-eos was poor. This lack of stability could result in the B-eos not being a reliable biomarker.