Nationwide study of blood eosinophils in COPD: impact of exacerbations and corticosteroids
- 1Department of Medicine, Lillebaelt Hospital, Vejle, Denmark
- 2Department of Regional Health Research, University of Southern Denmark, Odense, Denmark
- 3i2Minds, Aarhus C, Denmark
Abstract
Introduction: Blood eosinophils are increasingly used as biomarkers to guide inhaled corticosteroid (ICS) and biologic therapy in chronic obstructive pulmonary disease (COPD). However, the long-term stability of eosinophil count and the impact of proximate clinical events remain uncertain. This study examines the longitudinal stability of blood eosinophil counts in a nationwide cohort of COPD patients and identifies acute exposures temporally linked to eosinophil measurement variability.
Methods: We used routinely collected Danish national registry data including 63 517 patients with COPD aged ≥40 years with ≥4 eosinophil measurements during 2–6 years of follow-up (median 3.4). Eosinophils were categorised as <0.15, 0.15–0.29 and ≥0.30×10⁹/L. Logistic regression assessed associations between stability and clinical exposures, adjusting for baseline eosinophils, age, sex, comorbidities, oral corticosteroid (OCS) use, antibiotics and exacerbations. Transitions were visualised with Sankey diagrams.
Results: Overall, 26% of patients remained within the same eosinophil category across all repeated measurements (stable patient phenotype), while 74% experienced ≥1 category shift. Baseline eosinophils ≥0.30×10⁹/L predicted phenotypic stability (OR 1.70, 95% CI 1.63 to 1.77). Severe exacerbations, OCS and antibiotics prior to testing were associated with individual measurement variability, yet >80% of unstable measurements occurred without these exposures. Among patients with an unstable phenotype, 39.7% shifted once, 43.2% two times and 17.1% three times. Use of triple inhaler therapy (long-acting beta-agonist, long-acting muscarinic antagonist, ICS) was slightly more common among in the unstable group.
Conclusions: Blood eosinophil counts in COPD are highly dynamic, with most patients shifting categories over time independent of clinical exposures. Single eosinophil measurements may be unreliable for guiding therapy; repeated assessments could improve identification of patients most likely to benefit from type 2 inflammation-targeted treatments.
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BibTeX
@article{borg2026nationwide,
title = {{Nationwide study of blood eosinophils in COPD: impact of exacerbations and corticosteroids}},
author = {Morten Borg and Ole Hilberg and Rikke Ibsen and Anders Løkke},
journal = {BMJ Open Respiratory Research},
year = {2026},
month = oct,
doi = {10.1136/bmjresp-2026-004269},
url = {https://doi.org/10.1136/bmjresp-2026-004269},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Nationwide study of blood eosinophils in COPD: impact of exacerbations and corticosteroids
AU - Morten Borg
AU - Ole Hilberg
AU - Rikke Ibsen
AU - Anders Løkke
PY - 2026
DA - 2026/10/26
JO - BMJ Open Respiratory Research
DO - 10.1136/bmjresp-2026-004269
UR - https://doi.org/10.1136/bmjresp-2026-004269
AB - Introduction: Blood eosinophils are increasingly used as biomarkers to guide inhaled corticosteroid (ICS) and biologic therapy in chronic obstructive pulmonary disease (COPD). However, the long-term stability of eosinophil count and the impact of proximate clinical events remain uncertain. This study examines the longitudinal stability of blood eosinophil counts in a nationwide cohort of COPD patients and identifies acute exposures temporally linked to eosinophil measurement variability. Methods: We used routinely collected Danish national registry data including 63 517 patients with COPD aged ≥40 years with ≥4 eosinophil measurements during 2–6 years of follow-up (median 3.4). Eosinophils were categorised as <0.15, 0.15–0.29 and ≥0.30×10⁹/L. Logistic regression assessed associations between stability and clinical exposures, adjusting for baseline eosinophils, age, sex, comorbidities, oral corticosteroid (OCS) use, antibiotics and exacerbations. Transitions were visualised with Sankey diagrams. Results: Overall, 26% of patients remained within the same eosinophil category across all repeated measurements (stable patient phenotype), while 74% experienced ≥1 category shift. Baseline eosinophils ≥0.30×10⁹/L predicted phenotypic stability (OR 1.70, 95% CI 1.63 to 1.77). Severe exacerbations, OCS and antibiotics prior to testing were associated with individual measurement variability, yet >80% of unstable measurements occurred without these exposures. Among patients with an unstable phenotype, 39.7% shifted once, 43.2% two times and 17.1% three times. Use of triple inhaler therapy (long-acting beta-agonist, long-acting muscarinic antagonist, ICS) was slightly more common among in the unstable group. Conclusions: Blood eosinophil counts in COPD are highly dynamic, with most patients shifting categories over time independent of clinical exposures. Single eosinophil measurements may be unreliable for guiding therapy; repeated assessments could improve identification of patients most likely to benefit from type 2 inflammation-targeted treatments.
SN - 2052-4439
ER -