Routine Blood Biomarkers and Lung Function in Asthma-COPD Overlap versus Asthma-Only Among Hospitalized Asthma Patients: A Retrospective Cross-Sectional Study.

Abstract

Objective: To compare routine blood biomarkers, lung function, and medication-associated biomarker patterns between hospitalized asthma patients classified as having asthma-COPD overlap (ACO) and those with asthma-only.

Methods: This retrospective cross-sectional analysis included 505 hospitalized asthma patients admitted between January 2020 and December 2024, comprising 190 with ACO and 315 with asthma-only. Disease history, pulmonary function parameters, complete blood cell counts, differential percentages, immunoglobulin E, and medication exposure were extracted from electronic medical records and analyzed using complete cases. Multivariable logistic regression, multivariable linear regression, Spearman correlation, and receiver operating characteristic (ROC) analyses were used to evaluate associations and discriminatory performance. Medication analyses were exploratory because treatment was not randomized.

Results: Compared with asthma-only patients, patients with ACO were older, had a lower prevalence of allergy history, used inhaled corticosteroids, long-acting beta2-agonists, and long-acting muscarinic antagonists more frequently, and had worse airflow limitation and lower diffusing capacity. Higher neutrophil percentage (adjusted odds ratio: 2.15, 95% confidence interval: 1.62-2.85, p<0.001) and lower lymphocyte percentage (adjusted odds ratio: 0.51, 95% confidence interval: 0.39-0.67, p<0.001) were independently associated with ACO after Bonferroni correction. In ACO patients, inhaled corticosteroid and long-acting beta2-agonist exposure was nominally associated with higher neutrophil-related and lower lymphocyte-related measures, but these observational findings should not be interpreted as treatment effects. FEV1/FVC showed the best discrimination for ACO (area under the curve [AUC]: 0.696), whereas neutrophil percentage showed modest complementary discrimination (AUC: 0.596).

Conclusion: Within this hospitalized asthma cohort, ACO was associated with older age, more severe airflow limitation, impaired diffusing capacity, and a more neutrophil-dominant systemic inflammatory profile than asthma-only. Routine blood biomarkers, particularly neutrophil and lymphocyte percentages, may complement pulmonary function parameters in identifying ACO, but their standalone diagnostic performance was modest. Medication-associated biomarker differences were exploratory and require prospective validation.