Blood eosinophil count and clinical characteristics according to etiology in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a heterogeneous condition with multiple etiologies. We evaluated whether clinical characteristics differ according to COPD etiology.

Patients with infection as the sole etiology were classified as the infection-related group (COPD-I, Group I), whereas those with any smoking-related etiology were assigned to the smoking-related group (COPD-C, Group C).

Of 873 patients included, 41 were classified as Group I and 832 as Group C. A significantly higher proportion of patients in Group I had a blood eosinophil count < 100 cells/µL compared to Group C (44.4% vs. 27.8%; p = 0.031). The inhaled corticosteroid (ICS) prescription rate was lower in Group I compared to Group C (25.7% vs. 41.5%; p = 0.063). Multivariable logistic regression confirmed that Group I was independently associated with a lower likelihood of ICS use (p = 0.018). In addition, Group I exhibited a significantly higher residual volume to total lung capacity ratio (48.88% vs. 43.28%; p = 0.030), indicating greater air trapping and small airway involvement.

These findings support the notion that infection-related COPD (COPD-I) represents a clinically distinct phenotype.