Clinical Implications of Low Absolute Blood Eosinophil Count in the SPIROMICS COPD Cohort.

BACKGROUND: The Global Initiative for Chronic Obstructive Lung Disease (GOLD) considers blood eosinophil counts< 100 cells/μL (BEC≤100) in people with COPD to predict poor inhaled corticosteroid (ICS) responsiveness. However, the BEC≤100 phenotype is inadequately characterized, especially in advanced COPD. RESEARCH QUESTION: Are there differences between GOLD group D patients with high BEC and those with low BEC regarding baseline characteristics and longitudinal outcomes? STUDY DESIGN AND METHODS: We used multivariable mixed models and logistic regression to contrast clinical characteristics and outcomes of BEC≤100 vsBEC > 100 (BEC100+) in all subjects with COPD (n= 1,414) and GOLD group D subjects (n= 185) not receiving ICS. RESULTS: We identified n= 485 with BEC≤100 (n= 61 GOLD group D) and n= 929 people with BEC100+ (n= 124 GOLD group D). BEC≤100 status was stable at 6weeks and approximately 52weeks (intraclass correlations of 0.78 and 0.71, respectively). Compared with BEC100+, BEC≤100 comprised more women, with greater current smoking, and less frequent childhood asthma. Among all analyzed participants, the two BEC-defined subsets showed similar rates of lung function decline (mean slope, BEC≤100 vsBEC100+, -50 vs-39mL/y; P= .140), exacerbations (0.40 vs0.36/y; P= .098), subsequent ICS initiation (2.5%vs4.4%; P= .071), and mortality (7.8%vs8.4%; P= .715). However, in GOLD group D, people with BEC≤100 showed higher exacerbation rates within 365days of enrollment (0.62 vs0.33/y; P= .002) and total follow-up (1.16 vs0.83/y; P= .014). They also had greater lung function decline (mean slope of -68mL/y vs-23mL/y; P= .036) and had greater emphysema at baseline (voxels< 950 Hounsfield units at total lung capacity of 7.46%vs4.61%; P= .029). INTERPRETATION: In non-ICS-treated GOLD group D COPD, people with BEC≤100 had more baseline emphysema, prospective exacerbations, and lung function decline. Our analysis has identified a particularly vulnerable subpopulation of people with COPD, suggesting the need for ...