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) in people with COPD to predict poor inhaled corticosteroid (ICS) responsiveness. However, the BEC 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 vs BEC > 100 (BEC) 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 (n = 61 GOLD group D) and n = 929 people with BEC (n = 124 GOLD group D). BEC status was stable at 6 weeks and approximately 52 weeks (intraclass correlations of 0.78 and 0.71, respectively). Compared with BEC, BEC 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 vs BEC, -50 vs -39 mL/y; P = .140), exacerbations (0.40 vs 0.36/y; P = .098), subsequent ICS initiation (2.5% vs 4.4%; P = .071), and mortality (7.8% vs 8.4%; P = .715). However, in GOLD group D, people with BEC showed higher exacerbation rates within 365 days of enrollment (0.62 vs 0.33/y; P = .002) and total follow-up (1.16 vs 0.83/y; P = .014). They also had greater lung function decline (mean slope of -68 mL/y vs -23 mL/y; P = .036) and had greater emphysema at baseline (voxels < 950 Hounsfield units at total lung capacity of 7.46% vs 4.61%; P = .029).INTERPRETATION: In non-ICS-treated GOLD group D COPD, people with BEC 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 studies focused specifically on their therapeutic treatment.CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT01969344; URL: www.CLINICALTRIALS: gov.