COPD Phenotype Description Using Principal Components Analysis
C34. COPD PHENOTYPES
Airway inflammation in COPD can be measured using biomarkers such as induced sputum and Fe NO . This study set out to explore the heterogeneity of COPD using biomarkers of airway and systemic inflammation and pulmonary function by principal components analysis (PCA). Subjects and Methods: In 127 COPD patients (mean FEV 1 61%), pulmonary function, Fe NO , plasma CRP and TNF-α, sputum differential cell counts and sputum IL8 (pg/ml) were measured. Principal components analysis as well as
... s well as multivariate analysis was performed. Results: PCA identified four main components (% variance): (1) sputum neutrophil cell count and supernatant IL8 and plasma TNF-α (20.2%), (2) Sputum eosinophils % and Fe NO (18.2%), (3) Bronchodilator reversibility, FEV 1 and IC (15.1%) and (4) CRP (11.4%). These results were confirmed by linear regression multivariate analyses which showed strong associations between the variables within components 1 and 2. Conclusion: COPD is a multi dimensional disease. Unrelated components of disease were identified, including neutrophilic airway inflammation which was associated with systemic inflammation, and sputum eosinophils which were related to increased Fe NO . We confirm dissociation between airway inflammation and lung function in this cohort of patients.