Abstract
BackgroundAirway inflammation in COPD can be measured using biomarkers such as induced sputum and FeNO. 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 MethodsIn 127 COPD patients (mean FEV1 61%), pulmonary function, FeNO, plasma CRP and TNF-α, sputum differential cell counts and sputum IL8 (pg/ml) were measured. Principal components analysis as well as multivariate analysis was performed.ResultsPCA identified four main components (% variance): (1) sputum neutrophil cell count and supernatant IL8 and plasma TNF-α (20.2%), (2) Sputum eosinophils % and FeNO (18.2%), (3) Bronchodilator reversibility, FEV1 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.ConclusionCOPD 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 FeNO. We confirm dissociation between airway inflammation and lung function in this cohort of patients.
Highlights
Airway inflammation in Chronic obstructive pulmonary disease (COPD) can be measured using biomarkers such as induced sputum and FeNO
Unrelated components of disease were identified, including neutrophilic airway inflammation which was associated with systemic inflammation, and sputum eosinophils which were related to increased FeNO
COPD severity is graded by forced expiratory volume in 1 second (FEV1) [1], but this grading does not recognise the range of pathophysiological abnormalities that may be present in this heterogeneous condition
Summary
Airway inflammation in COPD can be measured using biomarkers such as induced sputum and FeNO. 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). COPD can be viewed as an umbrella term that encompasses a range of pulmonary and systemic manifestations. COPD severity is graded by forced expiratory volume in 1 second (FEV1) [1], but this grading does not recognise the range of pathophysiological abnormalities that may be present in this heterogeneous condition. Induced sputum is a safe and non-invasive method for studying biomarkers of airway inflammation in COPD patients, neutrophil [3] and eosinophil [4] numbers being the most valuable measures at present.
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