Identification of patients with chronic obstructive pulmonary disease (COPD) by measurement of plasma biomarkers

Introduction: Inflammation is an important constituent of the pathology of chronic obstructive pulmonary disease (COPD), leading to alveolar destruction and airway remodelling. Objective: The aim of this study was to assess the difference in plasma biomarkers of inflammation between asymptomatic smokers and patients with COPD. Methods: We used commercially available enzyme‐linked immunosorbent assay kits to measure the plasma levels of tumour necrosis factor‐α (TNF‐α), interleukin‐8 (IL‐8), matrix metalloproteinase‐9 (MMP‐9), monocyte chemotactic protein‐1 (MCP‐1), tissue inhibitor of metalloproteinase‐1 (TIMP‐1) and tissue inhibitor of metalloproteinase‐2 (TIMP‐2) on two occasions with a 2‐week interval in patients with COPD (n = 20), asymptomatic smokers (n = 10) and healthy lifelong non‐smokers (n = 10). The participants were characterised clinically, physiologically and by quantitative computed tomography by measuring the relative area of emphysema below −910 Hounsfield units (RA‐910). Results: The results of the biomarker measurements on the two occasions were highly reproducible. Patients with COPD had significantly higher plasma levels of IL‐8 (P = 0.004) and significantly lower levels of TIMP‐1 (P = 0.02) than smokers and non‐smokers. There was no statistically significant difference between the three groups in the level of TNF‐α, MMP‐9, MCP‐1 and TIMP‐2. The IL‐8/TIMP‐1 ratio correlated significantly with the degree of airway obstruction measured as forced expiratory volume in 1 second (FEV1) % predicted (r = −0.47, P