Systemic inflammatory markers in COPD: results from the Bergen COPD Cohort Study

Chronic obstructive pulmonary disease (COPD) is considered an inflammatory pulmonary disorder with systemic inflammatory manifestations. The aim of this study was to assess the systemic levels of six inflammatory mediators in a large cohort of COPD patients and controls. 409 COPD patients and 231 healthy subjects, aged 40-75 yrs, were included from the first phase of the Bergen COPD Cohort Study. All COPD patients were clinically diagnosed by a physician, and had a forced expiratory volume in 1 s/forced vital capacity ratio less than 0.7 and a smoking history of >10 pack-yrs. The plasma levels of C-reactive protein (CRP), soluble tumour necrosis factor receptor (sTNFR)-1, osteoprotegrin, neutrophil activating peptide-2, CXCL16 and monocyte chemoattractant protein-4 were determined by ELISA. After adjustment for all known confounders, COPD patients had significantly lower levels of osteoprotegrin than subjects without COPD (p<0.05), and higher levels of CRP (p<0.01). Among COPD patients, CRP was elevated in patients with frequent exacerbations (p<0.05). sTNFR-1 and osteoprotegrin were both related to Global Initiative for Chronic Obstructive Lung Disease stage and frequency of exacerbations in the last 12 months (p<0.05). In addition, sTNFR-1 was significantly associated with important comorbidities such as hypertension and depression (p<0.05). The present study confirms that certain circulating inflammatory mediators are an important phenotypic feature of COPD.