Chronic bronchitis sub-phenotype within COPD: inflammation in sputum and biopsies

The presence of chronic bronchitis predicts a more rapid decline of forced expiratory volume in one second (FEV1) in patients with chronic obstructive pulmonary disease (COPD). The hallmark of COPD is airway inflammation. It was hypothesised that COPD patients with chronic bronchitis are characterised by a distinct inflammatory cell profile, as measured in bronchial biopsies and sputum. From 114 COPD patients (male/female ratio 99/15, mean +/- SD age 62 +/- 8 yrs, current smoking 63%, post-bronchodilator FEV1 63 +/- 9% predicted, no steroids), with and without chronic bronchitis, inflammatory cell counts in bronchial biopsies and induced sputum were measured. Analysis was carried out by logistic regression. COPD patients with chronic bronchitis had lower eosinophil counts in biopsies and higher percentages of sputum eosinophils than patients without those symptoms, which remained after adjustment for smoking and sex. Patients with chronic bronchitis also showed higher percentages of macrophages and lower percentages of neutrophils in sputum, which could be explained by differences in smoking and sex. It was concluded that chronic bronchitis reflects an inflammatory sub-phenotype among patients with chronic obstructive pulmonary disease. The present results indicate a preferential distribution of eosinophils towards the airway lumen in patients with chronic bronchitis. This may have implications for anti-inflammatory treatment of chronic obstructive pulmonary disease patients with chronic bronchitis.