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

¹ Depts of Public Health and Primary Care; and Pulmonology
² Pulmonology
³ Depts of Pulmonology
⁴ Epidemiology & Bioinformatics and
⁵ Pathology, University Medical Center Groningen, University of Groningen, Groningen
⁶ Medical Decision Making, Leiden University Medical Center, Leiden
⁷ Pulmonology; and Pulmonology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands

^* To whom correspondence should be addressed. E-mail: J.B.Snoeck-Stroband{at}lumc.nl.

	Abstract

The presence of chronic bronchitis predicts more rapid decline of FEV₁ in patients with chronic obstructive pulmonary disease (COPD). The hallmark of COPD is airway inflammation. We hypothesized that COPD patients with chronic bronchitis are characterized by a distinct inflammatory cell profile as measured in bronchial biopsies and sputum.

From 114 COPD patients (M/F:99/15, 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 done by logistic regression.

COPD patients with chronic bronchitis had lower eosinophil counts in biopsies (p=0.019) and higher percentages of sputum eosinophils (p=0.033) than patients without those symptoms, which remained after adjustment for smoking and gender (p=0.028, p=0.057, respectively). Patients with chronic bronchitis also showed higher percentages of macrophages (p=0.039) and lower percentages of neutrophils (p=0.049) in sputum, which could be explained by differences in smoking and gender.

We conclude that chronic bronchitis reflects an inflammatory sub-phenotype among patients with COPD. Our results indicate a preferential distribution of eosinophils towards the airway lumen in those with chronic bronchitis. This may have implications for anti-inflammatory treatment of COPD patients with chronic bronchitis.

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