Background: Inflammation increases during exacerbations of COPD, but only a few studies systematically assessed these changes. Better identification of these changes will increase our knowledge and potentially guide therapy, for instance by helping with quicker distinction of bacterially induced exacerbations from other causes.
Aim: To identify which inflammatory parameters increase during COPD exacerbations compared to stable disease, and to compare bacterial and non-bacterial exacerbations.
Methods: In 45 COPD patients (37 male/8 female, 21 current smokers, mean age 65, FEV(1) 52% predicted, pack years 38) sputum was collected during a stable phase and subsequently during an exacerbation.
Results: Sputum total cell counts (9.0 versus 7.9 x 10(6)/mL), eosinophils (0.3 versus 0.2 x 10(6)/mL), neutrophils (6.1 versus 5.8 x 10(6)/mL), and lymphocytes (0.07 versus 0.02 x 10(6)/mL) increased significantly during an exacerbation compared to stable disease. A bacterial infection was demonstrated by culture in 8 sputum samples obtained during an exacerbation. These exacerbations had significantly increased sputum total cell and neutrophil counts, leukotriene-B4, myeloperoxidase, interleukin-8 and interleukin-6, and tumor necrosis factor-alpha (TNF-alpha) levels, and were also associated with more systemic inflammation compared to exacerbations without a bacterial infection. Sputum TNF-alpha level during an exacerbation had the best test characteristics to predict a bacterial infection.
Conclusion: Sputum eosinophil, neutrophil, and lymphocyte counts increase during COPD exacerbations. The increase in systemic inflammation during exacerbations seems to be limited to exacerbations caused by bacterial infections of the lower airways. Sputum TNF-alpha is a candidate marker for predicting airway bacterial infection.