Significance of sputum purulence to guide antibiotic therapy in exacerbations of COPD.

Besides bacteria, viruses and air pollution can also lead to exacerbations of COPD. These episodes are characterised by recruitment of leukocytes (neutrophils, eosinophils, etc.), which leads to sputum purulence. The sputum colour/purulence is strongly correlated with markers of bronchial inflammation, like myeloperoxidase (green coloured) and leukocyte elastase present within these inflammatory cells [2], and may not mandate the bacterial presence. Moreover, isolation of bacteria from sputum may represent bronchial colonisation, especially in conditions with co-existent architectural distortion like bronchiectasis.