To the Editor:
We read with interest the study by Soler et al. 1 evaluating role of sputum purulence as a guide for antibiotic use in hospitalised patients with exacerbations of chronic obstructive pulmonary disease (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.
In the study by Soler et al. 1, sputum purulence was used as a criterion to initiate antibiotics. It would have been more representative if serial sputum examinations (for purulence) were used to decide the duration of antibiotics as well, thus correlating sputum purulence with total antibiotic exposure. In addition, excluding sick and recently treated patients from the study might have decreased the predictive value of sputum purulence as these patients are more likely to suffer from bacterial infections.
Absence of sputum purulence cannot rule out bacterial infection reliably 3. In fact, comprehensive evaluation of presumptive signs and symptoms (fever, increased breathlessness and increase in sputum volume/purulence) along with relevant haematological investigations and supported by a physician’s decision to treat are the major parameters guiding the use of antibiotics. Instead of conducting randomised control trials on sputum purulence, it may be useful if studies are conducted to evaluate new biomarkers of bacterial infectivity with better sensitivity and specificity and correlate them with crude indicators like sputum purulence.
Footnotes
Statement of Interest
None declared.
- ©ERS 2013