Chronic obstructive pulmonary disease phenotyping: a possible role for 8-isoprostane measurement in exhaled breath condensate?

sis of sputum cells, a semi-invasive technique, in patients with stable COPD of different severity. The authors show that 8-isoprostane concentrations in EBC are correlated with the dyspnea score and emphysematous changes which were assessed by high-resolution computerized tomography. No correlation between 8-isoprostane levels in EBC and lung function and COPD severity based on Global Initiative for Chronic Obstructive Lung Disease classification was observed. These findings are relevant as they suggest that measurement of 8-isoprostane concentrations in EBC might help identify the patients with COPD with a predominant emphysematous component and might be used with high-resolution computerized tomography to assess the extension of emphysema. The association between 8-isoprostane concentrations in EBC and dyspnoea score can also prompt prospective studies aimed at investigating whether targeting elevated lipid peroxidation with pharmacological treatment improves symptoms in patients with COPD. As it is completely noninvasive, measurement of 8-isoprostane concentrations in EBC could also be used in the longitudinal assessment of patients with COPD and to evaluate the response to pharmacological therapy. However, larger studies are required to definitively establish the relationships between 8-isoprostane in EBC and clinical, functional and inflammatory parameters in patients with COPD. Oxidative stress, which is a central component of the inflammatory process, is functionally involved in the pathophysiology of chronic obstructive pulmonary disease (COPD) [1] . The presence of 8-isoprostane, one of the most reliable biomarkers of oxidative stress [2] , in exhaled breath condensate (EBC), a completely noninvasive method for studying the composition of airway lining fluid [3] , has been definitively demonstrated by gas chromatography/mass spectrometry [4] , a reference analytical technique. This study also excluded a possible salivary origin of 8-isoprostane in EBC samples as subjects were intubated. Using immunoassays, 8-isoprostane in EBC has been shown to be elevated in patients with COPD [5–7] . Identifying phenotypes of COPD with a predominant emphysema or chronic bronchitis may have important implications for the management of patients with COPD, as patients with emphysema are less likely to benefit from pharmacological treatment. This goal has been partially achieved by computed tomography measurements of airway dimensions and emphysema in smokers with or without airflow obstruction [8] . In the current issue of Respiration , Makris et al. [9] investigated the relationships between lipid peroxidation as reflected by 8-isoprostane concentrations in EBC and clinical parameters, lung function, radiologic parameters and airway inflammation, which was assessed by analy-