Sputum is recognized as a very useful sampling method in CF for both research and clinical use aiding both the diagnosis and monitoring of lung disease inflammatory status. A great advantage of the technique is that it enables sampling of the airways in a non-invasive manner, in contrast with other methods such as bronchial biopsy, bronchial brushing and broncho-alveolar lavage, all of which require bronchoscopy, discomfort and risk that it entails [15] . Furthermore, sputum may contain protein/peptide components that could act as biomarkers of disease or its severity [16] .