The purpose of this study is to determine whether sputum induction is a reproducible method to study airway inflammation in cystic fibrosis. Sputum induction using nebulized hypertonic saline represents a non-invasive method of studying airway inflammation in pulmonary diseases. It has been well established as a method to study airway inflammation in asthma, a disease that is also characterized by airway inflammation and chronic airway obstruction. Studies in asthmatics provide evidence that sputum induction samples the small airways rather than other compartments in the lung. Studies have also demonstrated this method to be safe and reproducible in children with asthma. For studies of airway inflammation in cystic fibrosis patients, investigators analyzed bronchoalveolar lavage fluid and spontaneously expectorated sputum for markers of inflammation. In studying the effects of anti-inflammatory medications, these methods are limited in their applicability. Bronchoscopy cannot be easily repeated in the same subject in a short enough interval to assess changes following an intervention. Additionally, it is invasive and can result in complications. The collection of spontaneously expectorated sputum is less invasive, however, only the more severe patients with cystic fibrosis produce sputum spontaneously, limiting the usefulness of this method. Bronchoalveolar lavage fluid and spontanously expectorated sputum sample the alveolar compartment or upper airway, respectively, not the small airways where disease occurs in cystic fibrosis. Despite the potential of using induced sputum to study airway inflammation in cystic fibrosis, almost no studies have utilized this methodology. If sputum induction proves to be a reproducible method of studying airway inflammation in patients with cystic fibrosis, it will be a powerful tool in studying the effects of new anti-inflammatory medications, specifically anti-elastases, where showing a change in markers of inflammation may be a more useful outcome measure than pulmonary function, which would need to be measured over a long period of time.
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