Analysis of Sequential Aliquots of Hypertonic Saline Solution-Induced Sputum
Hypertonic saline has recently been used as a form of airway clearance in patients with cystic fibrosis (CF),-2 and as a means to obtain a lower airway sample for clinical use from patients who are unable to expectorate spontaneously. However, in high concentration (10%), hypertonic saline solution has been shown to cause bronchospasm in some patients with CF. Although sputum induction (SI) has been recognized as a research tool for over a decade with other airway disease such as asthma and COPD, only very recently has SI has been introduced as an outcome measure in CF.
BAL has been held as the “gold standard” for airway sampling in patients with CF.> BAL has been used to follow serial microbiology cultures, in therapeutic trials, and to monitor inflammatory mediators and other markers of the underlying pathophysiologic mechanisms of CF.> However, there are problems with the BAL sampling technique in patients with CF.
Foremost is the safety issue: young children may require general anesthesia for bronchoscopy and adults require conscious sedation. In addition, the CF lung compartments are not uniform. Inflammation is higher in the upper lobes than in the lower lobes. Some investigators compromise by sampling the lingula.” Thirdly, the volume of saline solution instilled during BAL and whether to separate the first aliquot from later samples have not been standardized. The first aliquot from a CF BAL has a much higher percentage neutrophil count than subsequent samples. Finally, the BAL itself may cause an inflammatory response even in normal subjects. Thus, repeated BAL sampling to examine an airway inflammation outcome measure may lead to information reflecting adverse events from the bronchoscopy with BAL procedure rather than adverse events from the study drug.