Analysis of Sequential Aliquots of Hypertonic Saline Solution-Induced Sputum: Materials and Methods
We have previously shown that SI may provide a more representative airway sample than BAL in patients with CF. When SI is compared with BAL and expectorated sputum (ES), SI had a lower percentage of squamous cells than ES, all three techniques had a similar nonsquamous cell differential count, quantitative microbiology correlated best between ES and SI, and cytokine measurements by all three techniques were similar once corrected for the dilution of BAL.
The current study sought to determine whether a sputum sample obtained after a short time period (4 min) may reflect that of a longer time period, to examine whether 20 min of SI collection would sample the alveolar space as manifest by a change in WBC differential and surfactant concentration, and to determine if aliquots of induced-sputum samples showed changes in microbiologic and inflammatory indexes over time. Here
Subjects were recruited from the CF clinic at the University of Washington, Seattle, WA. All subjects had a proven diagnosis of CF. All subjects were > 18 years old and gave written informed consent for this study, which was approved by the Human Subjects Committee of the University of Washington. All subjects had an initial FEV1 > 40% predicted and were in clinically stable condition. Subjects remained receiving all long-term medications, including antibiotics.
On the day of SI, spirometry was performed at baseline, 10 min after inhalation of 180 μg of albuterol via metered-dose inhaler prior to SI, and 5 min following the completion of SI. Peak flow measurements were obtained every 4 min of the SI procedure to ensure that significant bronchospasm (20% fall) was not occurring. Spirometry was measured in all patients with a Cybermedic spirometer (Cybermedic; Boulder, CO) according to American Thoracic Society guidelines.