Analysis of Sequential Aliquots of Hypertonic Saline Solution-Induced Sputum: Summary
Microbiology results suggested SI may be a useful tool in the multicentered research setting. Aliquots of induced sputum appear to provide a representative sample as quantitative bacterial cultures only varied by approximately a half-log count over time. In standard induced-sputum sample processing, di-thiothreitol has to be added to the sputum sample to homogenize it. However, the addition of dithiothre-itol decreases microbiological counts after 2 h. Thus, for multicenter studies, when microbiological samples may be sent to a centralized laboratory, it appears that a sample from the first 4-min aliquot may vary from the last aliquot by a half-log count.
Inflammatory mediators were found in concentrations equivalent to or greater than those previously reported in patients with CF.- The presence of hypertonic saline solution may increase the amount of Na+ and Cl— in airway surface liquid and rehydrate the periciliary fluid. Hyperosmo-larity has been shown to stimulate IL-8 production in human bronchial epithelial cells in vitro,39 but we doubt that a 20-min exposure to hypertonic saline solution in vivo would allow adequate time to increase intracellular IL-8 production. Buy Flovent
Type II alveolar epithelial cells are responsible for producing and secreting surfactant and most of the surfactant-associated proteins (SP-A, SP-B, SP-C, and SP-D) into the alveolar lining fluid. Deficiencies in SP-A and SP-D in lavage fluid have been documented in various human inflammatory lung diseases, including pneumonia, ARDS, and CF. Greene et al demonstrated that reduced levels of SP-D in BAL fluid from patients with ARDS are associated with a worse outcome. Greene et al hypothesize that the low surfactant levels are not just a biomarker of acute lung injury, but that their absence exacerbates the dysfunctional inflammation characteristic of acute lung injury. As anticipated, the concentration of SP-A increased in the later time samples in our study, reflecting that the content of these later samples contained more alveolar fluid.
Sputum induction has become a well-validated research tool for evaluating a variety of indexes of inflammation, both cellular and humoral, in non-CF diseases of the airways such as asthma. This study demonstrates that SI is well tolerated and provides valid information regarding the markers of inflammation and the microbiology of the airways in subjects with CF. If patients or research subjects are able to expectorate at least 1 mL of sample using hypertonic saline solution, then this can provide an adequate sample for clinical information. However, further studies are needed to examine modest, but significant changes in CF pathogen density and PMN count for use of serial aliquots as outcome measurements in clinical trials.
In summary, fractional analysis of induced sputum from clinically stable CF subjects shows that aliquots of induced sputum provide representative samples for microbiologic and inflammatory indexes, and this suggests it should be possible to apply the varied processing methodologies necessary for different outcome measurements in multicenter studies.