Sputum induction as a research tool for sampling the airways of subjects with cystic fibrosis

Background-Sputum induction (SI) has proved to be a reliable non-invasive t ool for sampling inflammatory airway contents in asthma, with distinct adva ntages over collection of expectorated sputum (ES) and bronchoalveolar lava ge (BAL). A study was undertaken to evaluate the safety of SI and to assess if it might be an equally valuable outcome tool in patients with cystic fi brosis (CF). Methods-The safety of the procedure was examined and sample volume, cell co unts, cytokine concentrations, and bacterial culture results obtained by SI , spontaneous ES, and fibreoptic bronchoscopy were compared in 10 adults wi th CE Results-SI was well tolerated and was preferred to BAL by all subjects. The mean (SE) sample volume obtained by SI was significantly greater than ES ( 6.74 (1.46) ml v 1.85 (0.33)ml, p = 0.005). There was no significant differ ence in the number of cells per mi of sample collected. There was a differe nce in the mean (SD) percentage of non-epithelial, nonsquamous cells collec ted (67 (28)%, 86 (21)%, and 99 (1)% for ES, SI, and BAL, respectively). Th ese percentage counts were different between ES and both SI and BAL (p=0.03 and p=0.006, respectively). Cell differential counts (excluding squamous c ells) from all collection methods were similar (mean (SD) 84 (9)%, 87 (7)%, and 88 (11)% polymorphonuclear cells for ES, SI, and BAL, respectively). T he concentrations of interleukin (IL)-8 and tumour necrosis factor (TNF)-al pha were the same in all three samples when corrected for dilution using ur ea concentration. The test specific detection rate for recovery of bacterio logical pathogens was 79% for SI, 76% for ES, and 73% for BAL. Conclusion-SI offers safety advantages over BAL and may be a more represent ative airway outcome measurement in patients with CF.