Analysis of Sequential Aliquots of Hypertonic Saline Solution-Induced Sputum: Sample Size Calculations
The null hypothesis for these tests was that sampling times, taken together, had no effect on the outcome of interest. A test for linear time trend was also performed for each outcome measure by fitting a regression in which time was modeled as a continuous variable. Finally, the mean change calculated as the 20-min value minus the 4-min value with 95% confidence intervals (CIs) was calculated.
This was a pilot study. There was no prior information from which a sample size calculation could be made. However, we performed a post hoc power analysis to determine what size effect could have been missed given the sample and results of our pilot study.
Results Demographic and Safety Profile
Ten patients with CF (eight male) entered and completed the study. Three patients were homozygous for DF508, six patients were heterozygous for DF508, and one patient’s alleles were G551D/ N1303K. Mean age was 28 ± 7 years (range, 18 to 38 years). Three subjects were prescribed inhaled tobramycin and one patient was prescribed oral ciprofloxacin at the time of the collection. Four adverse events occurred in three subjects, including throat irritation in three subjects and headache in one subject. The baseline prealbuterol FEV1 was 2.58 ± 0.73 L/min (66 ± 16% predicted; range, 48 to 97%). The postalbuterol FEV1 was 2.74 ± 0.74 L/min (71 ± 16% predicted; range, 51 to 98%). The FEV1 fell an average of 7 ± 7% predicted, with a range of zero to 17.6% predicted. Two patients had a > 15% fall in FEV1. This fall in FEV1 was seen at the end of the 20-min collection, as no subject had to prematurely stop the collection because of a 20% fall in peak flow measurement at any time point. canada health and care mall
The sample volumes determined by weight were 3.0 ± 1.8 mL, 2.8 ± 1.5 mL, 4.6 ± 6.6 mL, 4.8 ± 5.1 mL, and 3.8 ± 2.1 mL, collected at 4, 8, 12, 16, and 20 min, respectively. The mean change from the 0- to 4-min sample to the 16- to 20-min sample was 0.81 mL (95% CI, — 0.43 to 2.05). There was no significant difference in volume of induced-sputum aliquots over time (p = 0.12).