Posthoc analysis of sample size calculations for secondary outcome measures
| Outcome analysis | Treatment effect* | Required sample size† |
| FEV1% predicted | –1.8±12.0 | 351 |
| FEV1 (litres) | –0.06±0.2 | 90 |
| FEF25–75% predicted | –5.3±22.3 | 141 |
| FEF25–75 (litres) | –0.1±0.6 | 285 |
| CFQ-R respiratory domain | –5.2±14.2 | 61 |
| CFQ-R parent respiratory domain | –5.9±16.2 | 62 |
↵* Treatment effect between isotonic saline and hypertonic saline treatment periods.
↵† Required number of patients for a crossover trial to achieve 80% power at a 5% significance level.
CFQ-R, Cystic Fibrosis Questionnaire-Revised; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; FEF25–75, forced expiratory flow at 25–75% of the forced vital capacity.