Validity of a modified shuttle test in adult cystic fibrosis.
BACKGROUND
The purpose of this study was to provide some evidence of the validity of a modified shuttle test (MST) by comparing performance on the MST with peak oxygen consumption (VO2peak) measured during a treadmill test in a group of adult patients with cystic fibrosis.


METHOD
Twenty patients with stable cystic fibrosis performed a ramped maximal treadmill test (STEEP protocol) and the MST using a randomised balanced design.


RESULTS
The relationship between the distance achieved on the MST and VO2peak was strong (r = 0.95, p<0.01) with 90% of the variance in VO2peak explained by the variance in MST distance. The relationship was represented by the regression equation (with 95% confidence intervals) VO2peak = 6.83 (2.85 to 10.80) + 0.028 (0.019 to 0.024) x MST distance.


CONCLUSION
This study provides evidence of the construct validity of the MST as an objective measure of exercise capacity in adults with cystic fibrosis.