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 ((V) over dot O-2 peak) 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 (V) over dot O-2 peak was strong (r = 0.95, p < 0.01) with 90% of the variance in (V) over dot o(2) peak explained by the variance in MST distance. The relationship was represented by the regression equation (with 95% confidence intervals) (V) over dot o(2) peak = 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.