To investigate the relationship between lung function and exercise capacity in adults with cystic fibrosis (CF), and to develop a CF-specific equation to predict Modified Shuttle Test (MST) performance from baseline data.
Cross-sectional, retrospective study.
Adult CF centre.
One hundred and twenty-seven patients with CF [61 male; mean age 25 years (range 17 to 52 years), mean forced expiratory volume in 1 second (FEV1) 56% predicted (range 15 to 124%)].
Main outcome measures
MST and FEV1.
Overall, a moderate-to-good relationship was found between lung function and MST performance (walking distance vs FEV1% predicted: r = 0.64, P = 0.01). This relationship between FEV1 and MST shows an obvious threshold at an FEV1 of 67% predicted. Above this threshold, no significant association was observed between FEV1 and MST performance. However, a strong relationship (MST vs FEV1% predicted: r ≥ 0.74, P < 0.01 for men and r = 0.79, P < 0.01 for women) was found below an FEV1 of 67% predicted.
This study suggests that a strong association exists between lung function (FEV1% predicted) and MST (walking distance) in adult patients with moderate-to-severe CF (FEV1 < 67% predicted). A reference equation for MST performance was developed for those patients with FEV1 ≤67% predicted, providing a tool to make an a-priori prediction of MST walking distance.
Relationship between lung function and Modified Shuttle Test performance in adult patients with cystic fibrosis: a cross-sectional, retrospective study.