Reliability, repeatability, and sensitivity of the modified shuttle test in adult cystic fibrosis.

STUDY OBJECTIVES

The purpose of this study was to investigate the test-retest reliability, repeatability, and sensitivity of the modified shuttle test (MST) in adult patients with cystic fibrosis (CF).

DESIGN

: Prospective study.

SETTING

Adult CF Unit, Belfast City Hospital.

PATIENTS

: Adult patients with CF.

INTERVENTIONS

Test-retest reliability-none; sensitivity-inpatient IV antibiotic therapy for an acute exacerbation of respiratory disease.

MEASUREMENTS

The test-retest reliability and repeatability of the MST was assessed by comparing performance on two consecutive MSTs performed in 12 patients with CF and stable disease. The sensitivity of the MST was assessed by measuring the change in MST performance after 2 weeks of IV antibiotic therapy in 24 patients admitted to hospital with acute exacerbations of their respiratory disease.

RESULTS

In the assessment of test-retest reliability and repeatability (n = 12), there was a significant and strong correlation between trials for distance completed (Pearson's r = 0. 99; p < 0.01), peak heart rate (Pearson's r = 0.99; p < 0.01), peak arterial oxygen saturation (SaO(2); Pearson's r = 0.99; p < 0.01), and peak Borg rating of perceived breathlessness (Pearson's r = 0. 99; p < 0.01). The coefficients of repeatability for these variables were small (coefficient of repeatability: distance completed, 4 shuttles; peak heart rate, 6 beats/min; peak SaO(2), 4%; and peak Borg rating of perceived breathlessness, 0.9). In the assessment of sensitivity (n = 24), the standardized response mean (SRM) for distance completed on MST (SRM = 1.18) was the SRMs for spirometric measures of lung function (FEV(1), SRM = 0.96; FEV(1) percent predicted, SRM = 0.88).

CONCLUSIONS

This study demonstrates that the MST is a reliable, repeatable, and sensitive measure of exercise capacity in adult CF. The MST may be of value in determining prognosis, evaluation for lung transplantation, exercise prescription, and establishing the impact of new treatments on the disability associated with CF.