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
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
(Sao2; 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
Sao2, 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
(FEV1, SRM = 0.96; FEV1 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.