Chest
Volume 117, Issue 6, June 2000, Pages 1666-1671
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Clinical Investigations
CYSTIC FIBROSIS
Reliability, Repeatability, and Sensitivity of the Modified Shuttle Test in Adult Cystic Fibrosis

https://doi.org/10.1378/chest.117.6.1666Get rights and content

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 (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.

Section snippets

Materials and Methods

This study consisted of two separate experiments. In the first experiment, the test-retest reliability and repeatability of the MST was assessed by comparing performance on two consecutive MST tests in a group of adult patients with stable CF disease. In the second study, the responsiveness of the MST was determined by assessing the ability of the MST to detect changes in exercise capacity after a course of IV antibiotic treatment for an acute exacerbation of respiratory disease. The study was

Assessment of Test-Retest Reliability of the MST

Table 1 shows the descriptive statistics for the physical characteristics and baseline measurements on each study day. A diversity of patients in terms of age (range, 15 to 69 years) and FEV1 (range, 14 to 72% predicted) were included in this study, demonstrating that the patients exhibited a wide range of disease impairment. There was no significant difference in FEV1, resting Sao2 and heart rate, or resting Borg rating of perceived breathlessness between the two study days (Table 1). This

Discussion

This study shows that the MST is a highly reproducible, repeatable, and responsive measure of exercise capacity in an adult CF population. The reproducibility of the SWT has been previously assessed in COPD and in cardiac populations.9, 14 The original authors of the test found that a practice test was necessary to ensure reliable results in COPD patients.9 This finding has important implications regarding the clinical utility of the SWT as a routine measure of exercise capacity because

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