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-ret est reliability, repeatability, and sensitivity of the modified shuttle tes t (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 antib iotic 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 p atients 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 the ir respiratory disease. Results: In the assessment of test-retest reliability and repeatability (n = 12), there was a significant and strong correlation between trials for di stance 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 (Pearso n's r = 0.99; p < 0.01). The coefficients of repeatability for these variab les were small (coefficient of repeatability: distance completed, 4 shuttle s; peak heart rate, 6 beats/min; peak Sao(2), 4%; and peak Borg rating of p erceived breathlessness, 0.9). In the assessment of sensitivity (n = 24), t he standardized response mean (SRM) for distance completed on MST (SRM = 1. 18) was the SRMs for spirometric measures of lung function (FEV1, SRM = 0.9 6; 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, exerc ise prescription, and establishing the impact of new treatments on the disa bility associated with CF.