Minimum clinically important improvement for the incremental shuttle walking test

Background: The incremental shuttle walking test (ISWT) is used to assess exercise capacity in patients with chronic obstructive pulmonary disease ( COPD) and is employed as an outcome measure for pulmonary rehabilitation. This study was designed to establish the minimum clinically important difference for the ISWT. Methods: 372 patients ( 205 men) performed an ISWT before and after a 7-week outpatient pulmonary rehabilitation programme. After completing the course, subjects were asked to identify, from a 5-point Likert scale, the perceived change in their exercise performance immediately upon completion of the ISWT. The scale ranged from better'' to worse''. Results: The mean (SD) age was 69.4 (8.4) years, forced expiratory volume in 1 s (FEV(1)) 1.06 (0.53) I and FEV(1)/forced vital capacity (FVC) ratio 50.8 (18.1)%. The baseline shuttle walking test distance was 168.5 (114.6) m which increased to 234.7 (125.3) m after rehabilitation (mean difference 65.9 m (95% CI 58.9 to 72.9)). In subjects who felt their exercise tolerance was slightly better'' the mean improvement was 47.5 m (95% CI 38.6 to 56.5) compared with 78.7 m (95% CI 70.5 to 86.9) in those who reported that their exercise tolerance was better'' and 18.0 m (95% CI 4.5 to 31.5) in those who felt their exercise tolerance was about the same''. Conclusion: Two levels of improvement were identified. The minimum clinically important improvement for the ISWT is 47.5 m. In addition, patients were able to distinguish an additional benefit at 78.7 m.