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) l 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.