CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Minimum clinically important improvement for the incremental shuttle walking test

S J Singh^1,2, P W Jones³, R Evans¹, M D L Morgan¹

¹ Pulmonary Rehabilitation Research Group, Department of Respiratory Medicine and Thoracic Surgery, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Leicester, UK
² Faculty of Health and Life Sciences, Coventry University, Coventry, UK
³ St George’s Hospital, University of London, London, UK

Dr S Singh, Pulmonary Rehabilitation Research Group, Department of Respiratory Medicine and Thoracic Surgery, Glenfield Hospital, University Hospitals of Leicester NHS Trust, Groby Road, Leicester LE3 9QP, UK; sally.singh{at}uhl-tr.nhs.uk

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 (FEV₁) 1.06 (0.53) l and FEV₁/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 to72.9)). 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.

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