Six-minute-walk test in chronic obstructive pulmonary disease: minimal clinically important difference for death or hospitalization

Abstract Rationale & OBJECTIVES: Outcomes other than spirometry are required to assess non-bronchodilator therapies for chronic obstructive pulmonary disease. Estimates of the minimal clinically important difference for the six minute walk distance have been derived from narrow cohorts using non-blinded intervention. METHODS: Data from the ECLIPSE cohort were used (N=2112). Death or first hospitalization were index events; we measured change in six minute walk distance in the 12 month period before the event and also related change in six minute walk distance to lung function and St Georges Respiratory Questionnaire (health status). Measurement and MAIN RESULTS: Of subjects with change in the six minute walk distance data, 94 died and 323 were hospitalized. Six minute walk distance fell by 29.7 (SD=82.9)m more in those who died than survivors (P <0.001). A change in distance of more than -30m conferred a hazard ratio of 1.93 (95% confidence interval: 1.29, 2.90; P = 0.001) for death. No significant difference was observed for first hospitalization. Weak relationships only were observed with change in lung function or health status. CONCLUSIONS: A fall in the six minute walk distance of 30m or more is associated with increased risk of death but not hospitalization due to exacerbation in patients with chronic obstructive pulmonary disease and represents a clinically significant minimally important difference.