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

Abstract

Rationale: Outcomes other than spirometry are required to assess nonbronchodilator therapies for chronic obstructive pulmonary disease. Estimates of the minimal clinically important difference for the 6-minute-walk distance (6MWD) have been derived from narrow cohorts using nonblinded intervention. Objectives: To determine minimum clinically important difference for change in 6MWD over 1 year as a function of mortality and first hospitalization in an observational cohort of patients with COPD. Methods:Data fromtheECLIPSEcohortwereused(n=2,112).Death or first hospitalizationwere indexevents;wemeasured change in6MWDin the 12-month period before the event and related change in 6MWD to lungfunctionandSt. George'sRespiratoryQuestionnaire (healthstatus). Measurement and Main Results: Of subjects with change in the 6MWD data, 94 died, and 323 were hospitalized. 6MWD fell by 29.7 m (SD, 82.9 m) more among those who died than among survivors (P<0.001). A reduction in distance of more than 30 m conferred a hazard ratio of 1. 93(95%confidenceinterval, 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 reduction in the 6MWD of 30 m or more is associated withincreased riskofdeath butnot hospitalizationdueto exacerbation in patientswith chronic obstructive pulmonary disease and represents a clinically significantminimally important difference. Copyright © 2013 by the American Thoracic Society.