Minimally Important Difference of the 20-m 6-Min Walk Test in Individuals With COPD.

Abstract

The 20-m 6-min-walk test (6MWT20) is a valid, reliable alternative for functional capacity assessment; however, its responsiveness and minimally important difference (MID) have yet to be investigated. The aim of this study was to assess the responsiveness and MID of the 6MWT20 in individuals with COPD. Fifty-three subjects completed the study from August 2011-March 2020. The following were assessed: lung function, activities of daily living (ADLs), functional capacity 6MWT20, dyspnea, health status, quality of life, and limitations in ADLs. The primary outcome was the 6MWT20 distance. The study demonstrated that the 6MWT20 is responsive to pulmonary rehabilitation (PR), with an average improvement of 39 ± 36.3 m (P < .001) and an effect size of 1.07. The learning effect declined to 1.45% after PR, with an intraclass correlation coefficient of 0.99 (95% CI 0.98-0.99). The receiver operating characteristic curve indicated a cutoff point of 20 m for the MID of the 6MWT20 based on the MIDs for the modified St George Respiratory Questionnaire (sensitivity 87%, specificity 69%, area under the curve 0.80 [95% CI 0.66-0.90], P < .001, Youden index 0.56) and the number of steps (sensitivity 92%, specificity 73%, area under the curve 0.83 [95% CI 0.70-0.92], P < .01, Youden index 0.56). The 6MWT20 is responsive to PR, and the MID for the test is 20 m (17-47 m).