Measuring walking speed in COPD: test-retest reliability of the 30-metre walk test and comparison with the 6-minute walk test

Abstract

To examine test-retest reliability of the 30-metre walk test (30mWT) in patients with chronic obstructive pulmonary disease (COPD) and to compare the 30mWT with the 6-minute walk test (6MWT). Forty-nine subjects with stable COPD were included. The 30mWT consists of walking at different walking intensities over a distance of 30 metres - self-selected speed (ss-30mWT) and maximal speed (ms-30mWT). The test was conducted twice and the time to walk 30 metres was recorded. The 6MWT was performed in duplicate on the same day. Test-retest reliability was high: intraclass correlation coefficient (ICC(2.1)) = 0.93 (95% CI 0.87 to 0.97) for maximal walking speed and 0.87 (95% CI 0.78 to 0.93) for self-selected walking speed. Both maximal and self-selected speed had a standard error of measurement (SEM) of 0.07 m/s and SEM% was 4.4 for maximal speed and 5.9 for self-selected speed. The correlation, criterion validity, between ms-30mWT and the 6MWT was r=0.78 (p<0.001). Heart rate, dyspnoea, exertion and oxygen saturation were more affected after the 6MWT than after the 30mWT (p<0.001). The 30mWT is a reliable submaximal test that is easy to perform and can be used to measure physical function (walking ability) in patients with COPD. It may be well suited for primary care settings.