Reliability, validity, and responsiveness of a 2-min walk test to assess exercise capacity of COPD patients

Purpose: To investigate the reliability, validity, and responsiveness of a 2-min walk test (2MWT) in Chinese COPD patients with moderate-to-severe disease. Methods: This study consisted of two parts. Forty-seven stable COPD patients with moderate-to-severe disease participated in the first part of study for the investigation of reliability and validity. The demographic and anthropomorphic data collected included age, gender, body weight, height, and body mass index. Each subject performed a pulmonary function test, a cardiopulmonary exercise test, three trials of a 2MWT, and two trials of 6-min-walk test (6MWT) in random order within a 5-day period. Fifteen of these subjects participated in the second part of study for the evaluation of the responsiveness of the 2MWT following pulmonary rehabilitation. The 2MWT and 6MWT were conducted before and after the program for comparison. Results: Forty-five subjects (mean [+/- SD] age, 71.8 +/- 8.3 years; mean FEV, 0.88 +/- 0.27 L) completed the first part of study, and 9 subjects (mean age, 74 8.7 years; mean FEV, 0.94 +/- 0.28 L) completed the second part of study. The intraclass correlation coefficient of the repeated 2MWTs was high (R = 0.9994; p < 0.05), mean differences across trials ranged from 0.3 to 0.8 in (95% confidence interval, -3.1 to 4.6 m) demonstrated its high test-retest reliability. Significant correlations were found between the 2MNW and the 6MWT, the maximum oxygen uptake (V(O2)max) in milliliters per minute, and the V(O2)max in milliliters per kilogram per minute (r = 0.937, 0.454, and 0.555 respectively; p < 0.0125). Following rehabilitation, there were significant improvements in the mean 2MMT and 6MWT walking distance of 17.2 +/- 13.8 m and 60.6 35.5 m, respectively, with moderate effect sizes (0.61 and 0.53, respectively) and large standardized mean responses (1.25 and 1.70, respectively). High correlation was found between changes in the 2MWT and the 6MWT (r = 0.70; p < 0.05). Conclusion: The 2MWT was shown to be a reliable and valid test for the assessment of exercise capacity and responsive following rehabilitation in patients with moderate-to-severe COPD. It is practical, simple, and well-tolerated by patients with severe COPD symptoms.