Reliability, agreement, and responsiveness of a 6-minute walk/run test in patients with heart disease

BACKGROUND: The 6-minute walk test (6 MWT) is widely used to assess exercise tolerance in cardiac rehabilitation (CR). However, previous research shows it to be insufficiently responsive, especially for patients with a relatively high maximal exercise tolerance at baseline. We therefore designed a 6-minute walk/run test (6 MWRT), which has the same duration as the 6 MWT but allows running. The objective of this study was to determine the test-retest reproducibility and responsiveness of this 6 MWRT. DESIGN: Responsiveness was investigated in a prospective cohort study among a group of patients entering CR at Maastricht University Medical Center, with a cross-sectional part to assess the test-retest reproducibility. METHODS: Test-retest reproducibility (reliability and agreement) was investigated using the intraclass correlation (ICC) and a Bland-Altman plot of two measurements implemented in the first week of rehabilitation. Responsiveness of the 6 MWT and the 6 MWRT was calculated using the standard response mean (SRM) over a 6-week period. RESULTS: The first reproducibility analysis included 34 patients, the second 22 patients. The ICCs were 0.935 and 0.906, respectively, with limits of agreement of ± 79 and ± 61 m. The responsiveness analysis included 27 patients. The SRM values were 0.83 for the 6 MWT and 0.71 for the 6 MWRT. CONCLUSIONS: Although the 6 MWRT is a reproducible test in CR, its responsiveness is not superior to that of the 6 MWT. We therefore prefer the conventional 6 MWT as an evaluative measurement in CR and advise against using the 6 MWRT as (evaluative) measurement in CR for this purpose.