Abstract
The aims of this study were to determine the test-retest reliability of the duplicated six-minute walk test (6MWT) in patients with chronic heart failure (HF), and to evaluate its variation over time. Forty-six patients (9 women) with HF performed duplicated 6MWT every third month for 1year (5 follow-ups), for a total of 198 paired tests. The patients completed two 6MWT on the same day with a 45-min seated rest between tests. The mean distance in metres, for the first (6MWT1) versus the second (6MWT2), for each follow-up, was 408±100 versus 411±96, 449±94 versus 465±94, 464±96 versus 473±100, 462±103 versus 468±104 and 472±105 versus 482±107. On average, a marginally, clinically insignificant longer walked distance, 9m (2.0%), was seen in the second 6MWT. The standard error of a single determination (Smethod ) ranged from 2.4% to 3.9% over the study period, and the intraclass correlation coefficient (ICC) ranged from 0.96 to 0.99 (CI 95% 0.94-0.99). The variation over time of ICC or Smethod was not statistically significant. The 6MWT is highly reliable over time in patients with HF, and one test is, therefore, sufficient in clinical follow-ups.
Highlights
We found an excellent (Demers et al, 2001) reliability at duplicate measurements during the follow-up of the 6MWT in patients with heart failure (HF), and the 6MWT is suitable for repeated assessments of walked distances
There is a need for a repeatable test capable of assessing the patient's baseline exercise capacity, and detecting any change over time, or as an effect of exercise training or other treatments (Eiser, Willsher, & Dore, 2003)
Patients having heart failure with reduced ejection fraction were studied, which makes it difficult to generalize to other populations with HF
Summary
This longitudinal reliability study reports data from two randomized controlled trials designed to evaluate physical fitness in an exercise programme of which one, far, has been published (Lans, Cider, Nylander, & Brudin, 2018). Of 230 theoretically duplicated 6MWTs (in total 460 walk tests), 35 (76%) patients performed all five follow-ups. The increase in walked distance at each follow-up may result from the exercise intervention in the studies (of which one is published; Lans et al, 2018) from where the data were collected. The Bland–Altman analysis, Figure 1, showed a mean test–retest positive bias of 9 m, that is on average a longer walked distance at the second test (95% limits of agreement −29.4 to 47.3 m) calculated on all performed follow-ups. Note: 6MWT: 6-min walk test; Smethod: the standard error of a single determination expressed as coefficient of variance in % (COV%); and ICC (CI 95%) is intraclass correlation coefficient with 95% confidence interval. There was no statistically significant difference between 6MWT1 and 6MWT2 in the rating of perceived exertion (RPE 6–20), dyspnoea (CR-10) or heart rate pre- and post-testing at any of the follow-ups
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