Researchers have found that the distance patients cover during the 6-minute walk test (6MWT) depends on the instructions they are given, indicating that changing the current protocol may enhance the accuracy and reproducibility of the test.
Steven Nathan and colleagues, from the Inova Fairfax Hospital in Falls Church, Virginia, USA, show that when patients were told to complete the test “as fast as possible” they walked over 50 m more than patients given the standard instruction to walk “as far as possible.”
“[W]ith the focus on endurance rather than speed, it is possible that patients may have variable strategies of how best to pace themselves, even from visit to visit,” the team comments.
“This may partly explain why change in the 6MWT distance is not a good predictor of outcomes, as opposed to the predictive ability of the baseline distance.”
The researchers studied 24 patients with pulmonary arterial hypertension, idiopathic pulmonary fibrosis, and other forms of interstitial lung disease. Each patient completed four 6MWT with a 15-minute interval between, and were given a different instruction each time: “walk as far as you can” (standard walk); “walk as fast as you can” (fast walk); “walk at your normal pace” (normal walk); and “walk at a leisurely pace” (leisure walk).
Patients walked the shortest distances during the leisure and normal walks, at 354 m and 413 m, respectively. They walked the furthest during the fast walk, at a mean of 547 m, which was significantly further than the mean of 494 m during the standard walk. Overall, 87.5% of patients walked further during the fast walk than the standard walk.
Writing in Chest, Nathan and colleagues say that the wide range of distances attained during the different tests, at an average intrapatient range of 199 m, underscores the importance of the pretest instruction on determining how far patients walk.
The team acknowledges that their findings will need further validation in a larger number of patients across different disease groups and severity. Nevertheless, they conclude that the data “suggest that consideration be given to changing the standard 6MWT instruction to maximize the distance and thereby possibly reduce the inherent intrapatient variability that undermines the usefulness of this test and its use in a serial fashion.”
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