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6-Minute Walk Distance6-Min Walk Distance: Effect of Instructions FREE TO VIEW

Nitin V. Vanjare, MSc; Rahul R. Kodgule, MD; Bill B. Brashier, MD
Author and Funding Information

From the Department of Pulmonary Research, Chest Research Foundation.

Correspondence to: Nitin V. Vanjare, MSc, Department of Pulmonary Research, Chest Research Foundation, Marigold Complex Kalyaninagar, Pune, Maharashtra 411014, India; e-mail: vanjarenitin@crfindia.com


Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;145(6):1439-1440. doi:10.1378/chest.14-0357
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To the Editor:

We read with great interest the article by Weir et al1 published in CHEST (December 2013). The authors compared the effect of the instruction “walk as fast as you can” (fast walk) with the standard instruction “walk as far as you can in 6 min” (standard walk) for the 6-min walk test (6MWT) in patients with pulmonary arterial hypertension, idiopathic pulmonary fibrosis, and other forms of interstitial lung diseases. They found that patients walked longer distances in 6 min with the fast walk compared with the standard walk. We would like to emphasize that an important component of the applicability of the 6MWT is its ability to reflect activities of daily living over other walk tests.2 In day-to-day life, patients are used to walking at their own pace and not fast. As a result, the reduction in distance of fast walk may not truly reflect an equivalent reduction in patients’ activities of daily living. In addition, for measuring functional capacity, we believe that repeatability of the test, which the authors did not study, is more important.

Another important limitation of the study is the lack of a comparative arm of healthy subjects. The 6-min walk distance is compared with the predicted values obtained from the healthy population for making an interpretation. It is logical that healthy subjects will also walk more distance with the fast walk compared with the standard walk. Hence, it would have been interesting to see whether the increase in walk distance with the fast walk is also seen in terms of percent predicted. We hypothesize that percent predicted values might in fact be lower in patient populations with the fast walk compared with the standard walk.

Guidelines by the American Thoracic Society3 arbitrarily recommend giving a rest of 1 h between successive 6MWTs. Subjects were given a rest of about 15 min between tests in this study, which may potentially have an effect on subsequent tests. We believe that this effect will be larger on tests done after the fast walk compared with the standard walk. If that is true, this effect cannot be nullified by randomization of test instructions. Hence, we believe that it is important to statistically analyze and adjust the effect of order or sequence on the primary outcome.

We appreciate the efforts of the authors in bringing attention to the importance of standardized instructions for 6MWT and the potential effect different instructions can have on the distance walked. However, we believe that the increase in distance walked with the instruction “walk as fast as you can” does not truly reflect the activities of daily living of the patients. We also believe that the effects of previous tests on subsequent tests were not adequately adjusted in analysis to draw reliable conclusions from the study.

References

Weir NA, Brown AW, Shlobin OA, et al. The influence of alternative instruction on 6-min walk test distance. Chest. 2013;144(6):1900-1905.
 
Solway S, Brooks D, Lacasse Y, Thomas S. A qualitative systematic overview of the measurement properties of functional walk tests used in the cardiorespiratory domain. Chest. 2001;119(1):256-270.
 
ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories. ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med. 2002;166(1):111-117.
 

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References

Weir NA, Brown AW, Shlobin OA, et al. The influence of alternative instruction on 6-min walk test distance. Chest. 2013;144(6):1900-1905.
 
Solway S, Brooks D, Lacasse Y, Thomas S. A qualitative systematic overview of the measurement properties of functional walk tests used in the cardiorespiratory domain. Chest. 2001;119(1):256-270.
 
ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories. ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med. 2002;166(1):111-117.
 
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