© 2003 American Thoracic Society
ATS statement on six-minute walk testTo the Editor:We read with interest the American Thoracic Society guidelines for the 6-minute walk test in the July 1 2002 issue of the American Journal of Respiratory and Critical Care Medicine (1). We commend and appreciate the effort to provide reference material to assist in standardizing administration of this useful test, as standardization is essential for comparison of test results. We were surprised to note that the guidelines did not recommend practice walks but rather stated that a practice test is "not needed in most clinical settings" (1). Despite this strong recommendation, the guidelines state in the next paragraph that performance plateaus after two tests. In fact, studies of repeated testing have shown that performance on the 6-minute walk test is unstable on the initial two walks and becomes consistent on the third, suggesting the necessity of two practice walks for individuals with cardiorespiratory disease (2–5). The issue of practice walks and the established learning effects are important to interpretation of outcomes. An improvement in distance walked as a result of learning may erroneously be interpreted as a positive treatment effect. Therefore, to allow for comparability of results across trials and to avoid misinterpretation of results for individuals with cardiorespiratory disease, we propose having subjects perform two practice walks as a routine procedure.
a University of Toronto Toronto, Ontario, Canada FOOTNOTES Dr. Crapo and his fellow committee members were given an opportunity to respond to this letter, but declined to do so. REFERENCES
To the Editor:I congratulate the committee members who composed the recent ATS Statement on the 6-minute walk test (1). This well crafted statement provides excellent guidance to clinicians in the international pulmonary rehabilitation community (1). However, I would like to respectfully point out an omission: the statement mentions on page 111 in the "Purpose & Scope" section that draft versions were based on a "... comprehensive Medline literature search from 1970 through 2001, augmented by suggestions from other committee members." Despite this, the statement mentions that certain published sets of reference values are available to clinicians to use in the absence of standardized procedures (2, 3). I respectfully submit that our work (4) published in 2001 had certain currently unique contributions that the other and published sets of 6-minute walk test reference values mentioned (2, 3) do not have: (1) it is the only published set of reference values so far that we are aware of that included healthy subjects below age 40, and (2) it is the only study where multiple repetitions (a total of four 6-minute walk test performed) were done. A comparison of our reference values (4) with other sets of reference values (2, 3) as applied to a population of patients with chronic obstructive pulmonary disease in our study yielded % predicted values on average 21% lower, which could change interpretation of 6-minute walk test performance significantly. Our "bottom line" message (which, by the way, agrees with recommendations on page 115 of the statement) was that the pulmonary rehabilitation clinician must use reference values appropriate to age group and number of repetitions employed during testing, among other considerations, to avoid misinterpretation of 6-minute walk test results in patients (e.g., overestimation of 6-minute walk test performance). Although this work (4) was unintentionally overlooked by the committee, the authors (4) believe it should be considered for use by pulmonary rehabilitation clinicians in selected circumstances as described until more standardized sets of reference values called for by the statement become available in the future.
Kaleida-Buffalo General Hospital Buffalo, New York FOOTNOTES Dr. Crapo and his fellow committee members were offered an opportunity to respond to Dr. Gibbons, but declined to do so. REFERENCES
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