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Original Research |

Optimizing the 6-Min Walk Test as a Measure of Exercise Capacity in COPDAdding a Walk to the 6-min Walk Test

Divay Chandra, MD; Robert A. Wise, MD, FCCP; Hrishikesh S. Kulkarni, MD; Roberto P. Benzo, MD, FCCP; Gerard Criner, MD, FCCP; Barry Make, MD, FCCP; William A. Slivka, RPFT; Andrew L. Ries, MD, MPH, FCCP; John J. Reilly, MD, FCCP; Fernando J. Martinez, MD, FCCP; on behalf of the NETT Research Group; Frank C. Sciurba, MD, FCCP
Author and Funding Information

From the Emphysema Research Center (Drs Chandra and Sciurba and Mr Slivka), Division of Pulmonary and Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA; Division of Pulmonary and Critical Care Medicine (Dr Wise), Johns Hopkins University School of Medicine, Baltimore, MD; Department of Medicine (Drs Kulkarni and Reilly), University of Pittsburgh Medical Center, Pittsburgh, PA; Division of Pulmonary and Critical Care Medicine (Dr Benzo), Mayo Clinic, Rochester, MN; Division of Pulmonary and Critical Care Medicine (Dr Criner), Temple University School of Medicine, Philadelphia, PA; Division of Pulmonary Sciences and Critical Care Medicine (Dr Make), National Jewish Medical and Research Center, Denver, CO; Department of Medicine and Family and Preventive Medicine (Dr Ries), University of California, San Diego, CA; and Division of Pulmonary and Critical Care Medicine (Dr Martinez), University of Michigan Medical Center, Ann Arbor, MI.

Correspondence to: Frank C. Sciurba, MD, FCCP, Kaufmann Bldg, Ste 1211, 3471 Fifth Ave, Pittsburgh, PA 15213; e-mail: sciurbafc@upmc.edu


Funding/Support: The National Emphysema Treatment Trial (NETT) is supported by contracts with the National Heart, Lung, and Blood Institute [N01HR76101 through N01HR76119, P50HL084948]; the Centers for Medicare & Medicaid Services; and the Agency for Healthcare Research and Quality. This article is subject to the National Institutes of Health public access policy (http://www.nhlbi.nih.gov/funding/policies/public-access.htm).

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


Chest. 2012;142(6):1545-1552. doi:10.1378/chest.11-2702
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Background:  It is uncertain whether the effort and expense of performing a second walk for the 6-min walk test improves test performance. Hence, we attempted to quantify the improvement in 6-min walk distance if an additional walk were to be performed.

Methods:  We studied patients consecutively enrolled into the National Emphysema Treatment Trial who prior to randomization and after 6 to 10 weeks of pulmonary rehabilitation performed two 6-min walks on consecutive days (N = 396). Patients also performed two 6-min walks at 6-month follow-up after randomization to lung volume reduction surgery (n = 74) or optimal medical therapy (n = 64). We compared change in the first walk distance to change in the second, average-of-two, and best-of-two walk distances.

Results:  Compared with the change in the first walk distance, change in the average-of-two and best-of-two walk distances had better validity and precision. Specifically, 6 months after randomization to lung volume reduction surgery, changes in the average-of-two (r = 0.66 vs r = 0.58, P = .01) and best-of-two walk distances (r = 0.67 vs r = 0.58, P = .04) better correlated with the change in maximal exercise capacity (ie, better validity). Additionally, the variance of change was 14% to 25% less for the average-of-two walk distances and 14% to 33% less for the best-of-two walk distances than the variance of change in the single walk distance, indicating better precision.

Conclusions:  Adding a second walk to the 6-min walk test significantly improves its performance in measuring response to a therapeutic intervention, improves the validity of COPD clinical trials, and would result in a 14% to 33% reduction in sample size requirements. Hence, it should be strongly considered by clinicians and researchers as an outcome measure for therapeutic interventions in patients with COPD.

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