Divay Chandra1, Robert A Wise2, Hrishikesh S Kulkarni3, Roberto P Benzo4, Gerard Criner5, Barry Make6, William A Slivka1, Andrew L Ries7, John J Reilly3, Fernando J Martinez8, Frank C Sciurba9. 1. Emphysema Research Center, Division of Pulmonary and Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA. 2. Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD. 3. Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA. 4. Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN. 5. Division of Pulmonary and Critical Care Medicine, Temple University School of Medicine, Philadelphia, PA. 6. Division of Pulmonary Sciences and Critical Care Medicine, National Jewish Medical and Research Center, Denver, CO. 7. Department of Medicine and Family and Preventive Medicine, University of California, San Diego, CA. 8. Division of Pulmonary and Critical Care Medicine, University of Michigan Medical Center, Ann Arbor, MI. 9. Emphysema Research Center, Division of Pulmonary and Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA. Electronic address: sciurbafc@upmc.edu.
Abstract
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.
RCT Entities:
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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