title: Six-minute-walk test in chronic obstructive pulmonary disease: minimal clinically important difference for death or hospitalization.
abstract: BACKGROUND
  Outcomes other than spirometry are required to assess nonbronchodilator therapies for chronic obstructive pulmonary disease. Estimates of the minimal clinically important difference for the 6-minute-walk distance (6MWD) have been derived from narrow cohorts using nonblinded intervention.
  
  
  OBJECTIVE
  To determine minimum clinically important difference for change in 6MWD over 1 year as a function of mortality and first hospitalization in an observational cohort of patients with COPD.
  
  
  METHODS
  Data from the ECLIPSE cohort were used (n = 2,112). Death or first hospitalization were index events; we measured change in 6MWD in the 12-month period before the event and related change in 6MWD to lung function and St. George's Respiratory Questionnaire (health status).
  
  
  RESULTS
  Of subjects with change in the 6MWD data, 94 died, and 323 were hospitalized. 6MWD fell by 29.7 m (SD, 82.9 m) more among those who died than among survivors (P < 0.001). A reduction in distance of more than 30 m conferred a hazard ratio of 1.93 (95% confidence interval, 1.29-2.90; P = 0.001) for death. No significant difference was observed for first hospitalization. Weak relationships only were observed with change in lung function or health status.
  
  
  CONCLUSIONS
  A reduction in the 6MWD of 30 m or more is associated with increased risk of death but not hospitalization due to exacerbation in patients with chronic obstructive pulmonary disease and represents a clinically significant minimally important difference.
authors.affiliation: NIHR Respiratory Biomedical Research Unit at the Royal Brompton Hospital and Imperial College London, London, United Kingdom. polkey@rbht.nhs.uk
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Spruit
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Edwards
authors.forename: Michael L
authors.initials: ML
authors.lastname: Watkins
authors.forename: Victor
authors.initials: V
authors.lastname: Pinto-Plata
authors.forename: Jørgen
authors.initials: J
authors.lastname: Vestbo
authors.forename: Peter M A
authors.initials: PM
authors.lastname: Calverley
authors.forename: Ruth
authors.initials: R
authors.lastname: Tal-Singer
authors.forename: Alvar
authors.initials: A
authors.lastname: Agustí
authors.forename: Per S
authors.initials: PS
authors.lastname: Bakke
authors.forename: Harvey O
authors.initials: HO
authors.lastname: Coxson
authors.forename: David A
authors.initials: DA
authors.lastname: Lomas
authors.forename: William
authors.initials: W
authors.lastname: MacNee
authors.forename: Stephen
authors.initials: S
authors.lastname: Rennard
authors.forename: Edwin K
authors.initials: EK
authors.lastname: Silverman
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Miller
authors.forename: Courtney
authors.initials: C
authors.lastname: Crim
authors.forename: Julie
authors.initials: J
authors.lastname: Yates
authors.forename: Emiel F M
authors.initials: EF
authors.lastname: Wouters
authors.forename: Bartolome
authors.initials: B
authors.lastname: Celli
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005080:Exercise Test / Q000379:methods* / Q000706:statistics & numerical data*; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006304:Health Status; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology*; D013147:Spirometry; D011795:Surveys and Questionnaires; D016019:Survival Analysis; D016138:Walking