title: Reliability, construct validity and determinants of 6-minute walk test performance in patients with chronic heart failure.
abstract: BACKGROUND
  In-depth analyses of the measurement properties of the 6-minute walk test (6MWT) in patients with chronic heart failure (CHF) are lacking. We investigated the reliability, construct validity, and determinants of the distance covered in the 6MWT (6MWD) in CHF patients.
  
  
  METHODS
  337 patients were studied (median age 65years, 70% male, ejection fraction 35%). Participants performed two 6MWTs on subsequent days. Demographics, anthropometrics, clinical data, ejection fraction, maximal exercise capacity, body composition, lung function, and symptoms of anxiety and depression were also assessed. Construct validity was assessed in terms of convergent, discriminant and known-groups validity. Stepwise linear regression was used.
  
  
  RESULTS
  6MWT was reliable (ICC=0.90, P<0.0001). The learning effect was 31m (95%CI 27, 35m). Older age (≥65years), lower lung diffusing capacity (<80% predicted) and higher NYHA class (NYHA III) were associated with a lower likelihood of a meaningful increase in the second test (OR 0.45-0.56, P<0.05 for all). The best 6MWD had moderate-to-good correlations with peak exercise capacity (rs=0.54-0.69) and no-to-fair correlations with body composition, lung function, ejection fraction, and symptoms of anxiety and depression (rs=0.04-0.49). Patients with higher NYHA classes had lower 6MWD. 6MWD was independently associated with maximal power output during maximal exercise, estimated glomerular filtration rate and age (51.7% of the variability).
  
  
  CONCLUSIONS
  6MWT was found to be reliable and valid in patients with mild-to-moderate CHF. Maximal exercise capacity, renal function and age were significant determinants of the best 6MWD. These findings strengthen the clinical utility of the 6MWT in CHF.
authors.affiliation: Department of Research & Education, CIRO, Center of Expertise for Chronic Organ Failure, Horn, The Netherlands; Department of Cardiology, Maastricht University Medical Center+ (MUMC+), Maastricht, The Netherlands. Electronic address: n.lencer@mumc.nl.
authors.forename: Nicole H M K
authors.initials: NHMK
authors.lastname: Uszko-Lencer
authors.affiliation: Department of Research & Education, CIRO, Center of Expertise for Chronic Organ Failure, Horn, The Netherlands; Department of Respiratory Medicine, Maastricht University Medical Center+ (MUMC+), Maastricht, The Netherlands.
authors.forename: Rafael
authors.initials: R
authors.lastname: Mesquita
authors.affiliation: Department of Research & Education, CIRO, Center of Expertise for Chronic Organ Failure, Horn, The Netherlands.
authors.forename: Eefje
authors.initials: E
authors.lastname: Janssen
authors.affiliation: Department of Cardiology, Laurentius Hospital, Roermond, The Netherlands.
authors.forename: Christ
authors.initials: C
authors.lastname: Werter
authors.affiliation: Department of Cardiology, Maastricht University Medical Center+ (MUMC+), Maastricht, The Netherlands.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Brunner-La Rocca
authors.affiliation: Laboratory of Research in Respiratory Physiotherapy, Department of Physiotherapy, State University of Londrina (UEL), Londrina, Brazil.
authors.forename: Fabio
authors.initials: F
authors.lastname: Pitta
authors.affiliation: Department of Research & Education, CIRO, Center of Expertise for Chronic Organ Failure, Horn, The Netherlands; Department of Respiratory Medicine, Maastricht University Medical Center+ (MUMC+), Maastricht, The Netherlands.
authors.forename: Emiel F M
authors.initials: EFM
authors.lastname: Wouters
authors.affiliation: Department of Research & Education, CIRO, Center of Expertise for Chronic Organ Failure, Horn, The Netherlands.
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Spruit
mesh_terms: D000368:Aged; D002908:Chronic Disease; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D000070857:Walk Test / Q000379:methods / Q000592:standards*
keywords: Exercise test; Heart failure; Reliability of results