title: Reproducibility of 6-minute walking test in patients with COPD.
abstract: The reproducibility of the 6-min walking test (6MWT) needs to be more solidly studied. This study aimed to investigate the reproducibility of two 6MWTs performed on subsequent days in a large and representative sample of patients with chronic obstructive pulmonary disease (COPD), and to quantify the learning effect between the two tests, as well as its determinants. In a retrospective observational study, 1,514 patients with COPD performed two 6MWTs on subsequent days. Other measurements included body composition (dual X-ray absorptiometry), dyspnoea (Medical Research Council scale) and comorbidity (Charlson index). Although the 6MWT was reproducible (intraclass correlation coefficient = 0.93), patients walked farther in the second test (391 m, 95% CI 155-585 m versus 418 m, 95% CI 185-605 m; p<0.0001). On average, the second 6MWT increased by 27 m (or 7%), and 82% of patients improved in the second test. Determinants of improvement ≥ 42 m in the second test (upper limit of the clinically important change) were as follows: first 6MWT <350 m, Charlson index <2 and body mass index <30 kg · m(-2) (OR 2.49, 0.76 and 0.60, respectively). The 6MWT was statistically reproducible in a representative sample of patients with COPD. However, the vast majority of patients improved significantly in the second test by an average learning effect of 27 m.
authors.affiliation: Program Development Centre, CIRO+, Centre of Expertise for Chronic Organ Failure, Hornerheide 1, 6085 NM Horn, The Netherlands. nyhernandes@gmail.com
authors.forename: N A
authors.initials: NA
authors.lastname: Hernandes
authors.forename: E F M
authors.initials: EF
authors.lastname: Wouters
authors.forename: K
authors.initials: K
authors.lastname: Meijer
authors.forename: J
authors.initials: J
authors.lastname: Annegarn
authors.forename: F
authors.initials: F
authors.lastname: Pitta
authors.forename: M A
authors.initials: MA
authors.lastname: Spruit
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D004417:Dyspnea / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016138:Walking / Q000502:physiology*