title: Six-minute walking test in children with ESRD: discrimination validity and construct validity.
abstract: The six-minute walking test (6MWT) may be a practical test for the evaluation functional exercise capacity in children with end-stage renal disease (ESRD). The aim of this study was to investigate the 6MWT performance in children with ESRD compared to reference values obtained in healthy children and, secondly, to study the relationship between 6MWT performance with anthropometric variables, clinical parameters, aerobic capacity and muscle strength. Twenty patients (13 boys and seven girls; mean age 14.1 +/- 3.4 years) on dialysis participated in this study. Anthropometrics were taken in a standardized manner. The 6MWT was performed in a 20-m-long track in a straight hallway. Aerobic fitness was measured using a cycle ergometer test to determine peak oxygen uptake (V O(2peak)), peak rate (W(peak)) and ventilatory threshold (VT). Muscle strength was measured using hand-held myometry. Children with ESRD showed a reduced 6MWT performance (83% of predicted, p < 0.0001), irrespective of the reference values used. The strongest predictors of 6MWT performance were haematocrit and height. Regression models explained 59% (haematocrit and height) to 60% (haematocrit) of the variance in 6MWT performance. 6MWT performance was not associated with V O(2peak), strength, or other anthropometric variables, but it was significantly associated with haematocrit and height. Children with ESRD scored lower on the 6MWT than healthy children. Based on these results, the 6MWT may be a useful instrument for monitoring clinical status in children with ESRD, however it cannot substitute for other fitness tests, such as a progressive exercise test to measure V O(2peak) or muscle strength tests.
authors.affiliation: Department of Pediatric Physical Therapy & Exercise Physiology, Wilhelmina Children's Hospital, University Medical Centre Utrecht, The Netherlands. t.takken@umcutrecht.nl
authors.forename: Tim
authors.initials: T
authors.lastname: Takken
authors.forename: Raoul
authors.initials: R
authors.lastname: Engelbert
authors.forename: Monique
authors.initials: M
authors.lastname: van Bergen
authors.forename: Jaap
authors.initials: J
authors.lastname: Groothoff
authors.forename: Jeroen
authors.initials: J
authors.lastname: Nauta
authors.forename: Koen
authors.initials: K
authors.lastname: van Hoeck
authors.forename: Marc
authors.initials: M
authors.lastname: Lilien
authors.forename: Paul
authors.initials: P
authors.lastname: Helders
mesh_terms: D000293:Adolescent; D001827:Body Height; D016022:Case-Control Studies; D002648:Child; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006400:Hematocrit; D006801:Humans; D007676:Kidney Failure, Chronic / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D012016:Reference Values; D015203:Reproducibility of Results; D016138:Walking / Q000502:physiology*