title: Agreements and discrepancies between the estimated walking distance, nongraded and graded treadmill testing, and outside walking in patients with intermittent claudication.
abstract: BACKGROUND
  Disease severity in patients with intermittent claudication (IC) is often assessed using walking distances and treadmill tests. The aim of this study was to determine the agreement between walking distance as estimated by the patient, as measured during outside walking, and as determined using a nongraded treadmill protocol (NGTP), and an incremental graded (Gardner-Skinner) treadmill protocol (GSP).
  
  
  METHODS
  In this prospective observational study, 30 patients with IC estimated their maximal walking distance (MWD) and completed a "Walking Impairment Questionnaire" (WIQ). Outside walking was determined using a measuring wheel and a GSP controlled device. Primary outcomes were differences in MWD and variability (coefficient of variation, COV). Secondary outcomes were results of WIQ and differences in walking speed.
  
  
  RESULTS
  Estimated walking distance was significantly higher than MWD as objectively measured during outside walking (400 m vs. 309 m, respectively, P = 0.02). A substantial variability (COV = 55%) was found between both parameters. A small 35-m MWD difference between outside walking and GSP was found with a substantial scatter (COV = 42%). In contrast, a much larger 122-m MWD difference was present between outside walking and NGTP (COV = 89%). Patients walked significantly faster in the open air than on treadmills (median outside walking speed = 3.8 km/hr, GSP = 3.2 km/hr, NGTP = 2.8 km/hr; P < 0.001).
  
  
  CONCLUSIONS
  An incremental graded (Gardner-Skinner) treadmill protocol demonstrated the best agreement to outside walking. Discrepancies between treadmill tests and outside walking may be explained by a difference in walking speed. A single determination of a walking distance is a poor reflection of true walking capacity.
authors.affiliation: Department of Surgery, Catharina Hospital, Eindhoven, The Netherlands; CAPHRI Research School, Maastricht University Medical Centre, Maastricht, The Netherlands. Electronic address: h.fokkenrood@gmail.com.
authors.forename: Hugo J P
authors.initials: HJ
authors.lastname: Fokkenrood
authors.affiliation: Department of Surgery, Catharina Hospital, Eindhoven, The Netherlands.
authors.forename: Marijn M L
authors.initials: MM
authors.lastname: van den Houten
authors.affiliation: Department of Education and Research, Catharina Hospital, Eindhoven, The Netherlands.
authors.forename: Saskia
authors.initials: S
authors.lastname: Houterman
authors.affiliation: Department of Surgery, Martini Hospital, Groningen, The Netherlands.
authors.forename: Jan C
authors.initials: JC
authors.lastname: Breek
authors.affiliation: Department of Surgery, Máxima Medical Centre, Veldhoven, The Netherlands; CARIM Research School, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Marc R M
authors.initials: MR
authors.lastname: Scheltinga
authors.affiliation: Department of Surgery, Catharina Hospital, Eindhoven, The Netherlands; CAPHRI Research School, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Joep A W
authors.initials: JA
authors.lastname: Teijink
mesh_terms: D056044:Actigraphy; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006304:Health Status; D006801:Humans; D007383:Intermittent Claudication / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D058729:Peripheral Arterial Disease / Q000175:diagnosis* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016138:Walking