title: Minimally Important Difference of the Absolute and Functional Claudication Distance in Patients with Intermittent Claudication.
abstract: OBJECTIVE
  Disease severity and treatment outcomes in patients with intermittent claudication (IC) are commonly assessed using walking distance measured with a standardized treadmill test. It is unclear what improvement or deterioration in walking distance constitutes a meaningful, clinically relevant, change from the patients' perspective. The purpose of the present study was to estimate the minimally important difference (MID) for the absolute claudication distance (ACD) and functional claudication distance (FCD) in patients with IC.
  
  
  METHODS
  The MIDs were estimated using an anchor based approach with a previously defined clinical anchor derived from scores of the walking impairment questionnaire (WIQ) in a similar IC population. Baseline and 3 month follow up data on WIQ scores and walking distances (ACD and FCD) were used from 202 patients receiving supervised exercise therapy from the 2010 EXITPAD randomized controlled trial. The external WIQ anchor was used to form three distinct categories: patients with "clinically relevant improvement," "clinically relevant deterioration," and "no clinically relevant change." The MIDs for improvement and deterioration were defined by the upper and lower limits of the 95% confidence interval of the mean change in ACD and FCD, for the group of IC patients that remained unchanged according to the WIQ anchor.
  
  
  RESULTS
  For the estimation of the MID of the ACD and FCD, 102 and 101 patients were included, respectively. The MID for the ACD was 305 m for improvement, and 147 m for deterioration. The MID for the FCD was 250 m for improvement, and 120 m for deterioration.
  
  
  CONCLUSIONS
  The MIDs for the treadmill measured ACD and FCD can be used to interpret the clinical relevance of changes in walking distances after supervised exercise therapy and may be used in both research and individual care.
authors.affiliation: Catharina Hospital, Department of Vascular Surgery, Eindhoven, The Netherlands.
authors.forename: M M L
authors.initials: MM
authors.lastname: van den Houten
authors.affiliation: Catharina Hospital, Department of Vascular Surgery, Eindhoven, The Netherlands; Maastricht University, CAPHRI Research School, Maastricht, The Netherlands.
authors.forename: L N M
authors.initials: LN
authors.lastname: Gommans
authors.affiliation: Radboud University Medical Centre, Scientific Institute for Quality of Healthcare, Nijmegen, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: van der Wees
authors.affiliation: Catharina Hospital, Department of Vascular Surgery, Eindhoven, The Netherlands; Maastricht University, CAPHRI Research School, Maastricht, The Netherlands. Electronic address: joep.teijink@catharinaziekenhuis.nl.
authors.forename: J A W
authors.initials: JA
authors.lastname: Teijink
mesh_terms: D000368:Aged; D005080:Exercise Test; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007383:Intermittent Claudication / Q000175:diagnosis / Q000503:physiopathology* / Q000534:rehabilitation; D008297:Male; D012189:Retrospective Studies; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D016896:Treatment Outcome; D016138:Walking / Q000502:physiology*
keywords: Intermittent claudication; Peripheral arterial disease; Supervised exercise therapy