title: Longitudinal construct validity and responsiveness of measures of walking capacity in individuals with lumbar spinal stenosis.
abstract: BACKGROUND
  Walking capacity is a primary outcome indicator for individuals with lumbar spinal stenosis (LSS). Therefore, there is a demand for psychometrically sound measures of walking that are responsive to change.
  
  
  OBJECTIVE
  The primary objective of this study was to examine longitudinal construct validity of the Physical Function Scale of the Swiss Spinal Stenosis Questionnaire (PF Scale), the Oswestry Disability Index (ODI), and the walking capacity items from these scales specifically for the assessment of walking capacity in LSS using the objective Self-Paced Walking Test (SPWT) as the external standard. A secondary objective was to examine responsiveness of measures of walking using a self-reported walking capacity change scale as the external criterion standard.
  
  
  METHODS
  Patients were prospectively enrolled.
  
  
  METHODS
  Twenty-six patients were included in this study (17 women and 9 men), with an average age of 68.5 years (SD, 9.2). All participants had LSS diagnosed by a spine specialist surgeon based on both clinical examination and imaging, as well as self-reported walking limitations (neurogenic claudication).
  
  
  METHODS
  The self-reported outcome measures included in this study were PF Scale, ODI, and self-reported walking capacity change score.
  The functional measure used in the study was SPWT.
  
  
  METHODS
  Longitudinal construct validity was assessed using the correlational method. Internal responsiveness was examined using Guyatt responsiveness index and external responsiveness using receiver operating characteristic analysis. Change in the SPWT and the self-reported walking capacity change score were used as external criteria for the analysis.
  
  
  RESULTS
  The highest correlations with change in the SPWT were 0.78 for the ODI walking item and 0.78 for the walking capacity change score. Changes in the PF Scale and ODI score were correlated with change in the criterion SPWT at r=0.56 and r=0.70, respectively. There were no differences observed between the PF Scale and ODI for any of the responsiveness indices.
  
  
  CONCLUSIONS
  The PF Scale, ODI, and walking capacity change score are able to detect changes in walking capacity in people with LSS. The individual walking capacity item from the ODI appears to be the most valid and responsive to changes in measured walking and may be a reasonable alternative for measuring walking when an objective test such as the SPWT is not feasible.
authors.affiliation: Mount Royal University, U243E, 4825 Mount Royal Gate SW, Calgary, Alberta, Canada T3E 6K6. Electronic address: clane@mtroyal.ca.
authors.forename: Christy C
authors.initials: CC
authors.lastname: Tomkins-Lane
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, 3-48 Corbett Hall, Edmonton, Alberta, Canada T6G 2G4.
authors.forename: Michele C
authors.initials: MC
authors.lastname: Battié
authors.affiliation: Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, 3-48 Corbett Hall, Edmonton, Alberta, Canada T6G 2G4.
authors.forename: Luciana G
authors.initials: LG
authors.lastname: Macedo
mesh_terms: D000368:Aged; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D013130:Spinal Stenosis / Q000145:classification / Q000175:diagnosis*; D011795:Surveys and Questionnaires; D015599:Trauma Severity Indices; D016138:Walking
keywords: Neurogenic claudication; Outcomes; Responsiveness; Spinal stenosis; Validity; Walking