title: Structural and construct validity of the Whiplash Disability Questionnaire in adults with acute whiplash-associated disorders.
abstract: BACKGROUND
  Few instruments are available to measure disability associated with whiplash-associated disorders (WAD). The Whiplash Disability Questionnaire (WDQ) was developed to measure disability resulting from WAD, but its validity is unknown for acute WAD.
  
  
  OBJECTIVE
  The aim was to determine the structural and construct validity of the WDQ in individuals with acute WAD.
  
  
  METHODS
  This was a cohort study.
  
  
  METHODS
  Ontario adults with WAD were enrolled within 3 weeks of their motor vehicle collision.
  
  
  METHODS
  The outcome measure was the WDQ.
  
  
  METHODS
  We included insurance claimants who were aged 18 years or older and diagnosed with acute WAD Grades I to III. All participants completed the WDQ, a 13-item questionnaire scored from 0 (no disability) to 130 (complete disability). We assessed the factor structure of the WDQ and tested its construct validity against self-perceived recovery, neck pain (Numerical Rating Scale [NRS]), neck disability (Neck Disability Index [NDI] and Neck Bournemouth Questionnaire), health-related quality of life (36-Item Short Form Health Survey [SF-36]), and depressive symptoms (Center for Epidemiologic Studies Depression Scale [CES-D]).
  
  
  RESULTS
  The mean age of the 130 participants was 42.1 years (standard deviation [SD]=13.2), and 70% were women. Twenty-six percent had WAD I, 73.1% had WAD II, and 0.8% had WAD III. Mean time since injury was 6.5 days (SD=4.9). The mean WDQ score was 49.8 (SD=29.1). Our analysis suggested that the WDQ includes two factors: daily activities and emotional status. This factor structure remained stable in sensitivity analyses (eg, zeros imputed for missing values, and the item with the most missing values or resulting in complex loading excluded). Strong correlations were found between the total WDQ score and the NDI, the Bournemouth questionnaire, the SF-36 physical function, and the NRS (for the neck, shoulder, mid and low back pain) satisfying a priori hypotheses. We found a priori hypothesized moderate correlations between the WDQ, and the CES-D and SF-36 mental function.
  
  
  CONCLUSIONS
  The WDQ includes two factors and has strong construct validity in individuals with acute WAD. Our results demonstrate that the WDQ is valid for use as an overall summative scale or as the daily activities and emotional subscales in clinical and research settings to determine disability status.
authors.affiliation: Institute of Health Policy, Management and Evaluation, University of Toronto, 155 College Street, Toronto, Ontario, Canada; Faculty of Health Sciences, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, Ontario, Canada; UOIT-CMCC Centre for the Study of Disability Prevention and Rehabilitation, 6100 Leslie St, Toronto, Ontario, Canada. Electronic address: maja.stupar@mail.utoronto.ca.
authors.forename: Maja
authors.initials: M
authors.lastname: Stupar
authors.affiliation: Institute of Health Policy, Management and Evaluation, University of Toronto, 155 College Street, Toronto, Ontario, Canada; Faculty of Health Sciences, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, Ontario, Canada; UOIT-CMCC Centre for the Study of Disability Prevention and Rehabilitation, 6100 Leslie St, Toronto, Ontario, Canada; Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, Ontario, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Côté
authors.affiliation: Institute of Health Policy, Management and Evaluation, University of Toronto, 155 College Street, Toronto, Ontario, Canada; Department of Occupational Science and Occupational Therapy, University of Toronto, Toronto, Ontario, Canada; Musculoskeletal Health and Outcomes Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, 30 Bond Street, Toronto, Ontario, Canada; Institute for Work & Health, 481 University Avenue, Toronto, Ontario, Canada.
authors.forename: Dorcas E
authors.initials: DE
authors.lastname: Beaton
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, Ontario, Canada; Department of Sports Science and Clinical Biomechanics, Faculty of Health, University of Southern Denmark, Campusvej 55, Odense, Denmark.
authors.forename: Eleanor
authors.initials: E
authors.lastname: Boyle
authors.affiliation: Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, 155 College Street, Toronto, Ontario, Canada; Department of Sports Science and Clinical Biomechanics, Faculty of Health, University of Southern Denmark, Campusvej 55, Odense, Denmark; Division of Health Care and Outcomes Research, Toronto Western Research Institute, University Health Network, 700 Bay Street, Suite 602, Toronto, Ontario, Canada.
authors.forename: J David
authors.initials: JD
authors.lastname: Cassidy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D011795:Surveys and Questionnaires / Q000592:standards*; D015599:Trauma Severity Indices; D014911:Whiplash Injuries / Q000473:pathology* / Q000503:physiopathology / Q000523:psychology
keywords: Construct validity; Outcomes research; Patient outcomes; Reproducibility of results; Structural validity; Whiplash-associated disorders