title: Measurement properties of the Disability Rating Index in patients undergoing hip replacement.
abstract: OBJECTIVE
  The aim of this study was to establish and validate the measurement properties of the Disability Rating Index (DRI) in a population of adults undergoing hip replacement.
  
  
  METHODS
  One hundred and twenty-six adults participating in a randomized controlled trial completed the Oxford Hip Score, Harris Hip Score, DRI and EuroQol Group-Five Dimensions (EQ-5D) questionnaires at four time points. The structural validity of the DRI was assessed using principal component analysis. Cronbach's α was used to determine the internal consistency and scale reliability was also assessed. Correlation between the DRI and the other functional and health-related quality of life scales was used to check criterion validity. DRI responsiveness was estimated and the interpretability of the scale was also assessed by checking for edge effects.
  
  
  RESULTS
  Results of analyses showed that the DRI was internally consistent (Cronbach's α = 0.92), had good association with both function-specific and general health-related quality of life scores and was sensitive to change (smallest detectable change = 2.7). No evidence of edge effects was found. Furthermore, structural assessment of the DRI revealed two novel subscales representing simple tasks and difficult tasks.
  
  
  CONCLUSIONS
  The DRI is structurally valid, responsive and concurs with functional assessment in adults undergoing hip replacement.
authors: Statistics and Epidemiology, Division of Health Sciences, Warwick Medical School and Warwick Clinical Trials Unit, Division of Health Sciences, University of Warwick, Coventry, UK. h.parsons@warwick.ac.uk.
authors: Helen
authors: H
authors: Parsons
authors: Statistics and Epidemiology, Division of Health Sciences, Warwick Medical School and Warwick Clinical Trials Unit, Division of Health Sciences, University of Warwick, Coventry, UK.
authors: Julie
authors: J
authors: Bruce
authors: Statistics and Epidemiology, Division of Health Sciences, Warwick Medical School and Warwick Clinical Trials Unit, Division of Health Sciences, University of Warwick, Coventry, UK.
authors: Juul
authors: J
authors: Achten
authors: Statistics and Epidemiology, Division of Health Sciences, Warwick Medical School and Warwick Clinical Trials Unit, Division of Health Sciences, University of Warwick, Coventry, UK.
authors: Matthew L
authors: ML
authors: Costa
authors: Statistics and Epidemiology, Division of Health Sciences, Warwick Medical School and Warwick Clinical Trials Unit, Division of Health Sciences, University of Warwick, Coventry, UK.
authors: Nicholas R
authors: NR
authors: Parsons
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D003627:Data Interpretation, Statistical; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D017063:Outcome Assessment, Health Care; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D016896:Treatment Outcome
keywords: DRI; disability evaluation; patient reported outcomes; validity