title: Validation of a prediction model to estimate health utilities index Mark 3 utility scores from WOMAC index scores in patients with osteoarthritis of the hip.
abstract: OBJECTIVE
  To examine the validity of a newly developed prediction model translating osteoarthritis (OA)-specific health-related quality of life (HRQL) scores measured using the Western Ontario and McMaster Osteoarthritis Index (WOMAC) into generic utility-based HRQL scores measured using the Health Utilities Index Mark 3 (HUI3).
  
  
  METHODS
  Preintervention data from 145 patients with hip OA and complete WOMAC and HUI3 baseline assessments from the Alberta Hip Improvement Project study were used to validate three utility prediction models. These models were estimated using data from a previous study of knee OA patients. Predictive performance was assessed using the mean absolute prediction error (MAE) criterion and several other criteria.
  
  
  RESULTS
  The validation sample appeared healthier (on the basis of the HUI3 and WOMAC) than the subjects used toestimate the prediction models. Nevertheless, the validation sample outperformed the predictive performance of the model sample. The results from the validation sample support the conclusions from the original study in that the primary model identified during model development (a model using WOMAC subscales, their interactions, their square terms, age, OA duration, their square terms, and gender) performed better on the MAE criterion than competing models.
  
  
  CONCLUSIONS
  These results support the external validity of the prediction model for the retrospective estimation of HUI3 utility scores for use in economic evaluation.
authors.affiliation: Global Health Economics and Outcomes, i3 Innovus, Burlington, ON, Canada. Deborah.Marshall@i3innovus.com
authors.forename: Deborah
authors.initials: D
authors.lastname: Marshall
authors.forename: Dan
authors.initials: D
authors.lastname: Pericak
authors.forename: Paul
authors.initials: P
authors.lastname: Grootendorst
authors.forename: Katherine
authors.initials: K
authors.lastname: Gooch
authors.forename: Peter
authors.initials: P
authors.lastname: Faris
authors.forename: Cy
authors.initials: C
authors.lastname: Frank
authors.forename: Nicholas
authors.initials: N
authors.lastname: Bellamy
authors.forename: George
authors.initials: G
authors.lastname: Torrance
authors.forename: David
authors.initials: D
authors.lastname: Feeny
mesh_terms: D001672:Biocompatible Materials / Q000627:therapeutic use*; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D006820:Hyaluronic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008297:Male; D015207:Osteoarthritis, Hip / Q000188:drug therapy*; D010147:Pain Measurement; D011237:Predictive Value of Tests; D011788:Quality of Life; D016032:Randomized Controlled Trials as Topic; D012044:Regression Analysis; D012720:Severity of Illness Index
chemical_list: D001672:Biocompatible Materials; C049816:hylan; D006820:Hyaluronic Acid