title: Comparison of a generic (SF-36) and a disease specific (WOMAC) (Western Ontario and McMaster Universities Osteoarthritis Index) instrument in the measurement of outcomes after knee replacement surgery.
abstract: OBJECTIVE
  The discriminant validity of a generic, health related quality of life (HRQL) measure, the SF-36, was compared with that of a disease specific HRQL measure, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), in patients aged 67-99 years who had undergone knee replacement surgery 2 to 7 years previously.
  
  
  METHODS
  A stratified random sample of 1750 Medicare beneficiaries was surveyed and 1193 usable responses were obtained (after adjustment for ineligible, incapacitated, and deceased individuals). Discriminant validity of scale scores common to both instruments (pain, physical functioning, and overall score) were compared.
  
  
  RESULTS
  Examination of discriminant validity, using Spearman correlations, showed that the WOMAC discriminates better among individuals with knee problems, while the SF-36 discriminates better among individuals with varying levels of self reported general health status and comorbidities.
  
  
  CONCLUSIONS
  These scales measure 2 distinct but important aspects of patients' health. These results support inclusion of both a generic and a disease specific HRQL measure in cross sectional studies.
authors.affiliation: Department of Medicine, Women's College Hospital, Toronto, ON, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Hawker
authors.forename: C
authors.initials: C
authors.lastname: Melfi
authors.forename: J
authors.initials: J
authors.lastname: Paul
authors.forename: R
authors.initials: R
authors.lastname: Green
authors.forename: C
authors.initials: C
authors.lastname: Bombardier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016002:Discriminant Analysis; D005260:Female; D006306:Health Surveys; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D011788:Quality of Life; D012219:Rheumatology / Q000379:methods*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome