title: Comparing the performance of the EQ-5D and SF-6D when measuring the benefits of alleviating knee pain.
abstract: OBJECTIVE
  To assess the practicality, validity and responsiveness of using each of two utility measures (the EQ-5D and SF-6D) to measure the benefits of alleviating knee pain.
  
  
  METHODS
  Participants in a randomised controlled trial, which was designed to compare four different interventions for people with self-reported knee pain, were asked to complete the EQ-5D, SF-6D, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at both pre- and post-intervention. For both utility measures, we assessed their practicality (completion rate), construct validity (ability to discriminate between baseline WOMAC severity levels), and responsiveness (ability to discriminate between three groups: those whose total WOMAC score, i) did not improve, ii) improved by <20%, and iii) improved by > or = 20%).
  
  
  RESULTS
  The EQ-5D was completed by 97.7% of the 389 participants, compared to 93.3% for the SF-6D. Both the EQ-5D and SF-6D were able to discriminate between participants with different levels of WOMAC severity (p < 0.001). The mean EQ-5D change was -0.036 for group i), 0.091 for group ii), and 0.127 for group iii), compared to 0.021, 0.023 and 0.053 on the SF-6D. These change scores were significantly different according to the EQ-5D (p < 0.001), but not the SF-6D.
  
  
  CONCLUSIONS
  The EQ-5D and SF-6D had largely comparable practicality and construct validity. However, in contrast to the EQ-5D, the SF-6D could not discriminate between those who improved post-intervention, and those who did not. This suggests that it is more appropriate to use the EQ-5D in future cost-effectiveness analyses of interventions which are designed to alleviate knee pain.
authors.affiliation: Health Economics Group, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, UK.
authors.forename: Garry R
authors.initials: GR
authors.lastname: Barton
authors.forename: Tracey H
authors.initials: TH
authors.lastname: Sach
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Avery
authors.forename: Michael
authors.initials: M
authors.lastname: Doherty
authors.forename: Claire
authors.initials: C
authors.lastname: Jenkinson
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Muir