Research

Comparing the performance of the EQ-5D and SF-6D when measuring the benefits of alleviating knee pain

Garry R Barton¹, Tracey H Sach^3,1,2*, Anthony J Avery³, Michael Doherty⁴, Claire Jenkinson³ and Kenneth R Muir³

• * Corresponding author: Tracey H Sach T.Sach@uea.ac.uk

Author Affiliations

¹ Health Economics Group, School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, UK

² School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, UK

³ School of Community Health Sciences, University of Nottingham, Nottingham, UK

⁴ Academic Rheumatology, University of Nottingham, Nottingham UK

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Cost Effectiveness and Resource Allocation 2009, 7:12 doi:10.1186/1478-7547-7-12

Published: 17 July 2009

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 ≥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.

Conclusion

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.

Trial registration

Current Controlled Trials ISRCTN93206785