Abstract
ObjectiveTo 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.MethodsParticipants 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%).ResultsThe 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.ConclusionThe 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 registrationCurrent Controlled Trials ISRCTN93206785
Highlights
In the UK it has been estimated that nearly 50% of those aged >50 years experience knee pain each year, and that 33% of these consult their general practitioner [1]
Within such studies outcomes are often measured on a utility scale, where 0 is equivalent to death and 1 is equal to full health, in order to enable the benefits of different interventions to be compared on a common scale [3,4] There are a number of different utility measures that can be used within such evaluations, including the EQ-5D [5], health utilities index [6], and SF6D [7], all of which aim to measure utility on the same scale
The WOMAC was chosen as primary outcome measure within the Lifestyle Interventions for Knee Pain (LIKP) study as the pain subscale of the WOMAC was considered to be the best way of capturing knee pain severity
Summary
In the UK it has been estimated that nearly 50% of those aged >50 years experience knee pain each year, and that 33% of these consult their general practitioner [1]. Economic evaluations have been undertaken to assess whether interventions which alleviate knee pain represent a cost-effective use of scarce health care resources [2]. Within such studies outcomes are often measured on a utility scale, where 0 is equivalent to death and 1 is equal to full health, in order to enable the benefits of different interventions to be compared on a common scale [3,4] There are a number of different utility measures that can be used within such evaluations, including the EQ-5D [5], health utilities index [6], and SF6D [7], all of which aim to measure utility on the same scale. The results of this study are important as both of these measures have recently been used in a randomised controlled trial which compared four interventions for people with knee pain (diet and strengthening exercise advice, dietary advice, strengthening exercise advice, and leaflet provision) and we wish to select the preferred outcome measure for the cost-effectiveness analysis of this study in a systematic and transparent way
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