Researchers recommend the use of generic health-related quality of life (HRQoL) measures to determine pain-related burden of disease, but consideration needs to be given to which one is used.
Their findings revealed that two widely used HRQoL questionnaires, EuroQol (EQ)-5D and SF-6D (from SF-12/36), generated widely differing scores for the same groups of chronic pain patients, which could have major implications for understanding the true health state of such patients.
“The rationale for generating health utility sores is that it provides a generic, preference-weighted, index that enables the severity of different conditions to be estimated consistently”, explain Nicola Torrance (University of Dundee, UK) and team in Pain.
“The ultimate intention is to assist health care planners to allocate resources on a consistent and transparent basis between different diseases and interventions.”
Among 4216 individuals who responded to one or both questionnaires, 1611 reported chronic pain without neuropathic characteristics and 399 chronic pain with neuropathic characteristics.
Both the EQ-5D and SF-6D were able to discriminate patients with chronic pain and neuropathic characteristics from those with chronic pain without such characteristics and those with no chronic pain.
But the average scores varied widely, particularly for patients with more severe pain. Based on a range of scores from 0 to 1, where 0 reflects equivalent to death and 1 full health, patients with chronic pain and neuropathic characteristics had an average EQ-5D score of 0.47 versus a SF-6D score of 0.62. For those with severe pain, the scores were 0.33 versus 0.58, respectively.
This finding “questions the validity of comparing studies that have used different instruments”, the team points out.
They also note that the difference in mean utility scores between patients with moderate and severe pain was five times greater when estimated using EQ-5D than when estimated using SF-6D, which has implications when assessing the effects of interventions in reducing pain.
“[T]he choice between using the EQ-5D and SF-6D may be not only important in estimating the absolute burden of disease, but may also have major implications regarding the economic evaluation of interventions that take a cost-utility approach”, the researchers say.
Other findings included a considerable ceiling effect with EQ-5D, which made it less sensitive at detecting small health changes in healthier patients than the SF-6D.
However, the researchers note that this may be less relevant in patients with chronic neuropathic pain, who rarely attained a maximum utility score on the EQ-5D.
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