Several preference-accompanied measures have composite domains that join 2 or more different but related domains of health in a single domain. The EQ-5D has 2 such domains: pain/discomfort and anxiety/depression. Little is known about how respondents use the composite domains to self-report their own health. Furthermore, there is conflicting evidence on the extent to which the current operationalization of pain/discomfort is able to capture discomfort.
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This study identified 6 different response behaviors in the EQ-5D composites: “uniform,” “most severe,” “least severe,” “average,” “synergistic,” and “inconsistent.” Discomfort is not solely pain related; it is an umbrella term for approximately 100 different nonpain physical sensations, mental problems, or feelings. Composites were found to be sources of measurement error, including under- and inconsistent reporting of health problems, ordering effect, potential differential item functioning, and interdomain dependency.
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This study sheds light on potential issues surrounding the composite domains in generic preference-accompanied measures. These findings may contribute to the development of new and further refinement of existing measures used to evaluate health outcomes in terms of quality-adjusted life-years and to facilitate decision making in healthcare.
Abstract
Objectives
The EQ-5D has 2 composite domains: pain/discomfort (PD) and anxiety/depression (AD). This study aims to explore how respondents use the composites to self-report health and what the meaning of discomfort is in the EQ-5D for the general public.
Methods
Both qualitative and quantitative data were collected in an online cross-sectional survey involving a nationally representative general population sample in Hungary (n = 1700). Respondents completed the 5-level version of EQ-5D, followed by the composites split into individual subdomains. Open-ended questions were asked to explore respondents’ interpretations and experiences of discomfort.
Results
Six different response behaviors were identified in the composites: “uniform” (21%-32%), “most severe” (30%-34%), “least severe” (16%-23%), “average” (2%-4%), “synergistic” (4%-5%), and “inconsistent” (13%-15%). Compared with the individual subdomains, many respondents under-reported their problems on both composites (PD 16%-22% and AD 6%-13%, P < .05). In respondents who scored differently in the 2 separate domains, mainly problems with the first subdomain determined responses in the composites (PD 66% and AD 61%). The discomfort subdomain in the EQ-5D captured more than 100 different problems, including pain, nonpain physical discomfort (eg, tiredness, dizziness, and nausea), and psychological discomfort (eg, anxiety, nervousness, and sadness). Women, older adults, and those in worse general health status more often considered discomfort as pain (P < .05).
Conclusions
We found empirical evidence of measurement error in the composite responses on the EQ-5D, including under- and inconsistent reporting, ordering effects, potential differential item functioning, and interdomain dependency. Our findings contribute new knowledge to the development of new and refinement of existing self-reported health status instruments, also beyond the EQ-5D.
