Understanding the composite dimensions of the EQ-5D: An experimental approach.

The EQ-5D(-5L) includes two composite dimensions: "Pain or Discomfort" (P/D) and "Anxiety or Depression" (A/D), which involves an inherent ambiguity. Little is known about how these composite dimensions are interpreted across contexts where (i) individuals self-report their own health; and (ii) individuals value stylised health states. We detail the nature of the ambiguity and present experimental evidence from two large online surveys (n = 1007 and n = 1415). In one survey, individuals reported both their current health and their health at the time they felt the worst because of their health. In the other, they valued stylised EQ-5D states using Discrete Choice Experiments with duration as an attribute. In both surveys, participants were randomised into treatments in which the presentation of one of the composite dimensions was altered, or a control. Our results suggest (1) In self-report, use of the composite dimensions differs across the dimensions, with P/D used mainly to report Pain, but A/D used mainly to mean the more severe component of Anxiety and Depression. (2) In valuation, Pain was perceived to be worse than Discomfort at the same level, and Depression was perceived to be worse than Anxiety at the same level. (3) In valuation, the composite dimension P/D was interpreted to mean Pain, whilst the composite dimension A/D was interpreted to lie between Anxiety and Depression. We conclude that care must be taken when interpreting responses to existing health (or wellbeing) descriptive systems that rely on composite dimensions, and that caution should be applied when designing new ones.