Implausible States: Prevalence of EQ-5D-5L States in the General Population and Its Effect on Health State Valuation

Abstract

The EQ-5D is made up of health state dimensions and levels, in which some combinations seem less “plausible” than others. If “implausible” states are used in health state valuation exercises, then respondents may have difficulty imagining them, causing measurement error. There is currently no standard solution: some valuation studies exclude such states, whereas others leave them in. This study aims to address 2 gaps in the literature: 1) to propose an evidence-based set of the least prevalent two-way combinations of EQ-5D-5L dimension levels and 2) to quantify the impact of removing perceived implausible states from valuation designs. For the first aim, we use data from 2 waves of the English General Practitioner Patient Survey ( n = 1,639,453). For the second aim, we remodel a secondary data set of a Discrete Choice Experiment (DCE) with duration that valued EQ-5D-5L and compare across models that drop observations involving different health states: 1) implausible states as defined in the literature, 2) the least prevalent states identified in stage 1, and 3) randomly select states, alongside 4) a model that does not drop any observations. The results indicate that two-way combinations previously thought to be implausible actually exist among the general population; there are other combinations that are rarer, and removing implausible states from an experimental design of a DCE with duration leads to value sets with potentially different characteristics depending on the criterion of implausible states. We advise against the routine removal of implausible states from health state valuation studies.

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“…Quality of life was impaired in the FND sample (Table 2); patients' mean EQ‐5D‐5L health state valuation score (0.55) was markedly less than (EQ‐5D‐3L) norms observed in age‐matched healthy UK populations (which across 10‐year age cohorts from 25–75 years range from 0.93–0.78 [23]). Problems concerning pain/discomfort (75.6%), mood disturbances (80.3%) and carrying out usual activities (83.4%) were domains most affected, with considerably higher rates than self‐reported EQ‐5D‐5L problems observed in a large sample of the general population in England (53.6%, 31.4% and 30.2%, respectively [24].…”

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“…This is because it is difficult to make a judgement, a-priori, that certain combinations are not realistic, particularly as what is considered implausible has been found to be respondent specific (Yang et al 2019). Marten et al (2017) found that EQ-5D-5L level combinations assumed to be implausible (for example no problems with self-care combined with unable to do usual activities) actually appear in general population self-report data.…”

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