What is new?
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Using a nationally representative sample of US adults, we found that the EQ-5D Y and 5L slightly reduced the prevalence of the best possible EQ-5D responses, mitigating the ceiling effect in the 3L.
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Using a nationally representative sample of US adults, we found that the EQ-5D Y and 5L reduced the prevalence of the worst possible Pain/Discomfort and Anxiety/Depression responses, mitigating the floor effect in the 3L.
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In comparison to the 3L and 5L, the Y did surprisingly well by mitigating ceiling effects, addressing issues with level descriptions, and predicting overall health. While it was designed for pediatric populations and may not capture extreme health problems as well as the 5L, this evidence suggests that it may substitute for the 3L when surveying across ages and literacy levels or in longitudinal studies that start in childhood.
Measures of general health based on self-reported losses in health-related quality of life (HRQoL) provide a holistic approach to evaluate treatment effectiveness and to make comparisons across clinical populations. For this purpose, short-form patient-reported outcome (PRO) instruments (often with less than a dozen items) have been developed for use across multiple disease areas, minimizing response burden. Although long-form and disease-specific PRO instruments have advantages in terms of their reliability, short-form instruments (e.g., 1 item per domain) provide a broad-based measure of respondent health.
The EQ-5D is a generic measure of HRQoL that has been widely used in clinical and economic evaluations of health care and to capture the health of populations [1]. The measure is composed of a simple descriptive profile that may be converted into a single summary index (EQ-5D index) and a visual analog scale (VAS). The measure is designed for self-completion, has a low respondent burden, and has been administered using a variety of modalities (e.g., postal surveys).
Widely used in adult populations, the EQ-5D 3-level version (EQ-5D-3L) has been translated into more than 150 languages. The EQ-5D-3L descriptive system consists of five domains (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression), with each dimension having three levels (no problems, some problems, and extreme problems; Table 1). In an effort to improve the appropriateness of the EQ-5D in children, adolescents, and low-literacy populations [2], a youth version of the EQ-5D (EQ-5D-Y)—a modified but similar version of the EQ-5D—was constructed and examined through cognitive interviews [3]. With its simplified wording (e.g., “a lot” vs. “extremely”; Table 1), the adjectival scales of the EQ-5D-Y may mitigate ceiling effects of the EQ-5D-3L, particularly among less-educated adults. A multinational study concluded that the EQ-5D-Y was a feasible, reliable, and valid instrument to measure HRQoL in children and adolescents but cautioned that the measure needed further testing in adult and clinical populations [4].
In addition to the EQ-5D-Y, a 5-level version of the EQ-5D (EQ-5D-5L) was recently developed to improve on the measurement properties of the EQ-5D-3L, namely ceiling effects in the general population [5] and in a few clinical conditions [6]. By adding two levels (slight problems and severe problems) to the existing three levels, the 5-level version was designed to have not only reduced ceiling effects but also greater reliability and discriminatory power. On finalizing the labels for the 5L descriptive system [7], a multicountry study generated evidence on the improved properties of the EQ-5D-5L compared with the EQ-5D-3L [8]. However, at present, no population study has simultaneously administered and compared the properties of the descriptive systems for the 3L, Y, and 5L.
For this study, we conducted a nationally representative survey of adults in the United States and examined the prevalence of the 3L, Y, and 5L responses. These results provide a general benchmark for the interpretation of EQ-5D responses across instruments. Furthermore, we assessed the external validity of these three instruments by estimating their relationship with a 0 to 100 numerical VAS. This study was designed to characterize general health in the United States and to inform researchers about the implications of their decision to use a given EQ instrument (3L, Y, or 5L). We hypothesized that the 5L and Y would perform better than the 3L in terms of discriminative ability and proportion of respondents susceptible to ceiling effects.
