EQ-5D

EuroQol five dimensions questionnaire (EQ-5D) is a standardized instrument for measuring generic health status. The health status measured with EQ-5D is used for estimating preference weight for that health status, then by combining the weight with time, quality-adjusted life year (QALY) can be computed. QALYs gained is used as an outcome in cost-utility analysis which is a type of economic evaluation that compares the benefit and cost of health care programs or interventions. Many countries generated a value set (preference weights) of their own population and have used it for estimating QALY to make decisions in resource allocation. There are currently 171 language versions of EQ-5D questionnaire available. EQ-5D is one of the most commonly used generic health status measurement, and its good validity and reliability have been reported in various health conditions.

EQ-5D was first introduced in 1990 by the EuroQol Group. This group was initially formed in 1987 with the researchers of multidisciplinary areas from five European countries; Netherlands, UK, Sweden, Finland, and Norway. They worked cooperatively with the aim of developing an instrument which is not specific to disease but standardized and can be used as a complement for existing health-related quality of life (HRQoL) measures. Other required characteristics of the new instrument were capable of being sent as a postal questionnaire for self-completion, easy to complete, applicable to everyone, can produce a single index value, and can take into account the health status ‘worse than dead’.

The EQ-5D questionnaire is made up for two components; health state description and evaluation.

In description part, health status is measured in terms of five dimensions (5D); mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Mobility dimension asks about the person's walking ability. Self-care dimension asks about the ability to wash or dress by oneself, and usual activities dimension measures performance in "work, study, housework, family or leisure activities". In pain/discomfort dimension, it asks how much pain or discomfort they have, and in anxiety/depression dimension, it asks how much anxious or depressed they are. The respondents self-rate their level of severity for each dimension using three-level (EQ-5D-3L) or five-level (EQ-5D-5L) scale.

In evaluation part, the respondents evaluate their overall health status using the visual analogue scale (EQ-VAS).

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