The EuroQOL Group. EuroQOL-a new facility for the measurement of health-related quality of life. Health Policy 1990; 16; 199 – 208.
The EQ-5D questionnaire is a measure of both clinical and economic value in health care. EQ-5D is a standardised measure of health status developed by the EuroQol Group in order to provide a simple, generic measure of health for clinical and economic appraisal. Applicable to a wide range of health conditions and treatments, it provides a simple descriptive profile and a single index value for health status that can be used in the clinical and economic evaluation of health care as well as in population health surveys.
Structure / Content
The EQ-5D has 3-level and 5-level versions. It consists of 2 pages: a descriptive system and a visual analogue scale (EQ VAS). The descriptive system has 5 dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each has 3 levels of severity (no problems, some problems, extreme problems) in 3-level version, and 5 levels of severity (no problems, slight problems, moderate problems, severe problems, and extreme problems) in 5-level version.
The VAS used to value EQ-5D health states is presented as a 20-cm vertical line calibrated from zero (“worst imaginable health sate”) to 100 (“best imaginable health state”). It is asked respondents to simply ‘mark an X on the scale to indicate how your health is today’ and then to ‘write the number you marked on the scale in the box below’.
The respondent is requested to indicate his/her health state by marking in the box against the most appropriate statement in each of the 5 dimensions. This decision results in a 1-digit number expressing the level selected for that dimension. Level 1 of severity is coded as a '1', Level 2 of severity is coded as a '2', and so on. The digits for 5 dimensions can be combined in a 5-digit number describing the respondent’s health state. In 3-level version (EQ-5D-3L), for instance, state 11223 would indicate no problems in mobility, and self-care, moderate problems in usual activities and pain/discomfort, and extreme problems in the dimension anxiety and depression. In EQ-5D-5L, for example, state 11111 indicates no problems on any of the 5 dimensions, while state 12345 indicates no problems with mobility, slight problems with washing or dressing, moderate problems with doing usual activities, severe pain or discomfort and extreme anxiety or depression. It should be noted that the numerals 1-3 (or, 1-5 in 5-level version) have no arithmetic properties and should not be used as a cardinal score.
Thus, in EQ-5D-5L, a total of 3125 possible health states is defined in this way.
Then, a conversion of these health states to to a single index value* is possible by applying a formula that essentially attaches values (also called weights) to each of the levels in each dimension. The index can becalculated by deducting the appropriate weights from 1, the value for full health (i.e.state 11111).
(*Many different terms are in use for these index values, such as preference weights, preference-based values, utilities, QALY weights, etc).
Indeed, the index values, presented in country specific value sets, are a major feature of the EQ-5D instrument, facilitating the calculation of quality-adjusted life years (QALYs) that are used to inform economic evaluations of health care interventions.
Value sets have been derived for EQ-5D in several countries using the EQ-5D visual analogue scale (EQ-5D VAS) valuation technique or the time trade-off (TTO) valuation technique. Most of the EQ-5D-3L value sets have been obtained using a representative sample of the general population, thereby ensuring that they represent the societal perspective. For anyone working with EQ-5D-3L data, an essential guide to the Group’s available value sets can be found in: EuroQol Group Monograph series: Volume 2: EQ-5D value sets: inventory, comparative review and user guide. Index values are population-based, thus, different for each countries. For example, the EQ-5D scores for the US population range from − 0.11 (worse than death) to 1.0 (full health), with a score of 0 indicating death.
Because EQ-5D-5L is a newer version, the dataset to convert its index-based values is not established yet. Pilot studies that directly elicit preferences from general populations in order to derive index-based values for the EQ-5D-5L are currently under way in a number of countries. However, it will take some time to complete and publish definitive valuation studies. Until then, a "crosswalk" (i.e., conversion) between the EQ-5D-3L index values and the new EQ-5D-5L descriptive system has been undertaken, resulting in "crosswalk" value sets for the new EQ-5D-5L descriptive system.
Documents containing information on scoring algorithms, the crosswalk project, tables of values for all 3125 health states, and syntax files for calculating the crosswalk index values can be ordered from the EuroQolExecutive Office.
Presentation and Interpretation of Data
EQ-5D data can be interpreted and presented in three ways: 1. Presenting results from the EQ-5D-5L descriptive system as a health profile, 2. Presenting results of the EQ VAS as a measure of overall self-rated health status, 3. Presenting results from the EQ-5D-5L index value.
Time to do
1,5 minutes (90 seconds).
All copyrights in the EQ-5D, its (digital) representations, and its translations exclusively vest in the EuroQol Group. EQ-5D™ is a trade mark of the EuroQol Group. Without the prior written consent of the EuroQol Executive Office, the researchers are not permitted to use, reproduce, alter, amend, convert, translate, publish or make available in any way (digital, hard-copy). Licensing fees are determined by the EuroQol Executive Office on the basis of information provided by the user. Whether a fee is appropriate depends upon the type of study, size and/or number of patients/respondents and requested languages.The researchers should fill a form in the EuroQol website (http://www.euroqol.org/), and request the permission to use the tool. In academic and non-profit researches, there may be no fee. However, for company researches, a fee will incur.
EQ-5D is primarily designed for self-completion by respondents and is ideally suited for use in postal surveys, in clinics and face-to-face interviews.The EQ-5D-5L self-complete paper version is currently available in more than 50 different language versions.
Development / Versions / Translations
Scientific Spine's Comment
EuroQol is applicable across many different states of health and disease, brief and easy to administer, and its use is increasingly common.
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