EQ-5D-3L

In 1987, an interdisciplinary, multinational European group of researchers founded the EuroQol Group with the aim of developing a general score to assess the quality of life of patients. In doing so, the group aspired to create the basis for standardisation in the collection and analysis of data on quality of life.¹

EQ-5D is a family of instruments to describe and value health of which include the original EQ-5D-3L, the updated EQ-5D-5L and the paediatric and adolescent quality of life measure EQ-5D-Y.²

The EQ-5D-3L was published in 1990 and consists of 3 possible answer levels within 5 different dimensions.

The scale used for the answers is the EQ visual analogue scale (EQ VAS). It consists of a vertical 100 point visual analogue scale with two extreme endpoints. Below the dimensions and levels are outlined:

• Mobility
• Self-care
• Usual activities
• Pain / discomfort
• Anxiety / depression

• No problems/ pain/ anxiety

• Some problems/ pain/ anxiety

• Extreme problems/ pain/ anxiety

   

The result of the descriptive EQ-5D system is defined as the EQ-5D health state. This allows 243 (3⁵) different health states to be identified. First, the descriptive EQ-5D system assigns 1 – 3 points depending on the answers/levels given, e.g. 1 point at level 1 (no problems) in the mobility dimension.

The numbers are then assigned their differently weighted scores according to a specific formula. This algorithm is currently not publicly available, but documents containing the scoring algorithms, information on the scores studied, tables of values for all 243 health states, and syntax files can be requested from EuroQol. The weighting of the scores has been done in studies from different countries using different scoring techniques.² Without the algorithm of the score however, it is not possible to determine whether the specific EQ-VAS score plays a role in the calculation of the EQ-5D-3L index.

The EQ VAS score is rated on a scale of 0-100 points. 0 points represent the worst possible health status, while 100 points represent the best possible health status.²

The EQ-5D-3L index is calculated by subtracting the values of the descriptive EQ-5D system from the numerical value 1. This corresponds to the best possible health status, while an index value of <0 represents the worst possible health status.^2,3

Overall, the health status perceived by the patients can be represented by the EQ-5D-3L index and the EQ-VAS score.

The EQ-5D-3L is an established and validated questionnaire used in many therapeutic settings.^1,4-8 With its small size of 5 items and a visual analog scale, its brevity and ease of use make it well suited for use in clinical research and practice.

The evaluation of the EQ-5D-3L is comparatively complicated and difficult to understand, as it is not clear from the user manual whether, for example, the EQ-VAS score still plays a role in the calculation of the EQ-5D-3L index. Furthermore, studies showed a statistical “ceiling effect”. This means that measurement errors are caused by exceeding the measurement range.^9-12 These results led to improvement measures, which resulted in the EQ-5D-5L in 2009.¹³

A license is required to use and evaluate the EQ-5D-3L. The amount of the license fee depends on the study type, cohort size, and language.¹⁴ Our PRO consultants will be happy to provide more detailed information.

The EQ-5D-5L differs from the EQ-5D-3L in the following ways:

• The number of levels of perceived problems per dimension was increased from 3 to 5, increasing sensitivity and decreasing the ceiling effect.
• The most severe expression for the Mobility dimension was changed from “bedridden” to “unable to walk,” improving applicability and increasing sensitivity.
• The instructions for the EQ VAS domain have been simplified, making it easier to complete and score.

The EuroQol Group has an excellent compilation of studies comparing the EQ-5D-3L and EQ-5D-5L on their website, with the latest publications updated regularly.

Overall, the EQ-5D-3L is a validated and meaningful score for many areas of medicine. With its short response time, the effort for the patient is minimal, while the evaluation is comparatively complex. However, a significant ceiling effect must also be considered. The relevance of the EQ-5D-3L has been demonstrated in countless studies measuring patients’ quality of life, but it has been increasingly superseded by the superior EQ-5D-5L over the past decade.