EQ-5D-5L

In 2005, a task force was formed within the so-called EuroQol group to further develop and thereby improve the EQ-5D-3L. The concrete goal was to increase the sensitivity and reduce the ceiling effect. Their efforts eventually resulted in the EQ-5D-5L as the successor to the EQ-5D-3L.¹

The task force decided to keep the number of 5 dimensions and to increase the number of response options from 3 to 5 “levels”. The reason for this was the evidence from 25 years in use which could confirm the validity of the 5 selected dimensions.^1-6

The EQ-5D-5L, like its predecessor, is a Patient Reported Outcome (PRO) instrument that uses 6 questions to generally assess patients’ quality of life, regardless of existing medical conditions. It also includes a vertical EQ visual analog scale (EQ VAS, 0-100 points) and a descriptive EQ-5D-5L system. The latter considers the following 5 dimensions or subscales over 5 levels or response options each.¹

As with the EQ-5D-3L, the descriptive EQ-5D-5L system defines so-called EQ5D Health States. A total of 3125 (5⁵) different health states can be recorded. Depending on the level, a number is assigned to each dimension, so that a 5-digit number combination is obtained.

Example: a patient has no problems with mobility (Level 1), Mild problems with self-care (Level 1), Moderate problems with general activities (Level 3), Moderate pain (Level 3) and is not anxious. Accordingly, his EQ5D Health State is 12331. A completely healthy patient would have a score of 11111.

This 5-digit number can be converted into a score using a special algorithm that is not publicly available. This point value is called the EQ-5D-5L Index and represents the patient’s health status. The algorithm used to calculate the EQ-5D-5L Index is based on the state-specific scores for the EQ-5D-3L. Via crosswalk studies with a collective of 3691 patients, an adequate link between them has been established and presented in mathematical functions for calculation. Thus EQ-5D-5L crosswalk value sets were created, with which one can calculate the respective EQ-5D-5L index on the basis of the EQ5D health states or their 5-digit numbers. An index value of 1 represents the best possible health state, while an index value of <0 (variable) represents the worst possible health state.

Due to the non-public algorithm, we cannot make any statement about whether the respective concrete EQ VAS score plays a role for the calculation of its EQ-5D-5L Index.

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

The EQ-5D-5L is a validated and established questionnaire, which can be implemented in clinical research and patient care without major effort due to its small content.^7-14 Studies of EuroQol members could further show that it has a higher statistical reliability and sensitivity compared to the EQ-5D-5L, while its ceiling effect is lower. Last but not least, it is able to distinguish between many more health states due to its finer subdivision of response options, making it even more meaningful.^15-18

Even though the ceiling effect of the EQ-5D-5L is lower than that of the EQ-5D-3L, it is still present.¹⁹

Use and analysis of the EQ-5D-5L requires a license. The amount of the license fee depends on study type, funder, cohort size, and language.²⁰ Our PRO consultants will be happy to provide more detailed information.

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

• The number of levels of experienced problems per dimension was changed from 3 to 5, increasing sensitivity and decreasing ceiling effect.
• The most severe label for the mobility dimension was changed from “bedridden” to “unable to walk,” improving applicability and increasing sensitivity of the mobility dimension.
• The instructions for the EQ-VAS domain have been simplified, making it easier to complete and score.
• The EuroQol Group provides 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-5L is a successful further development of the EQ-5D-3L, which has been validated many times and is widely used to date. Its strong validity combined with its small size provide ideal conditions for efficient use in clinical research and patient care.