EQ5D

EQ-5D is a standardized instrument for measuring health-related quality of life. Developed by the EuroQol Group, it is designed to provide a brief, generic assessment that can be used across diseases and treatments and in economic evaluations. The instrument combines a descriptive system with a quantitative scale to summarize health status in a single score.

Its descriptive system asks respondents to describe their health in five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. The original version, EQ-5D-3L, uses three levels of problems (no problems, some problems, extreme problems); the later EQ-5D-5L expands to five levels (no problems, slight, moderate, severe, extreme problems). In addition, respondents may rate their overall health on the EQ-VAS, a 0–100 visual analogue scale.

Descriptive responses can be converted into a single utility index using country-specific value sets, enabling calculation of quality-adjusted life years (QALYs) in health economics. The instrument has been translated and validated in many languages, and a pediatric version, the EQ-5D-Y, is available for children and adolescents.

EQ-5D is widely used in clinical trials, population health surveys, and HTA to compare health outcomes across interventions. As a generic measure, it may not capture condition-specific issues and can exhibit ceiling effects in healthier populations. Cross-cultural differences in interpretation also require careful selection of language versions and value sets.

Developed in the 1990s by the EuroQol Group, the instrument has evolved from the 3L to the 5L version to improve sensitivity and discrimination across health states.