Clinical Overview & History
The EQ-5D (EuroQol 5-Dimension) questionnaire is a standardized, non-disease-specific instrument developed by the EuroQol Group in 1987 to measure and value health-related quality of life (HRQoL). Unlike disease-specific surveys, the EQ-5D is a generic questionnaire, allowing it to compare health outcomes across diverse clinical populations, disease areas, and interventions. Its simplicity, brevity, and cognitive ease make it the most widely used patient-reported outcome measure (PROM) in clinical trials, observational research, and population health monitoring.
Additionally, it serves as the foundational tool for health economic evaluations—specifically Cost-Utility Analysis (CUA)—which is used by global regulatory agencies (such as the National Institute for Health and Care Excellence, or NICE, in the UK) to assess the value and cost-effectiveness of new clinical therapies.
Pathophysiology and Dimensions
Quality of life is a multi-dimensional construct encompassing physical, functional, mental, and social health. The EQ-5D captures these elements using a two-part descriptive system: a five-dimension questionnaire and a Visual Analogue Scale (VAS).
The five descriptive dimensions represent major components of health-related functioning:
- Mobility (M): Evaluates physical walking ability and lower extremity function.
- Self-Care (SC): Measures independence in activities of daily living, specifically washing and dressing.
- Usual Activities (UA): Assesses performance of typical daily roles, including work, study, housework, family responsibilities, and leisure activities.
- Pain/Discomfort (PD): Gauges the presence and severity of physical pain.
- Anxiety/Depression (AD): Evaluates the presence and severity of psychological distress.
In the classic EQ-5D-3L version, each dimension has three selectable severity levels:
- Level 1: No problems
- Level 2: Some/moderate problems
- Level 3: Extreme/unable to perform
Selecting a level for each dimension yields a 5-digit health state profile (e.g., '11111' represents perfect health; '33333' represents the worst possible health state). The second part of the assessment is the EQ-VAS (Visual Analogue Scale). It is a vertical, visual scale from 0 to 100 where patients rate their overall health state on that day, with 0 indicating the "worst imaginable health state" and 100 indicating the "best imaginable health state."
Formula & Scoring Interpretation
The 5-digit health profile is converted into a single utility index score (value set) ranging from $< 0$ (where some states are valued as worse than death, which is scored as $0.0$) to $1.0$ (perfect health). The index score is calculated by subtracting decrements (weights) from $1.0$ based on societal preferences derived from valuation surveys in specific countries (e.g., UK, US).
Health State Profile = 5-digit code generated from responses
Where the Constant represents any deviation from perfect health, the Dimension Decrements correspond to the level selected in each of the five categories, and N3 is an additional penalty if any dimension is at Level 3.
Step-by-Step Clinical Scenario
Consider a clinical case: A 62-year-old male recovering from a total hip arthroplasty completes the EQ-5D-3L questionnaire 6 weeks post-surgery.
- Mobility: He reports some problems walking (Level 2).
- Self-Care: He has no problems washing or dressing himself (Level 1).
- Usual Activities: He has some problems performing his usual work and leisure activities (Level 2).
- Pain/Discomfort: He reports moderate pain (Level 2).
- Anxiety/Depression: He reports no anxiety or depression (Level 1).
- Overall health today (EQ-VAS): He marks 75 on the visual scale.
His resulting 5-digit health profile is 21221. Using the UK preference-based tariff, the utility index is calculated by subtracting specific coefficients:
- Constant (for any problem): $0.081$
- Mobility (Level 2): $0.069$
- Self-Care (Level 1): $0.000$
- Usual Activities (Level 2): $0.036$
- Pain/Discomfort (Level 2): $0.123$
- Anxiety/Depression (Level 1): $0.000$
His utility index score is $0.691$, and his subjective self-rated health state is $75/100$ on the VAS. These scores represent his functional recovery baseline.
Clinical Utility and Limitations
The primary clinical utility of the EQ-5D index score is the calculation of Quality-Adjusted Life Years (QALYs). QALYs are calculated by multiplying the quantity of life (years gained by a treatment) by the quality of life (the EQ-5D utility index score during those years). For example, 10 years of life in a health state with a utility index of 0.6 yields 6 QALYs ($10 \times 0.6$).
The main limitation is the "ceiling effect" in the 3L version, where minor improvements in healthy populations are missed because many patients score a perfect 11111. The EQ-5D-5L version mitigates this by expanding response levels to 5.
⚠️ Medical Disclaimer: This calculator is for educational and reference purposes only. It is not intended to diagnose, treat, or cure any disease, and should not be used as a substitute for professional clinical judgment.