What is the difference between EQ-5D and SF-36?
The primary difference between the EQ-5D and SF-36 lies in their purpose, structure, and the type of health outcome measure they produce, particularly concerning the ability to generate preference-based utility scores. While both are widely used generic measures of health, the EQ-5D is designed to generate utility scores for economic evaluation, whereas the SF-36 provides a detailed health profile.
Understanding Health-Related Quality of Life (HRQoL) Measures
Both the EQ-5D (EuroQol Five-Dimension) and the SF-36 (Short Form 36 Health Survey) are standardized questionnaires used to assess an individual's health-related quality of life (HRQoL). These tools are invaluable in clinical research, public health, and health economics for understanding the impact of diseases, treatments, and interventions on people's lives.
EQ-5D: Preference-Based Utility for Economic Evaluation
The EQ-5D is a concise and generic preference-based measure of health-related quality of life. It is particularly designed to produce utility scores, which are numerical values reflecting the desirability of a health state, typically ranging from 0 (representing dead) to 1 (representing perfect health). These utility scores are crucial for economic evaluations, such as cost-utility analyses, where they are used to calculate Quality-Adjusted Life Years (QALYs).
Key Characteristics of EQ-5D:
- Structure: It comprises five dimensions of health:
- Mobility
- Self-care
- Usual activities
- Pain/discomfort
- Anxiety/depression
Each dimension is rated on a 3-level (EQ-5D-3L) or 5-level (EQ-5D-5L) scale, describing the severity of problems.
- Visual Analogue Scale (VAS): In addition to the five dimensions, the EQ-5D also includes a Visual Analogue Scale (EQ VAS), where respondents rate their overall health on a scale from 0 (worst imaginable health) to 100 (best imaginable health).
- Output: Generates a health state description that can be converted into a single utility score using country-specific value sets. These scores are anchored at 0 for dead and 1 for perfect health.
- Primary Use: Widely used in health technology assessment and economic evaluations to inform resource allocation decisions, making it the most widely used generic preference-based measure for this purpose.
SF-36: Comprehensive Health Profile
The SF-36 is a longer, more comprehensive generic health status questionnaire designed to measure functional health and well-being from the patient's perspective. Unlike the EQ-5D, the SF-36 itself does not directly produce preference-based utility scores. Instead, it generates a health profile across various domains.
Key Characteristics of SF-36:
- Structure: It consists of 36 items grouped into eight health domains:
- Physical Functioning
- Role-Physical (problems with work or other daily activities as a result of physical health)
- Bodily Pain
- General Health
- Vitality
- Social Functioning
- Role-Emotional (problems with work or other daily activities as a result of emotional problems)
- Mental Health
- Output: Provides scores for each of the eight domains, which can be summarized into two broader composite scores: the Physical Component Summary (PCS) and the Mental Component Summary (MCS). These scores offer a detailed profile of an individual's health status.
- Preference-Based Index: While the SF-36 itself is not a preference-based measure, it can be used to generate a preference-based index via the SF-6D. This means that a separate algorithm or mapping function is applied to SF-36 scores to derive utility values, allowing it to be used in economic evaluations similar to the EQ-5D.
- Primary Use: Frequently used in population health surveys, clinical trials, and observational studies to assess the burden of disease, monitor treatment effectiveness, and track changes in health over time.
Comparative Summary
Here's a table summarizing the key differences between EQ-5D and SF-36:
| Feature | EQ-5D (EuroQol Five-Dimension) | SF-36 (Short Form 36 Health Survey) |
|---|---|---|
| Type of Measure | Generic, Preference-Based Measure (Utility) | Generic, Health Profile Measure |
| Number of Dimensions/Items | 5 dimensions (+ VAS) | 36 items across 8 domains |
| Output | Single utility score (e.g., 0-1), health state description, VAS score | Scores for 8 health domains, 2 summary scores (PCS, MCS) |
| Primary Purpose | Economic evaluation (QALYs), health state valuation | Detailed health profiling, general health assessment |
| Utility Score Generation | Directly generates utility scores anchored at 0 (dead) and 1 (perfect health) using value sets | Does not directly generate utility scores; requires mapping to SF-6D to derive a preference-based index |
| Length | Shorter, less detailed | Longer, more comprehensive |
| Sensitivity | May be less sensitive to subtle changes in specific health domains due to fewer items | Generally more sensitive to changes in specific aspects of health due to broader coverage |
In essence, if the goal is to generate a single utility value for cost-effectiveness analysis, the EQ-5D is the more direct and widely used tool. If a more detailed understanding of various aspects of physical and mental health is required, the SF-36 provides a richer profile, though its data needs further processing (e.g., via SF-6D) to yield utility scores.
