SF-36: the 8 quality of life subscales and the official scoring algorithm
Complete SF-36 guide — 8 subscales, 3-step scoring algorithm, population normative values and clinical interpretation by domain.
What is the SF-36?
The SF-36 (Short Form Health Survey) is the most widely used generic quality of life questionnaire worldwide, developed by RAND Corporation in the context of the Medical Outcomes Study (Ware & Sherbourne, 1992). It assesses 8 physical and mental health domains across 36 questions.
Unlike condition-specific instruments for the knee (IKDC, KOOS) or spine (ODI), the SF-36 is generic — it can be applied to any condition or population, enabling comparisons across different diseases and treatments.
The SF-36 captures the impact of an orthopaedic condition on the patient's overall quality of life, including mental health and social function — dimensions not covered by specific scales like the IKDC or ODI. It is essential for assessing the total impact of a condition.
The 8 subscales (36 items)
| Subscale | Code | Items | What it assesses |
|---|---|---|---|
| Physical Functioning | PF | 10 (Q3a–Q3j) | Limitations in physical activities such as walking, climbing stairs, carrying weight |
| Role Physical | RP | 4 (Q4a–Q4d) | Work or ADL limitations due to physical problems |
| Bodily Pain | BP | 2 (Q7, Q8) | Pain intensity and interference with work |
| General Health | GH | 5 (Q1, Q11a–Q11d) | Perception of general health and comparison with others |
| Vitality | VT | 4 (Q9a,e,g,i) | Energy level and fatigue |
| Social Functioning | SF | 2 (Q6, Q10) | Interference of physical or emotional problems on social activities |
| Role Emotional | RE | 3 (Q5a–Q5c) | Work limitations due to emotional problems |
| Mental Health | MH | 5 (Q9b,c,d,f,h) | Anxiety, depression, emotional well-being |
Q2 (Health transition) — asks about health change compared to the previous year. It is not included in any subscale calculation, but is recorded separately for longitudinal analysis.
Calculate the SF36 for free
Apply the questionnaire online and get the score with exportable PDF.
Official scoring algorithm
2. Calculate mean of items in each subscale
3. Score = ((Mean − Minimum) / (Maximum − Minimum)) × 100
No official composite score — each subscale is independent
Option values are pre-recoded in the Orthoai calculator
The 8 subscales can be combined into two summary components: PCS (Physical Component Summary) and MCS (Mental Component Summary). These indices require population norms and specific software (SPSS/SAS with licensed algorithm from QualityMetric).
How to interpret each subscale
| Score (0–100) | Interpretation | Management |
|---|---|---|
| 75–100 | Good quality of life | Periodic monitoring |
| 50–74 | Moderate limitation | Intervention targeted at the affected subscale |
| 0–49 | Significant limitation | Priority specialist evaluation |
Interpretation must be done subscale by subscale. A patient with severe ODI (spine) may have low PF and RP, but preserved MH and VT — essential information for multidisciplinary treatment planning.
Normative values and population comparison
| Subscale | General population mean (USA) | General population mean (Brazil) |
|---|---|---|
| PF | 84.2 | 80.3 |
| RP | 80.9 | 72.4 |
| BP | 75.2 | 71.0 |
| GH | 72.0 | 68.9 |
| VT | 60.9 | 62.1 |
| SF | 83.3 | 79.8 |
| RE | 81.3 | 73.6 |
| MH | 74.7 | 72.3 |
Source: Ware (1993) for USA; Ciconelli et al. (1999) for Brazil. Patient scores below population means indicate the impact of the condition in that specific domain.
References
- 1. Ware JE, Sherbourne CD. “The MOS 36-Item Short-Form Health Survey (SF-36): I. Conceptual framework and item selection.” Medical Care, 1992;30(6):473–83.
- 2. Ciconelli RM, Ferraz MB, Santos W, Meinão I, Quaresma MR. “Tradução para a língua portuguesa e validação do questionário genérico de avaliação de qualidade de vida SF-36.” Rev Bras Reumatol, 1999;39(3):143–50.
- 3. Ware JE. “SF-36 Health Survey: Manual and Interpretation Guide.” Boston: The Health Institute, New England Medical Center, 1993.