FRAX Score
Assessment of the 10-year probability of major osteoporotic and hip fractures.
Understanding and Using the FRAX Score in Rheumatology
Developed by the World Health Organization (WHO) Collaborating Centre at the University of Sheffield, the FRAX (Fracture Risk Assessment Tool) has revolutionized osteoporosis management. It is no longer necessary to wait for a bone to break before acting. FRAX accurately calculates the probability that a patient (male or female over 40) will suffer a major osteoporotic fracture (spine, forearm, hip, shoulder) or a specific hip fracture in the next 10 years.
Why is the T-Score alone no longer enough?
Historically, the diagnosis of osteoporosis relied exclusively on measuring Bone Mineral Density (BMD) via dual-energy X-ray absorptiometry (DEXA). A T-Score less than or equal to -2.5 established the diagnosis. However, epidemiological studies have shown that many patients suffering fragility fractures only had osteopenia (T-score between -1 and -2.5), not strict osteoporosis. The FRAX score bridges this clinical gap by combining BMD with independent clinical risk factors:
- Age and Body Mass Index (BMI): Fracture risk increases exponentially with age and low body weight.
- Previous fractures: A prior fragility fracture doubles the risk of experiencing a new fracture.
- Corticosteroid use: Long-term corticosteroid therapy drastically weakens bone architecture, even if bone density appears acceptable.
Therapeutic Thresholds and Medical Decision
In many countries, the decision to initiate anti-osteoporotic treatment (like bisphosphonates) in an osteopenic patient relies heavily on FRAX. If the probability of a major fracture exceeds 20% or if the probability of a hip fracture exceeds 3%, preventive pharmacological treatment is strongly recommended, along with vitamin D and calcium supplementation.
Limitations of the FRAX Tool
Although it is the most widely used tool globally, clinicians must be aware of its limitations:
- It does not account for the risk of falls (neurological issues, visual impairments).
- The dose of corticosteroids is not precisely quantified (a low dose is treated the same as a high dose).
- It often underestimates the risk in patients with type 2 diabetes.
Global Risk Interpretation
| 10-Year Probability | Risk Level | Clinical Action |
|---|---|---|
| Major < 10% / Hip < 3% | Low Risk | Lifestyle and dietary rules (Exercise, Calcium). |
| Major 10-20% / Hip = 3% | Intermediate Risk | Evaluate BMD. Rheumatologist opinion. |
| Major > 20% / Hip > 3% | High Risk | Pharmacological treatment (e.g., Bisphosphonates). |
References:
1. Kanis JA, et al. FRAX and the assessment of fracture probability in men and women from the UK. Osteoporos Int. 2008.
[PubMed]
2. Cosman F, et al. Clinician's Guide to Prevention and Treatment of Osteoporosis. Osteoporosis International. 2014.
[PMC - NIH]
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