What is the significance of the FRAX (Fracture Risk Assessment) score?

Significance of FRAX Score in Osteoporosis Management

The FRAX (Fracture Risk Assessment) score is a critical clinical tool that provides an individualized 10-year probability of major osteoporotic fractures and hip fractures, allowing clinicians to make evidence-based treatment decisions based on absolute fracture risk rather than BMD alone. 1

What is the FRAX Score?

FRAX is a computer-based algorithm developed by the World Health Organization Collaborating Centre for Metabolic Bone Diseases that calculates fracture probability from easily obtainable clinical risk factors in men and women. 2

The FRAX calculation incorporates:

• Demographic factors: age, sex, weight, height (BMI), race/ethnicity
• Clinical risk factors:
  • Previous fragility fracture
  • Parental history of hip fracture
  • Current smoking status
  • Long-term use of oral glucocorticoids
  • Rheumatoid arthritis
  • Secondary osteoporosis
  • Excessive alcohol consumption
• Optional: Femoral neck bone mineral density (BMD) T-score 2, 1

Clinical Importance and Application

FRAX addresses a critical limitation of BMD testing alone - while BMD is specific for fracture risk, it lacks sensitivity. Most fractures occur in people with BMD above the osteoporosis threshold (T-score > -2.5) simply because there are more people in this population. 2

Key applications include:

• Risk stratification: FRAX provides a more comprehensive assessment of fracture risk than BMD alone by incorporating clinical risk factors that are partly independent of BMD 1

• Treatment decision guidance: The output helps determine which patients would benefit from pharmacologic intervention, especially those with osteopenia (T-scores between -1.0 and -2.5) 2

• Country-specific calculations: FRAX models are calibrated for different countries and ethnic groups, accounting for geographic variations in fracture incidence 2, 1

Interpretation of FRAX Results

The FRAX score is expressed as a percentage representing:

1. 10-year probability of a major osteoporotic fracture (hip, clinical spine, humerus, or wrist)
2. 10-year probability of hip fracture specifically 1

Treatment thresholds vary by country and guidelines, but generally:

• The National Osteoporosis Foundation recommends treatment for patients with:

  • 10-year probability of hip fracture ≥3% OR
  • 10-year probability of major osteoporotic fracture ≥20% 2, 1

• These thresholds apply to patients with osteopenia (T-scores between -1.0 and -2.5); patients with osteoporosis (T-score ≤ -2.5) generally warrant treatment regardless of FRAX score 2

Special Considerations and Limitations

Glucocorticoid Adjustment

For patients on glucocorticoids at doses >7.5 mg/day of prednisone, FRAX underestimates risk. The calculated risk should be increased by:

• 15% for major osteoporotic fracture
• 20% for hip fracture 1

Important Limitations

• Not validated for adults under 40 years 1
• Does not account for:
  • Dose-response relationships for risk factors (e.g., smoking amount)
  • Falls history or frailty
  • Lumbar spine BMD
  • Trabecular bone score 1
  • Quantification of glucocorticoid exposure (only yes/no) 1

Clinical Pearls

• FRAX with BMD is more accurate than FRAX alone or BMD alone 1, 3
• For women age 65+ with no risk factors, the baseline 10-year risk for any osteoporotic fracture is approximately 9.3% 2, 1
• For women age 70+ with a parent history of hip fracture, 99% of FRAX combinations exceed treatment thresholds 4
• For women 65+ with a previous fracture, 98% of FRAX combinations exceed treatment thresholds regardless of T-score 4

Evidence Quality and Implementation

Research shows FRAX provides incremental improvement in fracture prediction compared to simplified risk assessment tools. Only 36 individuals need to be assessed using FRAX instead of simpler tools to yield an improvement in prediction 5.

FRAX has been incorporated into more than 80 guidelines worldwide and is increasingly integrated into DXA software and electronic health record systems 1, 6. The website receives approximately 3 million visits annually, demonstrating its widespread clinical adoption 6.

While FRAX should not be used to assess reduction in fracture risk in individuals already on treatment, it may still have value for guiding the need for continued treatment or treatment withdrawal 7.