How is the FRAX (Fracture Risk Assessment Tool) score used to determine osteoporosis treatment?

Using FRAX Score to Determine Osteoporosis Treatment

The FRAX (Fracture Risk Assessment Tool) score should be used to calculate 10-year fracture probability, with treatment recommended when the 10-year risk is ≥3% for hip fracture or ≥20% for major osteoporotic fracture in patients with low bone mass.

Understanding FRAX and Its Purpose

• FRAX is a computer-based algorithm developed by the Sheffield WHO Collaborating Centre for Metabolic Bone Diseases that calculates fracture probability from easily obtainable clinical risk factors in men and women 1
• The output provides the 10-year probability of a major osteoporotic fracture (hip, clinical spine, humerus, or wrist) and the 10-year probability of hip fracture specifically 1
• FRAX was designed to overcome the limitations of using BMD alone, as BMD is specific but not very sensitive - most fractures occur in people with BMD above the osteoporosis threshold (T-score > -2.5) 1

FRAX Calculation Inputs

• FRAX incorporates the following risk factors: age, sex, BMI, prior fragility fracture, parental history of hip fracture, current tobacco smoking, long-term use of oral glucocorticoids, rheumatoid arthritis, other causes of secondary osteoporosis, and excessive alcohol consumption 1
• Femoral neck BMD can be optionally included to enhance fracture risk prediction 1
• Including BMD in the calculation significantly improves the accuracy of FRAX predictions compared to using clinical risk factors alone 1
• For patients on glucocorticoids at doses >7.5 mg/day, the fracture risk generated with FRAX should be increased by 15% for major osteoporotic fracture and 20% for hip fracture risk 1

Treatment Thresholds Based on FRAX

• According to National Osteoporosis Foundation guidelines, pharmacologic treatment is recommended for:
  • All postmenopausal women and men >50 years with a T-score ≤ -2.5 1
  • Patients with low bone mass (osteopenia) who have a 10-year probability of hip fracture ≥3% or major osteoporotic fracture ≥20% based on FRAX 1, 2
• European guidelines recommend setting the intervention threshold at a particular age to the age-specific probability of future fracture conveyed by the presence of a prior fragility fracture 1

Special Populations and Considerations

• For adults ≥40 years on glucocorticoids, risk stratification should be performed using FRAX with BMD and history of fracture 1
• High fracture risk in glucocorticoid users is defined as:
  • Prior osteoporotic fracture
  • Hip or spine BMD T-score ≤ -2.5
  • FRAX (GC-adjusted) 10-year risk of major osteoporotic fracture ≥20%
  • FRAX (GC-adjusted) 10-year risk of hip fracture ≥3% 1
• FRAX is not validated for patients <40 years of age; clinical risk assessment with BMD testing should be used instead 1, 2

Practical Application of FRAX

• FRAX should be calculated using country-specific versions that have been calibrated using local fracture incidence and mortality data 1
• T-scores should always be included when available for optimal application of FRAX, as calculations without T-scores may lead to inappropriate treatment recommendations 3
• FRAX can be used to predict fracture probability in women currently or previously treated for osteoporosis, though it should not be used to assess treatment response 4
• Reassessment using FRAX should be completed every 1-3 years for adults on continued glucocorticoid treatment who are not on osteoporosis medication 2

Limitations of FRAX

• FRAX uses binary (yes/no) rather than quantified exposure for factors like glucocorticoids and alcohol use 1, 2
• It doesn't account for falls or frailty, which are significant fracture risk factors 1, 2
• Race-specific FRAX calculators may lead to differences in treatment recommendations among persons with otherwise identical risk profiles 1, 2
• FRAX may overestimate risk in patients with rheumatoid arthritis who are already at high predicted risk 5

Clinical Decision Algorithm

1. For patients ≥40 years old, calculate FRAX score (preferably with BMD included)
2. For patients on glucocorticoids >7.5 mg/day, adjust FRAX score (multiply major osteoporotic fracture risk by 1.15 and hip fracture risk by 1.2) 1
3. Determine treatment based on these thresholds:
   • Treat if 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20% 1, 2
   • Treat if patient has osteoporosis (T-score ≤ -2.5) regardless of FRAX score 1
   • Treat if patient has a prior fragility fracture regardless of FRAX score 1
4. For patients <40 years old, use clinical risk assessment and BMD instead of FRAX 1, 2