At what Frax (Fracture Risk Assessment Tool) score should treatment for osteoporosis be considered based on bone density?

FRAX Score Thresholds for Osteoporosis Treatment Based on Bone Mineral Density

Treatment for osteoporosis should be initiated when the FRAX 10-year probability is ≥20% for major osteoporotic fracture or ≥3% for hip fracture, regardless of T-score, or when T-score is ≤-2.5 at any major site. 1, 2

Fracture Risk Categories and Treatment Thresholds

High Fracture Risk (Treatment Recommended)

• T-score ≤-2.5 at any major site (spine, hip, or forearm)
• Prior osteoporotic fracture
• FRAX 10-year probability of major osteoporotic fracture ≥20%
• FRAX 10-year probability of hip fracture ≥3%

Moderate Fracture Risk (Consider Treatment)

• FRAX 10-year probability of major osteoporotic fracture 10-19%
• FRAX 10-year probability of hip fracture >1% and <3%
• T-scores in the osteopenic range (-1.0 to -2.4) with additional risk factors

Low Fracture Risk (No Treatment)

• FRAX 10-year probability of major osteoporotic fracture <10%
• FRAX 10-year probability of hip fracture ≤1%

Special Considerations for FRAX Interpretation

Glucocorticoid Users

For patients on glucocorticoid therapy, FRAX scores should be adjusted:

• Increase the risk generated with FRAX by 1.15 for major osteoporotic fracture
• Increase the risk generated with FRAX by 1.2 for hip fracture if glucocorticoid dose is >7.5 mg/day 1

For example, if hip fracture risk is 2.0%, increase to 2.4% for patients on significant glucocorticoid therapy.

Age Considerations

• FRAX algorithm is country-specific and intended for previously untreated postmenopausal women and men aged 40-90 years 1
• For patients <40 years, different criteria apply, focusing on Z-scores and presence of fractures 1

Clinical Implementation

Diagnostic Approach

1. Measure BMD via DXA at lumbar spine and hip (femoral neck and total hip)
2. Calculate FRAX score incorporating BMD when available
3. Identify presence of prior fragility fractures
4. Assess for secondary causes of osteoporosis

Important Caveats

• Approximately 60% of osteoporotic fractures occur in patients with T-scores higher than -2.5, emphasizing the importance of FRAX assessment even in osteopenic patients 2
• The risk of subsequent fracture is highest immediately after an index fracture, necessitating prompt intervention 2
• FRAX can still be used to predict fracture probability in women currently or previously treated for osteoporosis, though it should not be used to assess treatment effectiveness 3

Potential Discordance

• FRAX scores with and without BMD may yield discordant results in approximately 16% of cases 4
• Discordance is more common in elderly patients, those with lower BMD, and when FRAX without BMD is near the intervention threshold 4
• When discordance occurs, treatment decisions should prioritize FRAX with BMD when available

Treatment Selection Based on Risk Category

High Risk

• First-line: Oral bisphosphonates (alendronate, risedronate)
• Alternative: IV bisphosphonate (zoledronic acid) or denosumab if oral medications are contraindicated

Very High Risk

• Consider anabolic agents (teriparatide, abaloparatide, romosozumab) followed by antiresorptive therapy, especially for:
  • Recent vertebral fractures
  • Multiple fractures
  • T-score ≤-3.5
  • FRAX ≥30% for major osteoporotic fracture or ≥4.5% for hip fracture 2, 5

By following these evidence-based thresholds for initiating treatment based on FRAX scores and BMD, clinicians can appropriately identify patients who would benefit from osteoporosis therapy to reduce fracture risk and associated morbidity and mortality.