When to Use the FRAX Calculator
The FRAX calculator should be used for adults aged 40-90 years to assess 10-year probability of hip fracture or major osteoporotic fracture, with particular value in patients with osteopenia to determine if pharmacologic treatment is warranted. 1
Primary Indications
- FRAX is designed for adults aged 40-90 years to predict 10-year probability of hip fracture or major osteoporotic fracture 2, 1
- FRAX is particularly valuable in patients with osteopenia (T-scores between -1.0 and -2.5) to determine if pharmacologic treatment is warranted 1, 3
- FRAX should be used in untreated patients only, as it is not validated for use in patients already receiving osteoporosis treatment 3
- For adults ≥40 years initiating glucocorticoid therapy ≥2.5 mg/day for >3 months, FRAX with glucocorticoid dose adjustment should be used within 6 months of starting treatment 2
Specific Clinical Scenarios
- For postmenopausal women and men over 50 years with low bone mass but not osteoporosis, FRAX helps identify those who would benefit from treatment 1, 3
- In patients on glucocorticoids, FRAX should be used with dose adjustment, increasing major osteoporotic fracture risk by 1.15 and hip fracture risk by 1.2 if prednisone dose >7.5 mg/day 2, 1
- For screening postmenopausal women younger than 65 years who have one or more risk factors for fracture 2
- When DXA results alone may not capture full fracture risk, especially in younger populations with risk factors 1
FRAX Inputs and Risk Factors
- FRAX incorporates age, sex, weight, height, previous fracture, parent hip fracture, current smoking, glucocorticoid use, rheumatoid arthritis, secondary osteoporosis, alcohol consumption, and femoral neck BMD (when available) 2, 4
- Age and T-score are the strongest contributors to hip fracture risk, while BMI has marginal contribution 4
- Of the clinical risk factors, parent history of fracture and ongoing glucocorticoid treatment have the largest additive effect on risk score 4
Reassessment Intervals
- For adults ≥40 years on continued glucocorticoid treatment who are not on osteoporosis medication, FRAX reassessment should be completed every 1-3 years 2
- Earlier reassessment within this timeframe is recommended for patients on very high-dose glucocorticoids (initial prednisone dose ≥30 mg/day or cumulative dose >5 gm in the previous year) 2
- For patients with history of osteoporotic fracture, reassessment should be performed more frequently 2
Treatment Thresholds Based on FRAX
- Treatment is recommended for patients with FRAX 10-year risk scores of ≥3% for hip fracture or ≥20% for major osteoporotic fracture 2, 3
- For women 65 years and older with a previous fracture, 98% of FRAX combinations exceed the treatment threshold, regardless of T-score or other factors 4
- For women age 70+ with a parent history of fracture, 99% of FRAX combinations exceed the treatment threshold 4
Limitations and Considerations
- FRAX has race-specific calculators which may lead to differences in treatment recommendations among persons with otherwise identical risk profiles 2
- The calculator does not account for dose-dependent effects of risk factors like glucocorticoids (only binary yes/no) and alcohol use 2
- FRAX does not include information about falls or frailty, which are important risk factors for fracture 2
- The predictive accuracy of FRAX improves when BMD is included in the risk assessment calculation 2, 1
- FRAX is not validated for use in patients under 40 years of age 2, 1
- The discriminative ability of FRAX is only moderate (AUC range: 0.60-0.70), which may limit its clinical utility in some populations 5
Integration with Other Assessment Tools
- FRAX should be used alongside clinical fracture risk assessment, which includes evaluation of falls, fractures, frailty, and other risk factors 2, 1
- When available, including BMD measurements from DXA improves the accuracy of FRAX predictions 2, 1
- For patients <40 years of age, clinical risk assessment with BMD testing should be used instead of FRAX 2, 1