8.3 FRAX Clinical Application & Treatment Thresholds
Key Takeaways
FRAX estimates 10-year hip fracture and major osteoporotic fracture probabilities with optional femoral neck BMD.
Use the appropriate population model and retain age, sex, weight and height when BMD is entered. Lumbar spine and total hip BMD are not standard FRAX BMD inputs.
For U.S. postmenopausal women and men aged 50 or older with low bone mass at the femoral neck or total hip, BHOF uses hip probability of at least 3% or major probability of at least 20% for treatment consideration.
A qualifying DXA T-score or hip or vertebral fracture can independently support treatment consideration without a high FRAX result.
Read the two probabilities correctly
The Fracture Risk Assessment Tool (FRAX) estimates 10-year absolute probabilities using clinical inputs, with optional femoral neck bone mineral density (BMD). It was developed by a team at the University of Sheffield and is now available through FRAXplus. The model uses country-specific fracture and mortality information. It accounts for death as a competing event, so the output is a probability over time rather than a count of fractures or a measure of BMD.
FRAX gives a hip fracture probability and a major osteoporotic fracture probability (MOF). MOF includes clinical vertebral, hip, distal forearm and proximal humerus fracture. Hip is already one of the sites in the MOF outcome. Do not add the two percentages.
Enter the appropriate model and inputs
Select the population model appropriate to the patient and clinical guidance, and record which model you used. Fracture incidence and mortality differ across populations, so the same inputs may yield different estimates in different models. Some countries have more than one model. The standard calculator is intended for ages 40 through 90. An output obtained at an age boundary does not validate extrapolation to a younger or older patient.
| Input group | What the standard calculator asks for |
|---|---|
| Demographics and body size | Age, sex, weight and height. Enter the measured values in the units requested. |
| Fracture history | Previous fragility fracture in adult life and parental hip fracture are separate fields. An existing morphometric vertebral fracture may count as a previous fracture. |
| Exposures | Current smoking, oral glucocorticoids as defined by the calculator's instructions, and alcohol of three or more units per day. Use the calculator's definition of a unit. |
| Clinical conditions | Rheumatoid arthritis has its own input. The secondary osteoporosis input is for specified conditions, such as type 1 diabetes, osteogenesis imperfecta in adults, longstanding untreated hyperthyroidism, hypogonadism or premature menopause, chronic malnutrition or malabsorption, or chronic liver disease. |
| Optional BMD | Use valid femoral neck BMD. When using the femoral neck T-score option, use the appropriate young-adult White female NHANES III reference for both sexes. |
Keep the body-size inputs even when supplying BMD. Standard FRAX accepts no lumbar spine or total hip BMD in the femoral neck field. If the femoral neck is unavailable or technically invalid, run FRAX without BMD if the risk estimate will be useful. Follow the calculator instructions for inputs rather than substituting another site or assuming that all secondary causes should be entered.
The generic secondary osteoporosis input in conventional FRAX is treated as acting through BMD when femoral neck BMD is supplied. Rheumatoid arthritis and glucocorticoids are separate fields. A disease history remains clinically relevant even when a particular calculator field does not increase the reported probability.
Apply the guideline that fits the patient
For U.S. postmenopausal women and men aged 50 or older, the Bone Health and Osteoporosis Foundation (BHOF, formerly NOF) advises considering pharmacologic treatment in the following settings:
- Low bone mass at the femoral neck or total hip with a U.S. FRAX 10-year hip fracture probability of at least 3% or 10-year MOF probability of at least 20%.
- A DXA T-score of −2.5 or lower at the lumbar spine, total hip, femoral neck or an indicated one-third radius. BHOF notes some uncertainty with the evidence for the radius.
- Hip or vertebral fracture regardless of BMD. Proximal humerus, pelvis or distal forearm fracture with low bone mass also supports consideration. Individualize the decision in those patients without low bone mass.
For example, a U.S. postmenopausal patient has a valid femoral neck T-score of −1.8 and supplied FRAX probabilities of 2.9% hip and 20.0% MOF. She meets the MOF threshold even though the hip probability is below 3%. Another patient with a valid spine T-score of −2.8 already meets the BMD treatment-consideration criterion, even if a hip-based FRAX estimate is below both cutoffs. Do not treat the U.S. thresholds as universal or select treatment from a probability alone. When conventional FRAX omits a material clinical factor, see FRAX limitations and adjustments.
FRAXplus calculator · FRAXplus FAQ · FRAX development history · BHOF Clinician’s Guide
Under U.S. BHOF guidance, what 10-year FRAX thresholds support treatment consideration in a postmenopausal woman or man aged 50 or older with low bone mass at the femoral neck or total hip?
MOF at least 10% or hip at least 1.5%.
MOF at least 15% or hip at least 5%.
MOF at least 20% or hip at least 3%.
MOF at least 25% or hip at least 2.5%.
A patient has valid total hip and lumbar spine DXA results, but the femoral neck measurement cannot be interpreted. What should be entered into the standard FRAX BMD field?
The lower of the two valid non-neck scores.
No BMD value. If clinically useful, calculate FRAX with the appropriate model and clinical inputs.
The total hip BMD adjusted by the spine T-score.
The lumbar spine BMD because the spine and hip use the same measurement units.
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