How do I calculate the FRAX (Fracture Risk Assessment Tool) score for a postmenopausal woman with a history of smoking and possible hormone replacement therapy (HRT)?

How to Calculate the FRAX Score

Access the free online FRAX calculator at https://www.shef.ac.uk/FRAX/ and input the required clinical risk factors—the tool automatically computes 10-year hip fracture and major osteoporotic fracture probabilities without requiring complex manual calculations. 1

Required Input Variables

The FRAX algorithm requires the following easily obtainable clinical information 1:

Mandatory Inputs

• Age (40-90 years) 2
• Sex (male or female)
• Body mass index (BMI) or weight and height 1
• Country/ethnicity (select appropriate population—U.S. tool includes White, Black, Asian, and Hispanic options) 1

Clinical Risk Factors (Yes/No Questions)

• Previous fragility fracture (any prior fracture from standing height or less) 1, 2
• Parental history of hip fracture 1
• Current smoking status 1
• Glucocorticoid use (≥5 mg prednisone daily for ≥3 months) 2
• Rheumatoid arthritis 2
• Secondary osteoporosis (conditions causing bone loss) 2
• Alcohol consumption (3 or more units daily) 1

Optional Input

• Femoral neck bone mineral density (BMD) T-score from DXA scan 1, 2

Critical Calculation Notes

When to Include BMD

Including the femoral neck T-score significantly improves prediction accuracy and should be used whenever available 3. FRAX can be calculated without BMD, but this may lead to treatment errors in two specific scenarios 3:

• Older patients with normal T-scores: FRAX without BMD may overestimate risk and recommend unnecessary treatment 3
• Younger patients with high BMI and low T-scores: FRAX without BMD may underestimate risk and miss patients who need treatment 3

Glucocorticoid Dose Adjustment

For patients taking prednisone >7.5 mg/day, manually adjust the calculated FRAX scores by multiplying the major osteoporotic fracture risk by 1.15 and hip fracture risk by 1.2 1, 4. The standard FRAX tool assumes moderate glucocorticoid doses and underestimates risk at higher doses 1.

Interpreting Results

The calculator provides two outputs 1, 4:

• 10-year probability of hip fracture (%)
• 10-year probability of major osteoporotic fracture (clinical vertebral, hip, forearm, or humerus) (%)

Treatment Thresholds

Pharmacologic treatment is recommended when FRAX indicates ≥3% 10-year hip fracture risk OR ≥20% 10-year major osteoporotic fracture risk 4, 5, 2.

Screening Thresholds for Younger Women

For postmenopausal women aged 50-64 years, screen with DXA if FRAX score (calculated without BMD) approaches or exceeds 9.3% for major osteoporotic fracture or 1.3% for hip fracture—this represents the baseline risk of a 65-year-old White woman with no other risk factors 1, 4.

Important Limitations and Pitfalls

Race-Based Disparities

FRAX systematically predicts lower fracture risk for Asian, Black, and Hispanic individuals compared to White individuals with identical clinical profiles, potentially leading to undertreatment in non-White populations 1, 4. Consider this when making treatment decisions for minority patients.

Missing Risk Factors

FRAX does not account for several important clinical factors 4:

• Fall history (independent fracture predictor)
• Number of prior fractures (only captures presence/absence)
• Frailty status
• Diabetes mellitus
• Lumbar spine BMD (only uses femoral neck)
• Trabecular bone score

Use clinical judgment to adjust treatment decisions when these additional risk factors are present, particularly for patients near treatment thresholds 2.

Validation Restrictions

FRAX is validated only for untreated patients aged 40-90 years—do not use it to monitor patients already receiving osteoporosis therapy 2.

Special Populations

For postmenopausal women with breast cancer, FRAX underestimates fracture risk because it does not account for cancer-specific treatments like aromatase inhibitors, which increase fracture risk by 40% compared to tamoxifen 1. Consider BMD testing and treatment at lower FRAX thresholds in this population 1.

Hormone Replacement Therapy

Do not input current HRT use into FRAX—the tool is designed for untreated patients and does not have a field for HRT 2. If the patient is currently on HRT, calculate FRAX as if she were not on treatment to assess her underlying fracture risk.

Practical Application for Your Patient

For a postmenopausal woman with smoking history and possible HRT:

1. Access the U.S. FRAX calculator at the WHO website 1
2. Input her age, BMI, and ethnicity
3. Answer "Yes" to current smoking
4. Do not adjust for HRT (calculate baseline risk) 2
5. Include femoral neck T-score if DXA available 3
6. Review the calculated 10-year probabilities
7. Recommend treatment if hip fracture risk ≥3% OR major osteoporotic fracture risk ≥20% 4, 5