FRAX Score Calculation and Interpretation

Patient Selection and Input Variables

• The World Health Organization recommends calculating the FRAX score using the online calculator by entering patient age, sex, clinical risk factors, and optionally femoral neck BMD T-score to generate a 10-year probability of hip fracture and major osteoporotic fracture, applicable to postmenopausal women and men aged 50 years and older 1, 2
• The National Osteoporosis Foundation suggests that pharmacologic treatment is recommended when the 10-year probability of hip fracture is ≥3% or the 10-year probability of major osteoporotic fracture is ≥20% 3, 4
• The American College of Rheumatology indicates that clinical risk factors for FRAX calculation include prior fragility fracture, parental hip fracture history, current tobacco smoking, glucocorticoid use, rheumatoid arthritis, secondary osteoporosis, and alcohol consumption 5

Clinical Risk Factors and Adjustments

• The European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis recommends adjusting the calculated FRAX scores for patients on glucocorticoids with prednisone dose >7.5 mg/day by multiplying major osteoporotic fracture risk by 1.15 and hip fracture risk by 1.2 3
• The International Osteoporosis Foundation notes that FRAX does not account for dose-dependent effects of glucocorticoids beyond the dichotomous yes/no input, and does not capture fall risk 3

Reassessment and Treatment Thresholds

• The National Osteoporosis Foundation suggests reassessing FRAX every 1-3 years for patients on glucocorticoids not receiving osteoporosis treatment, with earlier reassessment for very high-dose glucocorticoid users 3
• The American Academy of Orthopaedic Surgeons recommends repeating FRAX in 2 years for patients with osteopenia and low initial FRAX scores, or in 1 year if new risk factors develop 4

FRAX Score Clinical Application Guidelines

Patient Selection and Treatment Thresholds

• The American College of Radiology recommends using FRAX to calculate 10-year absolute fracture probability for untreated postmenopausal women and men aged 40-90 years, with treatment thresholds of ≥3% 10-year hip fracture risk or ≥20% 10-year major osteoporotic fracture risk 6
• The US Preventive Services Task Force uses a threshold equivalent to a 65-year-old white woman's baseline risk (9.3% 10-year major fracture probability) for screening younger postmenopausal women (ages 50-64) 7

Glucocorticoid Adjustments and Risk Stratification

• For patients on prednisone >7.5 mg/day, manually adjust the calculated FRAX scores by multiplying major osteoporotic fracture risk by 1.15 and hip fracture risk by 1.2, as recommended by Arthritis Care & Research 8
• Nature Reviews Rheumatology suggests categorizing patients into risk tiers to guide medication choice, with very high risk patients considered for anabolic therapy and high risk patients considered for oral bisphosphonates 9

Limitations and Pitfalls

• JAMA notes that FRAX has important constraints, including the use of binary glucocorticoid exposure, lack of incorporation of lumbar spine BMD or trabecular bone score, and limitations in accounting for fall history or frailty 7
• Arthritis Care & Research highlights the need for manual adjustment of FRAX scores for high-dose glucocorticoid users and the potential for disparities in race-specific calculators 8

Osteoporotic Fracture Risk Calculation

Introduction to FRAX Tool

• The American Medical Association recommends using the FRAX calculator to calculate 10-year probability of hip fracture and major osteoporotic fracture by entering patient age, sex, clinical risk factors, and femoral neck BMD T-score when available 10, 11
• The FRAX tool is the most studied and widely validated fracture risk assessment tool, incorporated into 120 guidelines worldwide and FDA-approved for integration into DXA software 11

Treatment Thresholds Based on Calculated Risk

• The Mayo Clinic recommends considering anabolic therapy first for patients with very high fracture risk, defined as MOF risk >30% or hip fracture risk >4.5% 12, 13
• The Mayo Clinic also recommends considering antiresorptive therapy for patients with high fracture risk, defined as MOF risk ≥20% or hip fracture risk ≥3% 12, 13
• For patients with intermediate fracture risk, age-dependent FRAX probability thresholds and T-score between -1.0 and -2.5 with MOF risk 10-20% or hip fracture risk 1-3% should be considered 12, 13

Alternative Risk Assessment Tools

• Other validated tools include the Garvan Fracture Risk Calculator, which calculates 5-year and 10-year risk and includes fall history 11
• The Fracture Risk Calculator (FRC) and CAROC (Canadian tool) are also alternative risk assessment tools 11, 12, 13

Important Limitations and Pitfalls

• The FRAX tool is only validated for untreated patients aged 40-90 years and does not account for dose-dependent effects of glucocorticoids beyond yes/no 11
• The FRAX tool also does not account for fall history, frailty, lumbar spine BMD, or trabecular bone score, and may underestimate risk in non-White populations 10, 11

FRAX‑Based Treatment Thresholds for Osteoporosis

Treatment Initiation Criteria

• For adults ≥ 50 years (postmenopausal women or men), start osteoporosis therapy when the 10‑year FRAX probability is ≥ 3 % for hip fracture or ≥ 20 % for a major osteoporotic fracture (clinical spine, hip, forearm, or humerus). 14
• A hip‑fracture probability of ≥ 3 % alone is sufficient to recommend treatment, regardless of the major‑fracture probability. [14][15]
• A major‑osteoporotic fracture probability of ≥ 20 % alone is sufficient to recommend treatment, regardless of the hip‑fracture probability. [14][15]

Risk Stratification Framework

Very High Risk (Immediate Treatment Required)

• Major‑osteoporotic fracture risk > 30 % (any sex, age ≥ 50). 14
• Hip‑fracture risk > 4.5 % (any sex, age ≥ 50). 14
• Recent fragility fracture within the past 12 months. 14
• Multiple fragility fractures at any time. 14
• T‑score < ‑3.0 at the hip or spine. 14
• Fracture occurring while on osteoporosis therapy. 14

High Risk (Strong Recommendation for Treatment)

• Major‑osteoporotic fracture risk ≥ 20 % (any sex, age ≥ 50). [14][15]
• Hip‑fracture risk ≥ 3 % (any sex, age ≥ 50). [14][15]
• T‑score ≤ ‑2.5 at the hip or spine in postmenopausal women or men ≥ 50 years. 15
• Any prior osteoporotic fracture (regardless of FRAX score). 14

Moderate Risk (Conditional Treatment)

• Major‑osteoporotic fracture risk 10–19 % (any sex, age ≥ 50). 15
• Hip‑fracture risk > 1 % and < 3 % (any sex, age ≥ 50). 15

Low Risk (Treatment Generally Not Indicated)

• Major‑osteoporotic fracture risk < 10 % (any sex, age ≥ 50). [15][16]
• Hip‑fracture risk ≤ 1 % (any sex, age ≥ 50). [15][16]

Adjustments for High‑Dose Glucocorticoid Use

• In patients receiving prednisone > 7.5 mg/day, increase the calculated FRAX estimates:
  
  • Multiply the major‑osteoporotic fracture risk by 1.15. [15][16]
  • Multiply the hip‑fracture risk by 1.20. [15][16]
• Example: a calculated hip‑fracture risk of 2.0 % becomes 2.4 % after adjustment, potentially shifting a patient from moderate to high risk and triggering treatment. [15][16]

Screening Threshold (Separate from Treatment Decision)

• The 2025 USPSTF guideline recommends a 9.3 % major‑osteoporotic fracture probability as the screening threshold to identify women aged 50–64 years who should undergo bone‑density testing; treatment decisions still rely on the ≥ 20 % major‑fracture or ≥ 3 % hip‑fracture cutoffs. 17