Designing an Iran FRAX model and defining intervention and assessment thresholds for osteoporosis

Background and Objectives: The purpose of this study was to adopt and calibrate the fracture risk assessment algorithm FRAX® for the Iranian population and to provide the required guidance on how to apply it in clinical practice.

Methods: The age-specific ten-year probability of major osteoporotic fractures was calculated in women with an average BMI to determine the fracture probability at two potential intervention thresholds. The first threshold was the age-specific fracture probability associated with a femoral neck T-score of -2.5 SD and the other was age-specific fracture probability in women with a history of fracture without BMD. Current Iranian guidelines were used to define these thresholds. The effect of adding BMD values to the assessment of these thresholds was also evaluated separately.

Results: Similar to women with a previous fracture, the 10-year probability of a major osteoporotic fracture increased from 4.9% at the age of 50 years to 17% at the age of 80 years. When using a BMD T-score of ≤−2.5 SD as the intervention threshold, the FRAX probability was twice as high in women aged 50 years as in women of the same age with an average BMD and no risk factor. The FRAX probability increased with age but a T-score of -2.5 SD was actually protective after 80 years or age.

Conclusion: Intervention thresholds based on BMD alone cannot effectively identify high-risk women for fracture, particularly in advanced ages. Using fracture probability based on ‘fracture threshold’ can help to improve the identification of these women.