FRAX-based intervention and assessment thresholds for osteoporosis in Iran

We compared the utility of the current Iranian guidelines that recommend treatment in women with a T-score ≤ - 2.5 SD with a FRAX-based intervention threshold equivalent to women of average BMI with a prior fragility fracture. Whereas the FRAX-based intervention threshold identified women at high fracture probability, the T-score threshold was less sensitive, and the associated fracture risk decreased markedly with age.

The fracture risk assessment algorithm FRAX® has been recently calibrated for Iran, but guidance is needed on how to apply fracture probabilities to clinical practice.

The age-specific ten-year probabilities of a major osteoporotic fracture were calculated in women with average BMI to determine fracture probabilities at two potential intervention thresholds. The first comprised the age-specific fracture probabilities associated with a femoral neck T-score of - 2.5 SD, in line with current guidelines in Iran. The second approach determined age-specific fracture probabilities that were equivalent to a woman with a prior fragility fracture, without BMD. The parsimonious use of BMD was additionally explored by the computation of upper and lower assessment thresholds for BMD testing.

When a BMD T-score ≤ - 2.5 SD was used as an intervention threshold, FRAX probabilities in women aged 50 years was approximately two-fold higher than in women of the same age but with an average BMD and no risk factors. The relative increase in risk associated with the BMD threshold decreased progressively with age such that, at the age of 80 years or more, a T-score of - 2.5 SD was actually protective. The 10-year probability of a major osteoporotic fracture by age, equivalent to women with a previous fracture rose with age from 4.9% at the age of 50 years to 17%, at the age of 80 years, and identified women at increased risk at all ages.

Intervention thresholds based on BMD alone do not effectively target women at high fracture risk, particularly in the elderly. In contrast, intervention thresholds based on fracture probabilities equivalent to a "fracture threshold" target women at high fracture risk.