FRAX-based intervention thresholds for Pakistan.

Abstract

The fracture risk assessment algorithm FRAX® has been recently calibrated for Pakistan, but guidance is needed on how to apply fracture probabilities to clinical practice. The age-specific 10-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. The second approach determined age-specific fracture probabilities that were equivalent to a woman with a prior fragility fracture, without bone mineral density (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 was used as an intervention threshold, FRAX probabilities in women aged 50years were approximately two-fold higher than in women of the same age but with no risk factors and average BMD. The relative increase in risk associated with the BMD threshold decreased progressively with age such that, at the age of 80years or more, a T-score of - 2.5 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 2.1% at the age of 40years to 17%, at the age of 90years, 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.