FRAX- vs. T-score-based intervention thresholds for osteoporosis.

Abstract

A FRAX® model been recently calibrated for Kuwait, but guidance is needed on how to utilise fracture probabilities in the assessment and treatment of patients. We compared age-specific fracture probabilities, equivalent to women with no clinical risk factors and a prior fragility fracture (without BMD), with the age-specific fracture probabilities associated with femoral neck T-scores of -2.5 and -1.5 SD, in line with current guidelines in Kuwait. Upper and lower assessment thresholds for BMD testing were additionally explored using FRAX. When a BMD T-score of -2.5 SD was used as an intervention threshold, FRAX probabilities of a major osteoporotic fracture in women aged 50years were approximately twofold higher than those in women of the same age but with an average BMD. The increase in risk associated with the BMD threshold decreased progressively with age such that, at the age of 83years or more, a T-score of -2.5 SD was associated with a lower probability of fracture than that of the age-matched general population with no clinical risk factors. The same phenomenon was observed from the age of 66years at a T-score of -1.5 SD. A FRAX-based intervention threshold, defined as the 10-year probability of a major osteoporotic fracture in a woman of average BMI with a previous fracture, rose with age from 4.3% at the age of 50years to 23%, at the age of 90years, and identified women at increased risk at all ages. Qualitatively comparable findings were observed in the case of hip fracture probability and in men. Intervention thresholds based on BMD alone do not optimally target women at higher fracture risk than those on age-matched individuals without clinical risk factors, particularly in the elderly. In contrast, intervention thresholds based on fracture probabilities equivalent to a 'fracture threshold' consistently target women at higher fracture risk, irrespective of age.