FRAX-based assessment and intervention thresholds: an exploration of thresholds in women aged 50 years and older in the UK

Summary: Under current guidelines, based on prior fracture probability thresholds, inequalities in access to therapy arise especially at older ages (≥70 years) depending on the presence or absence of a prior fracture. An alternative threshold (a fixed threshold from the age of 70 years) reduces this disparity, increases treatment access and decreases the need for bone densitometry. Introduction: Several international guidelines set age-specific intervention thresholds at the 10-year probability of fracture equivalent to a woman of average BMI with a prior fracture. At older ages (≥70 years), women with prior fracture selected for treatment are at lower average absolute risk than those selected for treatment in the absence of prior fracture, prompting consideration of alternative thresholds in this age group. Methods: Using a simulated population of 50,633 women aged 50–90 years in the UK, with a distribution of risk factors similar to that in the European FRAX derivation cohorts and a UK-matched age distribution, the current NOGG intervention and assessment thresholds were compared to one where the thresholds remained constant from 70 years upwards. Results: Under current thresholds, 45.1 % of women aged ≥70 years would be eligible for therapy, comprising 37.5 % with prior fracture, 2.2 % with high risk but no prior fracture and 5.4 % selected for treatment after bone mineral density (BMD) measurement. Mean hip fracture probability was 11.3, 23.3 and 17.6 %, respectively, in these groups. Under the alternative thresholds, the overall proportion of women treated increased from 45.1 to 52.9 %, with 8.4 % at high risk but no prior fracture and 7.0 % selected for treatment after BMD measurement. In the latter group, the mean probability of hip fracture was identical to that observed in women with prior fracture (11.3 %). The alternative threshold also reduced the need for BMD measurement, particularly at older ages (>80 years). Conclusions: The alternative thresholds equilibrate fracture risk, particularly hip fracture risk, in those with or without prior fracture selected for treatment and reduce BMD usage at older ages.