W D Leslie 1, S N Morin 2, L M Lix 3, N Binkley 4
The Canadian FRAX® tool used without bone mineral density (BMD) is highly sensitive for identifying individuals qualifying for pharmacotherapy based upon an intervention threshold of 20% for major osteoporotic fracture risk (MOF) computed with BMD.
Introduction: This analysis was performed to inform initial BMD testing as part of Osteoporosis Canada’s Guidelines Update for women and men at average risk, assuming a pharmacotherapy intervention threshold of 20% for FRAX® MOF computed with BMD.
Methods: Women and men age 50 + without previous low-trauma fracture or high-risk medication use were identified in a BMD registry for the province of Manitoba, Canada. Fracture probability assessments with the Canadian FRAX® tool were computed without and with BMD (denoted MOF-clinical and MOF-BMD, respectively).
Results: The study population consisted of 50,700 women (mean age 65.5 ± 9.4 years) and 4152 men (69.2 ± 10.0 years). FRAX MOF-clinical score was > 10% in 33.8% of women and 13.3% of men (P < 0.001). The median (interquartile range [IQR]) age for MOF-clinical to reach 10% in women was 70 (69-72) and 65 years (62-67) years in the absence and presence of additional FRAX clinical risk factors, respectively. In men, comparable ages were 83 years [82-86] and 76 [70-78] years. Using MOF-BMD of 20% as the intervention threshold, 4.3% of women and 0.7% of men qualified for treatment. MOF-clinical > 10% had high sensitivity to identify those qualifying for treatment (99.3% in women and 99.1% in men). An age-based rule («BMD testing is indicated at age 70 if no additional FRAX clinical risk factors are present, or at age 65 if one or more clinical risk factors exists») gave similarly high sensitivity (women 99.9% and men > 99.9%).
Conclusions: FRAX without BMD offers an effective strategy to identify individuals meeting the current Canadian treatment threshold based upon FRAX® with BMD (≥ 20%). Moreover, this can be operationalized using simple age cutoffs of 70 years in the absence of additional clinical risk factors and 65 years in the presence of additional clinical risk factors.