Direct comparison of eight national FRAX® tools for fracture prediction and treatment qualification in Canadian women.

SUMMARY We compared the calibration of FRAX tools from Canada, the US (white), UK, Sweden, France, Australia, New Zealand, and China when used to assess fracture risk in 36,730 Canadian women. Our data underscores the importance of applying country-specific FRAX tools that are based upon high-quality national fracture epidemiology. PURPOSE A FRAX® model for Canada was constructed for prediction of hip fracture and major osteoporotic fracture (MOF) using national hip fracture and mortality data. We examined the calibration of this model in Canadian women and compared it with seven other FRAX tools. METHODS In women aged ≥50 years with baseline bone mineral density (BMD) measures identified from the Manitoba Bone Density Program, Canada (n = 36,730), 10-year fracture probabilities were calculated with and without BMD using selected country-specific FRAX tools. FRAX risk estimates were compared with observed fractures ≤10 years (506 hip, 2,380 MOF). Ten-year fracture risk was compared with predicted probabilities, and proportions exceeding specific treatment thresholds contrasted. RESULTS For hip fracture prediction, good calibration was observed for FRAX Canada and most other country-specific FRAX tools, excepting Sweden (risk overestimated) and China (risk underestimated). For MOF prediction, greater between-country differences were seen; FRAX Sweden and FRAX China showed the largest over- and underestimation in this Canadian population. Relative to treatment qualification based upon FRAX Canada, treatment of high-hip fracture probability (≥3%) was greater by FRAX Sweden (ratio 1.41 without and 1.55 with BMD), and markedly less by FRAX China (ratio 0.09 without and 0.11 with BMD). Greater between-country differences were observed for treatment of high MOF (≥20%); FRAX Sweden again greatly increased (ratio 1.76 without and 1.83 with BMD), and FRAX China severely reduced treatment qualification (ratio 0.00 without and 0.01 with BMD). CONCLUSIONS The use of country-specific FRAX tools, accurately calibrated to the target population, is essential. Relatively small calibration differences can have large effects on high-risk categorization and treatment qualification.