Fracture Risk Scores Using Output from an Opportunistic Screen of Low Bone Density from Conventional X-ray

Fracture risk is commonly assessed by FRAX, a tool that estimates 10-year risk for major osteoporotic fracture (MOF) and hip fracture. FRAX scores are often refined by additionally including femoral neck (FN) bone mineral density (BMD) measured by dual-energy x-ray absorptiometry (DXA) as an input. Rho™, a novel AI-powered software, estimates FN BMD T-Scores from conventional x-rays, even when FN is not in the image. Whether a FRAX score using this estimate (FRAX-Rho) can improve a FRAX score without a T-Score input (FRAX-NoT) has not been studied. We conducted a retrospective analysis of Canadian Multicentre Osteoporosis Study participants who had x-rays of the lumbar and/or thoracic spine, FRAX risk factors, and DXA T-Scores acquired at the same time point, and follow-up fracture outcomes over 9 years. In 1361 participants with lumbar x-rays, FRAX-Rho and FRAX with DXA FN T-Scores (FRAX-DXA) had very good agreement in categorizing participants by MOF risk (Cohen's weighted kappa κ=0.80 [0.77-0.82]), which tended to be better than that between FRAX-NoT and FRAX-DXA (0.76 [0.73-0.79]). Agreement in categorizing participants by hip fracture risk was significantly greater between FRAX-Rho and FRAX-DXA (0.67 [0.63-0.71]) than FRAX-NoT and FRAX-DXA (0.52 [0.48-0.56]). In predicting true incident MOF, FRAX-Rho and FRAX-DXA did not differ in their discriminative power (c-index) (0.76 and 0.77; p=0.36) and both were significantly greater than that of FRAX-NoT (0.73; p<0.004). The accuracy of FRAX-Rho for predicting MOF (Brier Score) was better than FRAX-NoT (p<0.05) but not as good as FRAX-DXA. Similar results were observed in participants with thoracic x-rays. In conclusion, FN T-Scores estimated by Rho from lumbar and thoracic x-rays add value to FRAX-NoT estimates and may be useful for risk assessment when DXA is not available.