Prediction of incident major osteoporotic and hip fractures by Trabecular Bone Score (TBS) and prevalent radiographic vertebral fracture in older men
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Trabecular bone score (TBS) has been shown to predict major osteoporotic (clinical vertebral, hip, humerus, and wrist) and hip fractures in postmenopausal women and older men, but the association of TBS with these incident fractures in men independent of prevalent radiographic vertebral fracture is unknown. TBS was estimated on anteroposterior (AP) spine dual-energy X-ray absorptiometry (DXA) scans obtained at the baseline visit for 5979 men aged >/=65 years enrolled in the Osteoporotic Fractures in Men (MrOS) Study and its association with incident major osteoporotic and hip fractures estimated with proportional hazards models. Model discrimination was tested with Harrell's C-statistic and with a categorical net reclassification improvement index, using 10-year risk cutpoints of 20% for major osteoporotic and 3% for hip fractures. For each standard deviation decrease in TBS, there were hazard ratios of 1.27 (95% confidence interval [CI] 1.17 to 1.39) for major osteoporotic fracture, and 1.20 (95% CI 1.05 to 1.39) for hip fracture, adjusted for FRAX with bone mineral density (BMD) 10-year fracture risks and prevalent radiographic vertebral fracture. In the same model, those with prevalent radiographic vertebral fracture compared with those without prevalent radiographic vertebral fracture had hazard ratios of 1.92 (95% CI 1.49 to 2.48) for major osteoporotic fracture and 1.86 (95% CI 1.26 to 2.74) for hip fracture. There were improvements of 3.3%, 5.2%, and 6.2%, respectively, of classification of major osteoporotic fracture cases when TBS, prevalent radiographic vertebral fracture status, or both were added to FRAX with BMD and age, with minimal loss of correct classification of non-cases. Neither TBS nor prevalent radiographic vertebral fracture improved discrimination of hip fracture cases or non-cases. In conclusion, TBS and prevalent radiographic vertebral fracture are associated with incident major osteoporotic fractures in older men independent of each other and FRAX 10-year fracture risks, and these data support their use in conjunction with FRAX for fracture risk assessment in older men.