FRAX and risk of vertebral fractures: the fracture intervention trial

The validity of the WHO 10-yr probability of major osteoporotic fracture model (FRAX) for prediction of vertebral fracture has not been tested. We analyzed how well FRAX for major osteoporotic fractures, with and without femoral neck BMD (FN BMD), predicted the risk of vertebral fracture. We also compared the predictive validity of FRAX, FN BMD, and prevalent vertebral fracture detected by radiographs at baseline alone or in combination to predict future vertebral fracture. We analyzed data from the placebo groups of FIT (3.8-yr follow-up, n = 3221) with ORs and areas under receiver operating characteristics (ROC) curves (AUC). FRAX with and without FN BMD predicted incident radiographic vertebral fracture. The AUC was significantly greater for FRAX with FN BMD (AUC = 0.71) than FRAX without FN BMD (AUC = 0.68; p = 0.002). Prevalent vertebral fracture plus age and FN BMD (AUC = 0.76) predicted incident radiographic vertebral fracture as well as a combination of prevalent vertebral fracture and FRAX with FN BMD (AUC = 0.75; p = 0.76). However, baseline vertebral fracture status plus age and FN BMD (AUC = 0.76) predicted incident radiographic vertebral fracture significantly better than FRAX with FN BMD (AUC = 0.71; p = 0.0017). FRAX for major osteoporotic fractures (with and without FN BMD) predicts vertebral fracture. However, once FN BMD and age are known, the eight additional risk factors in FRAX do not significantly improve the prediction of vertebral fracture. A combination of baseline radiographic vertebral fracture, FN BMD, and age is the strongest predictor of future vertebral fracture.