Validation of the FRAX predictive model for major osteoporotic fracture in a historical cohort of Spanish women.

FRAX is a fracture risk assessment tool to estimate the 10-yr probability of a major osteoporotic fracture or a hip fracture. The aim of the study was to assess the predictive ability of FRAX for major osteoporotic fracture in a cohort of Spanish women. The study was based on a retrospective cohort of women aged 40-90 yr. Patients were followed from their first bone densitometry to the first major osteoporotic fracture event (forearm, proximal humerus, clinical spine, or hip fracture) or for 10 yr whichever comes first. A total of 1231 women were included. Bone mineral density data and self-reported data on risk factors for fracture were obtained. The predictive ability of FRAX was assessed by analyzing calibration and discrimination, with the calculation of observed-to-expected (O/E) fracture ratios and the receiver operating characteristic (ROC) curve, respectively. A total of 222 women (18.1%) reported at least 1 fracture after the first assessment. The incidence of fracture was 14 (95% confidence interval [CI]: 10-17), 19 (95% CI: 15-23), 28 (95% CI: 21-36), and 67 (95% CI: 8-125) cases per 1000 woman-years in women aged <55, 55-64, 65-74, and ≥75 yr, respectively. The O/E ratio was 3.9 (95% CI: 3.4-4.5; p<0.0001). The area under the ROC curve was 61% (95% CI: 57-65%). FRAX underestimated the risk of major osteoporotic fracture in this cohort of Spanish women, particularly in those with a low risk of fracture according to the clinical factors used in the FRAX tool. Our findings highlight the need for validation studies of FRAX in Spain.