A comparison of prediction models for fractures in older women: is more better?

A Web-based risk assessment tool (FRAX) using clinical risk factors with and without femoral neck bone mineral density (BMD) has been incorporated into clinical guidelines regarding treatment to prevent fractures. However, it is uncertain whether prediction with FRAX models is superior to that based on parsimonious models.

We conducted a prospective cohort study in 6252 women 65 years or older to compare the value of FRAX models that include BMD with that of parsimonious models based on age and BMD alone for prediction of fractures. We also compared FRAX models without BMD with simple models based on age and fracture history alone. Fractures (hip, major osteoporotic [hip, clinical vertebral, wrist, or humerus], and any clinical fracture) were ascertained during 10 years of follow-up. Area under the curve (AUC) statistics from receiver operating characteristic curve analysis were compared between FRAX models and simple models.

The AUC comparisons showed no differences between FRAX models with BMD and simple models with age and BMD alone in discriminating hip (AUC, 0.75 for the FRAX model and 0.76 for the simple model; P = .26), major osteoporotic (AUC, 0.68 for the FRAX model and 0.69 for the simple model; P = .51), and clinical fracture (AUC, 0.64 for the FRAX model and 0.63 for the simple model; P = .16). Similarly, performance of parsimonious models containing age and fracture history alone was nearly identical to that of FRAX models without BMD. The proportion of women in each quartile of predicted risk who actually experienced a fracture outcome did not differ between FRAX and simple models (P > or = .16).

Simple models based on age and BMD alone or age and fracture history alone predicted 10-year risk of hip, major osteoporotic, and clinical fracture as well as more complex FRAX models.