Troubling Aspects of the Trabecular Bone Score Adjustment for the Fracture Risk Assessment Tool (FRAX®)

The Fracture Risk Assessment Tool (FRAX®) is widely used to estimate the 10-year risk of hip fracture and major osteoporotic fracture (MOF, defined as a hip, humerus, wrist, or clinical vertebral fracture). In 2015, McCloskey and colleagues published an adjustment to FRAX® based on the trabecular bone score (TBS). In 2017, the adjustment was updated to use a different calculation for MOF when TBS was measured by Hologic in people assigned male sex at birth. However, this update occurred only on the website hosting FRAX® adjusted for TBS without any corresponding publication of the details of this update or its derivation or validation. In addition to this unpublished update, FRAX® adjusted for TBS also gives impossible results in certain situations, manifesting most clearly in people above a certain age who are at high 10-year risk. Further still, there are inexplicable divergences in the 10-year estimates of hip fracture between the equations published in 2015 and the estimates one obtains if using the website version, which manifest most clearly in people over 80 years old, even at lower 10-year risks. We call on the authors of the TBS adjustment to help the users of FRAX® and FRAX® adjusted for TBS by addressing these matters.