Comparison of different methods for monitoring changes in bone mineral density during follow-up measurements

Monitoring bone mineral density (BMD) changes can be challenging when both the spine and hips are included in follow-up assessments. This study aimed to evaluate BMD changes using different monitoring approaches, including comparisons between the mean bilateral total hip BMD and total hip BMD of each hip separately, spinal BMD and mean bilateral total hip BMD, and spinal BMD and trabecular bone score (TBS). Bone density was measured using dual-energy X-ray absorptiometry, and bone quality was assessed using the TBS. A total of 1,105 postmenopausal women who underwent simultaneous follow-up BMD measurements of the spine and both hips were retrospectively analyzed. In follow-up BMD measurements, the discordance between the mean bilateral total hip BMD and the individual total hip BMDs (right and left hips) was 11.3% when the least significant change (LSC) of the mean bilateral total hip was applied. In contrast, this discordance increased to 19.5% when the average LSC of the right and left hips was used. Spine-hip discordance was also observed, with a 43.5% discordance rate between changes in spinal BMD and mean bilateral total hip BMD. Additionally, discordance between changes in spinal BMD and TBS was noted, with a discordance rate of 58.0%. Analyzing each hip separately is more sensitive to detecting changes than using the mean bilateral total hip BMD. When monitoring mean bilateral total hip BMD on repeat tests, the LSC of the mean bilateral total hip BMD is recommended. Discordance between spine and hip BMD, as well as between spinal BMD and TBS, was observed in follow-up measurements.