A comparison of the longitudinal changes in quantitative ultrasound with dual-energy X-ray absorptiometry: The four-year effects of hormone replacement therapy

Quantitative ultrasound (QUS) has been proposed as a tool which can measure both the quantitative and qualitative aspects of bone tissue and can predi ct the future risk of osteoporotic fractures. However, the usefulness of QU S in long-term monitoring has yet Co be defined. We studied a group of earl y postmenopausal women over a 4-year period. Thirty subjects were allocated to hormone replacement therapy and 30 selected as controls matched for age , years past the menopause (YPM) and bone mineral density (BMD) at the ante roposterior spine (AP spine). The mean age of the subjects was 52.4 years ( SD 3.9 years), mean YPM 4.0 years (SD 3.2) and all subjects had a BMD T-sco re above -2.5 SD (number of standard units related to the young normal mean population), BMD was measured at baseline and annually by dual-energy X-ra y absorptiometry (DXA) at. the AP spine and total hip, and QUS carried out at the calcaneus, measuring broadband ultrasound attenuation (BUA), speed o f sound (SOS) and Stiffness. Mean percentage changes from baseline were ass essed at 2 and 4 years. The overall treatment effect (defined as the differ ence in percentage change between the two groups) was: AP spine BMD, 11.4%: total hip BMD 7.4%; BUA, 6.4%; SOS, 1.1%; and Stiffness, 10.4% (p<0.01), T o compare the long-term precision of the two techniques we calculated the S tandardized Precision, which for QUS was approximately 2-3 times that of DX A, for a given rate of change. The ability of each site to monitor response to treatment was assessed by calculating the Treatment Response Index (Tre atment Effect/Standardized Precision), which was: AP spine BMD, 10.4; total hip BMD, 3.9; BUA, 3.1; SOS, 0.3; and Stiffness, 4.2. This was then normal ized for AP spine BMD (to compare the role of QUS against the current stand ard, AP Spine BMD), which was: total hip BMD, 0.38; BUA, 0.30; Stiffness, 0 .30 (p<0.01); and SOS, 0.03 (NS). In summary, QUS parameters in the early m enopause showed a similar rate of decline as AP spine BMD and total hip BMD measured by DXA. Hormone replacement therapy results in bone gain at the A P spine and total hip, and prevents loss in BUA and SOS measured by QUS at the calcaneus, QUS has a potential role in long-term monitoring, although p resently the time period to follow individual subjects remains 2-3 times th at for DXA, for a given rate of change. Anteroposterior spine remains the c urrent optimal DXA monitoring site due to its greater rate of change and be tter long-term precision.