A Comparison of the Longitudinal Changes in Quantitative Ultrasound with Dual-Energy X-ray Absorptiometry: The Four-Year Effects of Hormone Replacement Therapy

Abstract

Quantitative ultrasound (QUS) has been proposed as a tool which can measure both the quantitative and qualitative aspects of bone tissue and can predict the future risk of osteoporotic fractures. However, the usefulness of QUS in long-term monitoring has yet to be defined. We studied a group of early 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 anteroposterior 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-score 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-ray absorptiometry (DXA) at the AP spine and total hip, and QUS carried out at the calcaneus, measuring broadband ultrasound attenuation (BUA), speed of sound (SOS) and Stiffness. Mean percentage changes from baseline were assessed at 2 and 4 years. The overall treatment effect (defined as the difference 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). To compare the long-term precision of the two techniques we calculated the Standardized Precision, which for QUS was approximately 2-3 times that of DXA, for a given rate of change. The ability of each site to monitor response to treatment was assessed by calculating the Treatment Response Index (Treatment 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 normalized for AP spine BMD (to compare the role of QUS against the current standard, AP Spine BMD), which was: total hip BMD, 0.38; BUA, 0.30; Stiffness, 0.40 (p<0.01); and SOS, 0.03 (NS). In summary, QUS parameters in the early menopause 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 AP 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 presently the time period to follow individual subjects remains 2-3 times that for DXA, for a given rate of change. Anteroposterior spine remains the current optimal DXA monitoring site due to its greater rate of change and better long-term precision.

Peripheral bone densitometry: clinical applications

“…It is vital to keep in mind that BMD changes in peripheral bones such as phalanx and forearm must be very carefully interpreted, taking this phenomenon into consideration. Changes expected in BUA, SOS or even in the index calculated with these two parameters are far smaller and slower than BMD variations as measured by central DXA (23). While with DXA of the hip, 30% BMD loss is expected from 50 to 70 years of age, only 5 to 15% are observed when ultrasound peripheral technologies are used.…”

Quantitative ultrasound for the detection and management of osteoporosis

“…[148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163][164] It has been observed that changes in heel QUS parameters, especially the stiffness index (SI), do mimic the treatment response observed in BMD. In two studies involving alendronate, for example, the Achilles SI was observed to significantly increase with treatment over time.…”

Quantitative ultrasound and bone health

“…[26][27][28] The precision of QUS is generally reported to be poorer than that of DXA. There are currently QUS devices available for measuring a range of anatomical sites including both predominantly trabecular and predominantly cortical bone sites.…”

“…10,105,106 However, Sahotal et al found a positive effect of HRT at the calcaneus in a longitudinal study over a four year period, although the individual increases for BUA and SOS were not as great as found for lumbar spine and total hip BMD. 26 A number of longitudinal studies have demonstrated a response of QUS to patients treated with bisphosphonates at the calcaneus and tibia. [107][108][109][110] However, as a result of the poorer precision, the follow-up period is generally required to be longer than that of DXA.…”