Original ArticleTrabecular Bone Score Is Associated With Volumetric Bone Density and Microarchitecture as Assessed by Central QCT and HRpQCT in Chinese American and White Women
Introduction
Measurement of areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) is the gold standard for fracture risk assessment. Despite its widespread use and utility, DXA has several limitations. It provides a 2-dimensional (areal) depiction of BMD rather than a 3-dimensional or volumetric bone mineral density (vBMD). aBMD is affected by bone size—it is underestimated in those with smaller bones and overestimated in those with larger bones (1). Importantly, DXA does not distinguish between cortical and trabecular bone, nor can it discern bone microarchitecture.
Newer methods such as central quantitative computed tomography (QCT) and high-resolution peripheral quantitative computed tomography (HRpQCT) can noninvasively assess vBMD, which is not affected by bone size. Furthermore, these technologies provide separate measures for the cortical and trabecular compartments and can characterize bone strength 2, 3, 4. HRpQCT has the advantage of noninvasively evaluating bone microarchitecture and has been shown to distinguish those with and without fracture in cross-sectional studies (4). QCT assesses central skeletal sites where the most important clinical fractures occur and can predict new vertebral fractures (3).
These techniques have provided insight into racial differences in bone quality and fracture risk. Asian Americans exhibit lower aBMD by DXA (5) but have lower rates of hip and forearm fractures than white women 6, 7. HRpQCT studies indicate that Chinese Americans have smaller bone size but denser and thicker cortices and more plate-like trabeculae at the radius and tibia than white women 8, 9, 10, 11. QCT has also demonstrated cortical advantages at the hip among Chinese American women but similar trabecular vBMD at both central skeletal sites between races (12). Furthermore, using micro finite element analysis, we demonstrated that these characteristics in Chinese Americans are associated with increased bone strength, despite smaller bone size 10, 13 compared with white women. These findings help explain lower rates of nonvertebral fractures in Chinese Americans, despite lower aBMD.
Although QCT and HRpQCT have improved the assessment of bone quality, they are not yet widely available. The trabecular bone score (TBS), a novel gray-scale textural analysis of spine DXA images, provides a quantitative estimate of trabecular microarchitecture using variograms of 2-dimentional projection images (14). TBS is independent of bone size and highly correlated with trabecular number, separation and connectivity density by micro-computed tomography, the gold standard for microarchitectural assessment (14). TBS uses the same region of interest as DXA and can be performed on previously acquired images from GE Lunar and Hologic densitometers. In prospective studies, TBS predicts fracture risk in postmenopausal women 15, 16. Now that the United States Food and Drug Administration has approved TBS (17), it might be applied more widely as an adjunct to aBMD testing.
In this study, we sought to assess racial differences in TBS and determine whether TBS reflects vBMD and microarchitecture at central and peripheral skeletal sites as measured by QCT and HRpQCT in our cohort of Chinese American and white women.
Section snippets
Subjects
As previously described, pre- and postmenopausal Chinese American and white women were evaluated cross-sectionally using DXA, QCT, and HRpQCT 8, 9, 10, 12, 13 at Columbia University Medical Center (CUMC). Participants enrolled in our prior studies were included in this analysis if measurements from all four modalities (TBS, DXA, QCT, and HRpQCT) were available. Forty-four postmenopausal (21 White and 23 Chinese American) and 71 premenopausal women (37 white and 34 Chinese American) were
Results
As shown in Table 1, the racial groups did not differ in age or years since menopause. Compared with white women, Chinese Americans weighed less, were shorter, and tended to have lower calcium intake and serum 25-hydroxyvitamin D levels. Premenopausal Chinese Americans had higher PTH levels than white women. aBMD at LS and one-third radius did not differ by race in premenopausal women, but it was lower at TH and FN in Chinese Americans. White and Chinese American postmenopausal participants had
Discussion
To our knowledge, this is the first investigation examining racial differences in trabecular microarchitectural texture using TBS and the associations between TBS and QCT indices. We found no differences in spine TBS between races, but TBS correlated with vBMD and microarchitecture by QCT and HRpQCT in white and Chinese American women. Our results suggest that TBS is generally reflective of skeletal indices measured by higher resolution imaging.
The finding that TBS was comparable between races
Acknowledgments
This work was supported by NIH K23 AR053507, a National Osteoporosis Foundation grant, the Mary and David Hoar Fellowship Program of the New York Community Trust, and the New York Academy of Medicine.
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Cited by (0)
Barbara C. Silva and Marcella D. Walker contributed equally to this work.
Conflict of interest: Didier Hans is a co-owner of the patent for TBS. All the other authors state that they have no conflicts of interest.