Inverse Correlation at the Hip Between Areal Bone Mineral Density Measured by Dual-Energy X-ray Absorptiometry and Cortical Volumetric Bone Mineral Density Measured by Quantitative Computed Tomography

TY - JOUR

T1 - Inverse Correlation at the Hip Between Areal Bone Mineral Density Measured by Dual-Energy X-ray Absorptiometry and Cortical Volumetric Bone Mineral Density Measured by Quantitative Computed Tomography

AU - Amstrup, Anne Kristine

AU - Jakobsen, Niels Frederik Breum

AU - Lomholt, Søren

AU - Sikjaer, Tanja

AU - Mosekilde, Leif

AU - Rejnmark, Lars

PY - 2016/4/1

Y1 - 2016/4/1

N2 - Quantitative computed tomography (QCT) is considered to measure true volumetric bone mineral density (vBMD; mg/cm 3) and enables differentiation between cortical and trabecular bone. We aimed to determine the value of QCT by correlating areal BMD (aBMD) by dual-energy X-ray absorptiometry (DXA) with vBMD when using a fixed threshold to delineate cortical from trabecular bone. In a cross-sectional study, 98 postmenopausal women had their hip scanned by DXA and by QCT. At the total hip and the trabecular bone compartment, aBMD correlated significantly with vBMD (r = 0.74 and r = 0.63; p < 0.01, respectively). A significant inverse correlation was found between aBMD and cortical vBMD (r = -0.57; p < 0.01). Total hip volume by QCT did not change with aBMD. However, increased aBMD was associated with a decreased trabecular bone volume (r = -0.36; p < 0.01) and an increased cortical volume (r = 0.69; p < 0.01). Changing the threshold used to delineate cortical from trabecular bone from default 350 mg/cm 3 to either 300 or 400 mg/cm 3 did not affect integral vBMD (p = 89) but had marked effects on estimated vBMD at the cortical (p < 0.001) and trabecular compartments (p < 0.001). Furthermore, increasing the threshold decreased cortical thickness (p < 0.001), whereas the strength parameter in terms of buckling ratio increased (p < 0.001). Our results show good agreement between aBMD and integral vBMD. However, using a fixed threshold to differentiate cortical from trabecular bone causes an apparent increase in cortical volume with a decrease in cortical density as aBMD increases. This may be caused by the classification of a larger part of the transition zone as cortical bone with increased aBMD.

AB - Quantitative computed tomography (QCT) is considered to measure true volumetric bone mineral density (vBMD; mg/cm 3) and enables differentiation between cortical and trabecular bone. We aimed to determine the value of QCT by correlating areal BMD (aBMD) by dual-energy X-ray absorptiometry (DXA) with vBMD when using a fixed threshold to delineate cortical from trabecular bone. In a cross-sectional study, 98 postmenopausal women had their hip scanned by DXA and by QCT. At the total hip and the trabecular bone compartment, aBMD correlated significantly with vBMD (r = 0.74 and r = 0.63; p < 0.01, respectively). A significant inverse correlation was found between aBMD and cortical vBMD (r = -0.57; p < 0.01). Total hip volume by QCT did not change with aBMD. However, increased aBMD was associated with a decreased trabecular bone volume (r = -0.36; p < 0.01) and an increased cortical volume (r = 0.69; p < 0.01). Changing the threshold used to delineate cortical from trabecular bone from default 350 mg/cm 3 to either 300 or 400 mg/cm 3 did not affect integral vBMD (p = 89) but had marked effects on estimated vBMD at the cortical (p < 0.001) and trabecular compartments (p < 0.001). Furthermore, increasing the threshold decreased cortical thickness (p < 0.001), whereas the strength parameter in terms of buckling ratio increased (p < 0.001). Our results show good agreement between aBMD and integral vBMD. However, using a fixed threshold to differentiate cortical from trabecular bone causes an apparent increase in cortical volume with a decrease in cortical density as aBMD increases. This may be caused by the classification of a larger part of the transition zone as cortical bone with increased aBMD.

KW - ABMD

KW - DXA

KW - QCT

KW - VBMD

UR - http://www.scopus.com/inward/record.url?scp=84923097194&partnerID=8YFLogxK

U2 - 10.1016/j.jocd.2015.01.002

DO - 10.1016/j.jocd.2015.01.002

M3 - Journal article

C2 - 25700661

SN - 1094-6950

VL - 19

SP - 226

EP - 233

JO - Journal of Clinical Densitometry

JF - Journal of Clinical Densitometry

IS - 2

ER -