Wren Tishya A L, Liu Xiaodong, Pitukcheewanont Pisit, Gilsanz Vicente
Department of Orthopedics, MS#81, 4650 Sunset Boulevard, Los Angeles, California 90027, USA.
J Clin Endocrinol Metab. 2005 Apr;90(4):1925-8. doi: 10.1210/jc.2004-1351. Epub 2005 Jan 5.
The effect that growth has on dual-energy x-ray absorptiometry (DXA) bone measurements is yet to be fully defined. The purpose of this study was to determine the best method for optimizing pediatric bone measurements using DXA. Height, weight, body mass index, skeletal age, and Tanner stage of sexual development were determined for 64 healthy boys and 60 healthy girls ages 6-17 yr. DXA of the lumbar vertebrae was performed to measure bone mineral content (BMC, grams) and areal bone mineral density (aBMD, grams per square centimeter), and geometric corrections were used to calculate volumetric bone mineral densities (vBMD): vBMD1 = aBMD/ radical(DXA-area) and vBMD2 = aBMD/bone height. Computed tomography (CT) imaging was performed to measure volumetric bone density (vBD) and vertebral volume (Vol) and to calculate CT-BMC = vBD * Vol. Linear regression was used to compare DXA-BMC vs. CT-BMC and CT vBD vs. DXA aBMD, vBMD1, and vBMD2. Multiple regression including the anthropometric and developmental parameters was also performed. DXA and CT BMC were highly correlated (r2= 0.94). However, DXA aBMD correlated more strongly with CT Vol (r2= 0.68) than with CT density (r2= 0.39), and calculation of DXA volumetric densities only slightly improved the density correlations (r2= 0.49 for vBMD1; r2= 0.55 for BMD2). The correlations for density were particularly poor for subjects in Tanner stages 1-3 (r2= 0.02 for aBMD; r2= 0.13 for vBMD1; r2= 0.27 for vBMD2). In contrast, multiple regression accounting for the anthropometric and developmental parameters greatly improved the agreement between the DXA and CT densities (r2= 0.91). These results suggest that DXA BMC is a more accurate and reliable measure than DXA BMD for assessing bone acquisition, particularly for prepubertal children and those in the early stages of sexual development. Use of DXA BMD would be reasonable if adjustments for body size, pubertal status, and skeletal maturity are made, but these additional assessments add significant complexity to the studies.
生长对双能X线吸收法（DXA）骨测量的影响尚未完全明确。本研究的目的是确定使用DXA优化儿科骨测量的最佳方法。测定了64名6至17岁健康男孩和60名健康女孩的身高、体重、体重指数、骨骼年龄和性发育的坦纳分期。进行腰椎的DXA测量骨矿物质含量（BMC，克）和面积骨矿物质密度（aBMD，克每平方厘米），并使用几何校正来计算体积骨矿物质密度（vBMD）：vBMD1 = aBMD/√（DXA面积），vBMD2 = aBMD/骨高度。进行计算机断层扫描（CT）成像以测量体积骨密度（vBD）和椎体体积（Vol），并计算CT - BMC = vBD×Vol。使用线性回归比较DXA - BMC与CT - BMC以及CT vBD与DXA aBMD、vBMD1和vBMD2。还进行了包括人体测量和发育参数的多元回归。DXA和CT的BMC高度相关（r2 = 0.94）。然而，DXA aBMD与CT Vol的相关性（r2 = 0.68）比与CT密度的相关性（r2 = 0.39）更强，并且DXA体积密度的计算仅略微改善了密度相关性（vBMD1的r2 = 0.49；vBMD2的r2 = 0.55）。对于坦纳分期1 - 3的受试者，密度相关性特别差（aBMD的r2 = 0.02；vBMD1的r2 = 0.13；vBMD2的r2 = 0.27）。相比之下，考虑人体测量和发育参数的多元回归极大地改善了DXA和CT密度之间的一致性（r2 = 0.91）。这些结果表明，在评估骨量获取方面，DXA BMC比DXA BMD是更准确和可靠的测量方法，特别是对于青春期前儿童和性发育早期的儿童。如果对身体大小、青春期状态和骨骼成熟度进行调整，使用DXA BMD是合理的，但这些额外的评估会使研究显著复杂化。
