Bolotin H H
School of Medical Sciences, RMIT University, Bundoora, Victoria 3083, Australia.
Bone. 2007 Jul;41(1):138-54. doi: 10.1016/j.bone.2007.02.022. Epub 2007 Mar 1.
The seemingly unqualified reliance and near-universal dependence upon in vivo dual-energy X-ray absorptiometric (DXA) methodology to provide accurate, quantitative, and meaningful in vivo (in situ cadaveric) bone mineral areal density ("BMD") determinations are proven to be unwarranted and misplaced. The underlying systematics of sizable, inherently unavoidable and un-correctable inaccuracies in the DXA output values of in vivo "BMD" are shown to be quantitatively consistent with being the root cause of unreliable, misdirected, and misinterpreted aspects of consensual knowledge of bone fragility, osteoporotic diagnostics/prognostics, and remodelling therapies. The "BMD" label that DXA ascribes to the output values of in vivo (in situ cadaveric) bone densitometry scans is shown to be a misnomer and an erroneous and invalid measure of bone mineral material. The DXA-derived "BMD" value does not correctly represent the areal density of bone mineral material, as it is contaminated by sizable, unavoidable, inextricable, independent soft tissue contributions. Due to intra- and extra-osseous soft tissue X-ray absorptiometric effects, it is unknown (and unknowable) exactly what DXA in vivo "BMD" is a measure of in any given case, or what proportion of the "BMD" value represents the actual bone mineral material areal density present in the DXA scan region of interest (ROI) of any predominantly trabecular bone-site (e.g., lumbar vertebrae, proximal femora). This inherent fundamental defect in DXA in vivo bone mineral areal density methodology adversely compromises both the validity and reliability of patient-specific diagnostic/prognostic evaluations, cross sectional and prospective studies, and DXA-based interpretations of bone quality and bone fragility. It further undermines the WHO characterizations (and definitions) of 'normal', 'osteopenic', and 'osteoporotic' classifications. It is also seen to make equivocal the qualitative and quantitative epidemiological estimates of the proportion of the population that is, or is deemed to become, osteoporotic. The present quantitative exposition shows DXA-measured in vivo "BMD" methodology to be an intrinsically flawed and misleading indicator of bone mineral status and an erroneous gauge of relative fracture risk.
事实证明，看似无条件地依赖并几乎普遍采用活体双能X线吸收法（DXA）来提供准确、定量且有意义的活体（原位尸体）骨矿物质面积密度（“BMD”）测定是毫无根据且不恰当的。活体“BMD”的DXA输出值中存在相当大的、内在不可避免且无法校正的不准确系统性误差，这些误差在数量上与骨脆性、骨质疏松症诊断/预后以及重塑治疗的共识性知识中不可靠、误导性和错误解读的方面的根本原因一致。DXA赋予活体（原位尸体）骨密度扫描输出值的“BMD”标签被证明是一个误称，是对骨矿物质材料的错误且无效的测量。DXA得出的“BMD”值不能正确代表骨矿物质材料的面积密度，因为它受到相当大的、不可避免的、无法分割的、独立的软组织贡献的污染。由于骨内和骨外软组织的X线吸收效应，在任何给定情况下，确切地说DXA活体“BMD”测量的是什么并不清楚（也无法知道），或者“BMD”值中代表DXA扫描感兴趣区域（ROI）中任何主要为小梁骨部位（例如腰椎、股骨近端）实际存在的骨矿物质材料面积密度的比例是多少。DXA活体骨矿物质面积密度方法学中的这一固有基本缺陷对患者特异性诊断/预后评估、横断面和前瞻性研究以及基于DXA的骨质量和骨脆性解释的有效性和可靠性都产生了不利影响。它进一步破坏了世界卫生组织对“正常”、“骨量减少”和“骨质疏松”分类的描述（和定义）。它还使得对骨质疏松症患者或被认为会患骨质疏松症的人群比例的定性和定量流行病学估计变得模棱两可。目前的定量阐述表明，DXA测量的活体“BMD”方法学是骨矿物质状态的固有缺陷且具有误导性的指标，是相对骨折风险的错误衡量标准。
