Introduction

Forearm BMD measurement has been critical to our understanding of osteoporosis epidemiology, fracture risk, and response to treatment in clinical trials (1-3). The ISCD have embraced understanding densitometric techniques, identified research needs and advancing standards for appropriate use in clinical practice. Central DXA today has supplanted many older methods and is used predominantly to measure hip and lumbar spine BMD, and occasionally other sites. The ISCD clearly outlines acceptable levels of measurement error for measurements at the hip and spine, with official positions for measuring and monitoring changes in place but has neglected an acceptable threshold for distal 1/3 radius and whole-body BMD. The Practice: Empirically centres usually have no L.S.C. for forearm/ distal 1/3 radius, despite repeating DXA measurements of that site in practice. Increasingly we note centres are less familiar with forearm measurement today, sometimes lack confidence in their knowledge, skill and competency for measurement or interpretation.

Objectives

The Problem: Forearm measurements are sometimes reported in clinical trials, and in practice the forearm may be the only suitable site such as when hips have been replaced, there have been fractures or surgery to the lumbar spine, or the patient is unable to mount or lie on the DXA table. Consistency and excellence in clinical practice suggest the same standards apply irrespective of which site is being measured. We aimed to calculate the L.S.C. for distal radial BMD as recommended by the ISCD.

Methods

We calculated the L.S.C. for our centre as part of a cross-calibration exercise when our DXA machines (G.E. Lunar Prodigy) were re-located from the radiology department to the rheumatology department in 2018 and new staff were trained in DXA technology. We scanned 30 patients twice on the same day repositioning between each scan, as we did for lumbar spine and total hip.

Results

We obtained an L.S.C. of 0.046g/cm2 for the 13 distal radius. While our spine and total hip BMD LSC values fell under the ISCD recommended acceptable threshold, we could not find Official Position guidance as to where the radial LSC value sits on the spectrum of acceptability. However, our results fall within the range published by Krueger et al in 2013 which included some technical errors when images were reviewed.

Conclusions

Diagnostic excellence suggests standards and consistency apply for clinical metrology. The ISCD should include and define acceptable forearm L.S.C. in their official positions.

References

PMID: 1150873, 2008103, 10527181, 15159268, 16234965.

中文翻译：

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失去径向骨密度：预先警告

介绍

前臂 BMD 测量对于我们了解骨质疏松症流行病学、骨折风险和临床试验中的治疗反应至关重要 (1-3)。ISCD 已经接受了对密度测量技术的理解，确定了研究需求并推进了在临床实践中适当使用的标准。如今，中央 DXA 已经取代了许多旧方法，主要用于测量髋部和腰椎 BMD，偶尔也用于测量其他部位。ISCD 清楚地概述了臀部和脊柱测量的可接受测量误差水平，并提供了测量和监测变化的官方位置，但忽略了远端 1/3 半径和全身 BMD 的可接受阈值。实践：经验中心通常没有前臂/远端 1/3 半径的 LSC，尽管在实践中重复了该站点的 DXA 测量。我们越来越多地注意到今天的中心对前臂测量不太熟悉，有时对他们的知识、技能和测量或解释能力缺乏信心。

目标

问题：临床试验中有时会报告前臂测量值，而在实践中，前臂可能是唯一合适的部位，例如髋关节置换、腰椎骨折或手术，或者患者无法坐骑或躺在 DXA 桌子上。临床实践的一致性和卓越性表明，无论测量哪个部位，都适用相同的标准。我们旨在按照 ISCD 的建议计算远端桡骨 BMD 的 LSC。

方法

当我们的 DXA 机器（GE Lunar Prodigy）于 2018 年从放射科重新定位到风湿科并且新员工接受了 DXA 技术培训时，我们计算了我们中心的 LSC 作为交叉校准练习的一部分。我们在同一天对 30 名患者进行了两次扫描，每次扫描之间重新定位，就像我们对腰椎和全髋所做的那样。

结果

我们获得了 13 个远端半径的 LSC 为 0.046g/cm2。虽然我们的脊柱和全髋 BMD LSC 值低于 ISCD 推荐的可接受阈值，但我们无法找到关于径向 LSC 值在可接受范围内的位置的官方立场指导。然而，我们的结果属于 Krueger 等人在 2013 年发布的范围内，其中包括审查图像时的一些技术错误。

结论

卓越的诊断表明标准和一致性适用于临床计量。ISCD 应在其官方职位中包括并定义可接受的前臂 LSC。

参考

PMID：1150873、2008103、10527181、15159268、16234965。