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Reproducibility of DXA Measurements of Bone Mineral and Body Composition: Application to Routine Clinical Measurements

  • Colin E. Webber
Chapter

Abstract

Measurements of bone mass and body composition using X-ray based dual photon absorptiometry (DXA) are used extensively to investigate patients suspected to be suffering from conditions that affect the skeleton or soft tissues. Commonly, such measurements seek to establish whether or not a change has occurred since a previous measurement. The ability to detect change is determined by perhaps the most important characteristic of a DXA system; that is the precision of the measurement. In this chapter, the results of precision assessments made in various groups of subjects using equipment housed in a routine, diagnostic Department of Nuclear Medicine are reviewed and compared to published values. In phantoms, the precision or reproducibility of a bone mineral density (BMD) measurement is better than 0.005 g cm−2 even if the number of measurements from which the precision is derived is accumulated over an extended time period. In children, same-day precision for spine BMD, whole body BMD and proximal femur BMD worsens to values of 0.007, 0.009, and 0.011 g cm−2, respectively. For adults, the same-day precision of spine BMD decreases further to 0.010 g cm−2 while femur BMD precision is virtually unchanged. Long-term precision for spine BMD and femur BMD decreases again to 0.029 and 0.023 g cm−2 while for the radius, long-term precision is 0.012 g cm−2. The precision attained by routine clinical laboratories for the measurement of BMD can be comparable to that obtained by research laboratories. The same-day precision of DXA measurements of body composition in children is about 20 g for whole body bone mineral content (WBBMC), 250 g for lean tissue mass (LBM) and 190 g for fat mass (FM). In adults, same-day precision for WBBMC is similar to that measured in children while for LBM and FM, same-day precision worsens to about 350 and 280 g, respectively. Extending the time interval between pairs of measurements to more than 1 day makes the reproducibility of soft tissue composition assessments much worse as the effect of daily fluctuations in dietary balances will be included in the reproducibility evaluation. The presence of obesity means that the precision of measurements in all body composition compartments deteriorates.

Keywords

Obesity Attenuation Osteoporosis 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations

BMD

Bone Mineral Density

BMI

Body Mass Index

CV

Coefficient of Variation

DOF

Degrees of Freedom

DXA

X-Ray based Dual Photon Absorptiometry

FM

Fat mass

ICC

Intra-class Correlation Coefficient

LBM

Lean Body Mass

LSC

Least Significant Change

SD

Standard deviation

WBBMC

Whole Body Bone Mineral Content

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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  1. 1.Department of Nuclear MedicineHamilton Health SciencesHamiltonCanada

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