A multinational study to develop universal standardization of whole-body bone density and composition using GE Healthcare Lunar and Hologic DXA systems

Abstract

Dual-energy x-ray absorptiometry (DXA) is used to assess bone mineral density (BMD) and body composition, but measurements vary among instruments from different manufacturers. We sought to develop cross-calibration equations for whole-body bone density and composition derived using GE Healthcare Lunar and Hologic DXA systems.This multinational study recruited 199 adult and pediatric participants from a site in the US (n ¼ 40, ages 6 through 16 years) and one in China (n ¼ 159, ages 5 through 81 years). The mean age of the participants was 44.2 years. Each participant was scanned on both GE Healthcare Lunar and Hologic Discovery or Delphi DXA systems on the same day (US) or within 1 week (China) and all scans were centrally analyzed by a single technologist using GE Healthcare Lunar Encore version 14.0 and Hologic Apex version 3.0. Paired t-tests were used to test the results differences between the systems. Multiple regression and Deming regressions were used to derive the crossconversion equations between the GE Healthcare Lunar and Hologic whole-body scans.Bone and soft tissue measures were highly correlated between the GE Healthcare Lunar and Hologic and systems, with r ranging from 0.96 percent fat [PFAT] to 0.98 (BMC). Significant differences were found between the two systems, with average absolute differences for PFAT, BMC, and BMD of 1.4%, 176.8 g and 0.013 g/cm 2 , respectively. After cross-calibration, no significant differences remained between GE Healthcare Lunar measured results and the results converted from Hologic.The equations we derived reduce differences between BMD and body composition as determined by GE Healthcare Lunar and Hologic systems and will facilitate combining study results in clinical or epidemiological studies. ß

Dual energy X-ray absorptiometry body composition reference values of limbs and trunk from NHANES 1999–2004 with additional visualization methods

“…Further, it should be noted that the values reports are only valid to directly compare in new measurements that use the same procedure and same machines as the NHANES dataset. Comparisons of these values to those derived on machines from different manufacturers could only be done after a cross-calibration process, as previously described for other NHANES DXA data [42,43]. Further studies will need to be performed in order to elucidate the usefulness of these regional values and how to best use them in conjunction with full body composition measures for risk assessment.…”

Are Men at Greater Risk of Lean Mass Deficits in Rheumatoid Arthritis?

“…In addition, DXA results from UCSF subjects were analyzed using earlier versions of the Lunar Prodigy software than the versions used in the adjustment published by Shepherd. (21) However, this should not have impacted the comparison between men and women. Furthermore, the analysis of the risk of sarcopenia (which supports the main conclusion) is not dependent on comparison to NHANES and, in addition, the confirmatory findings in the UPenn cohort do not carry this concern.…”

“…(20) Body composition measures for the UCSF subjects were adjusted based on the method by Shepherd et al to facilitate comparison to NHANES data that were generated on Hologic equipment. (21) Subjects from the UPenn cohort underwent whole-body DXA assessment using a Hologic densitometer (Delphi Systems, Hologic, Inc., Bedford, MA) and therefore did not require the Shepherd adjustment. The in vitro coefficient of variation for Hologic measurement of lean mass was less than 0.6% and the in vivo coefficient of variation in adults was less than 1%.…”

Body composition by DXA

“…Some attempts have been made to characterize body composition characteristics by sport (17), but how generally these are applicable to different age groups and level of competition is uncertain. Reference data can be collected on one make of DXA and applied to another using universal standardization equations (18). …”