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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #57198
Title: THE EFFECTS OF ANALYTIC SOFTWARE AND SCAN ANALYSIS TECHNIQUE ON THE COM- PARISON OF DUAL-X-RAY ABSORPTIOMETRY WITH DUAL PHOTON ABSORPTIOMETRY OF THEHIP IN THE ELDERLY

Author
item KIEL D P - HEBREW REHAB
item MERCIER C A - FRAMINGHAM HEART STUDY
item DAWSON-HUGHES B - TUFTS-HNRCA
item CALI C - HEBREW REHAB
item HANNAN M T - BOSTON UNIV
item ANDERSON J J - BOSTON UNIV

Submitted to: Journal of Bone and Mineral Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: With the changes and upgrades in bone measurement technology, investigators must often compare bone density results on two types of scanners. Previous studies comparing these two types of scanners, dual-photon (DPA) and dual energy x-ray absorptiometry (DXA), have been limited to scanning phantoms. This study was conducted to compare hip density measured by DPA and DEXA in 58 elderly men and women. A second aim was to compare DPA/DXA differences according to the method of scan analysis (computer- driven or operator-driven). Each volunteer had one DPA and one DPX hip scan no more than 4 weeks apart. The DXA scans we analyzed twice each, once with computer placement and once with operator placement of the specific region to be assessed. We found that bone density was 2 to 3% higher by DXA than by DPA and that agreement between the scan pairs was greater for the operator-driven than for the computer-driven analyses. These findings indicate the need to account for equipment upgrades and reveal that unwanted measurement variability can be reduced by allowing the operator to select the specific hip region to be analyzed.

Technical Abstract: As part of a longitudinal comparison of bone mineral density (BMD) results originally obtained using a Lunar DPA scanner and later, using a Lunar DXA scanner, we compared femur results between DPA and DXA according to DXA analytic software (versions 1.3 and 1.4), and according to the method of placement of the femoral neck box (software algorithm or operator placement according to the appearance of the pair of images) in 58 elderly men and women. The mean BMD at each of three femoral sites was higher using DXA version 1.3 than DPA. Of 58 scans, 12 (21%) were changed by the operator, resulting in an overall reduction in mean percent BMD difference between scan pairs of 79% (from 1.25% to 0.29%). Although the differences between the DPA/DXA software-driven analysis and the DPA/DXA operator driven analysis appeared small, in a longitudinal study setting, the software-driven analysis would require 33% more subjects than the operator-driven analysis for the same power to detect changes in BMD. The findings of this study highlight the need to account for upgrades in analytic software. Furthermore, we present a rational approach for the analysis of serial scans that has face validity, and that results in smaller differences between pairs of scans performed on the same individual. The decision to adapt these methods must be based on the relative costs of reducing unwanted scan variability.