Bone and body composition measurements of small subjects: discrepancies from software for fan-beam dual energy X-ray absorptiometry.
OBJECTIVE
A piglet model was used to determine the variations in measurements from different software algorithms used in the same type of dual energy X ray absorptiometry (DXA) instruments from the same manufacturer.


METHODS
Forty-one piglets (6190 +/- 5856g, mean +/- SD) were scanned in duplicate with a fan-beam densitometer (Hologic QDR4500A, Hologic Inc, Bedford, MA) in the infant whole body scan mode. The same scans were analyzed with two software versions: vKH6 (validated with carcass chemical measurement) and v11.2 (commercial software from the same densitometer manufacturer).


RESULTS
All analysis values were highly correlated (r = 0.90 to 1.00) and DXA values for total weights were almost identical. However, v11.2 results consistently overestimated bone mineral content (49.3 +/- 23.4%, mean +/- SD), bone area (21.1 +/- 8.2%), bone mineral density (24.1 +/- 22.2%), and fat mass (160.9 +/- 71.7%) but underestimated lean mass (-14.3 +/- 5.5%) when compared to the values from vKH6. Differences between software versions increased with heavier piglets.


CONCLUSIONS
The commercial software for fan-beam DXA measurement of piglets, matched for the size of human infants and young children, has major inaccuracies for bone mineral and body composition that become further exaggerated with increasing weight of the subject.
Koo
Winston W K
WW
Carmen and Ann Adams Department of Pediatrics, Obstetrics and Gynecology, Wayne State University, Detroit, Michigan, USA. wkoo@wayne.edu
Hammami
Mouhanad
M
Shypailo
Roman J
RJ
Ellis
Kenneth J
KJ
D015502:Absorptiometry, Photon / Q000379:methods / Q000592:standards*; D000465:Algorithms; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D015519:Bone Density; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D006801:Humans; D023421:Models, Animal; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012986:Software Validation; D013552:Swine