Estimates of Body Fat in Children by Hologic QDR-2000 and QDR-4500A Dual-Energy X-ray Absorptiometers Compared With Deuterium Dilution

摘要

We evaluated the accuracy with which the Hologic QDR-4500A and QDR-2000 densitometers measure fat mass (FM) in 95 children. FM was derived from total body water measured by deuterium dilution (DD) in all children, by QDR-4500A in 50, and by QDR-2000 in 45 children. Compared with DD, both instruments underestimated FM (QDR-4500A: 3.35 ± 2.5 kg, P < 0.0001; QDR-2000: 1.05 ± 1.5 kg, P < 0.0001). Both absorptiometers showed magnitude biases relative to DD (QDR-4500: r = +0.70, P < 0.001; QDR-2000: r = −0.51, P < 0.001). We conclude that neither densitometer is equivalent to DD for estimation of children’s FM. The QDR-4500A’s current calibration seems to provide an even greater underestimate of FM than the QDR-2000.