Accuracy of dual-energy x-ray absorptiometry for body-composition measurements in children.

The accuracy of body-composition measurements by dual-energy x-ray absorptiometry (DXA) was assessed by comparison with total carcass chemical analysis in 16 pigs with a weight range of 5-35 kg. Two software versions for body-composition analyses with the DXA instrument were evaluated. Although both software versions accurately predicted body weight, there were significant differences in the partitioning between bone mineral content (BMC), nonbone lean tissue, and body-fat compartments. All estimates of body composition were highly correlated (r2 > or = 0.98) with the results of the direct chemical reference method. SEEs were 226-271 g for body weight, 387-429 g for fat, 3.5-4.3 kg for fat-free mass, and 35.4-36.5 g for BMC. For bone, both software versions produced BMC values that were approximately 25% below the total carcass ash content. For the absolute mass of body fat, one DXA analysis provided underestimates that averaged 19.5% below the reference chemical method, whereas the alternate software version resulted in over-estimates, averaging 15.5%. Conversely, the average fat-free compartment was initially overestimated by 968 g, then underestimated by 892 g. The impact of these differences in the body-composition analyses by DXA were examined in a group of 18 young boys 4-12 y of age.