Validation and application of dual-energy x-ray absorptiometry to measure bone mass and body composition in small infants.

Precision and validity of dual-energy x-ray absorptiometry (DXA) for analysis of whole-body composition in infants were assessed by 1) scanning piglets in triplicate to calculate CVs, and 2) comparing DXA estimates with chemical analysis of whole carcass. The mean CVs for all DXA measures in small piglets and large piglets were < 2.5%, except for fat mass, which were 6.3% and 3.5%, respectively. In large piglets DXA provided reasonable estimates of chemical analysis for bone mineral content (BMC), lean body mass, and fat mass, but only for lean body mass in small piglets. DXA overestimated fat by twofold and underestimated BMC by a third in small piglets. Scans of prematurely born infants (n = 17) at term and at 3, 6, and 12 mo corrected age demonstrated that changes in BMC, lean body mass, and fat mass can be quantitated by DXA. However, further refinement of DXA technology is necessary before reliable measures of BMC and fat mass in small infants are attainable.