Reference values of body composition obtained by dual energy X-ray absorptiometry in preterm and term neonates.

Abstract

As previously reported, dual-energy x-ray absorptiometry provides reliable and accurate values for bone mineralization in piglets and infants, but overestimates fat content in small infants. The purpose of the current study was to determine an appropriate equation of correction for fat mass measurement and to establish reference values of body composition of preterm and term neonates. Fat mass and chemical whole-body fat content were evaluated by dual-energy x-ray absorptiometry in eight piglets with a body weight between 1408 and 5151 g. The results were combined with previous data obtained in 13 piglets, and two correction equations were determined according to fat mass content. Close to birth, 106 healthy appropriate-for-gestational-age preterm and term infants were scanned by dual-energy x-ray absorptiometry to determine bone mineral content, bone area, and fat mass. Fat mass content determined by dual-energy x-ray absorptiometry was corrected using the equations obtained in piglets after which lean body mass was recalculated. Multivariate analysis showed that dual-energy x-ray absorptiometry body weight was the best predictor of bone mineral content (r2 = 0.94), bone area (r2 = 0.95), lean body mass (r2 = 0.98), and fat mass (r2 = 0.84). Gender was an additional significant independent variable for fat mass and lean body mass. Body weight related curves of percentiles for bone mineral content, bone area, fat mass, and lean body mass, were constructed. In vivo dual-energy x-ray absorptiometry values of fat mass and calcium content estimated from bone mineral content were in accordance with previously reported whole-body carcass reference values in preterm and term neonates. Normative data of dual-energy x-ray absorptiometry body composition for healthy preterm and term infants are provided and can therefore be used in research and in clinical practice.