Reproducibility of dual-energy X-ray absorptiometry measurements in prepubertal girls.

OBJECTIVE: Regulation of growth and development, clinical assessment, and obesity are among the areas of nutrition-related research, wherein accurate assessment of body composition is important. We want to test the hypothesis that dual-energy X-ray absorptiometry (DXA) measurements are reproducible in healthy girls. RESEARCH METHODS AND PROCEDURES: We determined total body composition measurements in healthy prepubertal girls using DXA twice, 6 weeks apart.
RESULTS: We studied 61 healthy, normal-weight, prepubertal girls, aged 4.8 years to 10.3 years. The girls' DXA-derived mean weight between visits 1 and 2 significantly increased (27.14 kg vs. 27.80 kg, p<0.0001). The increased weight was due to significant increases in total body fat-free mass (FFM) (19.53 kg vs. 19.89 kg, p<0.001), total body bone mass (1.05 kg vs. 1.07 kg, p<0.0001), and total body fat mass (7.61 kg vs. 7.91 kg, p<0.03). The girls' DXA-derived mean total trunk mass between visits 1 and 2 significantly increased ( 11.23 kg vs. 11.63 kg, p<0.0001), as did total leg mass (9.33 kg vs. 9.53 kg, p<0.00), although no significant differences were observed in total arm mass (2.52 kg vs. 2.54 kg, p=0.37). The Pearson coefficient of correlation (r) and total coefficient of variation (CV) for intraindividual measurements by DXA were: weight--r=0.99, CV = 1.97%; total body FFM--r = 0.96, CV = 2.30%; total body bone mass--r = 0.99, CV=2.08%; total body fat mass--r=0.96, CV=6.55%; percentage total body fat--r=0.91, CV=5.69%; total trunk mass--r=0.96, CV= 3.59%; total arm mass--r= 0.95, CV =4.09%; and total leg mass--r = 0.99, CV = 2.75%. DISCUSSION: Total body FFM, total body bone mass, total body fat mass, percentage of total body fat mass, as well as regional mass determinations by DXA, were highly reproducible in healthy, normal-weight, prepubertal girls. We highly recommend the use of DXA for total body composition studies in girls aged 5 years to 10 years.