de Bruin N C, Westerterp K R, Degenhart H J, Visser H K
Department of Pediatrics, Erasmus University, The Netherlands.
Pediatr Res. 1995 Sep;38(3):411-7. doi: 10.1203/00006450-199509000-00023.
Body composition data are important for adequate monitoring of growth and nutritional status in infants. 18O Isotope dilution techniques (ID18-O) are widely used to estimate total body water (TBW) and calculate fat-free mass (FFM). A problem of isotope dilution is an underestimation of TBW by the extrapolation to t = O approach and an overestimation of TBW by the plateau approach. Using total body electrical conductivity (TOBEC) as the reference technique we validated the extrapolation approach by 149 measurements (boys, n = 76; girls, n = 73) in 50 healthy infants aged 1-12 mo. TOBEC-derived FFM and fat mass were in excellent agreement with Fomon's reference data. Strictly linear relationships with slopes not significantly different from one were found between FFM estimated by TOBEC (FFMTOBEC) and FFM estimated by ID18-O (FFM18-O) (r = 0.98 and residual SD = 0.29 for boys, r = 0.98 and residual SD = 0.32 for girls). FFM18-O was slightly but significantly lower than FFMTOBEC, the difference being on average 0.18 (+/- 0.24) kg for girls and 0.08 (+/- 0.21) kg for boys (i.e. respectively 4 (+/- 4.5)% (p < 0.0001) and 1.5 (+/- 3.9)% (p = 0.004) of FFMTOBEC). We conclude that ID18-O using the extrapolation to t = O approach is suitable for TBW and FFM estimations in groups of infants. Due to the considerable measurement error of ID18-O (estimated at approximately 6%), individual TBW18-O and FFM18-O estimates should be considered with some caution.
身体成分数据对于充分监测婴儿的生长和营养状况非常重要。18O同位素稀释技术（ID18 - O）被广泛用于估计总体水（TBW）并计算去脂体重（FFM）。同位素稀释的一个问题是通过外推到t = 0方法会低估TBW，而通过平台法会高估TBW。我们使用全身电阻抗（TOBEC）作为参考技术，通过对50名1 - 12个月大的健康婴儿进行149次测量（男孩，n = 76；女孩，n = 73）验证了外推法。TOBEC得出的FFM和脂肪量与Fomon的参考数据高度一致。在TOBEC估计的FFM（FFMTOBEC）和ID18 - O估计的FFM（FFM18 - O）之间发现了斜率与1无显著差异的严格线性关系（男孩r = 0.98，残差标准差 = 0.29；女孩r = 0.98，残差标准差 = 0.32）。FFM18 - O略低于但显著低于FFMTOBEC，女孩的平均差异为0.18（±0.24）kg，男孩为0.08（±0.21）kg（即分别为FFMTOBEC的4（±4.5）%（p < 0.0001）和1.5（±3.9）%（p = 0.004））。我们得出结论，使用外推到t = 0方法的ID18 - O适用于婴儿群体中TBW和FFM的估计。由于ID18 - O存在相当大的测量误差（估计约为6%），个体的TBW18 - O和FFM18 - O估计应谨慎考虑。
