Bedogni G, Bollea M R, Severi S, Trunfio O, Manzieri A M, Battistini N
Dipartimento di Scienze Biomediche, Università degli Studi, Modena, Italy.
Eur J Clin Nutr. 1997 Mar;51(3):129-33. doi: 10.1038/sj.ejcn.1600351.
To assess the reliability of bioelectric impedance analysis (BIA) for predicting total body water (TBW) and extracellular water (ECW) in obese children.
Comparison of five prediction models based on: (i) body weight (Wt), (ii) the impedance (Z) index (ZI = height2/Z), (iii) the association of Wt and ZI, (iv) the body surface area (SA) to impedance ratio (SA:Z) and, (v) the body volume (V) to impedance ratio (V:Z).
Thirty obese and 25 control children of 11.2 +/- 1.8 y of age.
TBW and ECW were assessed by deuterium and bromide dilution; Z was measured at frequencies of 5,50 and 100 kHz.
In controls, Wt explained 11% more variance of TBW than ZI (r2 = 0.977, SEE = 0.9 I, CV = 3.8%) and the association of Wt and ZI improved the prediction of TBW only slightly (r2 = 0.982, SEE = 0.8 I, CV = 3.5%). The SA:Z and V:Z indexes explained 6 and 33% less variance of TBW respectively as compared to Wt alone. In obese subjects, ZI explained 4% more variance of TBW than Wt (r2 = 0.914, SEE = 1.8 I, CV = 6.4%) and the SA:Z ratio was the most accurate predictor of TBW (r2 = 0.959, SEE = 1.2 I, CV = 4.4%). However, the increase in the explained variance of TBW associated to the use of the SA:Z ratio was of only 1% as compared to the association of ZI and Wt. The V:Z ratio explained 9% less of variance of TBW as compared to ZI. In both control and obese subjects, the association of Wt and ZI offered the best prediction of ECW (r2 = 0.807, SEE = 1.564 I and r2 = 0.826, SEE = 1.035 I, respectively). However, the values of CV were much higher in controls than in obese children (17.5% vs 8.4%) owing to their lower ECW and greater variability in ECW%. ZI was the most accurate predictor of TBW on the pooled sample (n = 55; r2 = 0.910, SEE = 1.932 I; CV = 7.4%). However, it was a poor predictor of ECW on the same sample owing to its high CV (n = 55; r2 = 0.866, SEE = 1.806 I, CV = 17.0%).
The body surface area to impedance ratio is the most accurate predictor of TBW in obese children but the association of ZI and Wt may be of more interest when BIA is used to estimate both TBW and ECW. The impedance index offers a good prediction of TBW but not of ECW in children with different levels of fatness.
评估生物电阻抗分析（BIA）预测肥胖儿童总体水（TBW）和细胞外液（ECW）的可靠性。
比较基于以下因素的五种预测模型：（i）体重（Wt），（ii）阻抗（Z）指数（ZI =身高²/Z），（iii）Wt与ZI的联合，（iv）体表面积（SA）与阻抗之比（SA:Z），以及（v）身体体积（V）与阻抗之比（V:Z）。
30名肥胖儿童和25名年龄为11.2±1.8岁的对照儿童。
通过氘和溴化物稀释法评估TBW和ECW；在5、50和100kHz频率下测量Z。
在对照组中，Wt对TBW变异的解释比ZI多11%（r² = 0.977，标准误 = 0.9L，变异系数 = 3.8%），Wt与ZI的联合对TBW预测的改善仅略有提升（r² = 0.982，标准误 = 0.8L，变异系数 = 3.5%）。与单独的Wt相比，SA:Z和V:Z指数对TBW变异的解释分别少6%和33%。在肥胖受试者中，ZI对TBW变异的解释比Wt多4%（r² = 0.914，标准误 = 1.8L，变异系数 = 6.4%），SA:Z比值是TBW最准确的预测指标（r² = 0.959，标准误 = 1.2L，变异系数 = 4.4%）。然而，与ZI和Wt的联合相比，使用SA:Z比值对TBW变异解释的增加仅为1%。与ZI相比，V:Z比值对TBW变异的解释少9%。在对照组和肥胖受试者中，Wt与ZI的联合对ECW的预测最佳（分别为r² = 0.807，标准误 = 1.
