VALIDATION OF BIOELECTRICAL IMPEDANCE ANALYSIS WITH A THREE-COMPONENT MODEL OF BODY COMPOSITION IN 4-7 YEAR OLD CHILDREN
Mrs. Marieke de Beer
1 slide(s) – English – 2010-10-23
Field methods to assess body composition in young children are scarce. The aim of this study was to validate bioelectrical impedance analysis (BIA) with the three-component (3C) model of body composition in primary school children.
We examined fifty-six 4-7 year old children, 36% boys. Total body water estimated by BIA was compared with deuterium dilution. An established equation was recalibrated using a validation sample of 36 children which was subsequently cross-validated in an independent sample of 20 children. Furthermore, commonly used gender-specific hydration constants for the conversion of total body water into fat free mass were compared to those calculated with the 3C model.
Compared to deuterium dilution, BIA for school age children underestimated total body water by 0.51 kg (p=0.002) and this varied across the range of TBW (r= 0.41; p=0.002). Recalibration of the equation yielded: Total body water = 0.439 (Height2/Resistance) + 0.027 Wt + 4.014 (R2 = 0.74, SEE = 0.96 kg). Application of this equation in the independent sample of 20 children showed a non-significant bias in total body water (mean bias -0,40 kg, p=0.223). This bias was not variable (r= -0.11; p=0.648). Hydration constants calculated with the 3C model were comparable to recently proposed hydration constants.
In conclusion, these data indicate that BIA underestimates total body water in 4-7 year old children, when using the Kushner equation for school age children. This underestimation is non-systematic. Recalibration and cross-validation enables more robust assessment of body composition for routine survey and clinical use in (pre)school aged children.