Validation of two portable bioelectrical impedance analyses for the assessment of body composition in school age children

Abstract

Bioelectrical impedance analysis (BIA) is a convenient and child-friendly method for longitudinal analysis of changes in body composition. However, most validation studies of BIA have been performed on adult Caucasians. The present cross-sectional study investigated the validity of two portable BIA devices, the Inbody 230 (BIA_8MF) and the Tanita BC-418 (BIA_8SF), in healthy Taiwanese children. Children aged 7–12 years (72 boys and 78 girls) were recruited. Body composition was measured by the BIA_8SF and the BIA_8MF. Dual X-ray absorptiometry (DXA) was used as the reference method. There were strong linear correlations in body composition measurements between the BIA_8SF and DXA and between the BIA_8MF and DXA. Both BIAs underestimated fat mass (FM) and percentage body fat (%BF) relative to DXA in both genders The degree of agreement in lean body mass (LBM), FM, and %BF estimates was higher between BIA_8MF and DXA than between BIA_8SF and DXA. The Lin’s concordance correlation coefficient (ρ_c) for LBM_8MF met the criteria of substantial to perfect agreement whereas the ρ_c for FM_8MF met the criteria of fair to substantial agreement. Bland-Altman analysis showed a clinically acceptable agreement between LBM measures by BIA_8MF and DXA. The limit of agreement in %BF estimation by BIA and DXA were wide and the errors were clinically important. For the estimation of ALM, BIA_8SF and BIA_8MF both provided poor accuracy. For all children, LBM measures were precise and accurate using the BIA_8MF whereas clinically significant errors occurred in FM and %BF estimates. Both BIAs underestimated FM and %BF in children. Thus, the body composition results obtained using the inbuilt equations of the BIA_8SF and BIA_8MF should be interpreted with caution, and high quality validation studies for specific subgroups of children are required prior to field research.