Comparison of hand-to-leg and leg-to-leg bioelectric impedance devices in the assessment of body adiposity in prepubertal children.: The STRIP study

The body composition of 30 seven-year-old children and of 50 of their parents was measured using two bioelectric impedance devices, the Model 101, RJL Systems, USA (conventional hand-to-leg device) and TANITA body fat analyser, TBF 105, Tanita Co, Tokio, Japan (newer leg-to-leg device). There were strong correlations between impedances obtained by these two devices [r = 0.95, r = 0.93, r = 0.82, r = 0.81 for girls (n = 22), boys (n = 18), mothers (n = 27) and fathers (n = 23), respectively (p < 0.0001 for all)]. However, there was a clear difference in the absolute impedance values due to the fact that the devices measure different segments of the body. Fat percentages based on inbuilt equations of the two devices correlated in girls, mothers and fathers (r = 0.71, r = 0.94, r = 0.80, respectively; p < 0.001) but not in boys (r = 0.21, p = 0.41). Using the Bland-Altman comparison method, a large intraindividual difference was observed in the fat percentages by the two devices, independent of adiposity level. Both devices detected significant gender differences in fat percentages in 7-y-old girls and boys with similar BMIs. Conclusion: When using the Tanita 105 leg-to-leg bioelectric impedance device to assess adiposity in children there is an obvious need for revised equations. For this, comparative studies using more validated methods, i.e. densitometry or DEXA, as part of a multi-compartment model are needed.