Measurement of body water by multifrequency bioelectrical impedance spectroscopy in a multiethnic pediatric population.

BACKGROUND

Bioelectrical impedance spectroscopy (BIS) may provide a noninvasive, rapid method for the assessment of total body water (TBW), extracellular water (ECW), and intracellular water (ICW). Few studies, however, have examined the accuracy of BIS in pediatric populations.

OBJECTIVE

Our objective was to evaluate the accuracy of BIS for the measurement of TBW, ECW, and ICW in healthy children.

DESIGN

Dual-energy X-ray absorptiometry (DXA), total body potassium (TBK), and BIS measurements were performed in 347 children (202 males and 145 females aged 4-18 y). The reference values for TBW, ECW, and ICW were defined by using a DXA+TBK model. BIS values were evaluated by using the method of Bland and Altman. A randomly selected calibration group (n = 231) was used to derive new BIS constants that were tested in the remaining group (n = 116).

RESULTS

BIS values were highly correlated with the reference values (r(2) = 0.94-0.97, P < 0.0001), but differences between the BIS and DXA+TBK models for individuals were significant (P < 0.001). Use of new BIS constants reduced the mean differences between the BIS and DXA+TBK models; the SDs of the mean differences were improved (1.8 L for TBW, 1.4 L for ICW, and 1.0 L for ECW) for the total population.

CONCLUSIONS

On a population basis, BIS can be calibrated to replace the DXA+TBK model for the assessment of TBW, ECW, and ICW in healthy children. The accuracy of the BIS measurement in individual children may be refined further by using age- and sex-specific adjustments for the BIS calibration constants.