Validation of bioelectrical-impedance measurements as a method to estimate body-water compartments.

Single-frequency bioelectrical-impedance analyses (BIA) and bioelectrical spectroscopy (modeling multifrequency measurements; BIS) were validated as methods to predict body water (BW) compartments in 29 healthy adults. Total body water (TBW) and extracellular water (ECW) were determined by deuterium- and bromide-dilution techniques. Contribution of BIA to anthropometry and influence of the position of electrodes were examined. Stepwise-regression analysis revealed that inclusion of BIA to anthropometric data greatly improved the fit with BW compartments. Highly significant correlations were observed between BIS and BW compartments (TBW: r2 = 0.98, SEE = 1.2; ECW: r2 = 0.95, SEE = 0.6). Cross-correlation (14 males, and 15 females) indicated predictive potential of the method. Results from BIS and BIA were comparable, but it is argued that BIS has the potential of improved standardization of the method.