A comparison of bioimpedance methods for detection of body cell mass change in HIV infection

The maintenance of body cell mass (BCM) is critical for survival in human i mmunodeficiency virus (HIV) infection. Accuracy of bioimpedance for measuri ng change (Delta) in intracellular water (ICW), which defines BCM, is uncer tain. To evaluate bioimpedance-estimated Delta BCM, the ICW of 21 weight-lo sing HIV patients was measured before and after anabolic steroid therapy by dilution (total body water by deuterium - extracellular water by bromide) and bioimpedance. Multiple-frequency modeling- and dilution-determined Delt a ICW did not differ. The Delta ICW was predicted poorly by 50-kHz parallel reactance, 50-kHz impedance, and 200 - 5-kHz impedance. The Delta ICW pred icted by 500 - 5-kHz impedance was closer to, but statistically different f rom, dilution-determined Delta ICW. However, the effect of random error on the measurement of systematic error in the 500 5-kHz method was 12-13% of t he average measured Delta ICW; this was nearly twice the percent difference between obtained and threshold statistics. Although the 500 - 5-kHz method cannot be fully rejected, these results support the conclusion that only t he multiple-frequency modeling approach accurately monitors Delta BCM in HI V infection.