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 immunodeficiency virus (HIV) infection. Accuracy of bioimpedance for measuring change (Delta) in intracellular water (ICW), which defines BCM, is uncertain. To evaluate bioimpedance-estimated Delta BCM, the ICW of 21 weight-losing 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 Delta 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 predicted by 500 - 5-kHz impedance was closer to, but statistically different from, 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 the 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 the multiple-frequency modeling approach accurately monitors Delta BCM in HIV infection.