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 DeltaBCM, 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 DeltaICW did not differ. The DeltaICW was predicted poorly by 50-kHz parallel reactance, 50-kHz impedance, and 200 - 5-kHz impedance. The DeltaICW predicted by 500 - 5-kHz impedance was closer to, but statistically different from, dilution-determined DeltaICW. 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 DeltaICW; 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 DeltaBCM in HIV infection.