Bioelectrical impedance analysis to assess changes in total body water in patients with cancer.

Predominantly based on studies in obese individuals, the applicability of single-frequency bioelectrical impedance analysis (BIA) to measure changes in total body water and fat-free mass has been questioned. To further clarify this issue, we compared changes in BIA-derived height(2)/resistance (ht(2)/R) with changes in total body water (deuterium dilution, delta-TBWdeu) in cancer patients participating in a clinical trial. Thirty-three patients (mean body mass index 23.2 +/- 3.5 kg/m(2)) were studied after an average follow-up of 11 weeks. Changes in TBWdeu occurred in both directions (mean +0.2 +/- 1.6 L, range -3.3 to +3.1 L). These changes were significantly predicted by changes in ht(2)/R (r(2)0.43, P < 0.0001, SEE 1.22 L), although precision was poor (residual SD 1. 2 L). There were in this regard no significant differences between patients with and without underweight. We conclude that in underweight and normal-weight cancer patients, BIA-derived changes in ht(2)/R significantly predict changes in total body water assessed by deuterium dilution.