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.