Significant differences between two commonly used bioimpedance methods in hemodialysis patients

Bioimpedance methods are currently used abundantly in patients on chronic hemodialysis. In this population, their most important role is to determine the level of fluid volume, respectively its intra- and extracellular components. There are several bioimpedance devices on the market. In this project, we compared two frequently used devices: Body Composition Monitor and InBody S10.

We invited patients on chronic hemodialysis who are being treated in our institution. Inclusion criteria were: clinically stable condition, lack of artificial joints, pacemakers, or other implanted metal objects. The examinations were performed just prior to hemodialysis by both methods 5 minutes apart. Patients were examined in the supine position after 15 minutes at rest to stabilize body fluids. Studied parameters were those that are obtainable by both methods: total body water (TBW) (L), extracellular water (ECW) (L) and intracellular water (ICW) (kg), lean tissue mass (LTM) (L), and fat tissue mass (kg).

We included 14 participants (aged 64.4 ± 18.0 years). Statistically and clinically significant differences between data from compared devices were observed for all variables. Inbody S10 overestimated TBW by 2.58 ± 2.73 L and ICW by 4.56 ± 2.27 L in comparison to BCM. The highest difference (27%) was measured for LTM and ICW 22%. LTM, fat, and ECW were higher when measured by BCM (LTM by 8.54 ± 6.43 kg, p < 0.001; fat by 3.41 ± 4.22, p = 0.01; ECW by 2.01 ± 0.89 L, p < 0.001).

The differences between tested devices were significant not only statistically, but also clinically. These two devices cannot be used interchangeably for dry weight setting of hemodialysis patients.