Agreement of single- and multi-frequency bioimpedance measurements in hemodialysis patients: an ancillary study of the Frequent Hemodialysis Network Daily Trial

Abstract

Background: Bioimpedance analysis (BIA) is well established to assess body composition. Agreements between single- and multi-frequency bioimpedance (SF-BIA, MF-BIS) measurements in subjects undergoing 6 or 3 times/week hemodialysis (HD) were analyzed.

Methods: Total body water (TBW) and intra- and extracellular fluid (ICF, ECF) of subjects enrolled in the Frequent Hemodialysis Network (FHN) Daily Trial (www.clinicaltrials.gov No. NCT00264758) were measured with a Hydra 4200 at baseline (BL) and at 5 months (M5). Volumes were computed using SF (at 50 kHz) and MF approaches. Agreement was assessed by means of linear regression and Bland-Altman analysis and treatment effects by t test.

Results: 35 subjects (17 on the more frequent regimen, 26 males, 20 African-American, 48 ± 9 years, pre-HD weight 84 ± 19 kg) were studied. Assessments with SF-BIA and MF-BIS correlated significantly at BL and M5 in both arms. No proportional errors, but systematic biases over the entire range of values were found at BL and M5. Agreement did not differ between subjects randomized to either HD treatment arm at both time points. MF-BIS appears to have better precision than SF-BIA allowing the observation of a significant treatment effect by the intervention [-1.5 (95% CI -2.5 to -0.5) l] on ECF, not found for ECF SF-BIA. Precision also affected the statistical power of the SF-BIA data in the current analysis.

Conclusion: Both methods showed agreement without significant proportional errors regardless of HD frequency and can be used for longitudinal analyses. SF-BIA has lower precision which needs thorough consideration in the design of future trials with similar outcomes.

Conflict of interest statement

Conflict of Interest: The authors hereby declare that the results presented in this paper have not been published previously in whole or part, except in abstract format at the Renal Week 2009 of the American Society of Nephrology in San Diego, CA, and at the XLVIII ERA-EDTA Congress in Prague, Czech Republic.

© 2014 S. Karger AG, Basel.

Figures

Figure 1

Regression Analysis of total body water (TBW) as estimated per single- and multi-frequency (SF; MF) bioimpedance in patients randomized in a) the conventional (3 times per week hemodialysis; N=18) and b) the interventional (more frequent hemodialysis 6 times per week hemodialysis; N=17) arm at baseline and 5 months after randomization.

Figure 2

Bland-Altman plot of total body water (TBW) as estimated per single- and multi-frequency (SF; MF) bioimpedance in patients randomized in the conventional (3 times per week hemodialysis; N=18) and the interventional (more frequent hemodialysis 6 times per week hemodialysis; N=17) arm at baseline [a) and b)] and 5 months [c) and d)] after randomization.

Figure 3

Regression Analysis of intracellular fluid volume (ICF) as estimated per single- and multi-frequency (SF; MF) bioimpedance in patients randomized in a) the conventional (3 times per week hemodialysis; N=18) and b) the interventional (more frequent hemodialysis 6 times per week; N=17) arm at baseline and 5 months after randomization.

Figure 4

Bland-Altman plot of intracellular water (ICF) as estimated per single- and multi-frequency (SF; MF) bioimpedance in patients randomized in the conventional (3 times per week hemodialysis; N=18) and the interventional (more frequent hemodialysis 6 times per week hemodialysis; N=17) arm at baseline [a) and b)] and 5 months [c) and d)] after randomization.

Figure 5

Regression Analysis of extracellular fluid volume (ECF) as estimated per single- and multi-frequency (SF; MF) bioimpedance in patients randomized in a) the conventional (3 times per week hemodialysis; N=18) and b) the interventional (more frequent hemodialysis 6 times per week hemodialysis; N=17) arm at baseline and 5 months after randomization.

Figure 6

Bland-Altman plot of extracellular fluid volume (ECF) as estimated per single- and multi-frequency (SF; MF) bioimpedance in patients randomized in the conventional (3 times per week hemodialysis; N=18) and the interventional (more frequent hemodialysis 6 times per week hemodialysis; N=17) arm at baseline [a) and b)] and 5 months [c) and d)] after randomization.