Determination of muscle mass, fat mass and body water. Is buíoimpedance with Impedimed SFB7 consistent with reference methods?

Abstract

Abstract Determination of muscle mass, fat mass and body water. Is bioimpedance with Impedimed SFB7 consistent with reference methods? Author: Jakob Nilsson Supervisor: Lars Ellegård, Associate Professor, Senior Consultant Degree project, Programme in Medicine, 2016, Department of Internal Medicine and Clinical Nutrition, Sahlgrenska Academy at University of Gothenburg, Sweden. Background: Malnutrition and fluid imbalance are common among hospitalized patients. Bioimpedance is a manageable and inexpensive method to estimate Total Body Skeletal Muscle Mass (TBSMM), Fat Mass (FM), Total Body Water (TBW), Extracellular Water (ECW) and Intracellular Water (ICW). However, further validations against reference methods are required before introducing it to everyday use in clinical practise. Aim: To validate SFB7 bioimpedance device’s ability to measure TBSMM, FM, TBW, ECW and ICW against reference methods in healthy subjects. Methods: 50 healthy adults (men, n=25; women, n=25) were measured with SFB7 and reference methods: Dual-energy X-ray Absorptiometry (DXA), Air Displacement Plethysmography (ADP), Dilution Techniques and Total Body Potassium (TBK). Paired-Samples T-Test, linear regression and Bland Altman plots were used to compare SFB7 estimates for TBSMM, FM, TBW, ECW and ICW with reference methods. Results: The correlations between estimates by SFB7 and reference methods in men were high for TBSMM (rP=0.914) and ECW (rP=0.931), however significant differences in mean and systematic bias were found in both variables. The correlations between SFB7 and reference methods for FM, TBW and ICW were not impressive. The correlations between estimates by SFB7 and reference methods in women were high for FM (rPDXA=0.898, rPADP=0.890) and ECW (rP=0.907). SFB7 underestimated FM and overestimated ECW significantly. The correlations between estimates by SFB7 and reference methods for TBSMM, TBW and ICW were not impressive. Conclusions: Bioimpedance by Impedimed SFB7 by proprietary software and equations does not correctly predict TBSMM, FM, TBW, ECW and ICW in healthy men and women.