Slightly superior performance of bioimpedance spectroscopy over single frequency regression equations for assessment of total body water

Abstract

Electrical bioimpedance has been used for several decades to assess body fluid distribution and body composition by using single frequency and bioimpedance spectroscopic (BIS) techniques. It remains uncertain whether BIS methods have better performance compare to single frequency regression equations. In this work the performance of two BIS methods and four different 50 kHz single frequency prediction equations was studied in a data set of wrist-to-ankle tetrapolar BIS measurements (5-1000 kHz) together with reference values of total body water obtained by tritium dilution in 92 patients. Data were compared using regression techniques and Bland-Altman plots. The results of this study showed that all methods produced similarly high correlation and concordance coefficients, indicating good accuracy as a method. Limits of agreement analysis indicated that the population level performance of Sun's prediction equations was very similar to the performance of both BIS methods. However, BIS methods in practice have slightly better predictive performance than the single-frequency equations as judged by higher correlation and the limits of agreement from the Bland-Altman analysis. In any case, the authors believe that an accurate evaluation of performance of the methods cannot be done as long as the evaluation is done using Bland-Altman analysis, the commonly accepted technique for this kind of performance comparisons.

Negative Energy Balance Does Not Alter Fat-Free Mass During the Yukon Arctic Ultra—The Longest and the Coldest Ultramarathon

“…In addition, alterations among various cohorts may also distort the results, for example, kidney diseases, cardiovascular conditions, etc., as well as ethnic group affiliation (Kyle et al., 2004). However, we have employed formulas appropriate for this cohort of healthy trained adults to estimate FM and FFM (Segal et al., 1988) and TBW (Sun et al., 2003) that have been shown to perform better than other formulas with smaller biases and better agreement (Seoane et al., 2015). In addition, great care was taken to perform the measurements under the same conditions by the same operator.…”

Classification of Hydration in Clinical Conditions: Indirect and Direct Approaches Using Bioimpedance

“…Other research supports these findings. In adults receiving growth hormone replacement therapy, the TBW was determined using isotope dilution and predicted from BI measurements, collected with the same multi-frequency instrument, using 50 kHz values and four published equations and the Hanai mixture [25] model with and without adjustment for BMI [38]. Measured and predicted TBW values were significantly and similarly correlated for linearity and concordance (r > 0.9).…”

“…Follow up analyses determined the comparability of these different approaches to estimate the TBW at the level of an individual [38]. The mean absolute error of BIS was slightly improved compared to multiple regression equations using 50 kHz values (5% vs. 7% or 2 L vs. 3 L).…”

“…Finally, use of different single-frequency mathematical prediction equations complicates comparisons. As suggested by Seone et al [38,39], volume prediction models that include more independent variables than Ht 2 /R and weight tend to produce greater errors in estimated TBW that indicates a specificity of that regression equation and, thus, excludes its application in any sample or individual differing in characteristics from the original sample in which the regression model was developed. These factors as well as the imprecision of the prediction models, single-frequency and BIS, impedes their use in point-of-care individual assessments of hydration.…”