Supplementary Material for: Comparison of Body Fluid Volumes Determined by Kinetic Modeling and by Bioimpedance Spectroscopy

Introduction: The bioimpedance spectroscopy (BIS) method is used in individual patients requiring body fluid volume measurement. In a hemodialysis facility, however, regular screening of body fluid volumes is also necessary. Such screening, by kinetic modeling, may become possible by calculating distribution volumes of urea and uric acid from regular blood test results. Objective: The aim is to compare uric acid distribution volumes with BIS-extracellular volume, urea distribution volume with BIS-total body water, and difference between urea and uric acid distribution volumes with BIS-intracellular volume. Methods: We reanalyzed stored blood test data of 53 hemodialysis patients obtained together with BIS data of the same patients in our previous study. Results: Significant correlations were found between urea distribution volume and total body water predicted by the BIS method, between uric acid distribution volume and extracellular volume predicted by the BIS method, and between the difference of uric acid distribution volume from urea distribution volume and intracellular volume predicted by the BIS method. In Bland-Altman analysis, comparison of each pair showed no systematic error. The mean difference between each pair was minimal. Conclusion: Fluid volumes in different body compartments can be estimated by kinetic modeling as well as by the BIS method.引言：生物电阻抗光谱法（bioimpedance spectroscopy, BIS）多用于需进行体液容量检测的个体患者。但在血液透析中心，体液容量的常规筛查同样至关重要。通过常规血液检验结果计算尿素与尿酸的分布容积，即可借助动力学建模实现此类筛查。 研究目的：本研究旨在对比尿酸分布容积与BIS测得的细胞外液容积、尿素分布容积与BIS测得的总体水，以及尿素与尿酸分布容积的差值与BIS测得的细胞内液容积。 研究方法：我们对既往研究中留存的53名血液透析患者的血液检测数据及同期采集的同一批患者的BIS检测数据进行了重新分析。 研究结果：本研究发现，尿素分布容积与BIS法预测的总体水之间、尿酸分布容积与BIS法预测的细胞外液容积之间，以及尿酸与尿素分布容积的差值与BIS法预测的细胞内液容积之间均存在显著相关性。通过布兰德-奥特曼分析法（Bland-Altman analysis）进行两两对比，未检出系统误差，且各组配对差值的均值极小。 研究结论：通过动力学建模与BIS法均可估算不同体液分区的容量。