A comparison of fluid status determination using bioelectric impedance and the isotope dilution method in hemodialysis and peritoneal dialysis patients

We aimed to compare fluid status as determined by multifrequency bioimpedance spectroscopy (MF-BIS, Xitron 4200, USA) with that determined by the isotope dilution method among a contemporary Chinese cohort. Healthy Chinese subjects (HS, n = 30) were recruited in Zhengzhou. Hemodialysis (HD, n = 49) and peritoneal dialysis (PD, n = 48) patients were screened at the First Affiliated Hospital of Zhengzhou University. Total body water (TBW) and extracellular water (ECW) were measured by deuterium (TBW(D)) and bromide (ECW(Br)) dilution, respectively, and by MF-BIS using the Moissl equation (ME). The results of MF-BIS were compared to the reference method by Pearson analysis and Bland–Altman analysis in the three groups. The accuracy of overhydration as determined by MF-BIS was analyzed by receiver operating characteristic (ROC) curves. The TBW(D) and TBW(ME) values were 34.67 ± 7.31 and 35.41 ± 5.76 L, 37.30 ± 8.58 and 37.02 ± 8.10 L, and 38.61 ± 10.02 and 38.44 ± 7.59 L in the HS, HD and PD groups, respectively. The ECW(Br) and ECW(ME) values were 14.88 ± 3.33 and 15.53 ± 2.39 L, 16.24 ± 5.08 and 16.90 ± 3.93 L, and 19.08 ± 6.41 and 18.23 ± 3.61 L in the HS, HD and PD groups, respectively. The mean bias between TBW(D) and TBW(ME) was −0.74 L, 0.28 L, and 0.17 L in the HS, HD and PD groups, respectively. The mean bias between ECW(Br) and ECW(ME) was −0.65 L, −0.66 L, and 0.85 L in the HS, HD and PD groups, respectively. Compared to the ECW(Br)/TBW(D) ratio, the area under the ROC curve (AUC) of the ECW(ME)/TBW(ME) ratio for the diagnosis of overhydration was 0.76 and 0.68 in the HD and PD groups, respectively. In summary, MF-BIS with ME could be used in Chinese HD and PD patients.