Association of bioimpedance-derived50-kHzphase angle as marker of body composition with electrical parameters regarding theCole-Colemodel

Our aim is to clarify the association of the bioelectrical impedance-derived 50-kHz phase angle (phi(50)) with electrical parameters regarding the Cole-Cole model and clinical parameters. A total of 440 sets of bioelectrical impedance data from pre- and post-hemodialysis from 157 patients were used. Resistance at infinite frequency (R-inf), resistance at 0 frequency (R-0), capacitance of the cell membrane (Cm), and a parameter for the distribution of the time constant (alpha) were examined as electrical parameters. Normally hydrated lean tissue mass as a percentage of the dry weight (P-NHLT), excess fluid mass as a percentage of the dry weight (P-ExF), body mass index (BMI), age, and sex (N-sex, 0 for male, 1 for female) were examined as clinical parameters. phi(50)increased with the decrease inR(inf)/R(0)and alpha and also with the increase in Cm (multiple regression coefficients [beta]: pre/post, -0.886/-0.936, -0.175/-0.212, and 0.167/0.141), which determined the ratio of intra- to extracellular fluid volume (ICV/ECV), tissue homogeneity, and total cell mass. phi(50)increased with an increase inP(NHLT)and BMI and decrease inP(ExF),N-sex, and age (beta: pre/post, 0.654/0.581, 0.466/0.412, -0.483/-0.473, -0.216/-0.154, and -0.145/-0.127). The concordance correlation coefficient between phi(50)for pre- and post-hemodialysis (rho= 0.772) may be improved (rho= 0.950) by adding a multiplication of 0.2 andP(ExF)to phi(50)for correction. phi(50)may be used to estimate body composition through the association with ICV/ECV, tissue homogeneity, and total cell mass. The correction for excess fluid is essential in order to use phi(50)as a marker of body composition related to nutrition.

Automated summary

The study found that phi (50) is associated with a decrease in R (inf) / R (0) and alpha, as well as an increase in Cm; simultaneously, it also increases with an increase in P (NHLT) and BMI, and a decrease in P (ExF), N-sex, and age.