Association of bioimpedance-derived 50-kHz phase angle as marker of body composition with electrical parameters...

Our aim is to clarify the association of the bioelectrical impedance-derived 50-kHz phase angle (φ₅₀ ) 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 (R₀ ), capacitance of the cell membrane (Cm), and a parameter for the distribution of the time constant (α) 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. φ₅₀ increased with the decrease in R_inf /R₀ and α and also with the increase in Cm (multiple regression coefficients [β]: 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. φ₅₀ increased with an increase in P_NHLT and BMI and decrease in P_ExF , N_sex , and age (β: 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 φ₅₀ for pre- and post-hemodialysis (ρ = 0.772) may be improved (ρ = 0.950) by adding a multiplication of 0.2 and P_ExF to φ₅₀ for correction. φ₅₀ 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 φ₅₀ as a marker of body composition related to nutrition.