Ratio of Capacitance/BMI Reflects Deficit in Nutritional Concentration While CH2 Reflects Total Nutritional Deficit in CAPD Patients and General Population

Abstract

Traditionally phase angle was the best predictor in BIA for nutrition and survival in dialysis population. We recently showed that normalized bioimpedance indices are a better risk discriminator for dialysis patients and the general popu-lation. We hereby aimed to explore discriminating factors behind them. Methods: We assessed the body capacitive index (BCI = Capacitance × Height2/Weight); body resistive index (BRI = Resistance × Weight/Height2); and also, CH2 (= Capacitance × Height2) which represents total body capacitive volume in physics. We initially performed BIA for 206 female, 116 male healthy volunteers, followed by, prospective study for 128 CAPD patients (47 diabetes mellitus (DM), 81 non-DM; 59 male, 69 female) for >2 years. Results: Moderately good negative correlation of albumin and BCI (r = -0.533, p < 0.001) with linear regression (BCI = 8.780 - 0.184 × [albumin], R2 = 0.339, p < 0.001) was shown in CAPD patients. BCI and CH2 were much higher in CAPD patients in comparison to healthy volunteers (3.4 ± 0.1 vs 2.0 ± 0.0 nFm2/kg, p < 0.001 and 203 ± 8 vs 125 ± 1 nFm2, p < 0.001, respectively). In age and gender adjusted logistic regression model of 128 CAPD patients versus 322 healthy volunteers, the best risk discriminator was BCI ( X 2 = 165.6), followed by CH2 ( X 2 = 140), phase angle ( X 2 = 59.3) and BRI ( X 2 = 52.2). Thirty five (27.3%) patients died during the study period (Fatal cause: infection (54%), cardiovascular (26%)). In Cox regression, CH2 ( X 2 4 = 32.4) was the best predictor for all-cause mortality, followed by BCI ( X 2 4 = 27.7) and phase angle ( X 2 4 = 19.3). Conclusion: The phase angle was a compound parameter of the body capacity index (BCI) and body resistive index (BRI). BCI has a mod-erately good negative correlation with albumin and this supports its role in reflecting the severity of malnutrition in CAPD patients. CH2 represents total nutrition deficit and thus the major risk indicator for the survival of CAPD pa-tients.