Usefulness of bioelectrical impedance analysis in monitoring nutrition status and survival of peritoneal dialysis patients.

Malnutrition is highly prevalent in peritoneal dialysis (PD) patients and is associated with higher mortality. Lower serum levels of markers of nutrition--such as albumin, creatinine, prealbumin, and total cholesterol--are important risk factors in PD patients. Usefulness of bioimpedance analysis (BIA) in hemodialysis (HD) patients has been reported. In the present study, we prospectively examined the relationship of bioimpedance indexes to the nutrition status and survival of 45 PD patients who were followed for more than 1 year. On patient enrollment, a BIA was performed (Bioelectrical Impedance Analyzer, Model BIA-101: RJL Systems, Clinton Township, MI, U.S.A.). Monthly blood was analyzed for biochemical markers. The mean age of the study group was 50 +/- 15 years. Of the 45 patients, 56% were female and 24% were diabetic. Mean body mass index was 25.7 +/- 5.1. Mean resistance, reactance, capacitance, and phase angle were 524 +/- 106 omega 57 +/- 20 omega, 678 +/- 223 pF, and 6.2 +/- 1.7 degrees respectively. Patients with diabetes had lower capacitance (555 pF vs. 713 pF, p = 0.007) and phase angle (5.35 degrees vs. 6.4 degrees, p = 0.05) than patients without diabetes. During the study period, 4 patients died. Patients who survived had higher capacitance (486 +/- 163 pF vs. 697 +/- 218 pF, p = 0.07) and phase angle (4.65 +/- 0.73 degrees, vs. 6.34 +/- 1.67 degrees, p = 0.008) than those who did not survive. The Kaplan-Meier method was used to compute observed survival. The cumulative observed survival of PD patients with an enrollment phase angle > or = 6 degrees was significantly (p = 0.01) higher than that of patients with an enrollment phase angle < 6 degrees. Reactance was directly correlated with albumin (r = 0.52, p < 0.0001) and total protein (r = 0.44, p < 0.05). Capacitance was directly correlated with body mass index (r = 0.35, p < 0.05), albumin (r = 0.32, p < 0.05), and blood urea nitrogen (BUN) (r = 0.44, p < 0.01), and inversely correlated with body weight (r = -0.51, p < 0.0001). Phase angle was directly correlated with all of the biochemical markers of nutrition, such as albumin (r = 0.54, p < 0.01), total protein (r = 0.38, p < 0.05), creatinine (r = 0.28, p < 0.01), and BUN (r = 0.39, p < 0.05). By stepwise multivariate regression analysis, body weight (beta = -0.60, p < 0.0001) and total protein (beta = 0.32, p = 0.012) were significant determinants of resistance. Body weight (beta = -0.31, p = 0.02) and albumin (beta = 0.59, p < 0.0001) were significant predictors of reactance. Serum albumin (beta = 0.53, p < 0.0001) was the only best predictor of phase angle in PD patients. The BIA indices reflect nutrition status in PD patients, and may be useful in monitoring nutrition interventions.