Relationship of bioelectrical impedance parameters to nutrition and survival in peritoneal dialysis patients

Background. Malnutrition is highly prevalent in peritoneal dialysis (PD) patients and is associated with higher mortality in these patients. In this study, we have prospectively examined the relationship of bioimpedance indexes to the nutritional status and survival in PD patients. Methods. We enrolled 48 PD patients beginning in November 2000. On enrollment, bioelectrical impedance analysis (BIA) (BIA-101; RJL/Akern, Clinton Township, MI, USA) was performed and monthly blood was analyzed for biochemical markers, including prealbumin. Patients were followed until April 2003. Results. The mean age of PD patients was 51+/-15 (SD) years. Fifty-eight percent of the patients were female and 23% of the patients were diabetic. Mean body mass index (BMI) was 25.7+/-5.0 kg/m(2). Mean resistance, reactance, and phase angle were 521+/-104 ohms, 57+/-19 ohms, and 6.16+/-1.6 degrees, respectively. During the study period, 8 patients (17%) expired. The Kaplan-Meier method was used to compute observed survival. The cumulative observed survival of PD patients with enrollment phase angle greater than or equal to 6 degrees was significantly higher (P=0.008) than that of patients with phase angle less than 6. Using Cox's multivariate regression analysis, phase angle was an independent predictor (relative risk=0.39, P=0.027) of more than two years' survival in PD patients. Serum prealbumin was directly correlated with phase angle (r=0.54, P<0.0001), reactance (r=0.55, P<0.0001), and resistance (r=0.29, P=0.06). Conclusion. BIA indexes reflect nutritional status and may be useful in monitoring nutritional status in PD patients. Phase angle is a strong prognostic index in PD patients. It is useful to incorporate prealbumin and BIA parameters in the regular assessment of PD patients, whose survival may be improved by better management of malnutrition and overall health status.