Extracellular mass/body cell mass ratio is an independent predictor of survival in peritoneal dialysis patients

Malnutrition is a strong predictor of mortality in peritoneal dialysis (PD) patients. Extracellular mass (ECM) contains all the metabolically inactive, whereas body cell mass (BCM) contains all the metabolically active, tissues of the body. ECM/BCM ratio is a highly sensitive index of malnutrition. The objective of this study was to explore the relationship between ECM/BCM ratio and survival in PD patients. We enrolled 62 patients from November 2000 to July 2008. On enrollment, demographic, clinical, and biochemical data were recorded. Bioimpedance analysis (BIA) was used to determine ECM and BCM in PD patients. Patients were followed up to November 2008. Mean age was 54 +/- 16 (s.d.) years; female, 55%; African Americans, 65%; diabetic, 24%. Mean ECM/BCM ratio was 1.206 +/- 0.197 (range: 0.73-1.62). Diabetics had higher ECM/BCM ratio than nondiabetics (1.29 vs 1.18, P = 0.04). ECM/BCM ratio correlated directly with age (r = 0.38, P = 0.002) and inversely with serum albumin (r = -0.43, P = 0.001), creatinine (-0.24, P = 0.08), blood urea nitrogen (r = -0.26, P = 0.06), and total protein (r = -0.31, P = 0.026). Using multivariate Cox regression analysis, adjusting for age, race, gender, diabetes, and human immunodeficiency virus status, enrollment ECM/BCM ratio was a significant independent predictor of mortality (relative risk 1.035, P = 0.018). For every 10% increase in the ECM/BCM ratio, the relative risk of death was increased by about 35%. In conclusion, BIA-derived enrollment ECM/BCM ratio, a marker of malnutrition, was an independent predictor of long-term survival in PD patients.