Predictive value of red blood cell distribution width on all-cause mortality in ESRD patients on peritoneal dialysis

Abstract

Background Red blood cell distribution width (RDW), which expresses variation in size of circulating erythrocytes, is routinely reported as a part of complete blood cell count test. Recent studies have demonstrated a strong independent association between increased RDW and the risk of adverse outcomes in patients with heart failure and coronary heart disease. In addition, RDW has been found to be predictive of all-cause mortality in two community-based cohorts irrespective of hemoglobin levels. Increased RDW levels are frequently observed in patients with end-stage renal disease (ESRD), however, little is known on the relationship between RDW and outcomes in this population. In this study, I sought to determine whether RDW value is associated with mortality in ESRD patients treated with continuous ambulatory peritoneal dialysis (CAPD). Methods A retrospective analysis was undertaken in 197 incident CAPD patients, who started CAPD between January 2005 and December 2010 at Yonsei University Health System and maintained CAPD for more than 3 months. Demographic, biochemical and echocardiographic data of the patients were collected based on their medical records. Patients were divided into 2 groups according to the RDW levels at 3-month, and all-cause and cardiovascular mortalities were compared between groups. Results The mean age was 55.1 years and 115 patients (58.4%) were male. The main cause of ESRD was diabetic nephropathy (43.1%), followed by hypertensive nephropathy (34.0%) and chronic glomerulonephritis (16.8%). RDW at 3-month ranged from 11.3 to 16.8% (mean 13.6±1.1%), and 51 patients (25.8%) had RDW above the upper limit of normal value (>14.5%). There were significant positive correlations between RDW levels and age (r=0.22, p<0.01), Charlson comorbidity index (CCI) score (r=0.27, p<0.01), left ventricular mass index (r=0.28, p<0.05), left atrial volume index (LAVI) (r=0.26, p<0.01), the ratio of early mitral inflow velocity to peak mitral annulus velocity (E/E’) (r=0.16, p<0.05) and left ventricular end diastolic dimension (r=0.271, p<0.01). In contrast, RDW values were negatively correlated with hemoglobin (r=-0.16, p<0.05) and albumin levels (r=-0.28, p<0.01). The all-cause mortality rates were significantly higher in the high RDW group compared to the normal RDW group (p<0.05). Cox regression analysis revealed that RDW was a significant independent predictor of all-cause mortality even after multivariate adjustment for age, gender, CCI score, hemoglobin, albumin, total cholesterol, LAVI, left ventricular ejection fraction (LVEF), and E/E’ (HR 1.20, p<0.05). Conclusion This study demonstrates that RDW provide a meaningful prognostic value on all-cause mortality in incident CAPD patients.