Comorbidity and acute clinical events as determinants of C-reactive protein variation in hemodialysis patients: implications for patient survival.

BACKGROUND: Patients with chronic kidney disease stage 5 have high comorbidity and are prone to inflammation that may contribute to the high cardiovascular mortality risk. STUDY DESIGN: Three-month observational cohort study of prevalent hemodialysis patients. SETTINGS & PARTICIPANTS: 228 hemodialysis patients (44% women) were included, median age of 66 years, median time on dialysis therapy of 29 months. PREDICTORS & OUTCOMES: In part 1, comorbidity and intercurrent illness were predictors and C-reactive protein (CRP) level was the outcome. In part 2, serial CRP values were predictors and survival was the outcome. MEASUREMENTS: High-sensitivity CRP was measured weekly and interleukin 6 (IL-6), tumor necrosis factor alpha, and IL-10 were measured monthly. Data for comorbidity were collected from patient records to calculate Davies comorbidity score, and self-reported clinical events were recorded weekly. RESULTS: Median baseline CRP level was 6.7 mg/L (25th to 75th percentiles, 2.5 to 21 mg/L). Baseline CRP level correlated with time-averaged CRP (Spearman rho = 0.76) and individual median of serial CRP values (rho = 0.78; both P < 0.001). Part 1: comorbidity score was significantly associated with greater CRP and IL-6 levels. Age, sex, comorbidity, and 7 of 12 clinical events had significant effects on CRP level variation. Part 2: during a mean follow-up of 29 months, 38% of patients died. Median and mean serial CRP levels were associated with a greater hazard ratio for death (1.013; 95% confidence interval, 1.004 to 1.022) and 1.012 (95% confidence interval, 1.004 to 1.020) than baseline, maximum, and minimum CRP values during the study. Other significant covariates were age, Davies risk group, dialysis vintage, and albumin level. LIMITATIONS: The study is based on observational data for prevalent dialysis patients. CONCLUSIONS: Comorbidity and clinical events are strongly associated with inflammation in hemodialysis patients. Despite variability over time, inflammation assessed by using CRP level is a strong predictor of mortality. Serial measurements provide additional information compared with a single measurement.