Comorbidity and Acute Clinical Events as Determinants of C-Reactive Protein Variation in Hemodialysis Patients: Implications for Patient Survival
Received 12 September 2008; accepted 12 February 2009. published online 27 April 2009.
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 α, 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 ρ = 0.76) and individual median of serial CRP values (ρ = 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.
Address correspondence to Peter Bárány, MD, PhD, Division of Renal Medicine K56, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Karolinska University Hospital Huddinge, 14186 Stockholm, Sweden
ABSTRACT