A linear relationship between serum high-sensitive C-reactive protein and hemoglobin in hemodialysis patients.

Background: Inflammatory process in hemodialysis patients involves hematopoiesis. The aim of the study was to determine the relationship between serum C-reactive protein (CRP) as a marker of inflammation with hemoglobin in patients under hemodialysis.
Methods: Patients under maintenance hemodialysis for more than 3 months were studied. Serum high-sensitive CRP (hs-CRP) was measured by immunoturbidimetric method and hemoglobin < 11 g/dl was considered as anemia. Iron deficiency anemia was confirmed by percent transferrin saturation < 20 %. Correlation coefficient, linear regression and odds ratio (OR) were used to determine the relationship.
Results: A total of 73 patients aged 50 ± 16.9 years with median hemodialysis duration of 24 (3-280) months entered the study. High serum hs-CRP (> 5 mg/l) was found in 42 (57.5 %) and anemia in 32 (43.8 %) patients. High CRP was significantly associated with anemia OR = 20.8 (95 % CI 5.35-81, p = 0.001). After adjustment for age, dialysis duration, blood indices and serum albumin, the odds of anemia in the high CRP group remained at a significant level of 16.7 (95 % CI 3.7-75, p = 0.001). Hemoglobin levels conversely correlated with serum hs-CRP (r = -0.607, r (2) = 0.36, p = 0.001). In linear regression analysis for each 1 mg/l increase in serum hs-CRP, hemoglobin value increased by 12.4 % (p = 0.002). Serum iron at cutoff level of 54 µg/dl discriminated patients with and without iron deficiency anemia with sensitivity of 93.3 %, specificity of 84 % and accuracy of 90 % (AUC ± SE = 0.901 ± 0.04 (95 % CI, 0.805-0.998, p = 0.001).
Conclusion: These findings indicate that in hemodialysis patients, the inflammatory process alters hemoglobin level in converse correlation with CRP concentration with a linear relationship pattern. Serum iron <54 µg/dl indicates iron deficiency anemia with high accuracy.