Is Transferrin Saturation a Useful Marker of Iron Metabolism in Patients with Chronic Kidney Disease Treated with Hemodialysis?

Abstract

Background: According to the currently applicable KDIGO-2012 and ERBP 2013 guidelines, iron metabolism assessments for patients with Chronic Kidney Disease (CKD) are performed using such parameters as ferritin concentration and Transferrin Saturation (TSAT). Their values are to be treated as a basis on which to decide on providing iron substitution. Patients with Stage 5 CKD on maintenance hemodialysis commonly suffer from malnutrition syndrome and inflammation. One of the markers for malnutrition and inflammation is low transferrin concentration. Our study focused on establishing what percentage of patients this applied to and whether or not the transferrin saturation figure was artificially inflated in such cases. Materials and Methods: The study group included 66 patients with Stage 5 CKD on maintenance hemodialysis. Such data were analyzed as complete blood count, iron and ferritin concentrations, and Transferrin Saturation (TSAT). Other parameters - age, sex, time from their first hemodialysis, and the quality of their dialysis in the last six months – the Kt/V average. Results: It was found that only 12% of the study group patients had their transferrin concentrations above the lower limit of normal. The TSAT value correlated negatively with transferrin concentration. Transferrin concentration correlated negatively with time from first hemodialysis or ferritin concentration, and positively with body weight. Normal transferrin concentration was only seen in patients with ferritin concentrations of up to 400 μg/L. The group was divided according to transferrin concentration of <1.5 g/L or >1.5 g/L. These groups differed significantly in ferritin concentration and transferrin saturation. (p = 0.0005 and p = 0.004, respectively). The 1.5 g/L transferrin concentration point divides patients with mild and medium malnutrition. It is also the minimum transferrin content necessary to achieve hemoglobin values ≥10 g/dL determined using the ROC curve. Conclusion: Low transferrin concentrations cause abnormally high TSAT values. In most patients on maintenance hemodialysis, this marker is not useful for assessing the availability of iron for erythropoiesis.