AbstractBackgroundThe aim of this study was to assess the value of the soluble serum transferrin receptor (sTfR) and the transferrin receptor‐ferritin index (sTfR/logF) as new markers of iron status in patients with anemia of chronic kidney disease (ACKD) both treated and not treated with recombinant human erythropoietin (rHuEPO) therapy.Materials and MethodsThe study included 53 patients and 61 controls. The concentration of sTfR was determined by an immunoturbidimetric assay. Values for the sTfR/logF index were calculated as the ratio of sTfR to logarithm ferritin level.ResultsThe results showed iron‐depleted patients had significantly higher median sTfR and sTfR/logF values (sTfR: 1.75 and 1.40 mg/L; sTfR/logF: 0.99 and 0.77) relative to those of iron‐repleted patients (sTfR: 1.07 and 0.73 mg/L; sTfR/logF: 0.39 and 0.26) in ACKD patients—both those treated and those not treated with rHuEPO. Receiver operating characteristic analysis showed a higher diagnostic accuracy of the sTfR/logF index (area under curve [AUC]=0.970) versus sTfR concentration (AUC=0.890) in the assessment of the iron status of ACKD patients. The tested parameters showed no significant differences according to C‐reactive protein concentration (p=0.108 and 0.147), in contrast to serum ferritin concentration (p=0.045).ConclusionThe study results showed the tested parameters to be reliable in the assessment of the iron status of patients with ACKD, with a higher discriminating power of the sTfR/logF index versus the sTfR. It is expected that combined measurements of ferritin and sTfR concentrations with sTfR/logF index calculation could improve diagnostic reliability for accurate evaluation of the iron status of patients with ACKD, particularly those with concomitant inflammatory or infective conditions.