Role of soluble transferrin receptor - An Iron marker in hemodialysis patients

Background: Iron status assessment is crucial in end-stage renal disease hemodialysis (ESRD-HD) patients because iron deficiency may cause unresponsiveness to erythropoiesis-stimulating agent. Soluble transferrin receptor (sTfR) is a potential iron marker that is not influenced by inflammation, and the results among studies are still conflicting. This study evaluated the role of sTfR in determining iron deficiency in ESRD-HD patients. Methods: This cross-sectional study was conducted at the Hemodialysis Unit in Cipto Mangunkusumo Hospital, Indonesia, from August to September 2018 and included 127 ESRD-HD patients. The sTfR level, sTfR index (sTfR/log ferritin), iron status, ferritin level, and complete blood count were assessed. Transferrin saturation (TSAT) was used as a reference. The role of sTfR was analyzed using the Chi-square test and receiver operating characteristic curve analysis. Results: The median sTfR was 3.0 (range, 1.0-8.5) mg/l, and the median TSAT was 23% (4.0%-100%). The sTfR level in ESRD-HD patients with absolute iron deficiency was 3.9 (1.9-8.5) mg/l, in those with functional iron deficiency was 3.5 (1.9-5.4) mg/l, and in those with no iron deficiency was 2.6 (1.0-6.4) mg/l. The previous sTfR cut-off value of 2.5 mg/l had a sensitivity of 83.3%, specificity of 48.2%, positive predictive value (PPV) of 44.3%, and negative predictive value (NPV) of 85.4%, whereas the new sTfR cut-off value of 2.71 mg/l had a sensitivity of 83.3%, specificity of 56.5%, PPV of 48.6%, and NPV of 87.3%. TSAT and index TSAT were not influenced by inflammation. Conclusion: The cut-off sTfR value of 2.71 mg/l is better than 2.5 mg/l to determine the iron status in ESRD-HD patients.