What is the significance of soluble transferrin receptor (sTfR) levels?

From the Guidelines

The soluble transferrin receptor (sTfR) is a crucial biomarker for assessing iron deficiency and erythropoiesis, particularly in patients with inflammatory conditions where traditional iron parameters like ferritin are unreliable 1.

Key Points

• Elevated sTfR levels are indicative of iron deficiency anemia and can be used to monitor response to iron supplementation 1.
• sTfR is not affected by inflammation, making it a valuable tool in diagnosing iron deficiency in patients with chronic diseases like inflammatory bowel disease 1.
• The measurement of sTfR can help differentiate between true iron deficiency and anemia of chronic disease in patients with complex anemia 1.
• sTfR levels can be elevated in conditions with increased erythropoietic activity, such as response to IV iron, hemolytic anemia, and ineffective erythropoiesis 1.

Clinical Applications

• sTfR can be used to guide iron supplementation therapy, with the goal of normalizing sTfR levels to indicate adequate iron stores 1.
• In patients with chronic kidney disease, sTfR levels can be used to guide epoetin alfa therapy, with a target dose of 50-100 units/kg intravenously three times weekly to maintain hemoglobin levels between 10-12 g/dL.
• The reticulocyte hemoglobin content (CHr) or reticulocyte hemoglobin equivalent (RET-He) can also be used as a direct assessment of the functional availability of iron to the erythropoietic tissue, and can be measured quickly and reliably on certain auto analyzers 1.

From the Research

Significance of Soluble Transferrin Receptor (sTfR) Levels

• sTfR levels are a valuable marker of erythropoietic activity and iron status in the body 2
• The main source of serum sTfR is erythroblasts, and its levels are influenced by marrow erythropoietic activity 2
• sTfR levels are decreased in situations with diminished erythropoietic activity and increased when erythropoiesis is stimulated by hemolysis or ineffective erythropoiesis 2

Diagnostic Value of sTfR

• sTfR is a useful marker for the diagnosis of iron deficiency anemia (IDA) and can help differentiate it from anemia of chronic disease (ACD) 3, 4, 5, 6
• sTfR levels are elevated in IDA and can be used to monitor the response to iron supplementation 5
• The sTfR/ferritin ratio can be used to describe iron availability and diagnose functional iron deficiency 2, 6

Clinical Applications of sTfR

• sTfR can be used to investigate the pathophysiology of anemia and evaluate the adequacy of marrow proliferative capacity 2
• sTfR can help identify concomitant iron deficiency in patients with inflammation, where ferritin values may be normal 2
• sTfR can be used to monitor the erythropoietic response to therapy and predict response early when changes in hemoglobin are not yet apparent 2

Analytical Evaluation of sTfR Measurement Systems

• Different measurement methods for sTfR have varying cutoff points for IDA diagnosis, which should be considered in clinical practice 4
• sTfR assays have promising analytical performances and meet clinical requirements for sensitivity and specificity 4