What is a unique characteristic of soluble transferrin receptor assay in iron deficiency evaluation?

The soluble transferrin receptor (sTfR) assay is a specific diagnostic test used in the evaluation of iron deficiency anemia. A unique characteristic of the sTfR assay is that it is elevated in cases of iron deficiency.

When iron stores are depleted, the body increases the production of transferrin receptors to enhance iron uptake from the bloodstream, resulting in higher levels of soluble transferrin receptors in the serum. This elevation occurs irrespective of inflammatory conditions, making the sTfR a reliable marker in distinguishing iron deficiency anemia from anemia of chronic disease, where transferrin receptors may not be elevated due to inflammation.

Other tests, such as serum iron or transferrin saturation, primarily focus on the iron available in circulation or the binding capacity of transferrin but can be influenced by factors like acute illness or inflammation, potentially leading to misleading results. The sTfR level serves as a more direct indicator of iron status, particularly in the context of anemia, thus making it significant for diagnosing iron deficiency.