At a Glance
Why Get Tested?
When to Get Tested?
When iron deficiency anemia is suspected
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
Soluble transferrin receptors are proteins found in blood that can be elevated with iron-deficiency. This test measures the amount of soluble transferrin receptors to help detect and evaluate iron deficiency and aid in the diagnosis of iron-deficiency anemia.
Iron is an essential nutrient absorbed from the diet. Transferrin is the main protein in the blood that binds to iron and carries it to tissues and cells throughout the body. About 80% of iron is transported to the bone marrow, where it is incorporated into the hemoglobin in red blood cells (RBCs), and the rest is stored in other cells and tissues as ferritin and hemosiderin.
When transferrin binds to iron, they form a complex. These complexes bind to transferrin receptors found on the surface of cells and the iron is then transported into the cells. Transferrin receptors are cleaved from the surface of cells, enter the bloodstream, and become soluble transferrin receptors (sTfR).
The number of transferrin receptors found on the surface of cells correlates with the level of iron within cells. When the iron level drops, the cells produce more transferrin receptors. As more receptors are produced, more are cleaved from cell surfaces and enter the blood, increasing the level of soluble transferrin receptors. Thus, measuring the level of sTfR is one way of evaluating the amount of iron available in the body.
Red blood cells have a lifespan of about 120 days. Because of this, the bone marrow must continually produce new RBCs. If there is insufficient iron taken in through the diet and/or increased iron loss (e.g., bleeding), iron reserve stored in the body is decreased. Over time, this can lead to iron deficiency, as the amount of iron stored in the body exhausts and the demand for iron exceeds the supply. As a result, fewer RBCs are produced and those newly formed RBCs are also smaller (microcytic) and contain less hemoglobin (hypochromic). This is a condition called iron deficiency anemia.
Usually, a ferritin test is used to evaluate the amount of iron reserve in the body and to help diagnose iron-deficiency anemia. However, the ferritin level can be elevated when an individual has inflammation or a chronic disease, such as autoimmune disorders or some cancers. In these conditions, the ferritin test is not useful and a test for soluble transferrin receptors may be ordered.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Ask a Laboratory Scientist
This form enables you to ask specific questions about your tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. If your questions are not related to your lab tests, please submit them via our Contact Us form. Thank you.
* indicates a required field
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 972-973.
(© 1995-2011). Unit Code 84283: Soluble Transferrin Receptor (sTfR), Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/84283 through http://www.mayomedicallaboratories.com. Accessed September 2011.
Lehman, C. and Roberts, W. (Updated 2011 April). Anemia. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/Anemia.html?client_ID=LTD through http://www.arupconsult.com. Accessed September 2011.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 1066-1067.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry. AACC Press, Washington, DC. Pp 407-408.
Conrad, M. (Updated 2011 May 26). Iron Deficiency Anemia. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/202333-overview through http://emedicine.medscape.com. Accessed September 2011.
González-Costello, J. and Comín-Colet, J. (2010 December 30). Iron Deficiency and Anaemia in Heart Failure: Understanding the FAIR-HF Trial. Medscape Today News from Eur J Heart Fail. 2010;12(11):1159-1162. [On-line information]. Available online at http://www.medscape.com/viewarticle/734494 through http://www.medscape.com. Accessed September 2011.
Wish, J. (2006 September). Assessing Iron Status: Beyond Serum Ferritin and Transferrin Saturation. Clin J Am Soc Nephrol 1: S4–S8, 2006. [On-line information]. Available online at http://cjasn.asnjournals.org/content/1/Supplement_1/S4.full.pdf+html through http://cjasn.asnjournals.org. Accessed September 2011.
Chen, Y. (Updated 2011 February 28). Iron deficiency anemia. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000584.htm through http://www.nlm.nih.gov. Accessed September 2011.
World Health Organization, Centers for Disease Control and Prevention (2007) Accessing the Iron Status of Populations. World Health Organization [On-line information]. Available online at http://www.who.int/nutrition/publications/micronutrients/anaemia_iron_deficiency/9789241596107/en/ through http://www.who.int. Accessed October 2011.
Harmening D. Clinical Hematology and Fundamentals of Hemostasis, Fifth Edition, F.A. Davis Company, Philadelphia, 2009, Pp 120-130.