The soluble transferrin receptor (sTfR) test is primarily ordered to help distinguish between anemia that is caused by iron deficiency and anemia that is caused by inflammation or a chronic illness (so-called anemia of chronic disease or inflammation). It is not a routine test but may be ordered if other tests that evaluate the amount of iron in the body do not provide a doctor with conclusive information.
Typically, a group of iron tests is ordered to evaluate iron availability if a person has anemia and/or if iron deficiency is suspected. These tests may include iron, transferrin, TIBC (total iron-binding capacity, which is either measured or calculated based on the level of transferrin), transferrin saturation (calculated based on levels of iron and TIBC), and ferritin.
Ferritin is usually the preferred test to evaluate stored iron, but it is an acute phase reactant, which means that it may be increased with inflammation or with chronic diseases such as autoimmune disorders, some cancers, and chronic infections. In these cases, ferritin may not be a good measure of stored iron. Since sTfR is not an acute phase reactant, it may be ordered as an alternative to ferritin if a chronic illness is present or suspected.
It may be ordered when a person has a normal or near normal ferritin level, but iron deficiency is still suspected. It may be ordered as an alternative to ferritin when a person has a chronic illness and/or inflammation is present or suspected.
The level of soluble transferrin receptor (sTfR) will be increased with iron deficiency. If the sTfR level is elevated in someone with anemia, then it is likely that the person has iron deficiency anemia. If the level is within the normal range, then it is more likely that the person's anemia is due to another cause, such as chronic disease or inflammation.
A decreasing sTfR level indicates an increase in iron reserve in a person being treated with iron supplements. A low level of sTfR may be seen with hemochromatosis (a condition associated with iron overload), but the test is not usually used to monitor this condition.
Those of African American descent may have moderately increased sTfR levels, as will those who live at higher elevations.
Testing may not be useful in those who have inherited disorders that affect hemoglobin production or function, such as thalassemia or sickle cell anemia. Test results may be elevated in those with red blood cell breakage (hemolysis) or recent blood loss and will not be accurate in those who have had a recent blood transfusion.
An elevated sTfR level is not as specific for iron deficiency as is, for example, a very low level of ferritin.
When a person is not iron deficient, the amount of sTfR present in the blood reflects the rate of red blood cell production by the bone marrow. Soluble transferrin receptor testing is not routinely performed to evaluate this process.
This article was last reviewed on December 15, 2011. | This article was last modified on July 21, 2013.
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