Type of test Blood
Normal findings
Men: 2-5 mg/L
Women: 1.9-4.4 mg/L
(Results vary depending on the testing method.)
Test explanation and related physiology
Both iron metabolism and transport are altered in chronic ill ness. Differentiation of the anemia of chronic disease (anemia of inflammation or anemia of aging) from iron deficiency anemia is by measurement of the serum TfR concentration.
TfR assists with absorption of iron into cells. TfR is increased when erythropoiesis is enhanced (such as often occurs in iron deficiency). The concentration of cell surface TfR is carefully regulated by TfR mRNA, according to the internal iron content of the cell and its individual iron requirements. Whereas iron deficient cells contain increased numbers of receptors, receptor numbers are downregulated in iron-replete cells.
An increased mean TfR concentration is noted in patients with iron-deficiency anemia compared with patients with anemia secondary to chronic disease. Calculation of the ratio of TfR/ log ferritin concentration provides an even higher sensitivity and specificity for the detection of Fe deficiency.
TfR is also useful in distinguishing iron-deficiency anemia from situations that are commonly encountered in childhood, adolescence, and during pregnancy when iron stores are uniformly low to absent. In these situations, iron-deficient erythropoiesis is not necessarily present, and TfR levels are not elevated. Finally, in situations in which iron-deficiency anemia coexists with anemia of chronic disease, TfR concentrations increase secondary to the underlying iron deficiency, thus avoiding the need for a bone marrow examination.
Interfering factors
• Individuals who live at high altitudes have a reference range that extends 6% higher than the upper level of this reference interval.
• Results are related to ethnicity. Individuals of African descent can be expected to have higher levels.
* Drugs that may cause increased TfR levels include recombinant human erythropoietins.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: red or green
Abnormal findings
Increased plasma TfR levels
- Iron-deficiency anemia
- Reticulocytosis
- Erythropoietin therapy
Decreased plasma TfR levels
- Hemochromatosis
