Transferrin Receptors, Soluble (STFR)

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Test Code: STFRSO

Overview
Ordering
Specimen
Performing
Clinical/Interpretive
Contacts
Coding

Synonyms/Keywords

sTfR (soluble transferrin receptor)

Useful For

Evaluation of suspected iron deficiency in patients who may have inflammation, infection, or chronic disease and other conditions in which ferritin concentration does not correlate with iron status, including:

-Cystic fibrosis patients who frequently have inflammation or infections

-Evaluating insulin-dependent diabetics who may have iron-deficiency resulting from gastric autoimmunity and atrophic gastritis

Specimen Requirements

Specimen Type	Preferred Container/Tube	Acceptable Container/Tube	Specimen Volume	Specimen Minimum Volume (allows for 1 repeat)	Pediatric Minimum Volume (no repeat)
Serum	Serum Separator Tube (SST)	Red Top Tube (RTT)	1.0 mL	0.25 mL

Collection Processing Instructions

Submit specimen in a plastic vial

Specimen Stability Information

Specimen Type	Temperature	Time
Serum	Frozen (preferred)	90 days
	Refrigerated	7 days
	Ambient	72 hours

Rejection Criteria

Hemolysis	Gross

Interference

The soluble transferrin receptor (sTfR) immunoassay should not be used for the routine clinical evaluation of patients for iron status when ferritin immunoassay (FERR / Ferritin, Serum) would be appropriate, such as in the absence of confounding pathologies (inflammation, infection, chronic disease, or malignancy).

Patients with hemolysis and recent blood loss may have falsely elevated sTfR levels.

sTfR is elevated in patients with thalassemia and sickle cell disease. Caution should be exercised in managing anemia in these individuals based on the sTfR test results.

Performing Laboratory Information

Performing Location	Day(s) Test Performed	Report Available	Methodology/Instrumentation
Mayo Clinic Laboratories	Monday through Sunday	1-2 days	Immunoturbidimetric Assay

Reference Lab

Mayo Clinic Laboratories

Test Information

Iron uptake into cells is mediated through internalizing iron-transferrin complexes. The iron-transferrin complex binds to transferrin receptors present on the external face of the plasma membrane, and is internalized through endosomes with ultimate release of iron into the cytoplasm. Plasma membrane-bound transferrin receptor is released by proteolytic cleavage of the extracellular domain, resulting in the formation of a truncated soluble transferrin receptor (sTfR) that circulates freely in the blood.

The concentration of sTfR is an indicator of iron status. Iron deficiency causes overexpression of transferrin receptor and sTfR levels, while iron repletion results in decreased sTfR levels. While ferritin measurement is the accepted method for assessment of iron deficiency, ferritin is an acute-phase reactant and elevates in response to processes that do not correlate with iron status, including inflammation, chronic disease, malignancy, and infection. sTfR is not an acute-phase reactant and the interpretation of iron status using sTfR measurement is not affected by these confounding pathologies.

Reference Range Information

1.8-4.6 mg/L

It is reported that African Americans may have slightly higher values.

Interpretation

Soluble transferrin receptor (sTfR) concentrations are inversely related to iron status; sTfR elevates in response to iron deficiency and decreases in response to iron repletion.

Outreach CPTs

CPT	Modifier (if needed)	Quantity	Description	Comments
84238

Synonyms/Keywords

sTfR (soluble transferrin receptor)

Ordering Applications

Ordering Application	Description
COM	Transferrin Receptors, Soluble (STFR)
Cerner	Transferrin Receptors, Soluble (STFR)

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