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Test Code SFEC Iron and Total Iron-Binding Capacity, Serum


Ordering Guidance


The recommended primary test for assessment of iron deficiency is serum ferritin. Order FERR1 / Ferritin, Serum.



Additional Testing Requirements


Although measurement of serum iron, total iron-binding capacity, and percent saturation should not be used as primary testing for iron deficiency, they may be helpful when used in conjunction with ferritin and soluble transferrin receptor, especially in patients with inflammation. Order both FERR1 / Ferritin, Serum; and STFR / Soluble Transferrin Receptor (sTfR), Serum with this test.



Specimen Required


Patient Preparation:

1. Fasting (12 hours)

2. For 24 hours before collection, patient should not take iron-containing supplements.

Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Draw blood before noon (preferred).

2. Within 2 hours of collection, serum gel tubes should be centrifuged.

3. Within 2 hours of collection, red-top tubes should be centrifuged, and the serum aliquoted into a plastic vial.


Useful For

Screening for chronic iron overload diseases, particularly hereditary hemochromatosis

 

Screening for iron deficiency as the cause of anemia

 

Monitoring treatment for iron deficiency anemia

 

This test should not be used as the primary test for iron deficiency.

Profile Information

Test ID Reporting Name Available Separately Always Performed
IRON Iron No Yes
TIBC Total Iron Binding Capacity No Yes
SAT Percent Saturation No Yes

Testing Algorithm

For more information see Hereditary Hemochromatosis Algorithm.

Method Name

IRON: Colorimetric Assay

TIBC: Turbidity/Calculation

SAT: Calculation

Reporting Name

Iron and Total Fe Binding Cap, S

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  180 days

Reject Due To

Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK

Clinical Information

Transferrin is the plasma iron transport protein that binds iron strongly to keep iron nonreactive in circulation and deliver it to cells with transferrin receptors. The rate of transferrin synthesis in the liver can be altered according to the body’s iron requirements and iron reserves. The circulating concentration increases in response to iron deficiency and decreases in response to iron overload. Transferrin is generally only 25% to 30% saturated with iron. Total iron-binding capacity (TIBC) is estimated from the transferrin concentration using the molecular weight of transferrin, accounting for each transferrin molecule that can bind 2 atoms of iron.

 

Iron deficiency, iron overload, and anemia of chronic disease are the most prevalent disorders of iron metabolism. Serum iron, TIBC, and percent saturation are widely used for the diagnosis of iron deficiency and iron overload disorders, such as hemochromatosis. Iron concentration and percent saturation decrease with iron deficiency and increase when iron is in excess. However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.

 

Anemia of chronic disease is often observed in patients with autoimmune diseases, chronic kidney diseases, inflammatory bowel disease, and chronic heart failure. It is diagnosed when serum iron concentrations are low despite normal serum ferritin concentrations indicating adequate iron stores. However, in the presence of inflammation, ferritin can mask iron deficiency; therefore, measuring soluble transferrin receptors is suggested.

 

The biologic variation of iron and, therefore, iron saturation is notable in normal healthy persons and in various clinical disorders owing to both diurnal variation and post-prandial effects. The intraindividual day-to-day variation of iron and iron saturation is approximately 25% to 30%.(1) Recommendations for blood sampling for iron and iron saturation measurements are contradictory, however; minimizing influence of these effects can be accomplished by collecting during the morning after an overnight fast.

Reference Values

IRON

Males: 50-150 mcg/dL

Females: 35-145 mcg/dL

 

TOTAL IRON-BINDING CAPACITY

250-400 mcg/dL

 

PERCENT SATURATION

14-50%

Interpretation

Serum iron concentration is elevated in iron overload conditions including hemochromatosis.(1)

 

Serum iron concentration is decreased in iron deficiency, iron deficiency anemia, and anemia of chronic disease.(1)

 

Total iron-binding capacity values are elevated in anemia of chronic disease and iron overload conditions.(1)

 

Total iron-binding capacity values are decreased in iron deficiency, iron deficiency anemia, and iron-refractory iron deficiency anemia.(1)

 

Percent saturation often exceeds 45% in hereditary hemochromatosis and 90% in advanced iron overload states.(2)

 

Percent saturation less than 16% is generally used to screen for iron deficiency, but a threshold of 20% is used in the presence of inflammation.(3)

 

For more information about hereditary hemochromatosis testing, see Hereditary Hemochromatosis Algorithm.

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 to 2 days

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

83540-Iron

83550-Iron-binding capacity

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SFEC Iron and Total Fe Binding Cap, S 50190-8

 

Result ID Test Result Name Result LOINC Value
SAT Percent Saturation 2502-3
IRON Iron 2498-4
TIBC Total Iron Binding Capacity 2500-7