Test ID: FE
Iron and Total Iron-Binding Capacity, Serum
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Screening for chronic iron overload diseases, particularly hereditary hemochromatosis.
Serum iron, TIBC, and percent saturation are widely used for the diagnosis of iron deficiency. However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Ingested iron is absorbed primarily from the intestinal tract and is temporarily stored in the mucosal cells as Fe(3+)-ferritin, a complex of ferric hydroxide-ferric phosphate attached to the protein apoferritin. On demand, iron is released into the blood as Fe(3+)-transferrin in equilibrium with a very small amount of free Fe(3+).
Transferrin is the plasma iron transport protein, which binds iron strongly at physiological pH. Transferrin is generally only 25% to 30% saturated with iron. The additional amount of iron that can be bound is the unsaturated iron-binding capacity (UIBC). The sum of the serum iron and UIBC represents the total iron-binding capacity (TIBC). TIBC is an indirect measurement of transferrin concentration. Each transferrin molecule has 2 iron-binding sites. On average, in normal persons, about 1/3 of the total iron-binding sites are occupied by iron.
Percent saturation (100 x serum iron/TIBC) is usually normal or increased in persons who are iron deficient, pregnant, or are taking oral contraceptive medications. Persons with chronic inflammatory processes, hemochromatosis, or malignancies generally display low TIBC.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
IRON
Males: 50-150 mcg/dL
Females: 35-145 mcg/dL
TOTAL BINDING CAPACITY
250-400 mcg/dL
PERCENT SATURATION
14-50%
Interpretation Provides information to assist in interpretation of the test results
In hereditary hemochromatosis, serum iron is usually >150 mcg/dL and percent saturation is >60%. In advanced iron overload states, the percent saturation often is >90%.
For more information about hereditary hemochromatosis testing, see Hereditary Hemochromatosis Algorithm in Special Instructions.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Measurement of serum iron, iron-binding capacity, and percent saturation should not be used as a test for iron deficiency. It is often unreliable for this purpose.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Tietz Textbook of Clinical Chemistry. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company. 1999
2. Fairbanks VF, Baldus WP: Iron overload. In Hematology. 4th edition. Edited by WJ Williams, AJ Erslev, MA Lichtman. New York, McGraw-Hill Book Company, 1990, pp 482-505
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