Join Now | Sign in

Iron Tests Health Article

Save

Marketplace

Licensed from

Page: 1 2 Next >

Definition

Iron tests consist of four assays performed on serum or plasma to aid in the diagnosis and treatment of iron deficiency or iron overload. These tests are serum iron, total iron binding capacity (TIBC), serum ferritin, and serum transferrin. Iron is an essential trace element needed for the production of hemoglobin as well as the function of cytochromes (compound molecules that are important in cell respiration) and certain enzymes. Iron in plasma is almost entirely bound to transport proteins. The total iron binding capacity (TIBC) is the maximum amount of iron that these proteins can bind. Transferrin, a beta globulin (molecular weight 75,000) is the principal transport protein for iron in plasma. Therefore, the TIBC is determined mainly by the concentration of serum transferrin. Iron is stored in the epithelial cells of the gastrointestinal tract and in the reticuloendothelial cells of the liver, spleen, and bone marrow. Ferritin is the principal form of storage iron. It consists of a protein (apoferritin) and iron in the form of ferric salts.

Purpose

Serum or plasma iron tests are used for the following purposes:

To help in the differential diagnosis of anemias. Iron deficiency anemia is the most common form of anemia worldwide and is quite common in the United States—especially in multiparous females, young children, and persons with chronic intestinal bleeding.
To assess the severity of anemia and monitor the treatment of patients with chronic anemia.
To diagnose conditions of iron excess, including iron ingestion, thalassemia, hemosiderosis, and hemochromatosis. Hemosiderosis and hemochromatosis are conditions produced by excessive iron stores in the tissues. Hemosiderosis, which results from repeated blood transfusions, is not associated with tissue damage. Hemochromatosis, which is a disorder of iron absorption, can cause painful joints, skin bronzing, diabetes, and liver damage if the iron concentration in the body is not lowered. Hemachromatosis is still underdiagnosed because of its long latency period and lack of awareness on the part of medical professionals.

A serum iron test can be used without the others to evaluate cases of iron poisoning.

Collection of blood samples

Patients should not have their blood tested for iron within four days of a blood transfusion or tests and treatments that use radioactive materials. Recent high stress levels or sleep deprivation are additional reasons for postponing iron tests. Clinicians should ask if patients are taking oral contraceptives or multivitamins, since these may alter results.

Blood samples for iron tests should be taken early in the morning because serum iron levels vary during the day, being higher in the morning and lower at night. This precaution is especially important in evaluating the results of iron replacement therapy.

Hemolysis must be avoided during collection of blood samples to prevent interference with test results from iron in the red blood cells.

Interpretation of test results

Some acute and chronic illnesses can increase the release of ferritin from the body stores, resulting in high serum levels. These disorders include infections, late-stage cancers, lymphomas, and severe inflammations. Alcoholics often have high ferritin levels owing to liver inflammation.

Medications and substances that can cause increased serum iron levels include chloramphenicol, estrogen preparations, dietary iron supplements, alcoholic beverages, methyldopa, and birth control pills. Medications that can cause decreased iron levels include aspirin, cholestyramine, cortisone, methicillin, and testosterone.

Medications and treatments that can cause increased ferritin levels include dietary iron supplements, oral contraceptives, theophylline, and x-ray therapy. Decreases in ferritin levels are seen with antithyroid therapy and high doses of ascorbic acid.

Medications that can cause increased transferrin levels include cortisone and cortisol. Those that can cause decreased transferrin levels include oral contraceptives and carbamazepine.

Description

Iron tests are performed on samples of the patient's blood, withdrawn from a vein into a vacuum tube. The amount of blood taken is between 6 mL and 10 mL (1/3 of a fluid ounce). The procedure, which is called a venipuncture, takes about five minutes.

Iron level test

Normal serum iron values are as follows:

Adult males: 65-175 micrograms/dL.
Adult females: 50-170 micrograms/dL.
Children: 50-120 micrograms/dL.
Infant: 40-100 micrograms/dL.
Newborns: 100-250 micrograms/dL.

Total iron-binding capacity (TIBC) test

The TIBC test measures the amount of iron that the blood would carry if the transferrin were fully saturated. Since transferrin is produced by the liver, the TIBC can be used to monitor liver function and nutrition.