Hemochromatosis (Iron Overload) (cont.)
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Exams and Tests
The diagnosis of hereditary hemochromatosis primarily requires a clinical suspicion by the doctor. In cases in which one family member already carries this diagnosis, the chance for another blood relative to have hemochromatosis is higher.
A complete medical history and a thorough physical examination are key components in the evaluation of a person suspected to have hemochromatosis. Particular attention to their family history and their personal history of the conditions associated with hereditary hemochromatosis is prudent.
Measurement of indices of iron in the blood plays an important role in making the diagnosis of hemochromatosis. There are a number of measurements that can be made to assess the amount iron in the blood and stored in the body. Normal levels of these tests may vary in different laboratories, and the numbers quoted in this article denote the general range.
Ferritin is a protein that correlates with the amount of iron stored in the body. In hemochromatosis, ferritin levels tend to be very high (900-6000 micrograms per liter), whereas, in iron deficiency anemia, these levels are usually low. Normal range for ferritin may range from 10-200 microgram per liter. Ferritin may also be elevated in any infection or inflammation (it is an acute phase reactant) and, therefore, this test is not totally specific.
Transferrin is a protein that carries iron from one part of the body to another. The iron level of the blood can also be measured, signifying the amount of iron circulating in the blood (normal 50-150 microgram per deciliter or one tenth of a liter). Total iron binding capacity or TIBC (normal 250-370 microgram per deciliter) is the total amount of iron that is carried in the blood by transferrin. Transferrin saturation is the percentage of transferrin in the blood that is used to carry oxygen and it is derived by dividing the serum iron level by TIBC.
Transferrin saturation in normal individuals runs between 25%-45%. In people with hemochromatosis, transferrin can be up to 100% saturated (range of 50%-100%), whereas, in people with iron deficiency anemia, it can be lower than 25%. The combination of elevated ferritin level and high transferrin saturation is a reliable test to screen for suspected hemochromatosis.
Biopsy of the liver can also be done in evaluating people with hemochromatosis. This test is especially useful if the diagnosis is still in doubt or if there is existing evidence of liver disease. This is the definitive test of hemochromatosis, by measuring the hepatic (liver) iron index. This number is derived from the measurement of the liver iron weight (the weight of iron in micrograms divided by the weight of liver in grams) divided by the age of the person. In normal people, the hepatic iron index is less than 1. In hemochromatosis, the index is greater than 2.
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