Hemoglobin electrophoresisDefinition: Hemoglobin electrophoresis is a test that measures the different types of the oxygen-carrying substance (hemoglobin ) in the blood. See also: Glycosylated hemoglobin
Alternative Names: Hb electrophoresis; Hgb electrophoresis
How the test is performed: Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The area is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the elastic band to fill with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. In an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a small glass tube (pipette), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test: No special preparation is necessary for this test.
How the test will feel: When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed: You may have this test if your health care provider suspects that you have a disorder caused by abnormal forms of hemoglobin (hemoglobinopathy). Many different types of hemoglobin (Hb) exist. The most common ones are HbA, HbA2, HbF, HbS, HbC, Hgb H, and Hgb M. Healthy adults only have significant levels of HbA and HbA2. Some people may also have small amounts of HbF (which is the main type of hemoglobin in an unborn baby's body). Certain diseases are associated with high HbF levels (when HbF is more than 2% of the total hemoglobin). HbS is an abnormal form of hemoglobin associated with sickle cell anemia . In people with this condition, the red blood cells have a crescent or sickle shape. These misformed cells then break down, or can block small blood vessels. HbC is an abnormal form of hemoglobin associated with hemolytic anemia . The symptoms are much milder than they are in sickle cell anemia. Other, less common, abnormal Hb molecules cause anemias .
Normal Values: In adults, these hemoglobin molecules make up the following percentages of total hemoglobin: - Hgb A1: 95% to 98%
- Hgb A2: 2% to 3%
- Hgb F: 0.8% to 2%
- Hgb S: 0%
- Hgb C: 0%
In infants and children, these hemoglobin molecules make up the following percentages of total hemoglobin:
- Hgb F (newborn): 50% to 80%
- Hgb F (6 months): 8%
- Hgb F (over 6 months): 1% to 2%
What abnormal results mean: The presence of significant levels of abnormal hemoglobins may indicate: - Hemoglobin C disease
- Rare hemoglobinopathy
- Sickle cell anemia
This test also may be performed if the health care provider suspects the condition thalassemia .
What the risks are: - Excessive bleeding
- Fainting or feeling lightheaded
- Blood accumulating under the skin (hematoma)
- Infection
- Multiple punctures to find veins
Special considerations: You may have false normal or abnormal results if you've had a blood transfusion within the previous 12 weeks. Veins and arteries vary in size from one patient to another, and from one side of the body to the other. Getting a blood sample from some people may be more difficult than from others.
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