| Subject | Contents |
| Definition | Hemoglobin electrophoresis is a test that measures the different types of hemoglobin in the blood. (See also hemoglobin; glycosylated hemoglobin .) |
| Alternative Names | Hb electrophoresis; Hgb electrophoresis
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| How the test is performed | Adult or child: Blood is drawn from a vein ( venipuncture ), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (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 tourniquet 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 . 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 pipette (small glass tube), 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 | Adults: No special preparation is necessary for this test. Infants and children: The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:Infant test or procedure preparation (birth to 1 year) Toddler test or procedure preparation (1 to 3 years) Preschooler test or procedure preparation (3 to 6 years) Schoolage test or procedure preparation (6 to 12 years) Adolescent test or procedure preparation (12 to 18 years) |
| 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 | This test is performed when a disorder associated with abnormal forms of hemoglobin ( hemoglobinopathy ) is suspected. Although many different Hb molecules have been described, the most common ones are HbA, HbA2, HbF, HbS, HbC, Hgb H, and Hgb M. In normal adults, only HbA and HbA2 are present at significant levels. Small amounts of HbF (which is the major Hb present in the fetus) may be present, but they are of no consequence unless levels are more than 2% of the total. HbS is an abnormal form associated with sickle cell anemia . HbS, in the presence of low O2 concentrations, precipitates. The precipitated HbS causes the red blood cells to sickle (form a crescent shape), which results in a blockage of small vessels and breakdown (lysis) of some of the cells. HbC is an abnormal hemoglobin form associated with a hemolytic anemia because the red blood cells are more fragile than normal. The symptoms are much milder than they are in sickle cell anemia. Other, less common, abnormal Hb molecules cause anemias of various degrees of severity. |
| Normal Values | Normal hemoglobin findings differ between adults and children. Adults (findings expressed as a percentage 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% Children (findings expressed as a percentage 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 diseaseRare hemoglobinopathySickle cell anemiaClinical thalassemia (major and minor) is an additional condition under which the test may be performed. |
| What the risks are | Excessive bleedingFainting or feeling lightheaded Hematoma (blood accumulating under the skin) Infection (a slight risk any time the skin is broken) Multiple punctures to locate veins |
| Special considerations | A blood transfusion within the previous 12 weeks can produce falsely normal or abnormal results. Veins and arteries vary in size from one patient to another, and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. |
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