Protein electrophoresis - serum
Alternative names:
lipoprotein electrophoresis; serum lipid protein
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.
Electrophoresis is a laboratory technique. The blood serum is placed on specially treated paper and exposed to an electric current. The various proteins migrate (move on the paper) to form bands that indicate the relative proportion of each protein fraction. Individual proteins, with the exception of albumin, are not usually measured. However, protein fractions or groups ARE measured. The levels of protein fractions can be roughly measured by measuring the total serum protein and multiplying by the relative percentage of each component protein fraction.
Lipoprotein electrophoresis is a type of protein electrophoresis that is focused on determining the amount of lipoproteins (materials such as LDL cholesterol).
How to prepare for the test:
Fast for 4 hours (before the lipoprotein electrophoresis test only).
The health care provider may advise you to discontinue drugs that could interfere with the test. (see "special considerations")
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 experience, 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:
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:
Proteins are important constituents of all cells and tissues. Proteins are made from amino acids. There are many different kinds of proteins in the body with many different functions, for example, enzymes, some hormones, hemoglobin (oxygen transport), LDL (cholesterol transport), fibrinogen (blood clotting), collagen (structure of bone and cartilage), and immunoglobulins (antibodies).
Serum proteins are grossly separated into albumin and globulins, i.e., total protein = albumin + globulin. Albumin is the protein of highest concentration in the serum (plasma is serum plus fibrinogen). Albumin is a carrier of many small molecules but is also of prime importance in maintaining the oncotic pressure of the blood (that is keeping the fluid from leaking out into the tissues).
Globulins are roughly divided into alpha-1, alpha-2, beta, and gamma globulins. These can be separated and quantitated in the laboratory by electrophoresis and densitometry.
The alpha-1 fraction includes alpha-1 anti-trypsin (see Alpha-1 antitrypsin) and thyroxine binding globulin (see T3, T4, RT3U). The alpha-2 fraction contains haptoglobin , ceruloplasmin , HDL, and alpha-2 macroglobulin. In general, alpha-1 and alpha-2 proteins levels increase in the presence of inflammation. The beta fraction includes Transferrin (see iron - serum), plasminogen (see Factor VIII assay) and beta-lipoproteins (see LDL). The gamma fraction includes the various types of antibodies (immunoglobulins M, G, and A).
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