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Protein electrophoresis - serum
DefinitionThis test roughly quantitates the various protein fractions in the serum portion of a blood sample. See also immunoelectrophoresis - serum ; immunofixation - serum ; serum globulin electrophoresis .
How the test is performed
Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site 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 band to swell with blood.
A needle is inserted into the vein, and the blood is collected in an airtight 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.
For 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 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
The health care provider may advise you to discontinue drugs that could interfere with the test. DO NOT discontinue any medication without discussing with your health care provider.
You may be advised to fast for 4 hours before a lipoprotein electrophoresis test.
For infants and children:
How the test will feelWhen 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 made from amino acids and are important constituents of all cells and tissues. 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 separated into albumin and globulins. In other words, total protein = albumin + globulin. Albumin is the protein of highest concentration in the serum. It carries 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 or portion 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).
What abnormal results meanDecreased total protein may indicate:
What the risks are
Special considerationsDrugs that can affect the measurement of total proteins include chlorpromazine, corticosteroids, isoniazid, neomycin, phenacemide, salicylates, sulfonamides, and tolbutamide.
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.
Update Date: 9/14/2003Corey Cutler, M.D., M.P.H., F.R.C.P.C., Department of Medical Oncology, Dana-Farber Cancer Institute; Instructor in Medicine, Harvard University, Boston, MA. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT