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.
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Why is the Test 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).
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