Health Encyclopedia

Protein electrophoresis - serum

Definition

This test roughly measures the types of protein in the fluid (serum) part of a blood sample.

How the test is performed

The health care provider draws blood from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. 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 tube attached to the needle (syringe). During the procedure, the band is removed to let blood flow again. Once the blood has been collected, the needle is removed. The puncture site is covered to stop any bleeding.

For an infant or young child, the area is cleaned with antiseptic and punctured with a sharp needle or a small blade (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 move on the paper (migrate) to form bands that show the proportion of each protein fraction.

Individual proteins, except 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 then multiplying that by the relative percentage of each protein fraction.

Lipoprotein electrophoresis is a type of protein electrophoresis that determines the amount of chemical compounds made up of protein and fat, called lipoproteins (such as LDL cholesterol).

How to prepare for the test

The health care provider may ask you to stop taking drugs that could affect the test. DO NOT stop taking any medication without first asking your health care provider.

You may be asked to fast for 4 hours before a lipoprotein electrophoresis test.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain. 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 components of all cells and tissues. There are many different kinds of proteins in the body with many different functions. Examples of proteins are: 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 important for keeping fluid from leaking out into the tissues (the oncotic pressure of the blood).

Globulins are divided into alpha-1, alpha-2, beta, and gamma globulins. These can be separated and measured in the laboratory by tests called electrophoresis and densitometry.

The alpha-1 portion (fraction) of globulins 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 protein levels increase when there is inflammation. The beta fraction includes transferrin (see iron - serum), plasminogen (see Factor VIII assay), and beta-lipoproteins (see LDL). The gamma fraction includes different types of antibodies (immunoglobulins M, G, and A).

Normal Values

Total protein: 6.4 to 8.3 g/dL
Albumin: 3.5 to 5.0 g/dL
Alpha-1 globulin: 0.1 to 0.3 g/dL
Alpha-2 globulin: 0.6 to 1.0 g/dL
Beta globulin: 0.7 to 1.2 g/dL
Gamma globulin: 0.7 to 1.6 g/dL

Note: g/dL = grams per deciliter

What abnormal results mean

Decreased total protein may indicate:

Malnutrition
Nephrotic syndrome
Gastrointestinal protein-losing enteropathy

Increased alpha-1 globulin proteins may indicate:

Chronic inflammatory disease (for example, rheumatoid arthritis, SLE)
Acute inflammatory disease
Malignancy

Decreased alpha-1 globulin proteins may indicate:

Alpha-1 antitrypsin deficiency

Increased alpha-2 globulin proteins may indicate:

Acute inflammation
Chronic inflammation

Decreased alpha-2 globulin proteins may indicate:

Hemolysis

Increased beta globulin proteins may indicate:

Hyperlipoproteinemia (for example, familial hypercholesterolemia)
Estrogen therapy

Decreased beta globulin proteins may indicate:

Increased gamma globulin proteins may indicate:

Multiple myeloma
Chronic inflammatory disease (e.g., rheumatoid arthritis, SLE)
Hyperimmunization
Acute infection
Waldenstrom's macroglobulinemia
Chronic liver disease

What the risks are

Excessive bleeding
Fainting 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

Drugs 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.

Review Date:3/8/2007
Reviewed By:Rita Nanda, M.D., Department of Medicine, Section of Hematology/Oncology, University of Chicago Medical Center, Chicago, IL. Review provided by VeriMed Healthcare Network.

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