Protein Electrophoresis
Immunofixation Electrophoresis

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Also known as: Serum Protein Electrophoresis (SPE), Urine Protein Electrophoresis (UPE), IFE
Formal name: Serum protein electrophoresis and urine protein electrophoresis

The Test Sample

What is being tested?

Protein electrophoresis is a method for separating the proteins found in blood (serum) or urine. During the test, an electric current is used to move the proteins across a thin layer of agarose gel. The distances that individual proteins travel depend on their size, shape, and electrical charge. These separated proteins may be detected by the use of a dye that binds to (stains) all of the proteins and reveals a characteristic pattern of bands. Each band indicates the presence of a particular protein or group of proteins, while the size of the band is a rough indication of the quantity. This pattern of bands is converted into a visual graph, showing vertical spikes or peaks where there is a lot of protein and smaller peaks or valleys where there is less. A newer method called capillary zone electrophoresis (CZE) separates proteins by passing them through a long, thin column, producing a graph that is very similar to the one made by running the protein through an agarose gel.

Specific proteins of interest can be identified by separating the proteins by gel electrophoresis and then adding an antibody. The antibody can recognise individual proteins and sticks to them making a big complex that gets caught in the gel. All the other proteins in the system are washed away and the gel stained so the proteins in question can be identified. This procedure is called immunofixation electrophoresis (IFE).

Serum proteins are separated into six major groupings by protein electrophoresis. These fractions are called albumin, alpha 1, alpha 2, beta 1, beta 2 and gamma. Albumin, which is produced in the liver, forms its own group and accounts for about 60% of the protein in the blood. 'Globulins' is a collective term used to refer to proteins other than albumin. With the exception of the immunoglobulins and some complement proteins, most of the globulins are produced in the liver. These groups are described more fully in the table, Protein Groups.

The bands seen on protein electrophoresis form characteristic patterns. Alterations to these patterns are associated with a variety of different diseases and conditions. For example in multiple myeloma (a cancer of certain types of white blood cells called plasma cells), the uncontrolled growth and division of a malignant plasma cell leads to the production of large amounts of a single type of immunoglobulin (antibody). In contrast to other proteins in serum, which are typically of a single type, antibodies (immunoglobulins) must differ from each other to be able to recognise bacteria, viruses and other 'foreign' substances. Each time the body is exposed to a virus, for example, one plasma cell replicates and makes a group (or clone) of plasma cells to produce antibody to eliminate it. Since our total immunoglobulin represents antibody made by many clones, we refer to it as a polyclonal pattern. When there is a cancer of plasma cells, only one type of antibody is produced, termed a monoclonal pattern. This abnormal protein can be seen as a characteristic band on the electrophoresis gel.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. Sometimes a random or 24-hour urine sample is required.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.