Protein electrophoresis is a laboratory technique that assesses the number and types of proteins in blood or urine. It is used to diagnose and monitor conditions that are associated with abnormal protein production. It is most often used in multiple myeloma, a cancer of certain types of white blood cells. Less commonly, it is used to investigate other cancers such as lymphoma, chronic lymphocytic leukemia, and Waldenstrom macroglobulinemia as well as kidney disease and inflammatory diseases such as autoimmune disorders, and liver disease.
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, while the intensity of the staining 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 after the electrophoresis step by first fixing them in the gel with antibodies, then washing away all the other proteins prior to staining. This procedure is called immunofixation electrophoresis (IFE). A slightly different method, immunoelectrophoresis, was used in the past to identify specific proteins. However, this technique has been largely superseded by IFE because IFE is easier to perform and interpret.
Serum proteins are separated into five or six major groupings by protein electrophoresis. These fractions are called albumin, alpha 1, alpha 2, beta and gamma (the beta fraction is sometimes divided into beta 1 and beta 2). 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 it used?
Electrophoresis is used to identify the presence or absence of abnormal proteins and to identify when different groups of proteins are increased or decreased in serum or urine. It is frequently used to detect and identify monoclonal proteins (an excessive production of one specific immunoglobulin). Protein and immunofixation electrophoresis are used to help detect, diagnose and monitor the course and treatment of conditions associated with these abnormal proteins, including multiple myeloma and a few related diseases.
Protein is usually excreted in the urine in very small amounts. When it is present in moderate to large amounts, it may indicate a problem with the kidneys or multiple myeloma. The primary reason protein and immunofixation electrophoresis are requested on urine is to look for monoclonal protein production. This protein may show up in both the serum and urine, or it may only be seen in the urine.
An example of this is Bence Jones protein, which is the free light chain component of antibodies (normally, antibodies are composed of four parts, two identical heavy chains and two identical light chains. Sometimes, in multiple myeloma, only one or the other is produced, or it may be produced in excess.) The small size of Bence Jones protein allows it to pass through the kidneys and enter the urine.
Urine protein electrophoresis may also be used to help diagnose the cause and estimate the severity of protein excretion due to kidney damage or disease. This damage or disease may be due to diabetes, chronic inflammation, an autoimmune condition or a malignancy. Electrophoresis is not usually necessary to assess the loss of small to moderate amounts of protein due to temporary conditions, such as a urinary tract infection or an acute inflammation.
When is it requested?
Protein electrophoresis may be requested when a doctor is investigating symptoms that suggest multiple myeloma, such as bone pain, anaemia, tiredness, unexplained fractures and recurrent infections. It may also be used as a follow-up to other laboratory tests, such as an abnormal total protein and/or albumin level, elevated urine protein levels, elevated calcium levels, decreased kidney function and low white or red blood cell counts.
Immunofixation electrophoresis is usually ordered when the protein electrophoresis test shows the presence of an abnormal protein band that may be an immunoglobulin.
Electrophoresis tests are most frequently requested when a doctor suspects a disease or condition that causes a monoclonal protein to be produced. Once a disease or condition has been diagnosed, electrophoresis may be used at regular intervals to monitor the course of the disease and the effectiveness of treatment. As disease progresses, the amount of protein goes up; with treatment, it goes down.
Monoclonal protein production may be due to a malignant disease, such as multiple myeloma, but it may also be due to a monoclonal gammopathy of undetermined significance (MGUS). Most patients with MGUS have no symptoms but they must continue to be monitored regularly as some may develop multiple myeloma after a number of years.
Serum protein electrophoresis may also be used when symptoms suggest an inflammatory condition, an autoimmune disease, an acute or chronic infection, a kidney or liver disorder, or a protein-losing condition, even if the total protein and/or albumin concentrations are apparently normal.
Urine protein electrophoresis may be used when there is protein detected in the urine or when the doctor suspects a monoclonal protein may be present.
What does the result mean?
Protein and immunofixation electrophoresis tests give your doctor a rough estimate of how much of each protein is present. The value of protein electrophoresis lies in the proportions of proteins and in the patterns they create on the electrophoresis graph. The value of immunofixation electrophoresis is in the identification of the presence of a particular type of immunoglobulin.
For example, certain conditions or diseases may be associated with decreases or increases in various serum proteins, as reflected below:
Albumin
Alpha1 globulin
Alpha2 globulin
Beta globulin
Gamma globulin
Is there anything else I should know?
Immunisations within the previous six months can increase immunoglobulins as can drugs such as phenytoin (Dilantin), procainamide, oral contraceptives, methadone and therapeutic gamma globulin.
Aspirin, bicarbonates, chlorpromazine (Thorazine), corticosteroids and neomycin can affect protein electrophoresis results.
Common questions
They may do a serum electrophoresis because you may have an abnormality even though the total protein and albumin are normal. This is because the body tries to maintain a constant amount of protein and may increase or decrease its production of other proteins to compensate for a deficiency or overproduction of others. Your doctor may request a urine electrophoresis when there is protein in your urine, because you may lose protein in your urine even if your blood levels are fairly stable.
Yes, any time separation of molecules is desired. DNA electrophoresis, for instance, is used to help study the genetic makeup of plants, animals and humans.
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