What is being tested?
Proteins are important building blocks of all cells and tissues. They form the structural part of most organs and make up enzymes and some hormones that regulate bodily functions. Protein electrophoresis is a lab method that separates proteins based on their size and electrical charge. Knowing which proteins are present, absent, elevated, or decreased in body fluids such as blood can help diagnose and/or monitor various diseases and conditions.
Body fluids, such as blood, urine, and cerebrospinal fluid (CSF) contain many different proteins that have various roles, such as transporting nutrients, removing toxins, and controlling body functions.
The two major types of proteins are:
- Albumin is produced in the liver 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 antibodies (immunoglobulins) and some complement proteins, most of the globulins are also produced in the liver.
The various proteins in body fluids are subjected to a controlled electric current, fractionating them into a typical pattern of bands or peaks that then can be measured. The proteins are divided into six groups, called prealbumin (rarely detected on serum or urine protein electrophoresis), albumin, alpha 1, alpha 2, beta, and gamma. The beta fraction may be further divided into beta 1 and beta 2 subgroups.
Each of these protein groups (electrophoresis fractions) is distinct and at specific concentrations. The patterns typically seen in certain conditions and diseases can help with diagnosis. The major serum proteins and their functions are listed according to their electrophoretic region or fraction (the visible band that they are part of) in the table titled Protein Groups.
Various conditions and diseases can affect protein production and/or protein loss, thus changing the pattern of bands seen on a protein electrophoresis. The most important example is the appearance of a distinct, monoclonal band in the gamma region. For example, uncontrolled growth and division of a malignant plasma cell as seen in multiple myeloma leads to the production of large amounts of a single type of immunoglobulin (monoclonal immunoglobulin).
When an abnormal protein (band or peak) is detected, additional tests are done to identify the type of protein (immunotyping). Immunofixation electrophoresis or immunosubtraction electrophoresis can be used to identify abnormal bands seen on protein electrophoresis, typically in the gamma region, in order to determine whether a type of antibody (immunoglobulin) is abnormally produced (e.g., IgG, IgA, IgM).
In most cases of multiple myeloma, a single type of intact (whole) immunoglobulin is produced in excess. In a minority of cases, only one section of an immunoglobulin called a “free light chain” is produced in large amounts. These excess free light chains are released into the bloodstream and since they are relatively small molecules, they are filtered by the kidneys and released into the urine. Another term for these excess free light chains in the urine is Bence Jones proteins.
How is the test used?
Protein electrophoresis is used to identify and measure the presence of abnormal proteins, the absence of normal proteins, and/or to detect various protein electrophoresis patterns associated with certain conditions, as found in blood, urine or other body fluids.
The information from protein electrophoresis can provide clues that a disease or condition is affecting protein production or loss of protein, but the results usually do not provide a definitive diagnosis. Instead, additional follow-up tests are needed to investigate the cause and to try to identify the nature of the underlying disease.
Serum electrophoresis may be used to:
- Help in the diagnose and monitoring of lymphoma, chronic lymphocytic leukemia or monoclonal gammopathies, such as multiple myeloma
- Investigate abnormal findings on other laboratory tests, such as total protein, albumin level, elevated calcium levels, or low white or red blood cell counts
- Evaluate someone for an inflammatory condition, an autoimmune disease, an infection, a kidney or liver disorder
Urine protein electrophoresis may be used:
- In the investigation of multiple myeloma
- To investigate the cause of abnormally high amounts of proteins in urine (various forms and causes of proteinuria)
When an abnormal band on either a serum or a urine electrophoresis pattern suggests the presence of a single type of immunoglobulin (monoclonal), immunofixation electrophoresis (IFE) or immunosubtraction electrophoresis can be used as follow-up tests to further identify abnormal proteins.
CSF protein electrophoresis may be used:
- To look for the characteristic banding pattern that may be seen in multiple sclerosis (oligoclonal bands)
- To evaluate a person with headaches or other neurologic symptoms and look for proteins suggestive of inflammation or infection that would explain the symptoms
When is it ordered?
Protein electrophoresis is a common test ordered when you have symptoms suggesting certain conditions. Some examples are listed below.
Serum and urine protein electrophoresis may be ordered when you have signs and symptoms of multiple myeloma, such as:
- Weakened bones that can result in soft spots, fractures, bone lesions and bone pain
- Carpal tunnel syndrome
- Destruction of bone that frequently increases the level of calcium in the blood, leading to symptoms such as loss of appetite, nausea, thirst, fatigue, constipation, and confusion
- Frequent infections
- Excessive bleeding and bruising
- Kidney disease—large amounts of protein in the urine due to some forms of multiple myeloma (i.e., Bence Jones proteins) can affect the kidneys and may permanently damage them.
- In some cases, an increase in the thickness (hyperviscosity syndrome) of the blood may lead to headaches, problems with vision, seizures, or even coma.
Urine protein electrophoresis may be ordered when you have abnormally high levels of protein in your urine.
Immunofixation electrophoresis or immunosubtraction electrophoresis may be ordered when an abnormal band suggestive of a monoclonal immunoglobulin is detected on either a serum or a urine electrophoresis.
CSF protein electrophoresis may be ordered:
- When you have signs and symptoms suggesting multiple sclerosis, including:
- Sensory symptoms such as numbness, tingling, pain, burning, itching, facial pain, and visual disturbances
- Motor symptoms such as speech impediments, weakness, tremor, difficulty walking, lack of coordination, constipation, and problems with the control of urination
- Psychological symptoms such as mood swings, depression, and problems with thinking, learning, and memory
- When you have headaches or other neurologic symptoms to look for proteins suggestive of inflammation or infection
Once a disease or condition has been diagnosed, electrophoresis may be ordered at regular intervals to monitor the course or recurrence of the disease and the effectiveness of treatment.
What does the test result mean?
Protein electrophoresis tests give a healthcare practitioner a rough estimate of how much of each of the protein fractions is present and whether any abnormal proteins or protein patterns are present.
Results are interpreted along with your signs and symptoms and medical history. The laboratory report usually includes an interpretation of the results.
Serum protein electrophoresis
The following table summarizes the conditions or diseases that may be associated with decreases or increases in various serum proteins.
|Electrophoretic zone/region||Major Proteins||May be decreased in:||May be increased in:|
|Beta (1 and 2)||
Urine protein electrophoresis
Usually there is very little protein in urine. Typically, if a significant amount of protein is present, it appears in one of three main patterns:
- Glomerular proteinuria: Normally, clusters of looping blood vessels in the kidneys called glomeruli prevent protein from leaking into the urine. When the glomeruli are damaged, as in some forms of kidney disease, albumin and other large plasma proteins may leak through and be detected in the urine.
- Tubular proteinuria: Normally, some very small proteins can pass through the glomeruli in the kidneys but are reabsorbed from the urine by tubules. When the tubules are damaged, these small proteins will appear in the urine (e.g., beta-2 microglobulin, marker of tubular damage), but large proteins will not.
- Specific proteins: Some other small proteins are not normally present in significant amounts in blood. When they are elevated in blood, they can pass through the kidneys and appear in the urine. Some examples are:
- Monoclonal immunoglobulins or free light chains (Bence Jones proteins)
- Myoglobin—this is a small, oxygen-binding protein found in heart and skeletal muscle. Myoglobin may be detected in urine when there is heart or muscle injury.
- Hemoglobin— this is the oxygen-carrying protein in red blood cells. Hemoglobin may be detected in the urine when there is damage to red blood cells (e.g., hemolytic anemia).
CSF protein electrophoresis
- The presence of multiple distinct bands in the gamma region (oligoclonal bands) that are present in CSF but not in serum suggests multiple sclerosis (MS). Most people with multiple sclerosis, as well as some other inflammatory conditions of the brain, have such oligoclonal bands. Oligoclonal bands are not a specific finding for MS because not all people whose CSF exhibits this pattern have MS. Further testing and evaluations (e.g., MRI or CT scan) are necessary to help make a diagnosis.
- Presence of higher than normal amounts of polyclonal immunoglobulins (antibodies produced by many different plasma cells) suggests an infection of the central nervous system.
Immunofixation electrophoresis or immunosubtraction capillary electrophoresis identifies the type of immunoglobulin protein(s) present as monoclonal bands on a protein electrophoresis pattern. Typically, this testing determines the presence and type of monoclonal proteins (e.g., IgG kappa).
What are some tests that may be done in follow up?
It depends on the condition or disease that is suspected. If your health care practitioner needs additional information to evaluate your condition and make a diagnosis, follow-up testing may include, for example:
- Serum free light chains
- Total immunoglobulins
- Alpha-1 antitrypsin
- Complete blood count, iron, transferrin, ferritin for assessment of potential anemia
- Estimated GFR
- Calcium and possible X-ray for evaluation of potential bone lesions
- Genetic testing if a lymphoma or chronic lymphocytic leukemia is suspected
What are free light chains and how are they related to immunoglobulins?
Immunoglobulins are part of the body’s natural defense system and are produced by plasma cells in the bone marrow. They are composed of four protein chains–two identical heavy (long) protein chains and two identical light (shorter) protein chains.
- The heavy chains may consist of one of five different types. The five major classes of immunoglobulins, defined by the type of heavy protein chains in their structure, are IgG, Ig A, IgM, IgD, and IgE.
- The light chains consist of one of two different types called kappa and lambda.
Within a plasma cell, two heavy chains of one type and two light chains of one type become attached to form one intact immunoglobulin molecule. Each particular plasma cell will produce only one type of immunoglobulin. These chains that are used to form the immunoglobulins are said to be “immunoglobulin-bound.” Normally, there is a slight excess of kappa and lambda light chains produced (free light chains).
However, in diseases such as in multiple myeloma, the plasma cells may produce excessive or mutated light chains that do not associate with heavy chains. These abnormal free light chains can be detected with a free light chain test. The ratios between the kappa and lambda free light chains also can be evaluated. An abnormal ratio and increased levels of one serum free light chain are often associated with diseases.
What are Bence Jones proteins?
They are free immunoglobulin light chains that are found in the urine. These free light chains can be caused by certain forms of multiple myeloma.
If I have an abnormal monoclonal immunoglobulin in my blood, does it mean that I have multiple myeloma or some other type of cancer?
Not necessarily. Monoclonal protein production may be due to a condition known as monoclonal gammopathy of undetermined significance (MGUS). Most people with MGUS initially have a benign course but may progress to a more serious condition. They must continue to be monitored regularly with a serum protein electrophoresis test, or sometimes a free light chain test, depending on which monoclonal protein is being produced. MGUS is present in about 4% of Caucasians over the age of 50 and progresses at a rate of 1% per year to multiple myeloma.
Is electrophoresis used for anything else?
Yes, it may be used any time a separation of molecules is desired. Hemoglobin electrophoresis, for instance, is used to help detect abnormal forms of hemoglobin, such as HbS variant that cause sickle cell anemia or in various forms of thalassemia. Electrophoresis is also used in certain circumstances to separate different forms of enzymes, called isoenzymes, lipoproteins (e.g., LDL, HDL) or DNA and RNA fragments. These are only a few examples of electrophoresis applications in clinical laboratories and research.
Is there anything else I should know?
Immunizations within the previous six months can increase antibodies (immunoglobulins), as can drugs such as phenytoin (Dilantin), procainamide, oral contraceptives, methadone, and intravenous immunoglobulin (IV Ig) and anti-cancer immunotherapy.
Aspirin, bicarbonates, chlorpromazine (Thorazine), corticosteroids, and neomycin can affect protein electrophoresis results.
For Health Professionals: Table of Protein Groups
|Albumin||Albumin||Main plasma protein; involved in the control of tissue water accumulation, transports many substances (ions, hormones) in circulation|
|Alpha1-globulin||Alpha1-Antitrypsin||Inactivates trypsin and other proteolytic enzymes, reduces damage from inflammation|
|Orosomucoid (Alpha-1-acidic glycoprotein)||Immune response modifier, binds acidic drugs such as lidocaine|
|High Density Lipoprotein (HDL)||Reverse transport of cholesterol (“good cholesterol”)|
|Alpha2-globulin||Alpha2-Macroglobulin||Binds to and inactivates proteolytic enzymes, preventing tissue damage|
|Ceruloplasmin||Copper-containing enzyme and copper carrier, also involved in normal iron metabolism|
|Beta-globulin||Transferrin||Iron transport and delivery to cells|
|Low Density Lipoprotein (LDL)||Cholesterol delivery to tissue|
|Complement component 3||Helps regulate inflammatory response to foreign substances and immunity|
|Gamma-globulin||IgA||Immunoglobulin involved in secretions (e.g., maternal milk)|
|IgG||Major immunoglobulin; long-term immunity|
|IgM||Initial response immunoglobulin|
|C-reactive protein||Inflammatory response mediator|
|Fibrinogen||Coagulation factor (found only in plasma, not serum)|