What is the Nature of Serum?

Also Known As: Serum Protein Electrophoresis, Protein ELP, SPE, SPEP, Gel Electrophoresis, Capillary Electrophoresis, Immunosubtraction Electrophoresis, Urine Protein Electrophoresis, UPE, UPEP, IFE, CSF Protein Electrophoresis, Electrophoresis

Formal Name: Protein Electrophoresis, Immunofixation Electrophoresis

Proteins are important building blocks of all cells and tissues. They form the structural part of most organs and makeup 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.
• Globulin 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 pre albumin (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 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 diagnosis 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