Immunofixation Electrophoresis

Definition

Immunofixation electrophoresis is a laboratory technique for determining the levels of three major immunoglobulins, also called antibodies, in the blood: immunoglobulin M (IgM), immunoglobulin G (IgG), and immunoglobulin A (IgA). It is a refinement of immunoelectrophoresis that increases the accuracy of the procedure.

Purpose

Immunofixation electrophoresis is an analytical technique with high resolving power as it combines separation of antigens by electrophoresis with immunodiffusion against an antiserum. The test aids in the diagnosis and evaluation of the therapeutic response in many disease states affecting the immune system. It is usually requested when a different type of electrophoresis, called a serum protein electrophoresis, has indicated an increase in the immunoglobulin level. Immunofixation electrophoresis is also used to diagnose multiple myeloma, a disease affecting the bone marrow. Immunofixation electrophoresis is replacing another test called immunoelectrophoresis, which is similar, but does not produce results as quickly and is less sensitive.

Precautions

Drugs that may cause increased immunoglobulin levels include therapeutic gamma globulin, hydralazine, isoniazid, phenytoin (Dilantin), procainamide, oral contraceptives, methadone, steroids, and tetanus toxoid and antitoxin. The laboratory should be notified if the patient has received any vaccinations or immunizations in the six months before the test. This is mainly because prior immunizations lead to the increased immunoglobulin levels resulting in false positive results.

Description

Serum proteins separate in agar gels under the influence of an electric field into albumin, alpha 1, alpha 2, and beta and gamma globulins. Immunofixation electrophoresis is performed by placing serum on a slide containing a gel designed specifically for the test. An electric current is then passed through the gel. Immunoglobulins, which contain an electric charge, migrate through the gel according to the difference in their individual electric charges. Once separated, the immunoglobulins are exposed to specific antisera. If they react with the antisera, they form specific immunoprecipitate bands. This banding technique improves the accuracy of electrophoresis results. The results are used to identify different disease entities, and to aid in monitoring the course of the disease and the therapeutic response of the patient to such conditions as immune deficiencies, autoimmune disease, chronic infections, chronic viral infections, and intrauterine fetal infections.

There are five classes of antibodies: IgM, IgG, IgA, IgE, and IgD. IgM is produced upon initial exposure to an antigen. For example, when a person receives the first tetanus vaccination, antitetanus antibodies of the IgM class are produced 10-14 days later. IgM is abundant in the blood but is not normally present in organs or tissues. IgM is primarily responsible for ABO blood grouping and is involved in the immunologic reaction to other infections, such as hepatitis. Since IgM does not cross the placenta, an elevation of this immunoglobulin in the newborn indicates intrauterine infection such as rubella, cytomegalovirus (CMV), or a sexually transmitted disease (STD).

IgG is the most prevalent type of antibody, comprising approximately 75% of the serum immunoglobulins. IgG is produced upon subsequent exposure to an antigen. As an example, after receiving a second tetanus shot, or booster, a person produces IgG antibodies in five to seven days. IgG is present in both the blood and tissues, and is the only antibody to cross the placenta from the mother to the fetus. Maternal IgG protects the newborn for the first months of life, until the infant's immune system produces its own antibodies.

IgA constitutes approximately 15% of the immunoglobulins within the body. Although it is found to some degree in the blood, it is present primarily in the secretions of the respiratory and gastrointestinal tract, in saliva, colostrum (the yellowish fluid produced by the breasts during late pregnancy and the first few days after childbirth), and in tears. IgA plays an important role in defending the body against invasion of germs through the mucous membrane-lined organs.

IgE is the antibody that causes acute allergic reactions; it is measured to detect allergic conditions. IgD, which constitutes the smallest portion of the immunoglobulins, is rarely evaluated or detected, and its function is not well understood.

Preparation

This test requires a blood or urine sample.

Aftercare

Because this test is ordered when either very low or very high levels of immunoglobulins are suspected, the patient should be alert for any signs of infection after the test, including fever, chills, rash, or skin ulcers. Any bone pain or tenderness should also be immediately reported to the physician.

Complications

No complications are expected to result from this procedure.

Risks

Risks for this test are minimal, but may include slight bleeding from the blood-drawing site, fainting, feeling lightheaded after venipuncture, or bruising.

Results

Reference ranges vary from laboratory to laboratory and depend upon the method used. For adults, normal values are usually found within the following ranges (1 mg = approximately 0.000035 oz. and 1 dL = approximately 0.33 oz.):

• IgM: 60-290 mg/dL
• IgG: 700-1,800 mg/dL
• IgA: 70-440 mg/dL

Increased IgM levels can indicate Waldenström's macroglobulinemia, a malignancy caused by secretion of IgM at high levels by malignant lymphoplasma cells. Increased IgM levels can also indicate chronic infections, such as hepatitis or mononucleosis and autoimmune diseases, like rheumatoid arthritis.

Decreased IgM levels can be indicative of AIDS, immunosuppression caused by certain drugs like steroids or dextran, or leukemia.

Increased levels of IgG can indicate chronic liver disease, autoimmune diseases, hyperimmunization reactions, or certain chronic infections, such as tuberculosis or sarcoidosis.

Decreased levels of IgG can indicate Wiskott-Aldrich syndrome, a genetic deficiency caused by inadequate synthesis of IgG and other immunoglobulins. Decreased IgG can also be seen with AIDS and leukemia.

Increased levels of IgA can indicate chronic liver disease, chronic infections, or inflammatory bowel disease.

Decreased levels of IgA can be found in ataxia, a condition affecting balance and gait, limb or eye movements, speech, and telangiectasia, an increase in the size and number of the small blood vessels in an area of skin, causing redness. Decreased IgA levels are also seen in conditions of low blood protein (hypoproteinemia), and drug immunosuppression.

KEY TERMS

Antibody— A protein manufactured by the white blood cells to neutralize an antigen in the body. In some cases, excessive formation of antibodies leads to illness, allergy, or autoimmune disorders.

Antigen— A substance that can cause an immune response, resulting in production of an antibody, as part of the body's defense against infection and disease. Many antigens are foreign proteins not found naturally in the body, and include germs, toxins, and tissues from another person used in organ transplantation.

Autoimmune disorder— A condition in which antibodies are formed against the body's own tissues; for example, in some forms of arthritis.

Resources

BOOKS

Daniels, Rick. Delmar's Manual of Laboratory and Diagnostic Tests. Albany, NY: Delmar Learning, 2003.

Fischbach, Frances Talaska, ed. Nurse's Quick Reference to Common Laboratory and Diagnostic Tests. Philadelphia: Lippincott, 2002.

Professional Guide to Diagnostic Tests. Philadelphia: Lippincott Williams and Wilkins, 2005.

Van Leeuwen, Anne M., Todd R. Kranpitz, and Lynette Smith. Davis's Comprehensive Handbook of Laboratory and Diagnostic Tests: With Nursing Implications. Philadelphia: F.A. Davis Co., 2006.

PERIODICALS

Roberts, G., J. Golding, and G. Lack. "Diagnosing Peanut and Tree Nut Allergy with SPT and Specific IgE Testing." Archives of Disease in Childhood 89 (April 2004): A5-7.