Serum immunofixation is a laboratory technique used to identify proteins or antibodies in blood.

Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.

A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the band is removed to restore blood flow. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a small glass tube (pipette), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if bleeding continues.

Immunofixation is a laboratory technique that identifies the types of proteins separated by immunoelectrophoresis. In standard protein electrophoresis, electric charges are used to separate proteins in a sample.

Immunoglobulins separate in the gamma band of proteins. Immunofixation uses antibodies to identify the types of proteins or antibodies separated by electrophoresis.

There is no special preparation for this test.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

The main use of this test is to identify and monitor certain antibodies (IgG, IgM, IgA, lambda light chain, and kappa light chain), that are present in multiple myeloma and Waldenstrom's macroglobulinemia.

Immunofixation has also been used to study changes in protein structure (for example, glucose-6-phosphate dehydrogenase), and in the genetic typing of alpha-1 antitrypsin.

Monoclonal immunoglobulins are not present.

The presence of monoclonal proteins may indicate:

• Immune system disorders such as multiple myeloma or Waldenstrom's macroglobulinemia.
• Cancer

• Excess bleeding
• Fainting or feeling lightheaded
• Blood pooling under the skin (hematoma)
• Infection
• Many needle sticks to find veins

Veins and arteries vary in size from one patient to another, and from one side of the body to the other. Getting a blood sample from some people may be harder than from others.

McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders; 2006.

Hoffman R, Benz E, Shattil S, Furie B, Cohen H. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2004.