Serum immunofixation is a laboratory technique used to identify proteins 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, and 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 circulation. 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 pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

Immunofixation is a laboratory technique. It is similar to immunoelectrophoresis, and enhances the results of standard protein electrophoresis. Electrical charges are used to separate proteins from a sample.

Immunoglobulins appear as a gamma band of proteins. Laboratory techniques are used to further identify the individual immunoglobulins. Immunofixation gives more rapid results than standard immunoelectrophoresis, and it is somewhat more sensitive.

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 primary use of this test is to identify and monitor certain monoclonal immunoglobulins (IgG, IgM, IgA, lambda light chain, and kappa light chain), such as are present in multiple myeloma and Waldenstrom's macroglobulinemia.

Immunofixation has also been used to study protein variations 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

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

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