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

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

Immunofixation uses antibodies to identify the types of proteins or antibodies separated by protein 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.

This test is most often used to check the levels of certain antibodies associated with multiple myeloma and Waldenstrom's macroglobulinemia.Those antibodies includeIgG, IgM, IgA, lambda light chain, and kappa light chain.

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

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

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; 2005.