The serum protein electrophoresis (SPEP) test measures specific proteins in the blood to help identify some diseases. Proteins are substances made up of smaller building blocks called amino acids. Proteins carry a positive or a negative electrical charge, and they move in fluid when placed in an electrical field. Serum protein electrophoresis uses an electrical field to separate the proteins in the blood serum into groups of similar size, shape, and charge.

Blood serum contains two major protein groups: albumin and globulin. Both albumin and globulin carry substances through the bloodstream. Using protein electrophoresis, these two groups can be separated into five smaller groups (fractions):

• Albumin. Albumin proteins keep the blood from leaking out of blood vessels. Albumin also helps carry some medicines and other substances through the blood and is important for tissue growth and healing. More than half of the protein in blood serum is albumin.
• Alpha-1 globulin. High-density lipoprotein (HDL), the "good" type of cholesterol, is included in this fraction.
• Alpha-2 globulin. A protein called haptoglobin, that binds with hemoglobin, is included in the alpha-2 globulin fraction.
• Beta globulin. Beta globulin proteins help carry substances, such as iron, through the bloodstream and help fight infection.
• Gamma globulin. These proteins are also called antibodies. They help prevent and fight infection. Gamma globulins bind to foreign substances, such as bacteria or viruses, causing them to be destroyed by the immune system. See a picture of the immune system .

Each of these five protein groups moves at a different rate in an electrical field and together form a specific pattern. This pattern helps identify some diseases.

Why It Is Done

Serum protein electrophoresis is most often done to:

• Screen for a disease such as multiple myeloma, macroglobulinemia, or amyloidosis.
• Find the cause of hypogammaglobulinemia (HGG), a condition characterized by low levels of gamma globulin antibodies. HGG can make a person more susceptible to infection.

How To Prepare

You do not need to do anything before you have this test.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?).

How It Is Done

The health professional drawing blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.