A cold agglutinins blood test is done to check for conditions that cause the body to make certain types of antibodies called cold agglutinins. Cold agglutinins are normally made by the immune system in response to infection. They cause red blood cells to clump together (agglutinate) at low temperatures. See a picture of the immune system .

Healthy people generally have low levels of cold agglutinins in their blood. But lymphoma or some infections, such as mycoplasma pneumonia, can cause the level of cold agglutinins to rise.

Higher-than-normal levels of cold agglutinins generally do not cause serious problems. Sometimes, high levels of cold agglutinins can cause blood to clump in blood vessels under the skin when the skin is exposed to the cold. This causes pale skin and numbness in the hands and feet. The symptoms go away when the skin warms up. In some cases, the clumped blood cells can stop the flow of blood to the tips of the fingers, toes, ears, or nose. This is like frostbite and can cause tissue damage. In rare cases, it can cause gangrene.

Sometimes high levels of cold agglutinins can destroy red blood cells throughout the body. This condition is called autoimmune hemolytic anemia.

Why It Is Done

The cold agglutinins test may be done to:

• See whether high cold agglutinin levels are causing autoimmune hemolytic anemia.
• Find pneumonia caused by mycoplasma. Over half of people with pneumonia caused by mycoplasma develop an increase in cold agglutinin levels in their blood within a week of being infected. Newer tests for mycoplasma pneumonia have replaced the cold agglutinins blood test.

How To Prepare

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

How It Is Done

The doctor 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. If the needle is not placed correctly or if the vein collapses, more than one needle stick may be needed.
• Hook a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure to the site and then a bandage.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.