Cryoglobulins are abnormal proteins. This article describes the blood test used to check for them.

When the body temperature is lower than 98.6 degrees F (37 degrees C), cryoglobulins no longer float in the blood. Instead, they separate out, forming clusters that can block small blood vessels, especially in the face and hands.

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.

There is no special preparation for this test.

Some people feel discomfort when the needle is inserted. Afterward, there may be some throbbing.

This test is most often done when a person's symptoms suggest a condition associated with cryoglobulins. Cryoglobulins are associated with several disorders, including those that affect the skin, joints, kidneys, and nervous system.

Normally, there are no cryoglobulins.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

A positive test may indicate:

• Hepatitis (especially hepatitis C)
• Infectious mononucleosis
• Leukemia
• Lymphoma
• Macroglobulinemia - primary
• Multiple myeloma
• Rheumatoid arthritis
• Systemic lupus erythematosus

• Nephrotic syndrome

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)