Cryoglobulins are abnormal antibody proteins. This article describes the blood test used to check for them.
In the laboratory, cryoglobulins come out of solution in blood when the blood sample is cooled below 98.6 degrees Fahrenheit (37 degrees Celsius). They dissolve again when the sample is warmed up.
Cryoglobulins come in three main types, but in 90% of cases, the cause is hepatitis C. The disease in which cryoglobulins are found is called cryoglobulinemia.
How the Test is Performed
Because they are temperature sensitive, cryoglobulins are hard to accurately detect. The blood specimen must be collected in a special way, and the test should only be done in laboratories that are equipped for it. It is important that the laboratory allows the blood sample to clot and to spin it down at 37 degrees Celsius. It is a good idea to learn the correct method for testing so you can check with the lab to make sure they are following the proper procedure.
Blood is drawn from a vein. A vein on the inside of the elbow or the back of the hand is used in most cases. Blood should NOT be drawn from a catheter that has heparin in it. 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. The vial should be at room or body temperature before it is used. Vials that are colder than room temperature may not give accurate results.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. The filled vial should immediately be placed in a temperature-controlled vessel to keep it at body temperature.
How to Prepare for the Test
You may want to call ahead to ask to have your blood drawn by a lab technician who has experience collecting blood for this test.
How the Test will Feel
Some people feel discomfort when the needle is inserted. Afterward, there may be some throbbing.
Why the Test is Performed
This test is most often done when a person has symptoms of a condition associated with cryoglobulins. Cryoglobulins are associated with cryoglobulinemia. They also occur in other conditions 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.
The example above shows the common measurement for results for these tests. Some laboratories use different measurements or may test different specimens.
Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.