The Donath-Landsteiner test detects an antibody in the fluid portion of blood (serum). This test is done to diagnose paroxysmal cold hemoglobinuria.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore normal blood flow. 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, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a small glass tube (pipette), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

No special preparation is needed.

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 sometimes performed when the health care provider suspects a diagnosis of paroxysmal cold hemoglobinuria.

No presence of antibodies is normal.

Abnormal results indicate paroxysmal cold hemoglobinuria (PCH). This disorder occurs when exposure to cold temperatures causes the immune system to produce antibodies that destroy red blood cells. These antibodies are called Donath-Landsteiner antibodies. As the cells are destroyed, the part of red blood cells (hemoglobin) that carries oxygen is removed in the urine.

PCH is an acquired syndrome. Sometimes the antibodies occur with a viral infection (for example, measles and mumps) or with syphilis. However, in some cases the disorder is not related to a disease and the cause is unknown.

• Excessive bleeding
• Fainting or feeling light-headed
• Blood accumulating under the skin (hematoma)
• Infection
• Multiple punctures to find veins

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Getting a blood sample from some people may be more difficult than from others.