A test for platelet-associated antibodies shows whether you have abnormal antiplatelet antibodies in your blood.

Blood is drawn from a vein, usually inside the elbow or on the back of the hand. The area is cleaned with antiseptic, and an elastic band is placed around the upper arm. This causes the vein to fill 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 blood flow. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants and young children.

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), 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 necessary for adults.

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 may be ordered when the person has a low platelet count (thrombocytopenia). It is used to detect antibodies against platelets.

A negative test is normal.

Abnormal results show the person has antiplatelet antibodies. These are that attach to platelets and destroy them. This causes a low platelet count, which can lead to excessive bleeding.

Antiplatelet antibodies may appear in the blood for unknown reasons (idiopathic thrombocytopenic purpura), or as a side effect of certain drugs such as heparin. These drugs can sometimes cause the immune system to identify its own platelets as abnormal or foreign, and attack them.

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Current tests cannot reliably confirm if a low platelet count (thrombocytopenia) is caused by immune problems. Therefore, your doctor will ultimately make a diagnosis based on symptoms.

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

McPherson RA and Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: WB Saunders; 2007:764.

Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2005:2361.