Platelet aggregation test
Key points
- This is a test of the ability of platelets, a component of blood, to clump together and cause blood clotting.
- Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand.
- The list of medications that may affect test results is increasing rapidly; notify your health care provider of any medications (including over-the-counter preparations) that you have taken within the preceding 2 weeks.
- When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation.
Definition
This is a test of the ability of platelets, a component of blood, to clump together and cause blood clotting.
How the test is performed
Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.
A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
For an infant or young child, 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.
The platelet aggregation test measures the rate and degree to which dispersed platelets in a sample of plasma (the liquid portion of blood) form clumps after the addition of a material that normally stimulates aggregation. These materials may include ADP (adenosine diphosphate), epinephrine, arachidonic acid, collagen, or ristocetin.
Clumping of platelets causes the sample to be more clear (less turbid). A machine measures the changes in turbidity (cloudiness) and prints a graphic recording of the results.
How to prepare for the test
The list of medications that may affect test results is increasing rapidly; notify your health care provider of any medications (including over-the-counter preparations) that you have taken within the preceding 2 weeks.
For infants and children, the preparation you can provide for this test depends on your child's age and previous experience. For general information regarding how you can prepare your child, see the following topics:
- Infant test or procedure preparation (birth to 1 year)
- Toddler test or procedure preparation (1 to 3 years)
- Preschooler test or procedure preparation (3 to 6 years)
- School age test or procedure preparation (6 to 12 years)
Written and revised by
Gerald Hurowitz, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.