Platelet aggregation test Health Article

Definition

The platelet aggregation test checks to see how well platelets, a part of blood, clump together and cause blood clotting.

How the test is performed

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.

The laboratory specialist will look at how the platelets spread out in the liquid part of the blood (plasma) and whether they form clumps after a certain chemical or drug is added. When platelets clump together, the blood sample is more clear. A machine measures the changes in cloudiness and prints a record of the results.

How to prepare for the test

Many medications may affect test results. Tell your health care provider about any medications (including over-the-counter drugs) you have taken within 2 weeks before the test.

Medications that may alter test results include:

• Aspirin
• Aspirin compounds
• Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen
• Tricyclic antidepressants
• Antihistamines
• Some antibiotics

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing.