A platelet aggregation test checks how well your platelets clump together to form blood clots. Platelets are a type of blood cell. They help form blood clots by sticking together. A clot is what stops the bleeding when you have a wound. Without platelets, you could bleed to death.
A platelet aggregation test requires a blood sample. The sample is initially examined to see how the platelets are distributed through the plasma, the liquid part of the blood. A chemical is then added to your blood sample to test how quickly your platelets clot.
This test may also be called a platelet aggregometry test or a platelet aggregation assay.
- excessive bleeding
- excessive bruising
- bleeding from the nose or gums
- excessive menstrual bleeding
- blood in the urine or stool
Your doctor may also order this test if you have a family history of bleeding problems.
The results of this test can help your doctor figure out the cause of bleeding problems. It can also help diagnose:
- an autoimmune disorder (such as systemic lupus erythematosus)
- genetic disorders (including Bernard-Soulier syndrome, Von Willebrand disease, Glanzmann’s thrombasthenia, or platelet storage pool disease)
- medication side effects (that affect platelet function)
- myeloproliferative disorders (such as certain types of leukemia)
- uremia (a condition caused by significant kidney disease)
Unless you’re told otherwise, you can eat and drink before this test. You may schedule it at any time during the day, unless your doctor specifies otherwise. You shouldn’t exercise 20 minutes before your test.
A number of medications can affect the results of this test. Inform your doctor of everything you’re taking, including over-the-counter and prescription drugs. Your doctor will tell you if you should stop taking a drug or change the dosage before your test.
Medications that can interfere with a platelet aggregation test include:
- nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin (or combo medications containing aspirin)
- antibiotics (including penicillins, certain cephalosporins, and nitrofurantoin)
- tricyclic antidepressants
- thienopyridine antiplatelet drugs (including prasugrel, clopidogrel, dipyridamole, and ticlopidine)
- theophylline (a medication used to relax airway muscles)
A platelet aggregation test requires a blood sample. The sample may be taken at a doctor’s office or a medical laboratory.
To begin, the technician will put on gloves and clean the area around your vein. Blood is usually drawn from a vein on the front of the arm near the elbow crease or the back of the hand.
Next, the technician will tie an elastic band around your upper arm. This helps the blood pool in your vein. It makes it easier for the technician to draw blood.
The technician will insert a sterile needle into your vein and draw blood. You may experience mild to moderate pain while they’re inserting the needle or drawing the blood. It may feel like a pricking or burning sensation. Relaxing your arm can help reduce the pain.
When the technician is done, they’ll remove the needle and apply pressure to the puncture to stop bleeding. You should keep pressure on the area to prevent bruising.
Your blood sample will be sent off to a laboratory for testing.
Blood tests are considered very low-risk procedures. However, a platelet aggregation test is usually performed on people with bleeding problems. The risk of excessive bleeding is slightly higher.
If you know you have a bleeding problem, tell the technician so they’re prepared. You should also inform the technician if you have experienced dizziness, fainting, or nausea during a previous blood test.
Possible risks of a blood draw include:
- multiple puncture wounds (due to trouble finding a vein)
- feeling lightheaded or fainting
- excessive bleeding
- hematoma (a collection of blood under the skin)
- infection at the site of the needlestick
Call your doctor to set up an appointment if you’re experiencing excessive bleeding, bruising, or other signs of a bleeding disorder. Your doctor can assess your symptoms and determine if treatment is in order.
If your doctor decides you need a platelet aggregation test, be sure to tell them what medications you’re currently taking. This can prevent unwanted interactions and may eliminate the possibility of excessive bleeding.