10 Platelet Aggregation Test Facts

Platelet Aggregation Test
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Platelet Aggregation Definition

What is platelet aggregation to begin with? To have a better understanding of the procedure, we have to first define platelet aggregation. It involves the clumping together of platelets (platelet-to-platelet adhesion) in the blood. It is part of a series of events necessary for effective hemostasis that leads to the formation of a thrombus or blood clot. It normally follows the activation of platelets which takes place after the initial adhesion of platelets to the site of injury.


Platelet Aggregation Test

Platelet aggregation test assesses how well the platelets, a crucial component of the blood, clump together, and result to blood clotting.

The test is used to evaluate platelet function in particular.  It is also a recommended procedure when an inherited or drug-induced platelet dysfunction is suspected.

Below are 10 important aspects that you can learn about platelet aggregation test:

1. Platelet Count is a different test

A platelets blood test or platelet count is a test to measure the amount of platelets circulating in the blood. Don’t confuse the two.

Platelets are components of the blood, smaller than red or white blood cells, which normally helps in the formation of blood clots. Platelet aggregation test is performed to determine this functionality of platelets adhering to each other.

2. How a Platelet Aggregation Test is performed

The test requires a blood sample, where an amount will be drawn from the patient.

A laboratory specialist will carefully examine the blood, analyzing the way platelets spread out in its liquid part (called plasma), identifying whether they form clumps after a certain drug or chemical is added.

When platelets clump together, the blood sample becomes clearer.  A machine measures the changes in cloudiness and prints a record of the results.

3. Other names for Platelet Aggregation Test

The platelet aggregation test is also referred as Aggregometer Test or Platelet Aggregation Assay.

4. Why is the test needed?

Laboratory tests are performed for several reasons.  Tests are usually carried with the purpose of routine health screening, medical check ups, or identification of any underlying disease or suspected toxicity.

The doctor may also order platelet aggregation test if the patient shows signs of bleeding disorders or low platelet count.  It is also ordered for patients with a family history of bleeding disorders or platelet dysfunction.

Platelet aggregation test can help diagnose problems related to platelet function.  It can help determine whether the problem is due to an underlying medical disorder, genetic factor, or side effect of medication.

5. When and how often should the test be performed?

Many factors come into play when determining when and how frequent medical laboratory tests of any sort are made. The timing for laboratory tests rely on factors like the diagnosis, severity, diagnostic results, or completion of other procedures, tests, and treatments.

Lab tests may also be delayed when the condition is under specific phase of treatment or monitoring. Performing tests may also become necessary when certain signs or symptoms appear.

Due to changes in the body’s natural functioning throughout the course of the day, lab tests may be needed to be done at a certain time of the day.

Sometimes, it is necessary for you to prepare for a test by making changes on food or fluid intake. Lab tests may be timed in accordance to those changes. Also, the timing of tests may be based on increased and decreased levels in the amount of medications, drugs, or other substances taken in the body.

The age and gender of the person to undergo the test may also affect when and how often the lab test is made. People with chronic or progressive medical disorder may require continuous monitoring mainly with the assistance of lab tests. This also applies to situations of whether it worsens or improves.

So, how often should platelet aggregation be performed? It depends on your doctor’s findings.

6. How to prepare for the test

There are some medications that can affect the results of a platelet aggregation test.  Make sure to let your healthcare provider know the medications (including over-the-counter drugs) you have taken within the past 2 weeks before the test.

Medications that may affect test results include:

Antibiotics:  penicillins, cephalosporins, nitrofurantoin



Aspirin-containing compounds



Nonsteroidal anti-inflammatory drugs (NAID) such as ibuprofen and naproxen



Tricyclic antidepressants

It’s not a complete list though. 

Before the process of blood collection is performed, immediately inform the healthcare provider any history of allergy to latex. Also, let the doctor know of any underlying medical condition for it may have a potential to affect the results.

You may also be asked by the healthcare worker of any previous experiences of nausea, lightheadedness, or history of fainting during blood withdrawal procedures you’ve had in the past. Moreover, inform the healthcare worker if you smoke.

Do not engage in any form of exercise within 15 to 20 minutes before the scheduled platelet aggregation test.

7. How does the actual procedure feel

When the needle is inserted for the drawing out of blood, some people may feel moderate pain.  Others may simply take it as a prick or stinging sensation.  Afterwards, there may be some throbbing.

When the blood is being taken, a hematoma (blood-filled bump under the skin) or slight bleeding from the puncture site may occur. The test may need to be performed more than once during the procedure.

A bruise or infection may develop at the puncture site with inadequate care.

8. Normal results

The normal time it takes for platelets to clump together can be affected by temperature. Normal results may vary from laboratory to laboratory. They may differ depending on gender, age, health history, method used for the test, and various other factors.

After undergoing the test and your results are different from what is usually considered normal, it does not necessarily mean that you have a disease.  The following is considered to be a normal result:

Adults:  Over 65% aggregation in response to adenosine diphosphate (ADP), arachidonic acid, collagen, epinephrine, and ristocetin.

9. What can affect test results?

Test results may display an increase due to:




10. How to follow up after the test?

Feel free to ask your healthcare provider how will you be informed of the test results.  Perhaps, you may be asked to make a call in order to have the results; schedule an appointment to discuss the results; or simply be notified of the results by mail. 

Follow-up care varies depending on several factors based on your results. Sometimes no follow-up is necessary. But in most occasions, a follow-up may be necessary. A referral visit to a specialist, frequent monitoring, or additional tests or procedures may also be advised.

Key Takeaway:

While the importance of undergoing a platelet aggregation test in the treatment course of patients cannot be understated, for most people it is something they don’t have to be totally concerned with.

However, if there may be suspected problems with the clotting of your blood, this type of test is an excellent procedure in determining what exactly is going on and how should it be dealt with.

If the procedure is one of the things your doctor recommends, you shouldn’t ignore. The procedure can provide essential information that your doctor can use in dealing with your treatment or whatever medical problem you may be experiencing.

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About the Author:

Melissa Gomez, RN, MSN is a board certified nurse and has been a contributing writer for the past five years. Ms. Gomez has a special focus on platelet-related illness prevention and health promotion.

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