10 Platelet Aggregation Test Details You Should Know

Platelet Aggregation Test

What is platelet aggregation to begin with? To better understand the procedure, let us first define platelet aggregation below.

Platelet Aggregation Definition

It involves the clumping together or platelet-to-platelet adhesion in the blood. It is part of a series of events necessary for effective hemostasis that leads to formation of a thrombus or clot.

It normally follows the initial adhesion of platelets to the site of injury and activation of platelets.


Platelet Aggregation Test

The platelet aggregation test assesses how well platelets, a crucial component of the blood, clump together and cause blood clotting.

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

Below are 10 important things you should know 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, so 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 how well they adhere to each other.

2. How a Platelet Aggregation Test is done

First off, this particular test requires a blood sample, thereby an amount will be drawn from the patient.

Subsequently, the laboratory specialist will carefully examine the blood, analyzing how 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 tougher, the blood sample is made 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 to as Aggregometer Test or Platelet Aggregation Assay.

4. Why is this test needed?

Laboratory tests are done for many reasons.  Tests may be performed for the purposes of routine health screening, medical check ups, or identification of any underlying disease or toxicity especially when suspected.

The doctor may order platelet aggregation test if patient show signs of bleeding disorders or low platelet count.  It is also ordered when a member of your family has any known bleeding disorder or platelet dysfunction.

Platelet aggregation test can help diagnose problems related to platelet function.  It is also used to determine whether the problem is due to any underlying medical disorder, genetic factors, 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 frequently medical laboratory tests of any sort are performed.

The timing for laboratory tests rely on many factors, like with regards to the diagnosis, severity, diagnostic results or after completion of other procedures, tests, or treatments.

Lab tests may also be delayed when the condition is being treated or monitored.  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 a day, lab tests may be needed to be done at a certain time of day.

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

The age or gender of the person to whom the test will be performed can also affect when and how often a lab test is made.

People with chronic or progressive medical conditions may require continuous monitoring through the use of lab tests.  This applies to conditions that worsen or improve too.

So, how often should platelet aggregation is performed? This usually depends on your doctor’s findings.

6. How to prepare for the test

There are some medications that can affect the results of platelet aggregation test.  So be sure to tell your healthcare provider about any 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 started, it is important to immediately tell the person who will be drawing the blood any history of allergy to latex.

Also, inform them if you have any underlying medical condition or currently using any medication or supplements that can potentially affect blood functionality or cause excessive bleeding.

Tell the healthcare worker any experience of nausea, lightheadedness, or history of fainting during any blood withdrawal procedures you’ve had in the past.

Do not perform any exercise within 15 to 20 minutes before undergoing a platelet aggregation test.

Moreover, tell the person who will be doing the test if you smoke.

7. How does the actual procedure feel

When the needle is inserted to draw out blood, some people may feel moderate pain.  Others may only feel a prick or stinging sensation.  Afterward, 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 done 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 is affected by temperature and results may vary from laboratory to laboratory. 

Also, laboratory test results may differ depending on gender, age, health history, method used for the test, and various other factors.

If you take this 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 for the test:

Adults:  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 is follow up made after the test?

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

Follow up care varies depending on the many factors with regards to your results.  Sometimes no follow up is necessary.  But in some occasions, follow up may be necessary.

A referral visit to a specialist, frequent monitoring, or additional tests or procedures may also be advised.

While the importance of undergoing a platelet aggregation test for those who need it cannot be understated, for most people it is something they never have to be totally concerned with.

However, if there may be problems with 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 it.  The procedure could provide essential information that your doctor can use in dealing with your treatment or whatever medical problems you may be experiencing.


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