- Also Known As:
- PLT Count
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Test Quick Guide
The platelet count test is a lab test which measures the number of platelets you have in your blood. Platelets, also known as thrombocytes, are tiny, round cell fragments which circulate in your blood and are essential for the formation of blood clots. A blood clot is a mass of blood that the body forms in order to stop bleeding.
Platelets are one of three main components of the blood along with red blood cells and white blood cells.
Platelet count testing can detect when platelet levels are too low or too high. Low platelet levels make it difficult for the body to form blood clots, which can cause excessive bleeding. High platelet levels can cause too much clotting. Blood clots in the blood vessels can become lodged in the lungs, intestines, brain or heart, and this can result in serious medical conditions.
About the Test
Purpose of the test
The purpose of a platelet count test is to assess your blood’s ability or inability to clot. While platelet counts are often included on multi-test panels such as the complete blood count, this test can also be done on its own.
The platelet count may be conducted by your doctor as part of routine blood testing. Platelet counts are also ordered to:
- Diagnose a platelet disorder
- Assess risk of bleeding before surgery
- Monitor you during medical treatments such as blood thinners or chemotherapy.
The platelet count is used to diagnose disease and to help determine the cause of excess bleeding or clotting. Both high platelet counts and low platelet counts can have associated risks that can range from either not causing any noticeable health problems to being very serious and life-threatening.
A platelet count test is also used to monitor patients who have been diagnosed with a clotting condition. Regularly conducting a platelet count allows doctors to check the effectiveness of medications that increase or decrease the blood’s ability to form a clot.
What does the test measure?
The platelet count measures the number of platelets in your sample of blood. The results are reported as a number of platelets per microliter. The number of platelets in your blood is important in determining the blood’s ability to form a blood clot as well as your body’s ability to form the cells that become platelets. These functions can be affected by disease or medication therapy.
Measuring a platelet count typically involves analyzing a blood sample using automated laboratory technology. In some cases, automated results need to be confirmed using a peripheral blood smear, which is a method of manually measuring the number of platelets in a blood sample.
When should I get a platelet count test?
Your doctor may recommend that you take a platelet count test during a check up as part of a broader screening panel such as a complete blood count. Your doctor might also recommend platelet count testing if you have symptoms that are associated with abnormal platelet levels. Low or high platelet counts may or may not cause signs and symptoms. It’s important to speak with your doctor anytime you notice concerning health changes.
Symptoms of low platelets levels
Bleeding is the main sign and symptom of a low platelet count. Early signs of a low platelet count and can occur in any part of the body and may include but are not limited to:
- Bruising that is purple, reddish, or brown, occurring easily and often
- Small red and purple dots on the skin
- Abnormally prolonged bleeding, including from minor cuts
- Bleeding from the nose or mouth
- Atypically heavy vaginal bleeding, especially during menstruation
- Excessive bleeding during dental work, including flossing, or surgery
- Blood in the urine or stool, or bleeding from the rectum
Symptoms of high platelet levels
Signs of high platelet levels are primarily related to blot clots and bleeding. They may include:
- Weakness or dizziness
- Unexpected headache
- Chest pain
- Tingling of the hands and feet
- Pain, swelling, warmth, and/or tenderness in one or both of the lower extremities
In some instances extremely high platelet counts may result in signs and symptoms that mirror low platelet counts. This occurs because too many clots have formed in the body and there are not enough platelets left to clot breaks in blood vessels. These signs and symptoms include:
- Bleeding from many sites of the body at once
- Shortness of breath
- Confusion and changes in memory or behavior
Monitoring platelet levels
Your health care provider may also order a platelet count test when monitoring other health conditions. If you have been diagnosed with a disease that puts you at risk for high or low platelets, or if you have had abnormal results on platelet count tests in the past, your doctor may test you for platelet levels periodically. This allows your doctor to monitor your overall health and assess the effectiveness of treatment.
Finding a Platelet Count Test
How to get tested
Typically, a platelet count test is done by a licensed professional in a health care setting using a blood sample. The test can be conducted on its own or as part of a complete blood count test that is done in a doctor’s office, clinic, laboratory, or hospital.
A platelet count test is normally prescribed by a doctor. Talk with your health care provider if you have symptoms that could be related to abnormal platelet levels or if you are interested in a platelet count test.
Can I take the test at home?
Currently there are no at-home testing options available for the platelet count. Platelet counts are conducted by a medical professional and analyzed by a laboratory from a blood draw sample in a health care setting.
How much does the test cost?
The cost of a platelet count test depends on whether or not you have insurance and if that insurance plan covers the test. Some other factors that affect the cost are the setting of the blood draw and the lab to which the sample is sent.
For details on the expected cost for a platelet count that you may be responsible for, check with your doctor or insurance provider about any associated copays or deductibles.
Taking a Platelet Count Test
The platelet count test requires a blood sample ordered by a doctor that is collected in a medical setting by a licensed professional, such as a phlebotomist.
Before the test
Special preparation is not required prior to a platelet count test unless specified by your health care provider. Your health care provider may order the platelet count by itself, as part of the complete blood count, or along with other blood tests.
If you are receiving more than one blood test, your provider may ask you to not eat anything for a certain amount of time prior to your test. If you have questions or concerns about any test preparation, contact your health care provider for detailed instructions.
During the test
A blood sample for a platelet count is taken from a vein in your arm or from your forearm by a health care professional trained in drawing blood called a phlebotomist. The phlebotomist will tie a tourniquet around the upper part of your arm to increase the blood pressure in the vein of your arm so it is easier to find. They will cleanse your skin around the area of the vein with an antiseptic wipe. They will then insert a needle to draw blood from the vein. They will then attach a vacuum tube on the needle to help pull blood from the vein and, if drawing blood for multiple tests, they may attach several different tubes.
There may be a brief stinging sensation when the needle is initially inserted into your arm. This pain usually does not last long, and the test itself can be completed in under one minute.
After the test
After the procedure is complete, the phlebotomist will apply folded gauze and a bandaid over the site to reduce bleeding, remove the tourniquet, and remove the needle.
The main risk associated with blood draws is local bruising at the site of the needle puncture. This bruising may last longer than usual if you are experiencing low platelets. Because low platelet counts reduce the clotting potential of your blood it may be suggested to keep the bandage on for a specified period of time.
The phlebotomist may ask you to stay at the facility for a few minutes so they can monitor you for dizziness before returning to normal activities including walking and driving.
Platelet Count Test Results
Receiving test results
The results from a platelet count can be available in a few minutes to a few days after the blood sample arrives at the laboratory depending on the laboratory equipment that is used.
If not available immediately, a copy of your results may be sent to you by mail or through an electronic health portal. It is also possible that your health care provider may also call you to discuss the results, retest, or to schedule an appointment to review them together.
Interpreting test results
Test results are interpreted in comparison with the test reference range. The reference range is the results range that is considered to be a normal result. Platelet test results that fall outside of the reference range indicate that platelet levels may be too low or too high.
The reference range for platelet counts gives a wide range of normal results. This reflects the range in platelet levels that allows most people to function without adverse health issues. Specific reference ranges vary from one laboratory to the next, and your results are considered in context of your overall health risk factors.
The American Board of Internal Medicine lists a typical platelet count reference range as 150,000 to 450,000 per microliter.
Platelet counts tend to be slightly higher in certain populations, including:
- Younger people when compared with older people
- Non-Hispanic Black individuals when compared with White individuals.
Your doctor may consider retesting if you have significant decreases or increases in your platelet numbers from one test to the next even if they are within normal range as this may indicate a potential problem.
If you have a platelet count test result that is lower than expected, your doctor will consider whether another condition may be causing or contributing to a decrease in platelets. Some causes and risk factors associated with low platelet counts are:
- Certain cancers
- Aplastic anemia
- Autoimmune diseases and conditions
- Certain medications
- Viral or bacterial infections
- Genetic condition
- Heavy alcohol use
Other conditions can cause or increase risk for high platelet counts:
- Rare genetic conditions
- Bone marrow conditions
- Certain cancers
- Iron deficiency or hemolytic anemia
- Inflammatory disease
- Infections such as tuberculosis
- Adverse medication reactions
- Severe blood loss
- Recovery from low blood platelet counts caused by heavy alcohol use or vitamin B12 or folate deficiency
- Physical activity
Are test results accurate?
The platelet count test is a common test that is generally accurate; however, as with any laboratory test, there are some factors that can affect test accuracy.
Most platelet count tests are performed in a laboratory using automated instruments, which are designed to “flag” potential inaccuracies in the results. If your platelet count results indicate a possible inaccuracy, your test may be repeated using a peripheral blood smear. Rather than using automated instruments, a peripheral blood smear involves having your blood sample viewed under a microscope by a trained laboratory professional.
In some cases, platelets may clump together resulting in falsely low platelet counts. Some genetic disorders that cause platelets to be larger than normal may also result in low platelet counts. In other instances, abnormal shapes of red blood cells and/or white blood cells result in abnormal platelet counts.
Do I need follow-up tests?
Depending on the results of your platelet count test, it is possible that your doctor will order follow up tests to learn more about your overall health. Commonly ordered follow up tests include:
- Complete blood count: If your platelet count does not match the context of your symptoms and other test results, your doctor may reorder a complete blood count panel to confirm the results prior to more extensive evaluations or interventions.
- Peripheral blood smear: Automated blood count instrumentation is most often used to measure blood counts, including platelet counts. A peripheral blood smear involves manually analyzing the blood sample under a microscope and can be used to confirm an abnormal result on an automated platelet count.
- HIV or HCV test: Low platelet counts are often seen in people who have human immunodeficiency virus (HIV) or Hepatitis C virus (HCV) infection. Follow up testing may be used to rule out or confirm the existence of HIV or HCV as the cause of low platelets.
Other tests may be conducted to diagnose the cause of abnormal platelets. Testing depends on the specific conditions that are suspected. If you receive an abnormal platelet count result, your doctor can help you understand what follow up testing is recommended for you and why.
Questions for your doctor about test results
It may be helpful to ask your doctor the following questions about your platelet count results:
- Was my test result abnormal? If so, was it abnormally high or low?
- What does my platelet count indicate about my health?
- Are there any diagnoses to be made based on my platelet count results?
- Will any follow up tests be needed?
- Will I be prescribed medication based on my results?
Platelet count test vs. platelet function test
A platelet count test strictly counts the platelets in your blood, whereas a platelet function test analyzes the functionality of your platelets including:
- The time it takes for your platelets to plug a small hole
- The strength of the clot
- The ability for your platelets to clump together or “aggregate”
- Any possible platelet defects
- Screening for abnormalities such as protein on your platelets, which may indicate a platelet disorder
- The amount of time that it takes a small cut to stop bleeding, though newer and more reliable tests are more often used to determine platelet dysfunction.
Platelet count vs. mean platelet volume test
A platelet count is often conducted as one of a series of tests that are included in a complete blood count (CBC). A mean platelet volume (MPV) is another test that may also be included as part of a CBC panel. Platelet counts reflect the number of platelets in your blood sample, while an MPV measures the average size of your platelets. An MPV is helpful in diagnosing bleeding disorders and bone marrow conditions.
Platelet count test vs. other coagulation tests
The number of platelets you have isn’t the only factor that affects clot formation, also called coagulation. There are a few other tests that provide information on your body’s ability to form blood clots. A partial thromboplastin time (PTT) test and a prothrombin time and international normalized ratio (PT/INR) test measure the amount of time that it takes your blood to form a clot.
Testing for levels of proteins C and S can indicate how your body regulates clot formation. While platelets help your body form clots, proteins C and S help prevent your blood from clotting too much. Without these proteins, you may end up with blood that clots partially or completely block the blood flow in a vein or artery.
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