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How Is ET Diagnosed?

If your blood count is above 450,000 platelets per microliter of blood, your Healthcare Professional will look for an underlying condition. Essential thrombocythemia (ET) can be diagnosed through a number of blood tests and/or bone marrow tests. Some of the blood tests that are used to help confirm a diagnosis of ET include:

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Complete blood count (CBC). This test measures the number of platelets in your blood, among other blood cells.

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Blood smear. A small amount of your blood will be examined under a microscope to look at the condition of your platelets. Specifically, your Healthcare Professional will be looking to see if your platelets are abnormally large or clumped together.

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Genetic testing. Special tests that can help identify whether you have certain genetic mutations that can cause a high platelet count.

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Other blood tests. The level of iron in your blood may be tested. Your blood may also be tested for certain indicators of inflammation. If there's no obvious cause of your high platelet count, and it remains high over time, a bone marrow test may be performed. There are two types of bone marrow tests that provide different but complementary information about your blood cells. They're often done together.

  • Bone marrow aspiration. Your Healthcare Professional removes a small amount of your liquid bone marrow through a needle and examines it under a microscope, looking for abnormal cells.
  • Bone marrow biopsy. Your Healthcare Professional takes a sample of solid bone marrow tissue (usually from the hip bone) through a needle for examination under a microscope. If you have essential thrombocythemia, your bone marrow has a higher than normal number of the large cells that make platelets (called megakaryocytes [mega-KAR-ee-uh-cytes]).
Image of Jen, an ET Community Member

In 2018 I finally went to an MPN specialist and have hope and am on the right track! —Jen, ET Community Member

How Is ET Monitored?

For people who are younger than 60 and have no symptoms or other risk factors for blood clots, ET is typically monitored by routine checkups. People who are over 60 and have had blood clots typically require medicine or procedures to lower their platelet counts.

All people with this condition need regular monitoring and medical care to detect any changes in their condition. Blood tests can show if the condition is getting worse. The goal is to control symptoms and reduce the risk of complications by working with the healthcare team.


Watch physician assistant and medical science liaison (MSL) at Incyte Amber Essenmacher explain the potential benefits of consulting a myeloproliferative neoplasm (MPN) specialist after your ET diagnosis.

Image of Susan, an ET patient

Although I didn't know it at the time, I had been experiencing symptoms related to ET for years…  —Susan, ET Community Member


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