Tests and treatment for essential thrombocythaemia (ET)

To find out if you have essential thrombocythemia (ET) your doctor will do several tests. They will also examine you and ask you questions about your general health and family history. 

Tests for essential thrombocythaemia

The first test to diagnose ET is a blood test. This will check the number of platelets Open a glossary item in your blood. In ET there is an abnormally high level of platelets.

If the first blood test suggests you have ET, you might have another blood test to look for a change in a gene Open a glossary item called JAK2. The JAK2 gene makes a protein that controls how many blood cells the stem cells make. A fault with your JAK2 gene means the stem cells Open a glossary item can start producing platelets when they're not meant to. Around 50 to 60 in 100 people (around 50 to 60%) with ET have a fault in the JAK2 gene.

You might also have a blood test to check for gene changes in the CALR and MPL genes. Changes in these genes are also linked to ET.

Doctors are learning more about genetic changes all the time. You might have tests for other gene changes.

Other tests

Other tests you might have to help diagnose ET include:

  • a bone marrow test

  • an ultrasound scan of your tummy (abdomen), to check the size of your spleen

Treatment for essential thrombocythaemia

Treatment for ET aims to reduce the number of platelets and lower the risk of blood clots. This helps to control your symptoms and to prevent any more serious problems.

To help them decide the best treatment for you. Your doctor works out your risk of developing blood clots. They might use a scoring system to do this.

As well as your platelet levels and risk of blood clots your doctor also considers:

  • your age

  • if you’ve had blood clots or bleeding before

  • any symptoms you might have

  • other medical conditions

  • if genetic test results show gene changes

You might have one or more treatments.

Very low, low, and intermediate risk of developing blood clots 

People with a very low risk may not need treatment if they don’t have symptoms. Instead, your doctor will check you regularly. They will let you know how often you need to see them. You usually have low dose aspirin if you are very low risk but have symptoms. 

 If you have a low or intermediate risk of developing clots, you have low dose aspirin. Your doctor sees you regularly to check on your general health. You may need to start other treatments if your symptoms are getting worse or your platelet levels are increasing. 

The main treatment is hydroxycarbamide, but you may have other treatments including: 

  • busulfan

  • anagrelide

  • peginterferon alfa-2a

High risk of developing blood clots

Treatments for people with a high risk of developing blood clots include: 

  • low dose aspirin

  • hydroxycarbamide

  • anagrelide

  • busulfan

  • peginterferon alfa 2a

Types of treatment

Low dose aspirin

You take aspirin as a tablet. This can help to lower the number of platelets in the blood. This is also known as an anti platelet therapy. There are alternatives to aspirin if it’s not suitable for you. 

You might have a high dose of aspirin if you have had a blood clot in the past.


Hydroxycarbamide is a type of chemotherapy. This treatment uses cell killing (cytotoxic) drugs to destroy the extra platelets. The drugs work by disrupting the growth of cells and stopping them from dividing.

Hydroxycarbamide is the most common type of chemotherapy that doctors use to treat ET. You have it as a tablet. There may be a small increase in the risk of developing a leukaemia if you take this for a long time. Your doctor will discuss this more with you.


Another type of chemotherapy is busulfan. This is usually used in older people who cannot take hydroxycarbamide. We know from research that it increases the risk of developing leukaemia if you take it for long periods of time. So, you might take it for a while and then stop for a period of time before starting again.


Anagrelide is a medicine that is used to reduce the number of platelets. You take it as a capsule.

Doctors use it to treat ET when hydroxycarbamide is no longer working. Or you may have the two treatments together. Anagrelide does cause side effects that some people find difficult to cope with. These include:

  • breathlessness and tiredness from a low level of red blood cells (anaemia)
  • a racing heart
  • headache
  • feeling sick
  • heart problems

The side effects of anagrelide usually settle within a couple of weeks of starting treatment. Speak to your doctor if you are having any problems with side effects. 

Peginterferon alfa 2a

Peginterferon alfa 2a is a type of immunotherapy Open a glossary item. It stimulates cells of the immune system Open a glossary item to attack the cancer. It can also help to control the number of platelets. You usually have it as an injection under the skin.

Side effects of peginterferon alfa 2a include flu-like symptoms and tiredness.

Extra support

You might need extra support from your specialist team during your treatment. For example, during pregnancy or if you are having an operation. 

Treatment during pregnancy

There is a risk of complications, including blood clots, during pregnancy if you have ET. Some treatments for ET may harm a developing baby. Your specialist will talk to you about treatments available and monitor you closely. Do speak to your specialist if you plan to have a baby in the future.

Having an operation

If you are having surgery for any reason, let your surgeon know you have ET and any treatment you may be taking. They may need to speak to your ET specialist. You might need to stop taking some treatments before your surgery. 

Healthy Lifestyle

Your healthcare team might discuss ways to maintain a healthy lifestyle and help with stopping smoking if you need it.

We have information on healthy diet and lifestyle on our causes of cancer and reducing your risk pages.

Research and clinical trials

Researchers are trying to improve the diagnosis and treatment of essential thrombocythaemia.

  • Pan-London Haemato-Oncology Clinical Guidelines, Acute Leukaemias and Myeloid Neoplasms Part 4: Myeloproliferative Neoplasms

    RM Partners, South East London Cancer Alliance, North Central and East London Cancer Alliance, 2020

  • Essential thrombocythaemia

    D Mukherjee and others

    BMJ Best Practice, Last updated: 05 Apr 2023 (accessed January 2024)

  • The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms

    J D. Khoury and others

    Leukemia, 2022. Volume 36, pages 1703–1719

  • REF 3 The use of genetic tests to diagnose and manage patients with myeloproliferative and myeloproliferative/myelodysplastic neoplasms, and related disorders

    N. C. P. Cross and others

    British Journal of Haematology, 2021. Volume 195, Pages 338–351

  • Electronic Medicines Compendium

    Accessed December 2023

Last reviewed: 
02 Feb 2024
Next review due: 
02 Feb 2027

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