Diagnosing Essential Thrombocythaemia

Diagnosing a myeloproliferative neoplasm (MPN) can be challenging. There are often no symptoms in the early stages of the conditions, and even when there are symptoms such as fatigue, these may be mistaken for signs of other diseases.


Your doctor will use a combination of laboratory tests, which examine the blood and bone marrow, and physical examinations to diagnose MPNs.

Here’s what to expect.

Physical exam: Your body is checked for anything else that seems unusual. Your doctor will also compile a history of your health, any relevant lifestyle information, past illnesses and treatments. Complete (or full) blood count: A sample of blood is taken and checked for:


  • The number of red blood cells and platelets.
  • The number and type of white blood cells.
  • The amount of haemoglobin (the protein that carries oxygen) in the red blood cells.
  • The portion of the blood sample made up of red blood cells.


Bone marrow aspiration and biopsy: Bone marrow, blood and a small piece of bone will be removed by inserting a hollow needle into the hipbone or breastbone. It will be checked for abnormal cells. Cytogenetic analysis: The cells in a sample of blood or bone marrow are checked under a microscope for changes in the chromosomes. One of the most commonly looked for changes to diagnose MPNs are the presence of the Philadelphia chromosome.


A persistently raised platelet count is the most common sign of ET. The platelet count can range from slightly higher than normal to many times higher than normal. A diagnosis of ET can only be made when other causes of a raised platelet count have been excluded. Normal platelet values vary in range between laboratories from about 150,000 to 400,000 platelets per microlitre of blood.


ET is a consideration if the platelet count is above 600,000 platelets per microlitre over a period of observation, and there is no other reason for the elevated count (e.g. iron deficiency anaemia, inflammatory disorders etc.).


If the results of your blood test suggest that you may have ET, further investigation and tests, including a bone marrow examination, may be required to help confirm the diagnosis and rule out other secondary causes of your raised platelet count. You will also be given tests for the gene mutations JAK2V617F – occurring in approximately 50% of ET cases.


Once an ET diagnosis is confirmed, other blood tests may be done to check your general health and to determine how well your kidneys, liver and other vital organs are functioning.