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This video refers to guidelines produced by a number of organisations (details below). Please note that the content on this channel reflects my professional interpretation/summary of the guidance and that I am in no way affiliated with, employed by or funded/sponsored by any of them.

My name is Fernando Florido and I am a General Practitioner in the United Kingdom. In this episode I cover what to do if thrombocytosis is found, always focusing on what is relevant in Primary Care only. The information is based on Haematological guidance by Camden CCG, Manchester Foundation Trust and King’s Health Partners.

I am not giving medical advice; this video is intended for health care professionals, it is only my summary and my interpretation of the guidelines and you must use your clinical judgement.  

Disclaimer:

The Video Content on this channel is for educational purposes and not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen on this YouTube channel. The statements made throughout this video are not to be used or relied on to diagnose, treat, cure or prevent health conditions.

In addition, transmission of this Content is not intended to create, and receipt by you does not constitute, a physician-patient relationship with Dr Fernando Florido, his employees, agents, independent contractors, or anyone acting on behalf of Dr Fernando Florido.

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There is a podcast version of this and other videos that you can access here:

Primary Care guidelines podcast:

·      Redcircle: https://redcircle.com/shows/primary-care-guidelines

·      Spotify: https://open.spotify.com/show/5BmqS0Ol16oQ7Kr1WYzupK

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There is a YouTube version of this and other videos that you can access here: 

• The Practical GP YouTube Channel: 

https://youtube.com/@practicalgp?si=ecJGF5QCuMLQ6hrk

My summary of the guidance consulted can be found here:

·      https://1drv.ms/b/s!AiVFJ_Uoigq0mQ4ZjYGRH1wkGBdc?e=Zuxx84

The resources consulted can be found here:

·      Camden CCG guidance: 1456246258-2f3891e610beaa6533f2c0ad7866e776.pdf(Review) - Adobe cloud storage

·      Manchester Adult anaemia guide: https://acrobat.adobe.com/id/urn:aaid:sc:EU:f96fe528-0a47-457c-b29a-a7efb87221e0

·      Manchester Haematology GP guide: https://mft.nhs.uk/app/uploads/2021/02/MFT-Haematology-GP-Pathway-Guide-v4-11.2.21.pdf

·      King’s Health Partners: https://www.kingshealthpartners.org/assets/000/002/294/KCH_-_king_s_health_partners_-_quick_guide_to_haematology_original.pdf

Transcript

If you are listening to this podcast on YouTube, for a better experience, switch to the video version. The link is in the top right corner of the video and in the episode description.

Hello and welcome, I’m Fernando, a GP in the UK. Today we are going to cover what to do when we encounter thrombocytosis on a full blood count, always focusing on what is relevant in Primary Care only.

I have based this episode on Haematological guidance by Camden CCG, Manchester Foundation Trust and King’s Health Partners. The links to them are in the episode description.

Right, let’s jump into it.

Thrombocytosis is when the number of platelets is high, which is usually defined as a raised platelet count above 450 × 10⁹/L.

But before moving on, let’s clarify the terminology: should we call it thrombocytosis or thrombocythemia? There is an important difference. Thrombocytosis is much more common and arises as a secondary response to another condition, which is why it is also known as reactive thrombocytosis. In contrast, thrombocythemia, also called primary or essential thrombocythemia, is far less common and represents a myeloproliferative disorder in which the bone marrow produces platelets in an uncontrolled, abnormal way.

Another important distinction is that patients with reactive thrombocytosis have normal platelets, so their risk of thrombosis and bleeding is relatively low. On the other hand, patients with thrombocythemia have abnormal platelets, which increases their risk of both blood clots and bleeding complications. From a clinical perspective, thrombocythemia often presents with splenomegaly and a platelet count greater than 1000 × 10⁹/L.

So, let’s have a look at the possible causes. Causes of thrombocytosis include:

• Iron Deficiency Anaemia: which is one of the most common causes of reactive thrombocytosis. When iron levels are low, the bone marrow increases its overall activity in an attempt to compensate for the anaemia. Although iron deficiency limits the production of red blood cells, platelet production is not restricted in the same way. As a result, the bone marrow produces more platelets. In addition, inflammatory signals associated with chronic iron deficiency can further stimulate thrombopoietin pathways, increasing platelet numbers even more. This is why thrombocytosis often resolves once the iron deficiency is corrected.

• Another cause is Malignancy, because some tumours release inflammatory cytokines that eventually increase platelet formation. This reactive response is common in several solid cancers, particularly the “LEGO” cancers, that is:

• Lung

• Endometrium

• Gastric

• and Oesophageal cancer

• Another cause is general Inflammation, where cytokines stimulate excessive platelet production.

• Also Infection, which can cause transient reactive thrombocytosis.

• Post-splenectomy and hyposplenism, such as in coeliac disease, since the spleen normally helps remove circulating platelets.

• Post-operative states, where inflammation and stress responses increase platelet counts.

• And finally, a primary myeloproliferative disorder, such as essential thrombocythemia.

How should we respond to thrombocytosis?

The criteria for urgent haematology referral are:

• A platelet count exceeding 1000 × 10⁹/L, which raises concern for a myeloproliferative disorder and a significant risk of thrombosis.

• Splenomegaly, which may indicate a primary haematological process such as essential thrombocythemia or myelofibrosis.

• A recent history of thromboembolism, as thrombocytosis can contribute to recurrent clotting events.

• A platelet count above 600 × 10⁹/L in a patient at high risk of thromboembolism or cardiovascular disease, since the combination significantly increases clinical risk.

• Neurological symptoms, which may reflect microvascular complications associated with very high platelet counts.

• Any signs of malignancy, given that multiple cancers can cause reactive thrombocytosis.

• any other significant abnormal full blood count indices, which may suggest a bone marrow disorder rather than a reactive process.

• And finally, if there is Abnormal bleeding. And let’s stop here for a moment and discuss how it is possible that thrombocytosis can be associated to a high risk of both thrombosis and bleeding.

On one hand, thrombosis risk in thrombocytosis is due to the high number of circulating platelets, which makes clots more likely. In addition, inflammation causing reactive thrombocytosis can also create a prothrombotic environment. Together, these factors increase the thrombosis risk.

On the other hand, bleeding risk in thrombocytosis can occur for two main reasons. First, in primary or essential thrombocythemia, the platelets produced by the bone marrow are structurally and functionally abnormal and these abnormal platelets do not work effectively, so clot formation is impaired. Secondly, thrombocytosis may affect the von Willebrand factor. Von Willebrand factor is a protein that helps platelets stick to damaged blood vessels and to each other, making it essential for the first steps of clot formation. However, when platelet counts become very high, the excess platelets bind and remove the most active forms of von Willebrand factor from the circulation. This leads to a functional depletion known as acquired von Willebrand syndrome. It explains the paradoxical situation in which a patient can have thrombocytosis and yet be at increased risk of bleeding.

If none of the urgent referral criteria are present, we will investigate for underlying causes by arranging the following initial tests:

• A repeat full blood count, to confirm that the thrombocytosis is persistent.

• A blood film, which may reveal abnormal platelet morphology or other features suggestive of a myeloproliferative process.

• Inflammatory markers such as ESR and CRP, since inflammation is a common cause of reactive thrombocytosis.

• Ferritin and iron studies, as iron deficiency frequently elevates platelet counts.

• And we will consider a coeliac screen, because coeliac disease can lead to hyposplenism or iron deficiency, both of which are associated with thrombocytosis.

If the patient is asymptomatic and no obvious cause is identified, we will repeat the full blood count 4 to 6 weeks later. If the thrombocytosis persists above 450 × 10⁹/L, we will refer to haematology routinely for further assessment.

So that is it, a review of the assessment and management of thrombocytosis.

We have come to the end of this episode. Remember that this is not medical advice but only my summary and my interpretation of the guidelines. You must always use your clinical judgement.

Thank you for listening and goodbye.