From the Research
High platelets, or thrombocytosis, become dangerous when counts exceed 450,000 platelets per microliter of blood, particularly if they rise above 1 million, as this significantly increases the risk of blood clots (thrombosis) and associated complications like stroke, heart attack, deep vein thrombosis, or pulmonary embolism, as indicated by studies such as 1. The primary danger of high platelets is the increased risk of thrombosis, which can lead to serious complications. Symptoms that indicate dangerous levels include unexplained headaches, dizziness, chest pain, weakness on one side of the body, or swelling and pain in the legs.
Causes and Risk Factors
High platelets can be reactive (a temporary response to infection, inflammation, or blood loss) or caused by bone marrow disorders like essential thrombocythemia. The danger level varies based on whether the elevation is temporary or persistent, the underlying cause, and individual risk factors for clotting such as smoking, hypertension, or previous clotting history, as discussed in 2 and 3.
Treatment Options
Treatment depends on the cause and risk factors, ranging from observation to medications like aspirin (81-325 mg daily), hydroxyurea, or anagrelide to reduce platelet counts. In severe cases with high clotting risk, plateletpheresis might be used to rapidly reduce platelet levels.
- Aspirin can be used for patients with platelet counts < 1,500 x 10(9)/L, as mentioned in 2.
- Hydroxyurea is recommended for high-risk patients, as indicated in 2 and 4.
- Anagrelide can be used as an alternative to hydroxyurea or for patients who cannot tolerate hydroxyurea, with evidence suggesting it reduces thrombotic risk in essential thrombocythaemia, as shown in 1.
- Interferon-alpha is suitable for use during pregnancy and for patients who are resistant or intolerant to hydroxycarbamide, as noted in 3. The choice of treatment should be based on the most recent and highest quality evidence, considering the patient's specific risk factors and condition, as discussed in 4 and 3.