Is Aspirin (acetylsalicylic acid) effective for treating thrombocytosis (elevated platelet count)?

From the Guidelines

Aspirin is recommended for patients with thrombocytosis, particularly those with essential thrombocytosis (ET) or reactive thrombocytosis with platelet counts above 450,000/μL, to reduce the risk of thrombotic complications, as supported by the most recent study 1. The use of low-dose aspirin (81-100 mg daily) is typically prescribed and should be continued indefinitely unless contraindications develop, such as bleeding complications or gastric intolerance. Aspirin works by inhibiting platelet aggregation through irreversible inhibition of cyclooxygenase-1 (COX-1), which prevents the formation of thromboxane A2, a potent platelet activator. This antiplatelet effect helps prevent clot formation that can occur with elevated platelet counts. Some key points to consider when prescribing aspirin for thrombocytosis include:

• Patients should take aspirin with food to minimize gastrointestinal side effects and should be monitored for signs of bleeding.
• For patients with very high platelet counts (>1,000/μL), cytoreductive therapy may be needed in addition to aspirin, as suggested by 1 and 1.
• Those with a history of gastrointestinal bleeding or other bleeding disorders may require alternative approaches, such as cytoreduction alone or different antiplatelet agents.
• The presence of JAK2 mutation or cardiovascular risk factors may also influence the decision to use aspirin, as noted in 1 and 1. It is essential to weigh the benefits and risks of aspirin therapy in each patient, considering their individual risk factors and medical history, as emphasized in 1.

From the Research

Aspirin Treatment for Thrombocytosis

• Aspirin is commonly used to treat thrombocytosis, particularly in patients with essential thrombocythemia (ET) 2, 3.
• Low-dose aspirin (81-100 mg) once daily is recommended for the control of vascular events in all ET risk categories, except patients at very low risk 2.
• However, some studies suggest that twice-daily aspirin administration may be more effective in overcoming the problem of inadequate inhibition of platelet thromboxane A2 production 2, 4.
• The use of aspirin in patients with reactive thrombocytosis (RT) is not recommended, as RT is not associated with an increased risk of thrombosis or bleeding 3.

Efficacy of Aspirin in Thrombocytosis

• Aspirin efficacy can be evaluated by measuring serum thromboxane B2 levels and platelet aggregation tests 5.
• Some studies have shown that aspirin may not be effective in inhibiting platelet aggregation in patients with myeloproliferative neoplasms (MPNs), including ET 5.
• However, other studies have demonstrated that low-dose aspirin can reduce platelet-leukocyte interactions and platelet activation in patients with ET 6.

Dosage and Administration of Aspirin

• The recommended dosage of aspirin for thrombocytosis is 81-100 mg once daily, but twice-daily administration may be more effective in some patients 2, 4.
• Plain aspirin is preferred over enteric-coated aspirin, as some patients may display poor responsiveness to the latter 2.
• The choice of aspirin formulation and dosage regimen should be individualized based on the patient's risk category and response to treatment 3.