Dual Antiplatelet Therapy in Essential Thrombocythemia
No, you should not routinely give both aspirin and clopidogrel in essential thrombocythemia (ET)—aspirin monotherapy is the standard treatment for most ET patients, with dual antiplatelet therapy (DAPT) reserved exclusively for patients who have a separate acute coronary syndrome or recent coronary stent placement.
Standard Antiplatelet Strategy for ET
Low-Dose Aspirin Monotherapy is the Foundation
Aspirin 81-100 mg once daily is recommended for all ET patients except those at very low risk (who only need aspirin for symptomatic vasomotor/microvascular disturbances like erythromelalgia) 1, 2.
Simple observation without aspirin should be preferred over aspirin prophylaxis in low-risk patients with platelet counts >1,000×10⁹/L or those harboring CALR mutations 2.
Symptomatic ET patients with erythromelalgia, transient ischemic attacks, minor stroke, or visual disturbances have a clear indication for regular-dose aspirin 1.
Aspirin Formulation and Dosing Considerations
Plain aspirin should be preferred over enteric-coated aspirin because some ET patients display poor responsiveness ("resistance") to enteric-coated formulations 2.
Twice daily aspirin administration (rather than once daily) may be considered because adequate inhibition of platelet thromboxane A2 production does not persist for 24 hours in most ET patients when treated with once daily dosing—this is due to high platelet production introducing new non-acetylated platelets 2.
Patients whose platelet count has been normalized with cytoreductive therapy can be treated with once daily aspirin 2.
When DAPT is Actually Indicated in ET Patients
Acute Coronary Syndromes
DAPT with aspirin plus clopidogrel (or preferably prasugrel/ticagrelor) is recommended for at least 12 months only if the ET patient develops an acute coronary syndrome 3, 4.
The European Society of Cardiology recommends aspirin 75-100 mg daily plus clopidogrel 75 mg daily for 12 months in non-ST-elevation acute coronary syndromes 4.
Post-Coronary Stenting
DAPT is recommended for 6-12 months following coronary stent implantation 3, 4.
After uncomplicated PCI, aspirin 75-100 mg daily and clopidogrel 75 mg daily for up to 6 months is the default strategy 3.
Duration may be shortened to 1-3 months in patients with very high bleeding risk (which ET patients with extreme thrombocytosis may qualify for) 3, 4.
Critical Pitfalls to Avoid
The Bleeding Risk in ET
High-risk ET patients with platelets >1,500×10⁹/L have a clear indication for platelet-reductive therapy rather than DAPT because extreme thrombocytosis paradoxically increases bleeding risk 1.
History of spontaneous or major bleeding, or bleeding elicited by low-dose aspirin at platelet counts <1,500×10⁹/L is a contraindication to aspirin and certainly to DAPT 1.
DAPT is NOT for Stroke Prevention in ET
Dual antiplatelet therapy is NOT routinely recommended for stroke prevention alone—it is indicated for acute coronary syndrome or recent coronary stent placement 5.
Recent ischemic stroke or TIA in ET patients should be treated with aspirin monotherapy (not DAPT), unless there is a concurrent ACS indication 5, 6.
High-Risk ET Patients Requiring Cytoreduction
When to Add Cytoreductive Therapy
Platelet-reductive therapy (hydroxyurea, anagrelide, or interferon) is indicated for: 1
- Platelets >1,500×10⁹/L
- History of major thrombosis (MI, stroke, peripheral vascular disease)
- Presence of vascular disease (arteriosclerosis)
- History of spontaneous or major bleeding
- Progressive myeloproliferative disease with splenomegaly or myelofibrosis
The goal is to reduce platelet count to normal (<350×10⁹/L) in high-risk patients 1.
Practical Algorithm
- Assess ET risk category and platelet count
- Very low risk (asymptomatic, no vascular risk factors): Observation or aspirin only for symptoms 1
- Low risk with platelets >1,000×10⁹/L or CALR mutation: Observation preferred over aspirin 2
- Symptomatic or standard risk: Aspirin 81-100 mg once or twice daily 1, 2
- High risk (platelets >1,500×10⁹/L or prior thrombosis): Cytoreductive therapy + aspirin 1
- If ACS or coronary stent occurs: Add clopidogrel to aspirin for 6-12 months 3, 4
- Never use DAPT for ET thrombosis prevention alone 5