Patients with myeloproliferative neoplasm (MPN) could have laboratory aspirin resistance and then increasing dose of aspirin from once daily to twice daily regimen is suggested. However, it is not routinely recommended to perform platelet function testing to determine aspirin resistance in MPN patients. Moreover, it is not known whether increasing dose of aspirin would always correct aspirin resistance and significantly prevent the thrombotic events in MPN patients. Therefore, this study aims to compare the efficacy of once daily versus twice daily aspirin in high-risk MPN patients with aspirin resistance. MPN patients with laboratory aspirin resistance will be included in this prospective randomized study and platelet function testing will be repeated at one and six months later. Clinical thrombosis and side effect from aspirin will be recorded for at least 2 years after intervention.
Philadelphia negative Myeloproliferative neoplasms aged at least 18 years old
Concomitant other active malignancy or cured less than 6 months
Platelet count less than 50,000/microL
Receiving anticoagulant
Active peptic ulcer
Parallel
81-mg aspirin once daily
Drug81-mg aspirin once daily
81-mg aspirin twice daily
Drug81-mg aspirin twice daily
prevalence of aspirin resistance
Laboratory aspirin resistance is determined by light transmission aggregometry using arachidonic acid (0.5 g/L) as agonist and result of aggregation \>= 20% is defined as resistance.
The incidence of thrombotic events
The thrombotic events will be recorded for at least 2 years after intervention.
The cut-of-point of PFA200 to define aspirin resistance
The standard definition of aspirin resistance in this study is determined by light transmission aggregometry (LTA) using arachidonic acid (0.5 g/L) as agonist and the result of aggregation of \>=20% is defined as aspirin resistance. PFA200 is used in parallel with LTA method to determine the concordance of these two methods and to determine the appropriate cut-of-point of PFA200 method to define aspirin resistance.
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