Platelets
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Ticagrelor is a novel direct-acting P2Y12 receptor antagonist used for preventing atherothrombotic events in patients with acute coronary syndromes (ACS). The current recommended dose is 90 mg bid, but a low dose of ticagrelor has not been previously studied in Chinese ACS patients. Therefore, we performed this study to observe the different effects of half- and standard-dose ticagrelor on platelet aggregation in Chinese patients with NSTE-ACS. ⋯ There were no significant differences in PRU and IPA between the two ticagrelor groups (P = 0.3085 and 0.4028, respectively). HPR rates were significantly lower in the two ticagrelor groups (0% for both) than those in the clopidogrel group (35%). In conclusion, half-dose ticagrelor had a similar inhibitory effect on platelet aggregation as standard-dose ticagrelor in Chinese patients with NSTE-ACS, which was significantly stronger than that of clopidogrel.
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Cangrelor is a rapid-acting, direct-binding, and reversible P2Y12 antagonist which has been studied for use during percutaneous coronary intervention (PCI) in patients with or without pretreatment with an oral P2Y12 antagonist. As cangrelor is administered intravenously, it is necessary to switch to an oral P2Y12 antagonist following PCI, such as the thienopyridines clopidogrel, and prasugrel or the non-pyridine ticagrelor. Previous studies have suggested a negative pharmacodynamic interaction between cangrelor and thienopyridines. ⋯ The thienopyridine AMs had limited ability to compete with cangrelor for binding to P2Y12 (% P2Y12 receptor blockade after co-incubation with cangrelor 1000 nmol/L: 11.7% for clopidogrel AM 3 µmol/L; 34.1% for prasugrel AM 3 µmol/L). In conclusion, in vitro cangrelor strongly inhibits the binding of clopidogrel and prasugrel AMs to the P2Y12 receptor, consistent with the previous observation of a negative pharmacodynamic interaction. Care may need to be taken to not overlap exposure to thienopyridine AMs and cangrelor in order to reduce the risk of thrombotic complications following PCI.
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Platelet function tests are suggested to assess platelet reactivity before cardiac and major non-cardiac surgery. Different point-of-care platelet function tests are available. Among these, electric impedance platelet aggregometry (EIPA) (Multiplate®, MP) is one of the most widely used techniques. ⋯ Platelet function assessment with RP greatly differs from the equivalent MP measure, and no correction value can be applied due to the low level of precision. This applies both to ADPtest and TRAPtest. The MP ADPtest is more reliable for platelet reactivity after discontinuation of P2Y12 receptor inhibitors.
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Rapid assessment of platelet production would distinguish between thrombocytopenia due to decreased platelet production or increased peripheral platelet destruction. We evaluated the value of immature platelet fraction (IPF) in differentiating immune thrombocytopenia (ITP) from thrombocytopenia secondary to bone marrow failure and its potential use as a prognostic marker. Forty-one young patients with ITP were compared with 14 patients with hematological malignancies under chemotherapy, representing a control group with thrombocytopenia due to bone marrow suppression and 30 age- and sex-matched healthy controls. ⋯ ROC curve analysis revealed that the cut-off value of IPF at 9.4% could be diagnostic for ITP patients with a sensitivity of 88% and a specificity of 85.7%. We suggest that IPF may be a rapid and inexpensive automated marker for etiology of thrombocytopenia and can be integrated as a standard parameter to evaluate the thrombopoietic state of the bone marrow. It may be considered as a potential prognostic marker for the development of chronic ITP.