Comparison of a New P2Y12 Receptor Specific Platelet Aggregation Test with Other Laboratory Methods in Stroke Patients on Clopidogrel Monotherapy

BACKGROUND: Clinical studies suggest that 10-50% of patients are resistant to clopidogrel therapy. ADP induced platelet aggregation, a widely used test to monitor clopidogrel therapy, is affected by aspirin and is not specific for the P2Y12 receptor inhibited by clopidogrel. OBJECTIVES: To develop a P2Y12-specific platelet aggregation test and to compare it with other methods used for monitoring clopidogrel therapy. PATIENTS/METHODS: Study population included 111 patients with the history of ischemic stroke being on clopidogrel monotherapy and 140 controls. The effect of clopidogrel was tested by a newly developed ADP(PGE1) aggregation test in which prostaglandin E1 treated platelets are used. Results of conventional ADP induced platelet aggregation, VerifyNow P2Y12 assay and ADP(PGE1) aggregation were compared to those obtained by flow cytometric analysis of vasodilator stimulated phosphoprotein (VASP) phosphorylation. Reference intervals for all assays were determined according to the guidelines of Clinical Laboratory Standards Institute. RESULTS: The P2Y12-specificity of ADP(PGE1) test was proven by comparing it with ADP aggregation in the presence of P2Y1 antagonist, adenosine 3', 5'-diphosphate. The method was not influenced by aspirin treatment. Approximately 50% of patients were clopidogrel resistant by conventional ADP aggregation and VerifyNow tests. The ADP(PGE1) method and the VASP phosphorylation assay identified 25.9% and 11.7% of patients as non-responders, respectively. ADP(PGE1) aggregation showed good correlation with VASP phosphorylation and had high diagnostic efficiency. CONCLUSION: The new ADP(PGE1) method is a reliable test for monitoring P2Y12 receptor inhibition by platelet aggregation. As a subset of patients are non-responders, monitoring clopidogrel therapy by adequate methods is essential

Intracardiac hemostasis and fibrinolysis parameters in patients with atrial fibrillation

Aims. To identify intracardiac hemostasis or fibrinolysis abnormalities, which are associated with atrial fibrillation (AF) and increase the risk of thromboembolism. Patients and Methods. Patient group consisted of 24 patients with AF and control group included 14 individuals with other supraventricular tachycardia undergoing transcatheter radiofrequency ablation. Blood samples were drawn from the femoral vein (FV), left atrium (LA), and left atrial appendage (LAA) before the ablation procedure. Fibrinogen, factor VIII (FVIII) and factor XIII activity, von Willebrand factor (VWF) antigen, thrombin-antithrombin (TAT) complex, quantitative fibrin monomer (FM), plasminogen, α2-plasmin inhibitor, plasmin-α2-antiplasmin (PAP) complex, PAI-1 activity, and D-dimer were measured from all samples. Results. Levels of FVIII and VWF were significantly elevated in the FV and LA of AF patients as compared to controls. TAT complex, FM, PAP complex, and D-dimer levels were significantly elevated in the LA as compared to FV samples in case of both groups, indicating a temporary thrombotic risk associated with the catheterization procedure. Conclusions. None of the investigated hemostasis or fibrinolysis parameters showed significant intracardiac alterations in AF patients as compared to non-AF controls. AF patients have elevated FVIII and VWF levels, most likely due to endothelial damage, presenting at both intracardiac and systemic level

Intracardiac Fibrinolysis and Endothelium Activation Related to Atrial Fibrillation Ablation with Different Techniques

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PAI-1 5G/5G genotype is an independent risk of intracranial hemorrhage in post-lysis stroke patients

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How to test the effect of aspirin and clopidogrel in patients on dual antiplatelet therapy?

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Results of VerifyNow P2Y12 and VASP phosphorylation tests.

<p>VerifyNow P2Y12 (A) and VASP phosphorylation (B) tests were performed in the control group (solid circles) and in the group of patients on clopidogrel therapy (open circles). Horizontal lines represent medians, the long broken line indicates the lower limit of reference interval, the long dotted line on panel B shows the cut-off for clopidogrel resistance established in clinical studies [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069417#B4" target="_blank">4</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069417#B5" target="_blank">5</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069417#B12" target="_blank">12</a>]. NR: non-responder, WR: weak responder, SR: strong responder.</p

Correlation of ADP-induced aggregation in platelet rich plasma pre-treated with PGE1 or with P2Y1 inhibitor.

<p>Platelet rich plasma was pre-treated with 0.31 µM PGE1 or 1 mM adenosine 3’, 5’-diphosphate (A3P5P), a P2Y1 receptor inhibitor, for 3 min at 37 °C. Broken lines represent 95% confidence interval, r=0.89, p=0.001.</p

Correlation of VASP phosphorylation and P2Y12 specific ADP(PGE1) aggregation tests in clopidogrel treated patients.

<p>Broken lines represent the lower limit of reference intervals, dotted lines separate presumed strong responders from weak responders. NR: non-responder, WR: weak responder, SR: strong responder.</p