A Synthetic Evaluation Of Genetic and Pharmacological Resistance To Clopidogrel and On Treatment Residual Platelet Aggregation In Patients With Atherothrombosis

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3631-3631
Author(s):  
Grigoris T Gerotziafas ◽  
Severin Bouffard ◽  
Patrick Van Dreden ◽  
Amir Kartechi ◽  
Ilias Evmorfiadis ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Light Transmission ◽  
Conflicts Of Interest ◽  
Platelet Reactivity ◽  
Platelet Rich Plasma ◽  
Diagnostic Algorithm ◽  
Poor Response ◽  
Wild Type ◽  
Functional Assays ◽  
Pharmacological Response

Abstract Background Clopidogrel is cornerstone treatment for atherothrombotic patients. The incidence of recurrent thrombotic events raises up to 10% of patients on treatment with clopidogrel. Intestinal absorption via the glycoproteine ABCB1, bioactivation by the cytochrome P450 (CYP) system, binding to P2Y12 receptor and inhibition of platelet aggregation are critical steps for the efficiency of clopidogrel treatment. Prospective independent clinical trials showed that the risk of recurrent thrombotic complications is associated with the presence of common polymorphisms of genes encoding ABCB1 (rs1045642C>T) or the CYP2C19 isoenzyme (*2_rs4244285G>A, *3_rs4986893G>A, *4_rs28399504A>G) or the inefficiency of clopidogrel to decrease intracellular VASP or the presence of high residual platelet reactivity (HRPR). Aim To evaluate the available pharmacogenetic, pharmacological and functional assays for the diagnosis of the resistance to clopidogrel treatment on the same population of patients with atherothrombosis. Materials and Methods A cohort of 94 out-patients with atherothrombosis receiving clopidogrel treatment (75 mg o.d) for more than 3 months were included. Polymorphisms ABCB1, CYP *2, *3, *4, *17 were assessed with rPCR method. VASP was measured with flow cytometry assay and poor response (PR) to the treatment was diagnosed if VASP index was > 50. Light Transmission Platelet Aggregation (LTPA) triggered by ADP (5 ìM and 10 ìM) was assessed on citrated platelet rich plasma. Multielectrode aggregometry (WBMEA) was performed on citrated whole blood using Multiplate instrument and ADP reagent (ADP-test®). The cut-off point for the diagnosis of HRPR on clopidogrel treatment was the lower value of the maximum aggregation or the AUC observed in the upper quintile of ADP triggered LTPA or WBMEA measurements. Results The frequency of heterozygous for CYP*2, *3, *4 and ABCB 1 polymorphisms was 28%, 0%, 1%, and 51% respectively. The frequency of the respective homozygocity was 2%, 0%, 0%, and 20%. Patients heterozygous for the CYP*2 G>A polymorphism showed significantly higher VASP index as compared to the wild type but LTPA and WBMEA were not significantly different. VASP index, LTPA and WBMEA were not significantly different in patients heterozygous or homozygous for the ABCB1 C>T polymorphism as compared to the wild type. The VASP index was significantly correlated with the LTPA (r=0.44, p<0.0001) and WBMEA (r=0.376, p=0.001). In addition LTPA was significantly correlated with the WBMEA (r=0.46, p<0.0001). With the VASP assay 42% of patients were diagnosed as PR to clopidogrel. HRPR was found in 12% and 28% of patients tested with LTPA ADP 5 ìM and 10 ìM respectively and in 19% of patients tested with WBMEA. Among patients with HRPR the frequency of PR with the VASP assay was 60% when they were tested with LTPA ADP 10 ìM, 70% when they were tested with LTPA ADP 5 ìM and 76% when they were tested with WBMEA. Less than 50% of patients with HRPR had at least one of the studied polymorphisms. One patient homozygous for CYP*2 and ABCB1 was PR with the VASP assay and had HRPR with the WBMEA. Conclusion The present study performed on a cohort of patients with atherothrombosis on treatment with clopidogrel demonstrates that the genotype of CYP and ABCB1 polymorphisms have limited influence on the pharmacological response to the treatment and on the residual platelet reactivity. Among the studied polymorphisms only the CYP*2G>A was related with increase of VASP index and WBMEA. Pharmacological response to clopidogrel is correlated with the level of residual platelet reactivity. However 25-30% of patients with HRPR showed good pharmacological response to clopidogrel. The present study underlines the need to a synthetic use of bioassays for the evaluation of the risk of failure of clopidogrel treatment to prevent the recurrence of atherothrombosis. The need for the construction of a diagnostic algorithm including the genetic, pharmacological and functional assays is revealed by the present study. Disclosures: No relevant conflicts of interest to declare.

Fucosyltransferase VI Induces Platelet Activation: A Novel Property of a Plasma Glycosyltransferase.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4016-4016
Author(s):  
José-Tomás Navarro ◽  
Shwan Tawfiq ◽  
Roland Wohlgemuth ◽  
Karin M. Hoffmeister ◽  
Robert Sackstein
Keyword(s):  
Flow Cytometry ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Light Transmission ◽  
Conflicts Of Interest ◽  
Platelet Rich Plasma ◽  
Surface Protein ◽  
Surface Flow ◽  
Platelet Surface ◽  
Biochemical Studies

Abstract Abstract 4016 Poster Board III-952 A number of glycosyltransferases are present in human plasma with the α(1→3) fucosyltransferase, Fucosyltransferase VI (FTVI), having the highest plasma concentration. Notably, elevated plasma levels of FTVI are associated with a variety of cancers and correlate with tumor load/progression. The well-known association of neoplasia with thromboembolic complications prompted us to examine whether FTVI has direct effect(s) on platelet function. We obtained human platelets from blood of healthy donors and separated from platelet-rich plasma by differential centrifugation. Freshly isolated platelets (x108/ml) were stirred and exposed at 37°C to varying concentrations (20, 40, 60 and 80 mU/mL) of glycosyltransferases FTVI, β-1-4-galactosyltransferase-I (βGalT-I), or α,2-3-N-sialyltransferase (α2,3-N-ST), or to 1 U/mL thrombin. Platelet aggregation and activation was assessed by aggregometry (light transmission) or by flow cytometry of FSC/SSC characteristics and of surface expression of P-Selectin, respectively. FT-VI reproducibly induced platelet aggregation and activation, whereas other glycosyltransferases (β4GalT-I and α2,3-N-ST) had no effect on platelets. FTVI activation of platelets was concentration-dependent, and the aggregation curve for FTVI was one wave, similar to that for thrombin. FTVI-induced platelet activation was independent of catalytic conversion of surface glycans, but was inhibited by FTVI denaturation, indicating that FTVI-induced platelet activation is a lectin-mediated process. To determine the membrane target(s) mediating FTVI-induced platelet activation, biochemical studies were performed after catalytic exofucosylation of the platelet surface. Flow cytometry after platelet exofucosylation showed formation of the carbohydrate structure sLex, detected by the mAb Heca452, but no formation of Lex (CD15). Western blot showed that enforced fucosylation induced sLex on a single platelet surface protein, and further biochemical studies revealed that this protein is GPIbα. These findings unveil a previously unrecognized property of FTVI as an activator of platelets, mediated via a specific lectin/carbohydrate interaction on GP1ba, and offer novel perspectives on the pathobiology of tumor-associated thrombogenesis. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Use of increased concentrations of adenosinediphosphate for high residual platelet reactivity in patients with coronary heart disease

2021 ◽  
Vol 70 (1) ◽  
pp. 129-132
Author(s):  
O.A. Trubacheva ◽  
S.N. Belyaeva ◽  
T.E. Suslova ◽  
I.V. Petrova
Keyword(s):  
Coronary Heart Disease ◽  
Heart Disease ◽  
Platelet Aggregation ◽  
Antiplatelet Therapy ◽  
Light Transmission ◽  
Platelet Reactivity ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Transmission Curve ◽  
Platelet Suspension

Detection of a tendency to increased thrombosis in patients with coronary heart disease (CHD) is of important prognostic value in the selection of drugs aimed at achieving a persistent antithrombotic effect. The aim of the study was to evaluate the use of elevated ADP inducer concentrations to improve the accuracy of ADP-induced platelet aggregation in patients with coronary heart disease. Material and method. Material and method. We studied 48 patients with CHD who were on continuous double antiplatelet therapy for 6 months (aspirin 75mg and clopidogrel 75mg per day). The aggregation activity of the platelet suspension was studied using the Born method G. in the modification of Gabbasov Z. A. Platelet activity was evaluated by the degree of aggregation of platelet-rich plasma along the light transmission curve under the influence of the inducer adenosine diphosphate (ADP) at a concentration of 2 mmol/l and by its own patented method against the background of additional ADP application. Results. In patients, platelet aggregation decreased to 5-35% (p<0.005) compared to the standard values, which are 50-60%. The values of platelet aggregation with the additional introduction of the inducer of aggregation ADP in a ratio of 2:1 to 2 µmol/l for 1, 2, 3, and 4-minute registration of platelet aggregation, resulted in increased aggregation from 55% to 75% (p<0.001), indicating high residual platelet reactivity on the background of double antiplatelet therapy. Correlations of the degree of aggregation for elevated ADP concentrations with multivessel arterial lesion and dyslipidemia were also found, r=0.86 and r=0.92, respectively. Conclusion. The use of elevated concentrations of adenosine diphosphate in platelet aggregation in patients with ischemic heart disease increases the accuracy of assessing ADP-induced platelet aggregation against the background of dual antiplatelet therapy and contributes to the detection of high residual platelet reactivity.

Abstract T P341: Impact Of Cytochrome P450 2C19 Polymorphism On High On-treatment Platelet Reactivity In Stroke Patients Treated With Clopidogrel

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Tomotaka Tanaka ◽  
Shigeki Miyata ◽  
Haruko Yamamoto ◽  
Toshiyuki Miyata ◽  
Kazuyuki Nagatsuka ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Light Transmission ◽  
Platelet Reactivity ◽  
Platelet Rich Plasma ◽  
Metabolic Activation ◽  
Japanese Patients ◽  
Paraoxonase 1 ◽  
Loss Of Function ◽  
Stroke Patients ◽  
The Impact

BACKGROUND: Clopidogrel is one of the most commonly used anti-platelet drugs. Recent reports suggested the association of allelic variants of the genes modulating metabolic activation (CYP2C19 and paraoxonase-1) and bioavailability (ABCB1) of clopidogrel with high on-treatment platelet reactivity (HTPR), possibly resulting in the recurrence of thrombotic events. However, these studies mostly examined patients with coronary heart disease and the impact of these polymorphisms in stroke patients is largely unknown. METHODS: We conducted a multicenter, prospective cohort study of 518 Japanese patients from 14 hospitals who were administrated clopidogrel. Residual platelet reactivity was determined by a change in light transmission induced by platelet aggregation in platelet-rich plasma after adding ADP. The vasodilator-stimulated phosphoprotein (VASP) index was also measured using flow cytometry. We investigated the association of polymorphisms of aforementioned enzymes with HTPR. RESULTS: In terms of CYP2C19 loss-of-function polymorphisms (*2 and *3), the prevalence of intermediate (IM: *1*2 or *1*3) or poor (PM: *2*2, *2*3, or *3*3) metabolizer was much higher (IM: 47% or PM: 15%) in Japanese than in Caucasian populations. Residual platelet reactivity was significantly higher in PM and IM groups than that in the wild-type extensive metabolizer (EM: *1*1) group assessed by 5 μM ADP-induced platelet aggregation (PM: 69.4% ± 17.1%, IM: 59.7% ± 16.2%, EM: 51.5% ± 17.5%, p < 0.0001) and VASP index (PM: 66.6% ± 14.1%, IM: 52.4% ± 16.0%, EM: 42.9% ± 15.0%, p < 0.0001). Furthermore, HTPR determined by both assays was associated with the ABCB1 polymorphism (rs1045642) but not with the paraoxonase-1 Q192R mutation. CONCLUSIONS: Our results indicate that both CYP2C19 and ABCB1 polymorphisms significantly contribute to HTPR in stroke patients treated with clopidogrel. At present, we are monitoring these patients for a two-year period to determine whether these genetic variants and HTPR affect the recurrence of thrombotic events.

Pharmacological Study of Antimyeloma Agents on Hemostasis

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3175-3175
Author(s):  
François Mullier ◽  
Severine Robert ◽  
Philippe Devel ◽  
Lutfiye Alpan ◽  
Nicolas Lufin ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Platelet Aggregation ◽  
Thrombin Generation ◽  
Light Transmission ◽  
Conflicts Of Interest ◽  
Platelet Reactivity ◽  
Pharmacological Effects ◽  
Thrombin Activity ◽  
Increased Risk ◽  
Spontaneous Aggregation

Abstract Abstract 3175 Introduction: Patients with multiple myeloma (MM) have an increasing risk of developing venous thromboembolism (VTE). The use of thalidomide or lenalidomide, two antimyeloma agents has been associated with an increased risk of VTE especially when associated with dexamethasone or melphalan-prednisone. This increased risk in less pronounced with the proteasome inhibitor bortezomib. The pharmacological effects of thalidomide, lenalidomide and bortezomib have never been studied on platelet aggregation or coagulation. These preliminary data are necessary to understand the differential effects of these drugs on thrombotic events. Aims: The aim of our study is to investigate the pharmacological effects of these drugs on primary hemostasis by light transmission agregometry (LTA) and on secondary hemostasis using thrombin generation test (TGT). Methods: LTA was performed with a Chrono-Log aggregometer (Kordia). Platelet-rich plasma (PRP) of healthy blood donors (n=3 to 10) was adjusted to 300,000 platelets/μl. Platelet-poor plasma (PPP) and PRP were used respectively to adjust the photometric measurement to the minimum and maximum optical density. The platelet reactivity of the healthy donors was previously checked by LTA. Thalidomide (racemic, enantiomer (+) and enantiomer (-)), lenalidomide and bortezomib were spiked at final concentration of 200 μM in PRP except for studying the influence of thalidomide on ADP-induced platelet aggregation where the maximal concentration usable was 100 μM. LTA was performed without (spontaneous aggregation) and with addition of 5μM ADP, 190μg/ml collagen, 600μM arachidonic acid (AA) and 10 μM PAR1-AP (final concentrations). Negative controls (physiological saline and DMSO at concentrations used to dissolve the drugs) were also included. TGT was performed both on PPP (from normal pool plasma (NPP)) and on PRP. We first validated the method on NPP and PRP with two anticoagulants: a thrombin direct inhibitor (i.e. argatroban) and a FXa direct inhibitor (i.e. ZK-807834). Thalidomide ((+/−), (+) and (-)), lenalidomide and bortezomid were tested at the final concentrations of 5, 10, 50, 100 and 200 μM. For the experiments on NPP, PPP reagent (5 pM TF + 4 μM PL in the final assays), PPP reagent low (1 pM TF + 4 μM PL in the final assays) and MP reagent (4 μM PL in the final assays) were used whereas for the experiments on PRP, PRP reagent (1 pM TF in the final assays) was used. Results: LTA Both three drugs did not induce spontaneous aggregation until 200 μM. Lenalidomide and bortezomib showed no effect on induced platelet aggregation until 200 μM, whatever the agonist used. On the contrary, for racemic thalidomide, platelet aggregation was reduced at 50 and 100 μM with 5 μM ADP and at 150 and 200 μM with 600 μM AA. These effects were more pronounced with thalidomide (+) than with thalidomide (-). So, the half maximal inhibitory concentrations (IC50) for platelet aggregation induced by 600 μM AA were 127, 143 and 221 μM for racemic, enantiomer (+) and enantiomer (-), respectively. When 190μg/ml collagen or 10 μM PAR1-AP were used as agonists, no effect was observed on platelet aggregation until 200 μM thalidomide. TGT. With argatroban and ZK-807834, we observed a concentration-dependent decrease and delay of the thrombin activity profiles in PRP and NPP, whatever the inducer used. No significant effect on thrombin activity in NPP or PRP has been observed for antimyeloma drugs at all concentrations tested, whatever the inducer used. Conclusions: Lenalidomide, thalidomide and bortezomid do not induce spontaneous platelet aggregation and do not affect platelet aggregation induced by collagen or PAR1-AP. Conversely to lenalidomide and bortezomib, thalidomide, and especially its enantiomer (+), moderately inhibits platelet aggregation induced by ADP and AA. Moreover, these antimyeloma agents have no effect on thrombin generation. The increased risk of VTE by thalidomide or lenalidomide in patients with multiple myeloma is thus not mediated by a direct impact on primary or secondary hemostasis at therapeutic concentrations. Disclosures: No relevant conflicts of interest to declare.

Clopidogrel pretreatment in primary percutaneous coronary intervention: Prevalence of high on-treatment platelet reactivity and impact on preprocedural patency of the infarct-related artery

2013 ◽  
Vol 110 (07) ◽  
pp. 110-117 ◽  
Author(s):  
Javier Berdejo ◽  
Gerard Roura ◽  
Josep Gómez-Lara ◽  
Rafael Romaguera ◽  
Luis Teruel ◽  
...  
Keyword(s):  
Percutaneous Coronary Intervention ◽  
Primary Percutaneous Coronary Intervention ◽  
Light Transmission ◽  
Platelet Reactivity ◽  
Poor Response ◽  
Antiplatelet Agents ◽  
Coronary Intervention ◽  
Platelet Inhibition ◽  
Percutaneous Coronary ◽  
Infarct Related Artery

SummaryTo date, there is limited data on levels of platelet inhibition achieved in patients with ST-elevation myocardial infarction (STEMI) who are loaded with clopidogrel and aspirin (ASA) prior to undergoing primary percutaneous coronary intervention (P-PCI). The aim of this investigation was to evaluate the percentage of STEMI patients with high on-treatment platelet reactivity (HPR) to clopidogrel at the time of initiating P-PCI and its association with the initial patency of the infarct-related artery (IRA). This prospective pharmacodynamic study included 50 STEMI patients, previously naïve to oral antiplatelet agents, who received 500-mg ASA and 600-mg clopidogrel loading doses prior to P-PCI. Platelet function assessment was performed at the beginning of the procedure using various assays, including VerifyNow™ system (primary endpoint), light transmission aggregometry and multiple electrode aggregometry. The percentage of patients with suboptimal response to clopidogrel and ASA assessed with the VerifyNow™ system was 88.0% and 28.6%, respectively. Similar results were obtained with the other assays used. A higher percentage of patients with initial patency of the IRA was observed among those patients without HPR compared with those with HPR to clopidogrel (66.7% vs 15.9%; p=0.013), while no differences were observed regarding postprocedural angiographic or electrocardiographic outcomes. In conclusion, this study shows that a high percentage of STEMI patients have inadequate levels of clopidogrel-induced and, to a lesser extent, aspirin-mediated platelet inhibition when starting a P-PCI procedure, and suggests that a poor response to clopidogrel might be associated with impaired initial TIMI flow in the IRA.

Computerized Platelet Aggregation Analysis: A New Method

1979 ◽  
Author(s):  
J.A. Zeller ◽  
R.E. Dayhoff ◽  
R.S. Ledley ◽  
Y.G. Kulkarni
Keyword(s):  
Platelet Aggregation ◽  
Light Transmission ◽  
Platelet Rich Plasma ◽  
Aggregate Size ◽  
Size Group ◽  
Mean Values ◽  
Minute Period ◽  
Size Groups ◽  
Platelet Aggregates ◽  
Aggregation Analysis

Computerized Platelet Aggregation Analysis (CPAA) is a new direct, microscopic methedo-logy using image analysis to quantitate thousands of free platelets and aggregates in platelet rich plasma suspensions and determine the percentage of platelets present in discrete aggregate size groups. CPAA is sensitive to the earliest stages of platelet aggregation which are not recognized by light transmission aggregometry (0% change in light transmission). Platelets of ten normal irxiividuals aged 20-40 years were stimulated by a spin bar (SB) (1100 rpm) for a one minute and a ten minute period. The mean values are shown below for different aggregate size groups.There is no significant increase in the number of aggregates between one and ten mirais of stimulation except for size group 9-40, which shows a minimal increment (P .025). All platelet suspensions contained aggregates of size group 3-8 platelets/aggregate and 4 of 10 specimens had aggregates of size 9-40,No aggregates larger than 41 platelets were found. CPAA can also be applied to the study of larger sized platelet aggregates induced in abnormal individuals.

scholarly journals Both Complement- and Fibrinogen-Dependent Mechanisms Contribute to Platelet Aggregation Mediated by Staphylococcus aureus Clumping Factor B

2007 ◽  
Vol 75 (7) ◽  
pp. 3335-3343 ◽  
Author(s):  
Helen Miajlovic ◽  
Anthony Loughman ◽  
Marian Brennan ◽  
Dermot Cox ◽  
Timothy J. Foster
Keyword(s):  
Staphylococcus Aureus ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Lag Time ◽  
Dependent Manner ◽  
Wild Type ◽  
Factor B ◽  
Fibrinogen Binding ◽  
Aggregation Of Platelets ◽  
Dependent Mechanism

ABSTRACT Staphylococcus aureus can stimulate activation and aggregation of platelets, which are thought to be factors in the development of infective endocarditis. Previous studies have identified clumping factor A (ClfA) and fibronectin binding proteins A and B (FnBPA and FnBPB) as potent platelet aggregators. These proteins are able to stimulate rapid platelet aggregation by either a fibrinogen- or a fibronectin-dependent process which also requires antibodies specific to each protein. Slower aggregation has been seen in other systems where specific fibrinogen binding ligands are absent and platelet aggregation is mediated by complement and specific antibodies. Bacteria expressing ClfB aggregate platelets with a longer lag time than ClfA or FnBPA and FnBPB. In order to investigate whether ClfB causes platelet aggregation in a complement- or fibrinogen-dependent manner, a non-fibrinogen-binding mutant of ClfB (ClfB Q235A) was constructed. Lactococcus lactis expressing ClfB Q235A was able to stimulate platelet aggregation in platelet-rich plasma without a significant increase in lag time. The requirements for platelet aggregation were investigated using gel-filtered platelets. Fibrinogen and specific anti-ClfB antibodies were found to be sufficient to allow platelet aggregation mediated by the wild-type ClfB protein. It seems that ClfB causes platelet aggregation by a fibrinogen-dependent mechanism. The non-fibrinogen-binding ClfB mutant was unable to stimulate platelet aggregation under these conditions. However, bacteria expressing ClfB Q235A caused platelet aggregation in a complement-dependent manner which required specific anti-ClfB antibodies.

Assessment of ADP-induced platelet aggregation with light transmission aggregometry and multiple electrode platelet aggregometry before and after clopidogrel treatment

2008 ◽  
Vol 99 (01) ◽  
pp. 121-126 ◽  
Author(s):  
Siegmund Braun ◽  
Stefan Jawansky ◽  
Wolfgang Vogt ◽  
Julinda Mehilli ◽  
Albert Schömig ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Whole Blood ◽  
Light Transmission ◽  
Platelet Rich Plasma ◽  
Platelet Aggregometry ◽  
Light Transmission Aggregometry ◽  
Before And After ◽  
Standardized Method ◽  
Multiple Electrode

SummaryThe level of platelet aggregation, measured with light transmission aggregometry (LTA) in platelet rich plasma (PRP), has been shown to predict outcomes after percutaneous coronary intervention (PCI). However, measuring parameters of platelet function with LTA is time consuming and weakly standardized. Thus, a fast and standardized method to assess platelet function after clopidogrel treatment would be of great value for clinical practice. A new method, multiple electrode platelet aggregometry (MEA), to rapidly measure platelet aggregation in whole blood has recently been developed. The aim of this study was to assess parameters of platelet function with MEA and LTA before and after administration of 600 mg clopidogrel. Blood samples from 149 patients scheduled for coronary angiography were taken after clopidogrel treatment; in addition, in 60 of the patients samples were available before clopidogrel treatment. ADP-induced platelet aggregation was measured with LTA and simultaneously in whole blood with MEA on the Multiplate analyzer. Platelet aggregation measured with MEA decreased significantly after clopidogrel treatment (P<0.0001). ADP-induced platelet aggregation assessed with MEA and LTA correlated significantly (Spearman rank correlation coefficient=0.71; P<0.0001).The results of MEA, a fast and standardized method to assess the platelet response to ADP prior to and after clopidogrel treatment, correlate well with LTA.

scholarly journals Ticagrelor as an Alternative Antiplatelet Therapy in Cardiac Patients Non-Sensitive to Aspirin

Medicina ◽  
2020 ◽  
Vol 56 (10) ◽  
pp. 519
Author(s):  
Hamzah Khan ◽  
Reid Gallant ◽  
Shubha Jain ◽  
Mohammed Al-Omran ◽  
Charles De Mestral ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Antiplatelet Therapy ◽  
Light Transmission ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Alternative Therapy ◽  
Promising Alternative ◽  
Patients At Risk ◽  
Artery Disease

Background and Objectives: Aspirin (acetylsalicylic acid—ASA) is a first-line antiplatelet therapy provided to patients with coronary artery disease (CAD). However, it has been demonstrated that 20–30% of these patients are non-sensitive to their ASA therapy. ASA non-sensitivity is a phenomenon where low-dose ASA (81–325 mg) does not completely inhibit arachidonic-acid-induced platelet aggregation, putting patients at risk of adverse cardio-thrombotic events. Ticagrelor is a P2Y12 receptor inhibitor and alternative antiplatelet that has been approved to reduce the risk of stroke, myocardial infarction, and overall cardiovascular-related death. In this study, we aimed to identify ASA non-sensitive patients and evaluate if they would be sensitive to ticagrelor. Materials and Methods: For this pilot study, thirty-eight patients with CAD taking 81 mg ASA were recruited. Blood samples were collected from each patient and platelet rich plasma (PRP) from each sample was isolated. Light-transmission aggregometry (LTA) was used to determine baseline ASA sensitivity in each patient using 0.5 mg/mL arachidonic acid as a platelet agonist. Patients with ≥20% maximal platelet aggregation after activation were considered ASA non-sensitive. Fresh PRP samples from all patients were then spiked with a clinical dosage of ticagrelor (3 μM—approximately equivalent to a loading dose of 180 mg ticagrelor). Sensitivity was determined using LTA and 5 μM ADP as a platelet agonist. Patients with ≥46% maximal platelet aggregation were considered ticagrelor non-sensitive. Results: Of the 38 CAD patients taking 81 mg ASA, 32% (12/38) were non-sensitive to their 81 mg ASA therapy. All 38 of the recruited patients (100%) were sensitive to ticagrelor ex vivo. In conclusion, we were able to identify ASA non-sensitivity using LTA and determine that ASA non-sensitive patients were sensitive to ticagrelor. Conclusions: Our results suggest that ticagrelor is a promising alternative therapy for patients who are non-sensitive to ASA.

Reproducibility of Platelet Functional Assays under Agonist and Shear Conditions - Methods for Characterizing Platelet Reactivity.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3531-3531
Author(s):  
Donald L. Yee ◽  
Angela Bergeron ◽  
Carol Sun ◽  
William May ◽  
Jennifer Wood ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Clinical Laboratory ◽  
Interindividual Variability ◽  
Platelet Reactivity ◽  
Bimodal Distribution ◽  
Variance Component Analysis ◽  
Repeated Testing ◽  
Thrombotic Risk ◽  
Functional Assays

Abstract Clinical laboratory tests that reliably measure the contribution of platelets to thrombotic risk are virtually non-existent. Optimal testing of “platelet hyperreactivity” requires assays that are able to identify reproducible differences among individuals. We have studied over 280 healthy individuals with a panel of over 100 assays of platelet function. This panel includes measurements of aggregation, activation, receptor density and other candidate markers of platelet reactivity. Platelets were studied under conditions of agonist stimulation (including arachidonic acid, ADP, epinephrine, collagen, collagen related peptide and ristocetin) and under shear (from 0 to 10,000 sec-1). We assessed the reproducibility of these assays by studying a subgroup of 27 individuals (mean age=33 years, range=24–53 years, 30% males) four times each (108 total sets of studies). The time between each phlebotomy was one week. Subjects were asked to fast overnight and to refrain from certain exposures (e.g. heavy exercise, caffeine use) immediately prior to testing. The reproducibility of assay results was assessed using variance component analysis. We observed significant interindividual variability in most assays of platelet aggregation and activation. We established agonist concentrations that yield wide interindividual variability in maximal platelet aggregation. When these data are depicted on a histogram, a bimodal distribution is observed, with one group of subjects clearly demonstrating lower inherent aggregation (< 40%) and the other group exhibiting higher levels (>60%) (see figure for epinephrine example). We determined shear rates (0 to 2000 sec-1) and identified platelet receptors (CD32, GPIa-IIa, GPIb-IX-V) and markers of platelet activation (CD62P under shear and ADP stimulation) that maximized detection of differences between individuals while minimizing variations within subjects. Individual subjects demonstrated consistent results over time on repeated testing. We have thus identified a subset of platelet assays that demonstrate striking interindividual variability (overall coefficients of variation range from 0.15 to 0.9) while maintaining good reproducibility (contribution of intraindividual to overall variance < 35%). Other functional assays we have tested demonstrated poor reproducibility, such that they should not be utilized as measures of platelet reactivity. Using assay conditions and techniques not routinely utilized in clinical practice (but that could easily be adapted for such use), we have shown that different individuals demonstrate distinct levels of platelet reactivity. Despite only minimal restrictions on environmental exposures for these healthy subjects studied repeatedly over several weeks, these assays appear to reliably characterize individuals’ platelet reactivity and are appropriate candidates for its measurement in populations of patients at risk for thrombosis or bleeding. As these assays facilitate categorization of platelet reactivity, they may also be useful for the study of genetic and environmental influences on platelet function. Figure Figure

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