Evaluation of the role of the new INNOVANCE PFA P2Y test cartridge in detection of clopidogrel resistance

Identification of High Platelet Reactivity Despite ADP P2Y 12 Inhibitor Treatment: Two Populations in the Vasodilator-Stimulated Phosphoprotein Assay and Variable PFA-P2Y Shapes of Curve

Introduction  Response to ADP P2Y ₁₂ receptor inhibition by clopidogrel can be evaluated by various techniques. Here, we compared a functional rapid point-of-care technique (PFA-P2Y) with the degree of biochemical inhibition assessed by the VASP/P2Y ₁₂ assay. Methods  Platelet response to clopidogrel was investigated in 173 patients undergoing elective intracerebral stenting (derivation cohort n  = 117; validation cohort n  = 56). High platelet reactivity (HPR) was defined as PFA-P2Y occlusion time <106 seconds or VASP/P2Y ₁₂ platelet reactivity index (PRI) >50%. Results  In the derivation cohort, receiver operator characteristics analysis for the ability of PFA-P2Y to detect biochemical HPR showed high specificity (98.4%) but poor sensitivity (20.0%) and a very low area under the curve (0.59). The VASP/P2Y ₁₂ assay revealed two coexisting platelet populations with different levels of vasodilator-stimulated phosphoprotein (VASP) phosphorylation: a fraction of highly phosphorylated, inhibited platelets and another of poorly phosphorylated, reactive platelets. Analysis of the PFA-P2Y curve shape revealed different types, categorized by time of occlusion (<106 seconds, 106 to 300 seconds, >300 seconds), and pattern (regular, irregular, and atypical). Noteworthy, curves with late occlusion and permeable curves with an irregular or atypical pattern correlated with VASP-PRI >50% and smaller sizes of the inhibited platelet subpopulation. Considering the PFA-P2Y shape of the curve for the detection of HPR improved sensitivity (72.7%) and preserved specificity (91.9%), with a rather high AUC (0.823). The validation cohort confirmed the VASP/P2Y ₁₂ assay data and the usefulness of considering the PFA-P2Y curve shape. Conclusion  In patients treated with acetylsalicylic acid and clopidogrel for 7-10 days, the VASP/P2Y ₁₂ assay reveals two coexisting subpopulations of differentially inhibited platelets, whose relative sizes predict global PRI and distinct PFA-P2Y curve patterns, indicating incomplete clopidogrel efficacy. The detailed analysis of both VASP/P2Y ₁₂ and PFA-P2Y is necessary for optimal detection of HPR.

Comparison of Clopidogrel, Prasugrel and Ticagrelor Response of Patients by PFA-100-Innovance Test Results

Devices such as stents and flow diverters require the use of safe and fast antiplatelet therapy. We aimed to compare the responses to clopidogrel, prasugrel, and ticagrelor by assessing the Platelet Function Analysis (PFA-100)-Innovance test results of patients undergoing endovascular stenting to determine their resistance rates. Sixty-one women and 55 men, aged 18-87 years, were included in this study. Patients were divided into three groups: clopidogrel treatment, prasugrel treatment, and ticagrelor treatment. The systemic diseases of the patients, especially hypertension and diabetes, were recorded. The test results were evaluated according to the results for the collagen/epinephrine (COL-EPI), collagen/adenosine (COL-ADP), and P2Y results. The PFA-100-Innovance results for COL-EPI and P2Y were significantly higher for patients treated with prasugrel and ticagrelor compared with patients treated with clopidogrel (COL-EPI, p = 0.001; P2Y, p = 0.001). Clopidogrel resistance was identified in 31 patients (26.7%), and prasugrel resistance was identified in 4 patients (3.4%). Ticagrelor resistance was not detected. Therefore, 30.1% of patients were classified as drug-resistant. Perioperative bleeding was not detected in any patient. Hypertension was the most common disease recorded for patients being treated for cerebral aneurysm, and diabetes was the most common disease recorded for patients who underwent peripheral artery stenting (p = 0.002). Potent antiplatelet agents, such as prasugrel and ticagrelor, have a low rate of resistance but are associated with an increased bleeding risk. Thus, the choice of a suitable drug during the treatment window remains a critical factor when determining treatment strategies.

Ticagrelor Resistance in Cardiovascular Disease and Ischemic Stroke

Ticagrelor, acting as a reversible platelet aggregation inhibitor of P2Y12 receptors (P2Y12R), is regarded as one of the first-line antiplatelet drugs for acute cardiovascular diseases. Though the probability of ticagrelor resistance is much lower than that of clopidogrel, there have been recent reports of ticagrelor resistance. In this review, we summarized the clinical application of ticagrelor and then presented the criteria and current status of ticagrelor resistance. We further discussed the potential mechanisms for ticagrelor resistance in terms of drug absorption, metabolism, and receptor action. In conclusion, the incidences of ticagrelor resistance fluctuated between 0 and 20%, and possible mechanisms mainly arose from its absorption and receptor action. Specifically, a variety of factors, such as the drug form of ticagrelor, gut microecology, and the expression and function of P-glycoprotein (P-gp) and P2Y12R, have been shown to be associated with ticagrelor resistance. The exact mechanisms of ticagrelor resistance warrant further exploration, which may contribute to the diagnosis and treatment of ticagrelor resistance.

Novel Platelet Function Analyzer 200 Predicts Blood Transfusion After Elective Cardiac Surgery in Patients Suspended on Dual Antiplatelet Therapy

The value of platelet function test in timing of cardiac surgery remains uncertain. Researches on correlation between Platelet Function Analyzer 200 (PFA-200) and bleeding after elective cardiac surgery are still inadequate. The objective of this study was to investigate the predictive value of PFA-200 in blood transfusion after cardiac surgery. A total of 71 patients on aspirin and P2Y12 receptor inhibitors undergoing cardiac surgery in Fuwai Hospital were enrolled. Platelet function after discontinuing of antiplatelet drugs was assessed by PFA-200 using closure time (CT). PFA-200 results before surgery were included in the statistics. The primary endpoint was postoperative blood transfusion. Seventeen patients (21.9%) received blood transfusion after cardiac surgery. The preoperative PFA-200 CT value in the transfused group was significantly higher than that in the non-transfused group (147.24 ± 85.54 s vs 98.06 ± 61.59 s, P = .011). Using 106 seconds as the dividing point, the incidence of blood transfusion in the elevated PFA-200 (CT > 106 s) group was significantly higher than those in normal PFA-200 (CT ≤ 106 s) group (10/24 patients, 41.9% vs 7/47 patients, 14.7%, P = .012). Multivariate logistic regression analysis showed that PFA-200 CT value > 106 s was an independent predictor of postoperative blood transfusion (OR: 4.05, 95%CI: 1.19-13.86, P = .026). The platelet function test PFA-200 had a predictive value for postoperative blood transfusion in elective cardiac surgery and had a promising prospect in the timing of cardiac surgery.

Monitoring of Antiplatelet Therapy

In the late 1990s, the antithrombotic antiplatelet agent, clopidogrel, a P2Y12 inhibitor, was introduced. Around the same time, there was an increase in a number of new methods to measure platelet function (e.g., PFA-100 in 1995), and this has continued. It became evident that not all patients responded to clopidogrel in the same way and that some patients had a relative "resistance" to therapy, termed "high on-treatment platelet reactivity." This then led to some publications to advocate platelet function testing being used for patients on antiplatelet therapy. Platelet function testing was also suggested for use in patients awaiting cardiac surgery after stopping their antiplatelet therapy as a way of balancing thrombotic risk pre-surgery and bleeding risk perioperatively. This chapter will discuss some of the commonly used platelet function tests used in these settings, particularly those that are sometimes referred to as point-of-care tests or that require minimal laboratory sample manipulation. The latest guidance and recommendations for platelet function testing will be discussed following several clinical trials looking at the usefulness of platelet function testing in these clinical settings.

Screening and diagnosis of inherited platelet disorders

Inherited platelet disorders are important conditions that often manifest with bleeding. These disorders have heterogeneous underlying pathologies. Some are syndromic disorders with non-blood phenotypic features, and others are associated with an increased predisposition to developing myelodysplasia and leukemia. Platelet disorders can present with thrombocytopenia, defects in platelet function, or both. As the underlying pathogenesis of inherited thrombocytopenias and platelet function disorders are quite diverse, their evaluation requires a thorough clinical assessment and specialized diagnostic tests, that often challenge diagnostic laboratories. At present, many of the commonly encountered, non-syndromic platelet disorders do not have a defined molecular cause. Nonetheless, significant progress has been made over the past few decades to improve the diagnostic evaluation of inherited platelet disorders, from the assessment of the bleeding history to improved standardization of light transmission aggregometry, which remains a "gold standard" test of platelet function. Some platelet disorder test findings are highly predictive of a bleeding disorder and some show association to symptoms of prolonged bleeding, surgical bleeding, and wound healing problems. Multiple assays can be required to diagnose common and rare platelet disorders, each requiring control of preanalytical, analytical, and post-analytical variables. The laboratory investigations of platelet disorders include evaluations of platelet counts, size, and morphology by light microscopy; assessments for aggregation defects; tests for dense granule deficiency; analyses of granule constituents and their release; platelet protein analysis by immunofluorescent staining or flow cytometry; tests of platelet procoagulant function; evaluations of platelet ultrastructure; high-throughput sequencing and other molecular diagnostic tests. The focus of this article is to review current methods for the diagnostic assessment of platelet function, with a focus on contemporary, best diagnostic laboratory practices, and relationships between clinical and laboratory findings.

Comparison of acetylsalicylic acid and clopidogrel non-responsiveness assessed by light transmittance aggregometry and PFA-100® in patients undergoing neuroendovascular procedures

Objectives

Dual platelet inhibition is commonly used for prevention of cardiovascular events in patients undergoing neuroendovascular procedures. Non-responsiveness to platelet inhibitors may be associated with adverse outcomes. The aim of this study was to evaluate the reliability of the platelet function analyzer PFA-100® in comparison to light transmittance aggregometry (LTA) for monitoring clopidogrel and acetylsalicylic acid (ASA) non-responsiveness in a cohort of patients treated for intracranial aneurysm or cranial artery stenosis.

Methods

Non-responsiveness to clopidogrel and ASA was assessed by LTA using adenosine diphosphate (ADP) and arachidonic acid and by PFA-100® with the ADP/prostaglandin E1 (PGE1) and collagen/epinephrine cartridges, respectively.

Results

A total of 203 patients (145 females; median age, 57 years) were analyzed. Agreement between the two tests was poor for clopidogrel non-responsiveness (ƙ=0.19) and not better than chance for ASA non-responsiveness (ƙ=0.01). Clopidogrel non-responsiveness by LTA and PFA-100® was associated with higher von Willebrand factor antigen and activity levels. ADP-induced platelet disaggregation was lower in patients with clopidogrel non-responsiveness as assessed by PFA-100®. Clopidogrel non-responsiveness by LTA was associated with a higher prevalence of diabetes and a higher body mass index (BMI). Adverse outcomes (death, thromboembolism, or in-stent thrombosis) occurred in 13% (n=26) of all patients independently of ASA and clopidogrel non-responsiveness as assessed by both devices.

Conclusions

Our results show that LTA and PFA-100® are not interchangeable in the assessment of ASA and clopidogrel non-responsiveness in patients undergoing neuroendovascular interventions.

Current methods of measuring platelet activity: pros and cons

: Platelets play a pivotal role in controlling hemorrhaging from vessels of the human body. The impairment of platelets may lead to the development of bleeding manifestations. Unraveling the precise defects of platelets by means of suitable laboratory methods paves the way for the effective control and management of platelet disorders. Choosing the most appropriate approach for the detection of platelet disorders may be difficult for a researcher or clinical internist when faced with ordering a platelet-function test. The aim of the current study was to provide a user-friendly overview of the advantages and disadvantages of the available detection systems. To reach this goal, 11 commonly used methods of studying platelet activity were evaluated and compared in detail. A literature search, with no time or language limitations, was conducted in Google Scholar and Medline. All publications published before June 2019 were analyzed. The following laboratory methods were compared: number and size of platelets, bleeding time, clot retraction time, platelet function assay 100 & 200, Rapid platelet function assay, flow cytometry, light transmission aggregometry, multiple electrode aggregometry, 96-well plate aggregometry, cone and plate(let) analyzer (Impact-R), and Plateletworks (single platelet counting system). This article provides the reader with a rapid comparison of the different systems used to study platelets activities.

A comparison of three platelet function tests in ischemic stroke patients with antiplatelet therapy

Predicting the effectiveness of antiplatelet drugs is critical to precision antiplatelet therapy. However, there is a lack of an acceptable method, although there are a variety of methods for detecting platelet function. In this study, we compared three major platelet function tests to assess their performance and found better methods for platelet function evaluation after aspirin or clopidogrel treatment in ischemic stroke patients by comparative study. A total of 249 ischemic stroke patients were enrolled who were treated with aspirin or clopidogrel or both. Three platelet function tests including light transmittance aggregometry (LTA), thromboelastography (TEG), platelet function analyzer (PFA) were performed as well as CYP2C19 genotype determination. Correlation analyses and kappa statistics were used. All three methods were effective in evaluating aspirin function. However, only LTA and TEG had good correlation and consistency (r = -0.37, kappa = 0.634). TEG-ADP was the least sensitive for clopidogrel, as the platelet inhibition ratio did not differ between the clopidogrel-user group and the control (P = 0.074), while LTA and PFA were sensitive (P ＜ 0.001). Correlations between platelet assays were poor for clopidogrel (the absolute value of r range from 0.13 to 0.35) and so was the agreement (Kappa from 0.232 to 0.314). LTA and PFA have a good correlation with CYP2C19 genotyping (P = 0.034 and 0.014). In conclusion, all three tests were able to evaluate aspirin effect, LTA-AA and TEG-AA had a good correlation. TEG perform badly for clopidogrel effect detection. The fair-to-modest agreement among assays indicated further study was indispensable.

Effects of clopidogrel and prednisone on platelet function in healthy dogs

Background

Glucocorticoids cause hypercoagulability, but it is unknown if they counteract clopidogrel's antiplatelet effects.

Hypothesis/Objectives

Determine the effects of clopidogrel and prednisone on platelet function.

Animals

Twenty‐four healthy dogs.

Methods

Double‐blinded, placebo‐controlled randomized trial. Platelet function was evaluated using a platelet function analyzer and impedance aggregometry (days 0, 14, and 28) for dogs treated with placebo, clopidogrel (2‐3 mg/kg/d), prednisone (2 mg/kg/d), or prednisone with clopidogrel PO for 28 days. Results were categorized as nonresponder versus responder (platelet function analyzer), and inadequate, ideal, or excessive response (aggregometry). Results were compared using mixed model, split‐plot repeated measures analysis of variance and generalized estimating equation proportional odds models. P < .05 was considered significant.

Results

Closure times differed by treatment (F [3, 20] = 10.5; P < .001), time (F [2, 40] = 14.3; P < .001), and treatment‐by‐time (F [6, 40] = 3.4; P = .01). Area under the curve (AUC) differed by treatment (F [3, 20] = 19.6; P < .001), time (F [2, 40] = 35.4; P < .001), and treatment‐by‐time (F [6, 40] = 13.5; P < .001). Based on closure times, 5/6 dogs each in the clopidogrel and prednisone/clopidogrel groups were responders. All dogs in the prednisone/clopidogrel group were overcontrolled based on AUC (days 14 and 28), whereas 5/6 (day 14) and 2/6 (day 28) dogs treated with clopidogrel were overcontrolled. Compared to clopidogrel, dogs receiving prednisone/clopidogrel were 11 times (P = .03) more likely to have an excessive response.

Conclusions and Clinical Importance

Administration of clopidogrel/prednisone increases platelet dysfunction in healthy dogs.

β-Amyloid and mitochondrial-derived peptide-c are additive predictors of adverse outcome to high-on-treatment platelet reactivity in type 2 diabetics with revascularized coronary artery disease

BACKGROUND AND AIMS

Increased β-amyloid and decreased mitochondrial-derived peptide (MOTS-c), are reported in diabetes. We investigated their additive value to high on-clopidogrel platelet reactivity (HPR) for adverse outcome in type 2 diabetics after recent revascularization.

PATIENTS AND METHODS

In 121 type II diabetics, treated with clopidogrel and aspirin, (93 males, mean age 67.2 years) we measured: (a) maximum platelet aggregation to adenosine diphosphate (ADP) by light transmission aggregometry (LTAmax), (b) malondialdehyde (MDA), as oxidative stress marker, (c) MOTS-c, (d) β-amyloid blood levels. Cardiac death and acute coronary syndromes (MACE) were recorded during 2 years of follow-up.

RESULTS

Out of 121 patients, 32 showed HPR (LTAmax > 48%,). At baseline, HPR was associated with β-amyloid > 51 pg/ml (p = 0.006) after adjusting clinical variables, HbA1c, MOTS-c, MDA and medication. During follow-up, 22 patients suffered a MACE. HPR, β-amyloid > 51 pg/ml and MOTS-c < 167 ng/ml were predictors of MACE (relative risk 3.1, 3.5 and 3.8 respectively, p < 0.05) after adjusting for confounders and medication. There was significant interaction between HPR and β-amyloid or MOTS-c for the prediction of MACE (p < 0.05). Patients with HPR and β-amyloid > 51 mg/dl or HPR and MOTS-c concentration < 167 ng/ml had a fourfold higher risk for MACE than patients without these predictors (relative risk 4.694 and 4.447 respectively p < 0.01). The above results were confirmed in an external validation cohort of 90 patients with diabetes and CAD.

CONCLUSIONS

Increased β-amyloid or low MOTS-c are additive predictors to high on-clopidogrel platelet reactivity for adverse outcome in diabetics with CAD during 2-years follow-up. Clinical Trial Registration-URL: https://www.clinicaltrials.gov. Unique identifier: NCT04027712.

Interaction of CYP2C19 G681A polymorphism and omeprazole on clopidogrel responsiveness and impact in patients with acute coronary syndrome

OBJECTIVE

The aim of this study was to explore the individual effects of the CYP2C19 G681A polymorphism and omeprazole use and their interaction on clopidogrel responsiveness in acute coronary syndrome (ACS). The CYP2C19 G681A polymorphism and omeprazole use were both known for retarding the effects of clopidogrel under broad cardiovascular conditions; however, data from ACS patients were limited.

METHODS

We conducted a cross-sectional study of 102 ACS patients who received clopidogrel before percutaneous coronary intervention. The platelet function was assessed by a Platelet Function Analyzer-200, in which clopidogrel hyporesponsiveness was defined as a closure time (CT) of ≤ 106 s. The CYP2C19 G681A polymorphism was investigated using the PCR-RFLP technique. Statistical analysis was performed by using χ test, Student's t-test, binary logistic regression, and receiver-operating characteristic (ROC) curve.

RESULTS

Carriages of the CYP2C19 681A allele and omeprazole use were present in 47.1 and 37.3% patients, respectively. The mean CT ± SD was 103.1 ± 1.7 s and the prevalence of clopidogrel hyporesponsiveness was 66.7%. The CT was significantly shorter in carriages of the 681A allele compared with the 681G allele (P = 0.002), but had no significant difference in patients with vs. without omeprazole use (P = 0.467). The ROC analysis of an effect on clopidogrel hyporesponsiveness of CYP2C19 G681A alone and combination with omeprazole use had area under the curve values of 0.654 and 0.672, respectively.

CONCLUSION

In ACS patients, the effect of the CYP2C19 G681A polymorphism on clopidogrel responsiveness, but not omeprazole use, is strong. However, a combination of both factors enhances clopidogrel hyporesponsiveness.

The prognostic value of multiple electrode aggregometry and light transmittance aggregometry in stable cardiovascular patients with type 2 diabetes mellitus

AIM

Limited data are available regarding the clinical relevance of platelet function measurements in stable patients with coronary artery disease (CAD). Our aim is to evaluate the agreement between multiple electrode aggregometry (MEA) and light transmittance aggregometry (LTA) in detecting clopidogrel low responders and their prognostic value in CAD patients with type 2 diabetes mellitus (T2DM) on dual platelet inhibition.

METHODS

LTA and MEA were performed in 122 stable cardiovascular patients with T2DM. The upper quartile of patients according to maximum LTA (LTAmax) and MEA measurements were defined as clopidogrel low responders. Agreement between the two methods was evaluated by kappa statistics. We assessed the potential correlation between antiplatelet response and clinical outcome and the optimal cutoff value according to ROC analysis to predict the occurrence of major adverse cardiovascular events (MACE), during 1-year follow-up period.

RESULTS

Cohen's kappa coefficients (0.214) indicated fair agreement (70.2%) between LTA and MEA. A total of 25 MACE occurred in 108 patients (23.1%). Patients with MACE had higher LTAmax than those without (57.1 ± 16.5 vs 49.3 ± 18.3, respectively, p = 0.023). MEA measurements were similar between patients with and without MACE (30.1 ± 15.4 vs 30.6 ± 20.8, respectively; p = 0.84). Multiple logistic regression showed LTAmax response as an independent predictor of death from cardiovascular causes (Odds Ratio, adjusted:0.2;0.05-0.81). ROC analysis indicated that LTAmax cutoff of 62.5% best predicted death (AUC = 0.67, sensitivity = 78%, specificity = 61.5%).

CONCLUSIONS

The assessment of platelet responsiveness remains highly test-specific. Our results support the prognostic role of LTA, but not MEA testing, for death risk evaluation in stable cardiovascular T2DM patients.

Platelet Function Testing in Neurovascular Procedures: Tool or Gimmick?

Background

Platelet inhibitors are used to prevent thromboembolic complications related to neurovascular stenting (NVS) procedures. Despite substantial inter-individual variability of functional platelet inhibition, the value of platelet function tests (PFT) to assess inhibition remains controversial.

Objective

This study was conducted to compare differences in thromboembolic complication rates associated with NVS in platelet-inhibited patients with and without PFT. Clinical neurological outcomes were assessed by differences in the modified Rankin Scale (mRS).

Materials and Methods

One hundred seventeen consecutive patients underwent elective NVS procedures within a 7-year period. All patients received aspirin and clopidogrel 8 days before the procedure. Fifty-two patients were treated without assessment of platelet inhibition, and 65 patients were tested for clopidogrel resistance. When clopidogrel resistance was revealed, corresponding patients were converted to ticagrelor. Changes in mRS and thromboembolic event rates were compared between the 2 cohorts.

Results

Thirty-five percent of patients from the cohort subjected to PFT tests showed inadequate platelet inhi-bition under clopidogrel and were converted to ticagrelor. Compared to the non-PFT test -cohort, neurological deficits were significantly reduced (12 vs. 0%; p = 0.009) and a lower number of thromboembolic events was found (12 vs. 3%; p > 0.05) within the test cohort.

Conclusion

PFT appears to identify patients with clopidogrel resistance prior to NVS procedures. When non-responders are converted to alternative platelet inhibitors, neurological outcomes and thromboembolic complication rates may improve. Consequently, this study provides preliminary evidence that PFT may be a useful clinical tool to enhance procedural safety and improve clinical outcomes in NVS procedures.

Comparative evaluation of Plateletworks, Multiplate analyzer and Platelet function analyzer-200 in cardiology patients

The objective of this study was to comparatively evaluate three commercial whole-blood platelet function analyzer systems: Platelet Function Analyzer-200 (PFA; Siemens Canada, Mississauga, Ontario, Canada), Multiplate analyzer (MP; Roche Diagnostics International Ltd., Rotkreuz, Switzerland), and Plateletworks Combo-25 kit (PLW; Helena Laboratories, Beaumont, TX, USA). Venipuncture was performed on 160 patients who visited a department of cardiology. Pairwise agreement among the three platelet function assays was assessed using Cohen's kappa coefficient and percent agreement within the reference limit. Kappa values with the same agonists were poor between PFA-collagen (COL; agonist)/adenosine diphosphate (ADP) and MP-ADP (-0.147), PFA-COL/ADP and PLW-ADP (0.089), MP-ADP and PLW-ADP (0.039), PFA-COL/ADP and MP-COL (-0.039), and between PFA-COL/ADP and PLW-COL (-0.067). Nonetheless, kappa values for the same assay principle with a different agonist were slightly higher between PFA-COL/ADP and PFA-COL/EPI (0.352), MP-ADP and MP-COL (0.235), and between PLW-ADP and PLW-COL (0.247). The range of percent agreement values was 38.7% to 73.8%. Therefore, various measurements of platelet function by more than one method were needed to obtain a reliable interpretation of platelet function considering low kappa coefficient and modest percent agreement rates among 3 different platelet function tests.

Platelet Function Analyzer-200 P2Y Results Are Predictive of the Risk of Major Adverse Cardiac Events in Korean Patients Receiving Clopidogrel Therapy Following Acute Coronary Syndrome

BACKGROUND

Clopidogrel is one of the most commonly used anti-platelet agents in cardiovascular diseases. We analyzed the relationship between the platelet function analyzer (PFA)-200 P2Y (INNOVANCE PFA-200 System, Siemens Healthcare, Germany) results and occurrence of major adverse cardiac events (MACEs) in Korean patients with recent-onset acute coronary syndrome (ACS) taking clopidogrel.

METHODS

Between August 2013 and June 2016, we prospectively enrolled 106 patients with recent-onset ACS who had been treated with clopidogrel. We obtained blood samples and measured closure time (CT) using the PFA-200 P2Y test. Patients were divided into two groups on the basis of a CT cut-off value of 106 seconds. We compared patient characteristics and various MACEs that occurred during the follow-up period.

RESULTS

The CTs for 78 patients exceeded the cut-off value. At the time of these analyses, 11 patients had been diagnosed with MACEs. In the time-to-event analysis, there was a difference between the two groups (P<0.001). After adjusting other variables associated with MACE occurrence, CT value was the strongest predictor of MACEs, with a 7.30-fold occurrence risk (P=0.002).

CONCLUSIONS

We found a strong relationship between CT and MACE risk in Korean patients with recent-onset ACS taking clopidogrel. Accordingly, PFA-200 P2Y results could be used as a predictive marker for MACE risk in such patients.

Point of Care Tests VerifyNow P2Y12 and INNOVANCE PFA P2Y Compared to Light Transmittance Aggregometry After Fibrinolysis

Detection of high on-treatment platelet reactivity (HPR) by point-of-care tests has not been validated after successful fibrinolysis for ST-elevation myocardial infarction. We assessed the validity of the point-of-care VerifyNow P2Y12 (VN) and INNOVANCE PFA P2Y (PFA) tests on HPR compared to light transmittance aggregometry (LTA) in these patients. The HPR was identified in 10 (34.5%) patients, 15 (51.7%) patients, and 14 (50%) patients using LTA, VN, and PFA, respectively. Discrepancies were observed between the tests despite significant correlations between platelet reactivity measures by LTA and VN (r = 0.74; P < .0001) and LTA and PFA (r = .75; P < .0001). Compared to LTA, VN and PFA were associated with a 92% and 53% and 92% and 64% positive predictive value (PPV) and negative predictive value (NPV), respectively, in detecting HPR. When combined, VN and PFA results yielded 90% and 100% PPV and NPV values if discrepancies between the 2 tests were considered as non-HPR. The VN or PFA identify patients without HPR correctly but overestimate the proportion of HPR patients. The association of the 2 tests, in case of HPR, improves the accuracy of the detection of HPR.

Comparison of current platelet functional tests for the assessment of aspirin and clopidogrel response

The two most widely used antiplatelet drugs in the world are aspirin and clopidogrel. However, some patients on aspirin and/or clopidogrel therapy do not respond appropriately to either aspirin or clopidogrel. This phenomenon is usually called “aspirin/clopidogrel resistance”. Several platelet function tests have been used in various studies for the assessment of aspirin and clopidogrel resistance in healthy individuals and patients admitted in cardiology departments. An accurate assessment of platelet response to aspirin/clopidogrel could benefit patients by proposing tailored-antiplatelet therapy based on test results. However, there is a clear lack of standardisation of such techniques and their analytical variability may induce misinterpretation. After a quick report of the mechanisms responsible for aspirin/clopidogrel resistance, we describe the pre-analytical aspects and the analytical performances of current platelet function tests (Light-transmission aggregometry, whole-blood aggregometry, VerifyNow®, Platelet Function Analyzer®, thromboelastography, VASP assay) that are used for the assessment of aspirin/clopidogrel resistance in clinical studies. Considering the different variables that have to be taken into account with each of the platelet function tests, a particular attention should be paid when interpreting results.

Comparison of pharmacodynamic effects of ticagrelor vs prasugrel in type 2 diabetes mellitus patients with coronary heart disease

WHAT IS KNOWN AND OBJECTIVE

Patients with type 2 diabetes mellitus (T2DM) are at higher risk of thrombotic complications. Studies have indicated that patients with T2DM have impaired clopidogrel-induced antiplatelet effect. Ticagrelor and prasugrel are two latest generation P2Y₁₂ inhibitors with advantageous platelet inhibitory profiles. However, the pharmacodynamic differences between the two drugs in patients with T2DM remain poorly explored.

METHODS

This study, involving 140 patients with T2DM following percutaneous coronary intervention (PCI), evaluated the efficacy of aspirin upon concomitant use of prasugrel (10 mg/d) or ticagrelor (90 mg/d). Platelet reactivity was assessed by value of ADP-induced light transmittance aggregometry (LTA) and vasodilator-stimulated phosphoprotein phosphorylation-platelet reactivity index (VASP-PRI) at baseline, 7 and 30 days after randomized P2Y₁₂ inhibitor treatment.

RESULTS

The study showed a decreased platelet reactivity after use of P2Y₁₂ inhibitors (both P < .001). On the basis of comparison between regimens, apart from the prasugrel group having a significantly higher LTA value at the 30-day time point (P = .043), there existed no significant differences in platelet reactivity at separate time points (all P > .05). As for intragroup measurements, when compared with 7-day and 30-day time points, similar platelet reactivity was documented in the ticagrelor group (both P > .05), but LTA tests showed a significant increase with time (days 7-30) in the prasugrel group (P = .050).

WHAT IS NEW AND CONCLUSION

Although ticagrelor and prasugrel have similar platelet inhibitory effects in patients with T2DM, if a P2Y₁₂ inhibitor is necessitated in patients with T2DM, ticagrelor might exert a more stable antiplatelet effect with 30-day short-term treatment.

The effects of clopidogrel and omeprazole on platelet function in normal dogs

Omeprazole is used concurrently with clopidogrel to reduce gastrointestinal adverse effects. In humans, the concurrent use of these two drugs can reduce the antiplatelet efficacy of clopidogrel. Our objective was to determine the effects of omeprazole and clopidogrel on platelet function in healthy dogs. A crossover study utilized turbidimetric aggregometry (ADP and collagen) and the PFA-100^® with the collagen/ADP cartridge to evaluate platelet function in eight healthy dogs during the administration of clopidogrel (1 mg/kg/24 h p.o.), omeprazole (1 mg/kg/24 h p.o.), and a combination of clopidogrel and omeprazole. Drug metabolite concentrations were also measured. Compared to pretreatment, on Days 3 and 5, with ADP as the agonist, there was a significant decrease in maximum amplitude on aggregometry for both clopidogrel and clopidogrel/omeprazole groups. The following revealed no significant differences between clopidogrel and clopidogrel/omeprazole groups when compared on Days 3 and 5: maximum amplitude on aggregometry with ADP or collagen agonists, and PFA-100^® closure times. When compared to the clopidogrel group, clopidogrel metabolite concentrations in the clopidogrel/omeprazole group were significantly higher on Days 3 and 5. The concurrent administration of omeprazole and clopidogrel in healthy dogs was associated with an increase in the plasma concentration of an inactive metabolite of clopidogrel, but does not significantly alter the antiplatelet effects of clopidogrel.

[Evaluation of PFA P2Y assay in monitoring platelet function in elderly patients with cardiovascular disease receiving clopidogrel treatment]

OBJECTIVE

To evaluate the value of a new platelet function test PFA P2Y (PFA-200) in monitoring clopidogrel treatment for cardiovascular disease in elderly patients.

METHODS

Fifty-six elderly patients receiving clopidogrel therapy in the Department of Cardiology of General Hospital of PLA from March to August in 2016 and 85 healthy volunteers were recruited for analysis. All the subjects underwent PFA P2Y, LTA (light transmittance aggregometry) and TEG (Thromboelastograph) tests, and Spearman correlation coefficients were used to test the associations between test results. The agreement among the 3 platelet function test methods was assessed using Cohen's kappa coefficient.

RESULTS

Correlation coefficient (r) was -0.701 (P<0.001) between PFA P2Y and LTA, and 0.475 (P<0.001) between PFA P2Y and TEG. The agreement was 75% between PFA P2Y and LTA and 67.9% between PFA P2Y and TEG. The κ value was 0.434 (P=0.001) between PFA P2Y and LTA and 0.242 (P=0.046) between PFA P2Y and TEG. With ADP-induced maximum platelet aggregation rate of LTA >50% as the laboratory clopidogrel resistance, the cut-off value of PFA P2Y was 119 s (AUC=0.733) with a sensitivity of 75.6% and a specificity of 73.3%.

CONCLUSION

PFA P2Y has a moderate correlation and agreement with LTA, but has a poor correlation and agreement with TEG. PFA P2Y can be useful for assessing the effects of clopidogrel therapy and the association of the cut-off value (119 s) with the long-term clinical ischemic events needs be confirmed in further study.

Assays of different aspects of haemostasis - what do they measure?

Haemostasis is a complex process affected by many factors including both cellular and plasma components. It is a multistep process starting with platelet adhesion to damaged endothelium and ending in clot fibrinolysis. There are several methods available to study different aspects of haemostasis including adhesion, aggregation, coagulation and fibrinolysis. This review describes the different methods, what aspects of haemostasis they measure and their limitations. Methods discussed include methods to study adhesion (e.g. PFA-100, cone and platelet(let) analyzer and perfusion chambers) and aggregation (e.g. Multiplate, VerifyNow and Plateletworks). Furthermore the principles behind viscoelastic haemostatic assays are presented as well as methods that can analyse aspects of haemostasis in plasma or platelet-rich-plasma samples (thrombin generation, overall haemostasis potential and Thrombodynamics Analyzer).

Monitoring aspirin and clopidogrel response: testing controversies and recommendations

Antiplatelet therapy is the cornerstone of the treatment for patients with coronary artery disease (CAD). Dual therapy with clopidogrel and aspirin is currently the standard treatment after percutaneous coronary interventions. However, despite the use of clopidogrel, a considerable number of patients continue to suffer major adverse cardiac events. There is a growing degree of evidence supporting high on-treatment platelet reactivity (HPR) as a predictive factor for recurrent ischemic complications. Numerous studies have shown an interindividual variability of responsiveness to clopidogrel and aspirin, which is one of the reasons for HPR. There is yet to be established an assay for antiplatelet drug response as the gold standard. This paper provides a background to the current controversies surrounding the issue of testing for the effectiveness of antiplatelet therapy and reviews the various genetic and phenotype-based laboratory tests to measure aspirin and clopidogrel response and their correlation with clinical outcomes. On the basis of the current evidence and trying to be cost-effective, testing should be considered on a case-by-case basis, especially in patients who present with an acute coronary syndrome or stent thrombosis. In the case of stable CAD, we think that testing might be helpful in particular risk groups of patients to avoid ischemic or bleeding complications.

PlaCor PRT measurement of shear-activated platelet aggregate formation in stable patients treated with single and dual antiplatelet therapy

Shear forces play a key role in thrombus formation and shear-based tests may better reflect physiological conditions in vivo compared with agonist-based tests. We evaluated the PlaCor PRT®, a novel platelet reactivity test based on shear-induced platelet aggregation, in patients with stable coronary artery disease (CAD) treated with single (SAPT) and dual antiplatelet therapy (DAPT). We examined 100 patients with multiple risk factors for CAD and/or documented stable CAD: 38 treated with SAPT, aspirin 100 mg qd, 62 treated with DAPT, aspirin 100 mg + clopidogrel 75 mg qd, compared with age- and sex-matched healthy volunteers without antiplatelet therapy (HV, n = 35). Measures of shear-induced platelet aggregation were performed with the PlaCor PRT®. In 25 patients in SAPT, the PlaCor test was also performed before and after a 12-hour-loading dose of clopidogrel 600 mg. The mean ± SD PRT time (seconds) in HV was 78 ± 13 and was significantly lower compared with SAPT (118 ± 16, p = 0.030) and to DAPT patients (242 ± 11, p < 0.0001). A statistically significant difference was also reported between SAPT and DAPT patients (p < 0.0001). After a loading dose of clopidogrel, the PRT time of SAPT patients increased significantly from 112 ± 20 to 254 ± 17, p < 0.0001. 2.7 and 26% of patients were considered as "poor responders" to single and dual antiplatelet therapy, respectively. This study shows that in patients with multiple risk factors for CAD and/or documented stable CAD, SAPT and DAPT play an important role in reducing platelet aggregation mediated by shear forces as evaluated with the novel PlaCor PRT®. Further studies will be required to confirm and assess the extent of these findings in patients with acute coronary syndromes.