Platelet function testing: dead or alive

Thrombus aspiration is associated with improved platelet inhibition rate following dual antiplatelet therapy in acute myocardial infarction patients

BACKGROUND

It is well-established that thrombus aspiration during primary percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI) indicates a higher thrombus burden and necessitates more intensive antithrombotic therapy. The bidirectional association between adverse events in AMI patients and platelet reactivity is typically observed during dual antiplatelet therapy (DAPT).

OBJECTIVE

To investigate platelet reactivity after DAPT in AMI patients with thrombus aspiration performed during PCI.

METHODS

In this retrospective study, we examined 269 consecutive AMI patients who underwent PCI and recorded their demographic, clinical and laboratory data. The platelet reactivity was measured with thromboelastogram (TEM).

RESULTS

Ultimately, 208 patients were included in this study and divided into a Thrombus Aspiration group (N = 97) and a PCI Alone group (N = 111) based on whether thrombus aspiration was performed or not. The adenosine diphosphate (ADP)-induced platelet inhibition rate in the Thrombus Aspiration group was higher than that in the PCI Alone group (P < 0.001). Furthermore, multivariate linear regression analysis revealed that the ADP-induced platelet inhibition rate was independently associated with leukocyte count, thrombus aspiration and the combination of aspirin and ticagrelor as DAPT after adjusting for potential covariates in all AMI patients.

CONCLUSION

In conclusion, clinicians should exercise heightened attention towards the bleeding risk among patients undergoing PCI concomitant with Thrombus Aspiration postoperatively.

Elevated High-Sensitivity C-Reactive Protein Level Enhances the Impact of Lipoprotein(a) on Platelet Reactivity in PCI Patients Treated with Clopidogrel

BACKGROUND

Recently, the effect of Lipoprotein(a) [Lp(a)] on thrombogenesis has aroused great interest, while inflammation has been reported to modify the Lp(a)-associated risks through an unidentified mechanism.

PURPOSE

This study aimed to evaluate the association between platelet reactivity with Lp(a) and high-sensitivity C-reactive protein (hs-CRP) levels in percutaneous intervention (PCI) patients treated with clopidogrel.

METHODS

Data were collected from 10,724 consecutive PCI patients throughout the year 2013 in Fuwai Hospital. High on-treatment platelet reactivity (HTPR) and low on-treatment platelet reactivity (LTPR) were defined as thrombelastography (TEG) maximum amplitude of adenosine diphosphate-induced platelet (MAADP) > 47 mm and < 31 mm, respectively.

RESULTS

6615 patients with TEG results were finally enrolled. The mean age was 58.24 ± 10.28 years and 5131 (77.6%) were male. Multivariable logistic regression showed that taking Lp(a) < 30 mg/dL and hs-CRP < 2 mg/L as the reference, isolated Lp(a) elevation [Lp(a) ≥ 30 mg/dL and hs-CRP < 2 mg/L] was not significantly associated with HTPR (P = 0.153) or LTPR (P = 0.312). However, the joint elevation of Lp(a) and hs-CRP [Lp(a) ≥ 30 mg/dL and hs-CRP ≥ 2 mg/L] exhibited enhanced association with both HTPR (OR:1.976, 95% CI 1.677-2.329) and LTPR (OR:0.533, 95% CI 0.454-0.627).

CONCLUSIONS

The isolated elevation of Lp(a) level was not an independent indicator for platelet reactivity, yet the concomitant elevation of Lp(a) and hs-CRP levels was significantly associated with increased platelet reactivity. Whether intensified antiplatelet therapy or anti-inflammatory strategies could mitigate the risks in patients presenting combined Lp(a) and hs-CRP elevation requires future investigation.

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.

Short dual antiplatelet therapy and dual antiplatelet therapy de-escalation after primary percutaneous intervention: For whom and how

Dual antiplatelet therapy (DAPT) for 6-12 months, followed by lifelong aspirin monotherapy is considered an effective standard therapy for the prevention of thrombo-ischemic events in patients with acute and chronic coronary syndrome (ACS, CCS) undergoing percutaneous coronary intervention (PCI) or after a primarily conservative treatment decision. In ACS patients, the stronger P2Y12-inhibitors ticagrelor or prasugrel are recommended in combination with aspirin unless the individual bleeding risk is high and shortening of DAPT is warranted or clopidogrel is preferred. However, also in patients at low individual bleeding risk, DAPT is associated with a higher risk of bleeding. In recent years, new antithrombotic treatment strategies, such as shortening DAPT followed by early P2Y12-inhibitor monotherapy and de-escalating DAPT from potent P2Y12-inhibitors to clopidogrel by maintaining DAPT duration time, have been investigated in clinical trials and shown to reduce bleeding complications in cardiovascular high-risk patients without negative effects on ischemic events. In this review, we summarize the current knowledge and discuss its implication on future antithrombotic strategies in terms of a personalized medicine.

Impact of Prasugrel and Ticagrelor on Platelet Reactivity in Patients With Acute Coronary Syndrome: A Meta-Analysis

Background

This meta-analysis mainly aimed to compare the impact of prasugrel and ticagrelor on platelet reactivity (PR) in patients with acute coronary syndrome (ACS).

Methods

We searched four electronic databases to identify randomized controlled trials and cohort studies comparing the impact of prasugrel and ticagrelor on PR in patients with ACS. We performed group analyses according to three detection methods, drug dose [loading dose (LD) and maintenance dose (MTD)] and LD effect time, and assessed the robustness of the results through sensitivity analysis.

Results

Twenty-five studies with 5,098 patients were eligible. After LD, the incidence of high on-treatment platelet reactivity (HTPR) of ticagrelor was significantly lower than that of prasugrel within 6–18 h based on vasodilator-stimulated phosphoprotein (VASP) test [RR = 0.25 (0.07, 0.85), P = 0.03], there was no significant difference between ticagrelor and prasugrel in the following results: platelets inhibitory effect within 24–48 h based on VerifyNow P2Y12 (VN) assay (P = 0.11) and VASP test (P = 0.20), and the incidence of HTPR within 2–6 h based on VN assay (P = 0.57) and within 24–48 h based on VN assay (P = 0.46) and VASP test (P = 0.72), the incidence of low on-treatment platelet reactivity (LTPR) within 6–18 h based on VASP test (P = 0.46) and 48 h based on VN assay (P = 0.97) and VASP test (P = 0.73). After MTD, the platelet inhibitory effect of ticagrelor was stronger than that of prasugrel based on VN assay [WMD = −41.64 (−47.16, −36.11), P &lt; 0.00001]and VASP test [WMD = −9.10 (−13.88, −4.32), P = 0.0002], the incidence of HTPR of ticagrelor was significantly lower than that of prasugrel based on VN assay [RR = 0.05 (0.02, 0.16), P &lt; 0.00001], the incidence of LTPR of ticagrelor was significantly higher than prasugrel based on VN assay [RR = 6.54 (4.21, 10.14), P &lt; 0.00001] and VASP test [RR = 2.65 (1.78, 3.96), P &lt; 0.00001], the results of Multiple Electrode Aggregometry (MEA) test was inconsistent with the other two detection methods in platelet inhibitory effect and the incidence of HTPR and LTPR. There was no significant difference between ticagrelor and prasugrel in the following clinical outcomes: all-cause death (P = 0.86), cardiovascular death (P = 0.49), myocardial infarction (P = 0.67), stroke (P = 0.51), target vessel revascularization (P = 0.51), stent thrombosis (P = 0.90), TIMI major bleeding (P = 0.86) and bleeding BARC type ≥ 2 (P = 0.77). The risk of bleeding BARC type 1 of ticagrelor was significantly higher than prasugrel [RR = 1.44 (1.03, 2.02), P = 0.03].

Conclusions

Compared with prasugrel, ticagrelor might have a stronger platelet inhibition effect, with a lower incidence of HTPR and a higher incidence of LTPR and bleeding BARC type 1, while there might be no significant difference in the risk of thrombosis/ischemic, bleeding BARC Type ≥ 2 and TIMI major bleeding. A higher incidence of LTPR might indicate a higher risk of bleeding BARC type 1. The results of VN assay were consistent with that of VASP test, and not with the MEA test.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022304205, identifier: CRD42022304205.

Why Me? To Be an Ultra-Responder to Antiplatelet Therapy: A Case Report

Background: Platelet function testing is a valid tool to investigate the clinical response to antiplatelet therapy in different clinical settings; in particular, it might supply helpful information in patients with cerebrovascular disease. Oral antiplatelet treatment, such as Aspirin (ASA) and Clopidogrel, is the gold standard in secondary stroke prevention of non-cardiogenic ischemic stroke; conversely, its application as a primary prevention therapy is not routinely recommended in patients with vascular risk factors. Multiple electrode platelet aggregometry (MEA) impedance aggregometer is a validated device to test platelet inhibition induced by ASA or Clopidogrel.

Case Report: We report the case of a 78-year-old patient without relevant clinical history, taking ASA as primary prevention strategy, who was admitted for sudden onset of dysarthria and left facial hyposthenia during physical effort. Brain CT revealed two small subcortical bilateral spontaneous intracranial hemorrhages. Platelet aggregometry with MEA performed upon admission revealed a very strong platelet inhibition induced by ASA (result of the ASPI Test was 5 U, consistent with an ultra-responsiveness to ASA, and the cutoff value of correct responsiveness is <40 U). MRI at longitudinal follow-up revealed the presence of two small cavernous angioma underlying hemorrhagic spots.

Conclusion: The evaluation of platelet reactivity in stroke patients undergoing antiplatelet therapies, not commonly performed in clinical practice, could be useful to optimize prevention strategies; the verification of the biological effectiveness of ASA or Clopidogrel could be a valid tool in the definition of each patient's risk profile, particularly in patients with cerebrovascular disease known to be at increased risk for both hemorrhagic and thrombotic complications.

Aspirin I.V. Loading during Elective Percutaneous Coronary Intervention

Additional loading dose of acetylsalicylic acid (ASA) during percutaneous coronary interventions (PCIs) despite permanent oral ASA medication is frequently applicated. The impact on platelet reactivity and clinical events is not known. In this pilot study, we aimed to analyze high on-treatment platelet reactivity (HTPR) to aspirin in patients undergoing elective PCI. Platelet reactivity was measured using light-transmission aggregometry in 100 patients on permanent low-dose ASA medication undergoing elective PCI. Platelet reactivity measured by arachidonic acid-induced maximum of aggregation (MoA) in patients with versus without additional peri-procedural ASA loading (500 mg i.v.) was compared. HTPR was defined as MoA >20% for ASA. Major adverse cerebro- and cardiovascular events (MACCEs) and bleeding events were evaluated during hospital course. HTPR rate was similar in both groups (HTPR to ASA: loading vs. control 6% vs. 16%, odds ratio [OR] = 0.33, 95% confidence interval [CI] 0.08-1.35, p = 0.12). In-hospital MACCEs were not different between groups (MACCE: loading vs. control: 0 vs. 0 patient, OR = 1.32, 95% CI 0.03-67.95, p = 0.89). Thrombolysis in myocardial infarction minimal bleedings were numerically higher in patients without ASA loading dose. In this pharmacodynamic pilot study, additional ASA loading did not reduce HTPR to ASA. Furthermore, ASA loading did not increase in-hospital MACCE and bleeding complications.

Impact of Platelet Reactivity in ACS Patients on Clinical Outcomes with Triple Antithrombotic Therapy

Optimal antithrombotic therapy after percutaneous coronary intervention (PCI) in patients on oral anticoagulants (OAC) remains a clinical conundrum. In fact, combining an OAC with dual antiplatelet therapy (triple antithrombotic therapy, TAT) increases the risk of bleeding. Clopidogrel is the only thienopyridine recommended in TAT patients. Whether its response plays a relevant role in this setting remains uncertain. We aimed to evaluate the level of platelet reactivity inhibition (PRI) achieved by oral TAT in Acute Coronary Syndrome (ACS) patients undergoing PCI and its relationship with outcomes. We performed a multicenter prospective observational study and assessed PRI by vasodilator-stimulated phosphoprotein (VASP) index following a loading dose of clopidogrel. The primary endpoint was the incidence of major adverse cerebral or cardiovascular events (MACCE) at six months based on High on Treatment Platelet Reactivity (HTPR, VASP > 50%). The secondary endpoint was the incidence of bleeding at six months based on Low on Treatment Platelet Reactivity (LTPR, VASP < 16%). 491 patients were followed up for six months: 7.7% experienced MACCE and 17.3% experienced bleeding. There was no significant relationship between HTPR and MACCE, neither between LTPR and bleeding. Vitamin-K antagonist (VKA) treatment was associated with more MACCE and bleeding events, and the majority of events occurred within the first months. VASP index failed to predict outcomes in post-ACS patients with TAT. We confirm that direct acting OAC should be prioritized over VKA in TAT regimen.

Once- versus Twice-Daily Aspirin in Patients at High Risk of Thrombotic Events: Systematic Review and Meta-Analysis

BACKGROUND

Acetylsalicylic acid (ASA) is a frequently used antiplatelet agent, although some individuals have reduced antiplatelet responses on ASA, with recurrent ischemic events. It has been proposed that shortening the ASA dosing interval may overcome the time-dependent renewal of the drug target, leading to a greater antiplatelet effect. We conducted a systematic review of randomized controlled trials (RCTs) to determine the efficacy of once- versus twice-daily ASA in conditions with increased platelet turnover.

METHODS

We conducted a systematic review and meta-analysis by searching the CENTRAL, MEDLINE, and Embase databases for RCTs assessing once- versus twice-daily ASA. Data were screened, extracted, and appraised by two independent reviewers, and were pooled using a random-effects model. The primary outcomes were major adverse cardiovascular events (MACEs) and serum thromboxane B2 (TxB2). Other pharmacodynamic measures were retrieved as secondary outcomes. Results were reported as mean differences with corresponding 95% confidence intervals (CIs). We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Seven RCTs were included, enrolling 379 participants overall. None of the studies reported clinical outcomes. Pooled results showed that compared with once-daily ASA, twice-daily ASA was associated with a decrease in mean TxB2 of 1.42 ng/mL (95% CI - 2.71 to - 0.13; I² = 66%). We found no differences in subgroup analyses based on disease subtype, trial blinding, or trial design. A greater antiplatelet activity of the twice-daily regimen was also found when using PFA-100-ADP methods, although not when using the VerifyNow, LTA-AA, and multiplate methods.

CONCLUSIONS

Twice-daily ASA was associated with a greater antiplatelet effect compared with standard once-daily ASA.

Effectiveness and safety of high dose clopidogrel plus aspirin in ischemic stroke patients with the single CYP2C19 loss-of-function allele: a randomized trial

Background

Dual antiplatelet aggregation therapy leads to better outcomes in patients with carotid artery stenosis, intracranial artery stenosis, minor strokes, or transient ischaemic attacks. However, carriers of the CYP2C19 loss-of-function allele may not experience the desired effects. We attempted to increase the clopidogrel dose to determine whether it would improve the outcomes of stroke patients who carry a single loss-of-function allele.

Methods

We recruited 131 patients with minor ischaemic stroke, within less than 7 days of stroke onset and a CYP2C19 loss-of-function allele, who had moderate-to-severe cerebral artery stenosis. Patients were divided into the high dose group (clopidogrel 150 mg per day + aspirin 100 mg per day over 21 days.) and a normal dose group (clopidogrel 75 mg per day + aspirin 100 mg per day over 21 days). The reported outcomes included any vascular or major bleeding events as the primary and safety endpoints, respectively.

Results

One and six vascular events occurred in the high dose and normal dose groups during the 3-months follow-up period, respectively. However, no significant difference was found between the two groups when adjusted for history of diabetes (hazard ratio, 5482; 95% confidence interval, 0.660 to 45.543; P = 0.115). No major bleeding events occurred.

Conclusions

In patients with ischaemic stroke who had a single CYP2C19 loss-of-function allele and moderate to severe cerebral stenosis, fewer vascular events occurred within 3 months with high dose of clopidogrel and aspirin than with normal dose of clopidogrel and aspirin. However, the difference between the two groups was not significant.

Trial registration

Clinical study of clopidogrel in the treatment of patients with symptomatic moderate to severe cerebral artery stenosis with intermediate metabolites of CYP2C19, URL: http://www.chictr.org.cn/. Unique identifier: ChiCTR1800017411, 07/28/2018;

Comparison of Light Transmission Aggregometry With Impedance Aggregometry in Patients on Potent P2Y12 Inhibitors

Since data on the agreement between light transmission aggregometry (LTA) and multiple electrode aggregometry (MEA) in patients on the more potent P2Y₁₂ inhibitors are missing so far, we investigated if the evaluation of the responsiveness to therapy by LTA can be replaced by MEA in 160 acute coronary syndrome (ACS) patients on dual antiplatelet therapy with aspirin and prasugrel or ticagrelor (n = 80 each). Cut-off values for high on-treatment residual platelet reactivity (HRPR) in response to adenosine diphosphate (ADP) or arachidonic acid (AA) were defined according to previous studies showing an association of HRPR with the occurrence of adverse ischemic outcomes. ADP- inducible platelet aggregation was 33% and 37% (P = 0.07) by LTA and 19 AU and 20 AU (P = 0.38) by MEA in prasugrel- and ticagrelor-treated patients, respectively. AA- inducible platelet aggregation was 2% and 3% by LTA and 15 AU and 16 AU by MEA, (all P ≥ 0.3) in patients on prasugrel and ticagrelor, respectively. By LTA, HRPR ADP and HRPR AA were seen in 5%/5% and in 4%/ 13% of patients receiving prasugrel- and ticagrelor, respectively. By MEA, HRPR ADP and HRPR AA were seen in 3%/ 25% and 0%/24% of prasugrel- and ticagrelor-treated patients, respectively. ADP-inducible platelet reactivity by MEA correlated significantly with LTA ADP in prasugrel-treated patients (r = 0.4, P < 0.001), but not in those receiving ticagrelor (r = 0.09, P = 0.45). AA-inducible platelet aggregation by LTA and MEA did not correlate in prasugrel- and ticagrelor-treated patients. Sensitivity/specificity of HRPR by MEA to detect HRPR by LTA were 25%/99% for MEA ADP and 100%/79% for MEA AA in prasugrel-treated patients, and 0%/100% for MEA ADP and 70%/83% for MEA AA in ticagrelor-treated patients. In conclusion, on-treatment residual ADP-inducible platelet reactivity by LTA and MEA shows a significant correlation in prasugrel- but not ticagrelor-treated patients. However, in both groups LTA and MEA revealed heterogeneous results regarding the classification of patients as responders or non-responders to P2Y₁₂ inhibition.

The need of a multicomponent guiding approach to personalize clopidogrel treatment

Patients bearing polymorphisms termed CYP2C19 loss of function (LoF) alleles and ABCB1-C3435T may do not properly respond to standard dosage of clopidogrel and have an increased risk of thrombosis. Moreover, co-administration of proton pump inhibitors (PPIs) and clopidogrel may attenuate the antiplatelet effect. The role of pharmacogenetics and PPIs/clopidogrel drug-drug interaction has been extensively investigated in patients with acute coronary syndrome after stent implantation (ACS/PCI), while data in patients undergoing vascular surgery are scarce. Here we have performed a systematic review to evaluate the available literature in such a clinical setting and have discussed the controversies about the use of CYP2C19 pharmacogenetics and platelet function testing to personalize clopidogrel treatment. In addition, we have made a comparison of the literature data with our findings concerning patients eligible for vascular surgery and treated with clopidogrel, in whom we used a combined management based on the CYP2C19 and ABCB1 pharmacogenetic testing with monitoring of therapeutic adherence and PPIs-clopidogrel interaction. Both our data and those produced during both observational studies and randomized clinical trials confirm the validity of pharmacogenetics to personalize clopidogrel treatment and stress the importance to make a drug monitoring considering all the known variables, potentially responsible for treatment failure. However, the American Heart Association and the European Cardiovascular Society recommend against the routine use of clopidogrel pharmacogenetic testing. An update of the international guidelines on antiplatelet therapy, incorporating the evidence related to CYP2C19 pharmacogenetics and PPIs-clopidogrel drug-drug interactions is warranted both in ACS/PCI patients and subjects undergoing vascular surgery.

Perioperative management of antiplatelet therapy in noncardiac surgery

PURPOSE OF REVIEW

Perioperative management of antiplatelet agents (APAs) in the setting of noncardiac surgery is a controversial topic of balancing bleeding versus thrombotic risks.

RECENT FINDINGS

Recent data do not support a clear association between continuation or discontinuation of APAs and rates of ischemic events, bleeding complications, and mortality up to 6 months after surgery. Clinical factors, such as indication and urgency of the operation, time since stent placement, invasiveness of the procedure, preoperative cardiac optimization, underlying functional status, as well as perioperative control of supply-demand mismatch and bleeding may be more responsible for adverse outcome than antiplatelet management.

SUMMARY

Perioperative management of antiplatelet therapy (APT) should be individually tailored based on consensus among the anesthesiologist, cardiologist, surgeon, and patient to minimize both ischemic/thrombotic and bleeding risks. Where possible, surgery should be delayed for a minimum of 1 month but ideally for 3-6 months from the index cardiac event. If bleeding risk is acceptable, dual APT (DAPT) should be continued perioperatively; otherwise P2Y12 inhibitor therapy should be discontinued for the minimum amount of time possible and aspirin monotherapy continued. If bleeding risk is prohibitive, both aspirin and P2Y12 inhibitor therapy should be interrupted and bridging therapy may be considered in patients with high thrombotic risk.

Platelet Reactivity in Patients on Aspirin and Clopidogrel Therapy Measured by a New Bedside Whole-Blood Assay

Various tests are available for measuring on-treatment platelet reactivity. The pharmacologically most specific assays are time-consuming and elaborate. A highly specific and convenient assay would be desirable for clinical routine. In this pilot study, we aimed to examine the ability of a novel bedside whole-blood assay-ROTEM platelet-to evaluate platelet inhibition compared with established assays. Platelet reactivity was investigated in 93 patients. Forty-Seven patients were on permanent aspirin therapy and 46 on dual antiplatelet therapy (DAPT) with aspirin and clopidogrel. We used ROTEM platelet impedance aggregometry (ROTEM-PTL), light transmission aggregometry (LTA), Multiplate electrode aggregometry (MEA) and vasodilator-stimulated phosphoprotein flow cytometry. Receiver operating characteristic (ROC) analyses showed ROTEM-PTL differentiates well between patients on medication and healthy individuals: aspirin: ROCAUC 0.99 (95% confidence interval, 0.97-1.01); P < 0.0001; DAPT treatment: ROCAUC 0.80 (95% confidence interval, 0.69-0.91); P < 0.001. Pearson regression analyses showed moderate correlations between assays. Aspirin: MEA versus ROTEM-PTL r = 0.435, P ≤ 0.001; LTA versus ROTEM-PTL r = 0.048, P = 0.180. DAPT: MEA versus ROTEM-PTL r = 0.398, P = 0.001; LTA versus ROTEM-PTL r = 0.409, P = 0.001; vasodilator-stimulated phosphoprotein versus ROTEM-PTL r = 0.164, P = 0.055. ROTEM platelet distinguished well between treated and healthy individuals but correlated moderately with other assays. Clinical trials are needed to investigate the ability of this new assay to identify patients at risk of adverse events.

Laboratory Monitoring of Platelet P2Y12 Receptor Inhibitors and Reversal of Antiplatelet Agents

OBJECTIVES

To review the use of laboratory tests for antiplatelet agents to determine escalation of antiplatelet therapy and for emergent reversal of P2Y12 inhibitors.

METHODS

A case scenario and review of cardiovascular and neurointerventional literature are described.

RESULTS

In cardiovascular disease patients, large randomized trials failed to demonstrate superiority of tailored antiplatelet regimens using the VerifyNow P2Y12 assay, where earlier studies had shown promise. Platelet transfusions restored platelet function measured by vasodilator-stimulated phosphoprotein, light transmission aggregometry, or thromboelastography but not VerifyNow P2Y12, with the most restoration for clopidogrel and the least for ticagrelor.

CONCLUSIONS

Current evidence does not support changing antiplatelet therapy based on the results of platelet function monitoring tests. For emergent reversal of P2Y12 inhibitors, test method can affect platelet dosing recommendations, as different methods may give different results.

Multiple electrode aggregometry and thromboelastography in thrombocytopenic patients with haematological malignancies

BACKGROUND

In thrombocytopenic patients better assessment of bleeding risk than that provided by platelet count alone is required. Multiplate® aggregometry and thromboelastography (TEG) could be used, but information on their role in such patients is limited. The primary aim of this study was to investigate the feasibility of Multiplate® analyses in patients with haematological malignancies. A secondary aim was to explore whether a multiple logistic regression model combining Multiplate®, TEG, clinical and laboratory variables was associated with risk of bleeding.

MATERIALS AND METHODS

This was an exploratory, prospective observational study of thrombocytopenic patients with haematological malignancies. Total platelet count (TPC), white blood cell count, C-reactive protein (CRP) level, temperature and bleeding status were recorded daily. TEG and Multiplate® analyses with four agonists were performed on weekdays.

RESULTS

Ten patients were enrolled into the study. The median number of days in a study period was 21. Bleeding was observed on 64 of 298 study days. TPC <20×109/L and <10×109/L occurred on 119 and 25 days, respectively. When TPC was <33×109/L, many samples showed no aggregation, regardless of bleeding status. Despite this, the odds of World Health Organization (WHO) grade 2 bleeding decreased significantly as aggregation increased and Multiplate® had a negative predictive value (NPV) of 96% and a positive predictive value (PPV) of 19% for significant bleeding. In the multiple logistic regression model collagen-activated Multiplate® aggregation, TEG angle, TEG reaction time and CRP significantly affected the odds of WHO grade 2 bleeding. The combined model had a NPV of 99% and a PPV of 19%.

DISCUSSION

Our findings suggest that the markers of platelet function and haemostasis provided by Multiplate® aggregometry and TEG may add information to support prediction of bleeding, although platelet count still remains the most accessible analysis for routine testing.

Whole blood platelet aggregation determined by the ROTEM platelet equipment; reference intervals and stability

Point of care testing of residual effect of antiplatelet therapy in trauma patients or during major surgery may result in improved clinical management of significant bleeding. We included 121 healthy individuals (57 females and 64 males, aged 22-65 years) in order to establish reference intervals for platelet aggregation induced by adenosine diphosphate (ADPTEM, 10 µM), arachidonic acid (ARATEM, 0.42 mM) and thrombin activating peptide (TRAPTEM, 36 µM) employing the ROTEM platelet module. Further, the impact of citrate (3.2%) and hirudin (>15 µg/ml) as anticoagulants was evaluated. Finally, we investigated assay stability (15, 30, 60, and 120 min after blood sampling) (n = 8) and between-day variation (n = 5). We report reference intervals for 121 healthy individuals and reference intervals by gender. We observed significantly higher platelet aggregation in females than in males (all P-values < 0.05). No correlation between age and platelet aggregation was observed, except for the parameter TRAPTEM amplitude (A6), in which a decline in A6 was observed with increasing age (P = 0.03). We observed significantly lower levels of platelet aggregation in citrate tubes than in hirudin tubes (all P-values < 0.05), except from TRAPTEM maximum slope, where no significant difference was observed (P = 0.40).The stability was acceptable (≤20% deviation) for up to 120 min for ARATEM in citrate tubes, and up to 60 min for the ADPTEM and TRAPTEM assays in citrate tubes. In hirudin tubes we found ADPTEM and ARATEM assays to be stable for 60 min, while the stability of TRAPTEM in hirudin tubes was found to be stable for 30 min. Using citrate tubes, the between-day variation (mean coefficient of variation, CV) was 19-20% for ADPTEM, 19-26% for TRAPTEM, and 10% for ARATEM, whereas the mean CV was 11-13% for all three assays in hirudin tubes.In conclusion, we established combined and gender-specific reference intervals for three platelet aggregation assays in both citrate- and hirudin tubes. In citrate tubes, the stability of the ROTEM platelet assays was 60-120 min, while the stability in hirudin tubes was 30-60 min. The between-day variation was lowest for samples obtained in hirudin tubes.