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Laboratory coagulation assays
Published in John Edward Boland, David W. M. Muller, Interventional Cardiology and Cardiac Catheterisation, 2019
Multiple electrode aggregometry can be used in a point of care setting or in the routine coagulation laboratory for assessment of platelet function. The most commonly available system is the Multiplate® system (Roche Diagnostics). This system uses impedance aggregometry to detect platelet function. Whole blood is added to a test cell containing a magnetic stirrer and two sets of silver-coated probes. As platelets aggregate to the probes in the presence of agonist, the ability of platelets to impede the electrical current between these probes is detected and converted to an aggregation trace (Figure 6.1b) of time (x-axis) and aggregation units (y-axis). The assay is run for 6 minutes, following which an area under the curve is then calculated as a measure of platelet function.
Higher body mass index raises immature platelet count: potential contribution to obesity-related thrombosis
Published in Platelets, 2022
Lucy J. Goudswaard, Laura J. Corbin, Kate L. Burley, Andrew Mumford, Parsa Akbari, Nicole Soranzo, Adam S. Butterworth, Nicholas A. Watkins, Dimitri J. Pournaras, Jessica Harris, Nicholas J. Timpson, Ingeborg Hers
Age and sex were reported at baseline. Height and weight were obtained from medical notes. BMI was derived from weight and height (kg/m2). Smoking was reported as a categorical variable (0 = never smoker, 1 = ex-smoker for >5 years, 2 = ex-smoker for 1–5 years, 3 = ex-smoker for 30 days-1 year, 4 = current smoker). Platelet variables (PLT, MPV, IPF, and IPC) were measured using the Sysmex XE-2100 Automated Hematology System (Oxford, UK). Blood samples were taken pre-operatively into 3.2% sodium citrate vacutainers (BD Biosciences, Milton Keynes, UK). Platelet aggregation was measured using Multiplate multiple electrode aggregometry (MEA) (Roche, Rotkreuz, Switzerland), which detects change in electrical impedance when platelets aggregate on metal electrodes. Aggregation was determined by the area under the curve (AUC) in response to platelet agonists, including adrenaline (100 mg/mL), thrombin receptor activator peptide 6 test (TRAP-test), ADP-test, and ASPI-test. Using of a combination of agonists enables evaluation of platelet activation via different pathways: adrenaline acts at the α2 adrenergic receptor, TRAP-6 acts at the protease-activated receptor-1 (PAR-1), ADP acts at the P2Y12 receptor and arachidonic acid at the Thromboxane A2 (TxA2) receptor.
Recovery of platelet reactivity following cessation of either aspirin or ticagrelor in patients treated with dual antiplatelet therapy following percutaneous coronary intervention: a GLOBAL LEADERS substudy
Published in Platelets, 2022
Barry W. Hennigan, Richard Good, Carly Adamson, William A.E. Parker, Lynn Martin, Lynne Anderson, Michael Campbell, Patrick W. Serruys, Robert F. Storey, Keith G. Oldroyd
Blood samples were drawn at baseline, prior to discontinuation of DAPT, and 2, 7, and 14 days following discontinuation of DAPT in both groups. Phlebotomy was carried out after the patient had been sitting for 10 min with minimal tourniquet time and care given to avoid unnecessary trauma to the vein or agitation of blood sample. The first 3 ml were discarded, then venous blood was collected in hirudin-anticoagulated tubes. Samples were analyzed within 60 minutes of sample collection but with the aim of performing assays at 30 minutes post-phlebotomy. Analysis was undertaken by multiple-electrode aggregometry (MEA) using the Multiplate system in concordance with manufacturer’s guidelines. MEA assays measure changes in electrical impedance caused by adhesion of platelets to silver-covered electrodes. The degree of platelet aggregation is measured in arbitrary units (U) generated by the area-under-the-curve in a given time (10 AU*min = 1 U). The agonists used were adenosine diphosphate (ADP, final concentration 6.5 μmol/L), arachidonic acid (AA, 0.5 mmol/L), thrombin receptor activating peptide 6 (TRAP, 32 μmol/L) and collagen (3.2 μg/mL).
Inflammatory state does not affect the antiplatelet efficacy of potent P2Y12 inhibitors in ACS
Published in Platelets, 2021
Benedikt S. Biesinger, Aleksandra Gasecka, Thomas Perkmann, Johann Wojta, Maciej Lesiak, Marek Grygier, Ceren Eyileten, Marek Postuła, Krzysztof J. Filipiak, Aurel Toma, Christian Hengstenberg, Jolanta M. Siller-Matula
Platelet function was determined using Multiple Electrode Aggregometry (MEA) on a new generation impedance aggregometer (Multiplate Analyzer, Verum Diagnostica GmbH, Munich, Germany) using AA test (arachidonic acid, 0.5 mM), and ADP test (ADP, 6.5 µM) according to the manufacturer’s instructions. MEA measures the change of electrical impedance due to the adhesion and aggregation of platelets on the electrodes. The higher the aggregation, the larger the area under the curve (AUC). MEA was showed to be superior to other assays, such as vasodilator-stimulated phosphoprotein assay [38,39]. High on-treatment platelet reactivity (HTPR) determined with MEA was predictive for stent thrombosis, whereas low on-treatment platelet reactivity (LTPR) was predictive for bleeding in patients treated with clopidogrel [40,41]. After measuring platelet aggregation, all patients were divided into three groups: HTPR (AUC>46), medium on-treatment platelet reactivity (MTPR; AUC 20–45) and LTPR (AUC<20) [42–45].