Platelet Dysfunction Research Articles

Platelet Lipidome Fingerprint: New Assistance to Characterize Platelet Dysfunction in Obesity.

Obesity is associated with a pro-inflammatory and pro-thrombotic state that supports atherosclerosis progression and platelet hyper-reactivity. During the last decade, the platelet lipidome has been considered a treasure trove, as it is a source of biomarkers for preventing and treating different pathologies. The goal of the present study was to determine the lipid profile of platelets from non-diabetic, severely obese patients compared with their age- and sex-matched lean controls. Lipids from washed platelets were isolated and major phospholipids, sphingolipids and neutral lipids were analyzed either by gas chromatography or by liquid chromatography coupled to mass spectrometry. Despite a significant increase in obese patient’s plasma triglycerides, there were no significant differences in the levels of triglycerides in platelets among the two groups. In contrast, total platelet cholesterol was significantly decreased in the obese group. The profiling of phospholipids showed that phosphatidylcholine and phosphatidylethanolamine contents were significantly reduced in platelets from obese patients. On the other hand, no significant differences were found in the sphingomyelin and ceramide levels, although there was also a tendency for reduced levels in the obese group. The outline of the glycerophospholipid and sphingolipid molecular species (fatty-acyl profiles) was similar in the two groups. In summary, these lipidomics data indicate that platelets from obese patients have a unique lipid fingerprint that may guide further studies and provide mechanistic-driven perspectives related to the hyperactivate state of platelets in obesity.

Defective RAB31-mediated megakaryocytic early endosomal trafficking of VWF, EGFR, and M6PR in RUNX1 deficiency

AbstractTranscription factor RUNX1 is a master regulator of hematopoiesis and megakaryopoiesis. RUNX1 haplodeficiency (RHD) is associated with thrombocytopenia and platelet granule deficiencies and dysfunction. Platelet profiling of our study patient with RHD showed decreased expression of RAB31, a small GTPase whose cell biology in megakaryocytes (MKs)/platelets is unknown. Platelet RAB31 messenger RNA was decreased in the index patient and in 2 additional patients with RHD. Promoter-reporter studies using phorbol 12-myristate 13-acetate–treated megakaryocytic human erythroleukemia cells revealed that RUNX1 regulates RAB31 via binding to its promoter. We investigated RUNX1 and RAB31 roles in endosomal dynamics using immunofluorescence staining for markers of early endosomes (EEs; early endosomal autoantigen 1) and late endosomes (CD63)/multivesicular bodies. Downregulation of RUNX1 or RAB31 (by small interfering RNA or CRISPR/Cas9) showed a striking enlargement of EEs, partially reversed by RAB31 reconstitution. This EE defect was observed in MKs differentiated from a patient-derived induced pluripotent stem cell line (RHD-iMKs). Studies using immunofluorescence staining showed that trafficking of 3 proteins with distinct roles (von Willebrand factor [VWF], a protein trafficked to α-granules; epidermal growth factor receptor; and mannose-6-phosphate) was impaired at the level of EE on downregulation of RAB31 or RUNX1. There was loss of plasma membrane VWF in RUNX1- and RAB31-deficient megakaryocytic human erythroleukemia cells and RHD-iMKs. These studies provide evidence that RAB31 is downregulated in RHD and regulates megakaryocytic vesicle trafficking of 3 major proteins with diverse biological roles. EE defect and impaired vesicle trafficking is a potential mechanism for the α-granule defects observed in RUNX1 deficiency.

Olive Oil Phenolics and Platelets-From Molecular Mechanisms to Human Studies.

Chronically activated, dysfunctional platelets mediate the progression of the majority of non-communicable diseases in a pleiotropic fashion. Antiplatelet therapy remains an attractive therapeutic means which however hasn't reached the expected targets according to the promising preclinical studies. It is therefore obvious that the consumption of foods demonstrating antiplatelet activity may be a less drastic but on the other hand a more sustainable way of achieving daily antiplatelet therapy, either alone or in combination with antiplatelet drugs. Olive oil is probably the main cardioprotective component of the Mediterranean Diet according to the results of observational and dietary intervention studies. Among all phytochemicals of olive oil, its unique phenolics seems to be responsible for the majority of its cardioprotective properties. This review article aims to highlight the platelet modulating roles of olive oil polyphenols, trying to critically assess whether those properties could partially explain the cardioprotective role of olive oil. The cellular and animal studies clearly show that extra virging olive oil (EVOO) phenolics, mainly hydroxytyrosol, are able to inhibit the activation of platelets induced by several endogenous agonists and pathologies. However, the outcomes of the pre-clinical studies are difficult to be translated to humans mainly because the dosages and the chemical forms of the phenolics used to these studies are much higher and different to that found in human circulation. Despite the heterogeneity of the few human trials on the field so far, the results are promising showing that EVOO can exert antiplatelet actions in real, acute or long-term, trials and at least part of this antiplatelet action can be attributed to the phenolic content of EVOOs. Although we clearly need better, well-powered studies to give certain answers on this field the antiplatelet properties of olive oil phenolics is a promising, emerging mechanism which may explain some of the health properties of EVOO and the Mediterranean Diet.

Viscoelastic Hemostatic Assays for Orthopedic Trauma and Elective Procedures.

The application of viscoelastic hemostatic assays (VHAs) (e.g., thromboelastography (TEG) and rotational thromboelastometry (ROTEM)) in orthopedics is in its relative infancy when compared with other surgical fields. Fortunately, several recent studies describe the emerging use of VHAs to quickly and reliably analyze the real-time coagulation and fibrinolytic status in both orthopedic trauma and elective orthopedic surgery. Trauma-induced coagulopathy—a spectrum of abnormal coagulation phenotypes including clotting factor depletion, inadequate thrombin generation, platelet dysfunction, and dysregulated fibrinolysis—remains a potentially fatal complication in severely injured and/or hemorrhaging patients whose timely diagnosis and management are aided by the use of VHAs. Furthermore, VHAs are an invaluable compliment to common coagulation tests by facilitating the detection of hypercoagulable states commonly associated with orthopedic injury and postoperative status. The use of VHAs to identify hypercoagulability allows for an accurate venous thromboembolism (VTE) risk assessment and monitoring of VTE prophylaxis. Until now, the data have been insufficient to permit an individualized approach with regard to dosing and duration for VTE thromboprophylaxis. By incorporating VHAs into routine practice, orthopedic surgeons will be better equipped to diagnose and treat the complete spectrum of coagulation abnormalities faced by orthopedic patients. This work serves as an educational primer and up-to-date review of the current literature on the use of VHAs in orthopedic surgery.

PLATELET FUNCTION IN TRAUMA: IS CURRENT TECHNOLOGY IN FUNCTION TESTING MISSING THE MARK IN INJURED PATIENTS?

Platelets are subcellular anucleate components of blood primarily responsible for initiating and maintaining hemostasis. After injury to a blood vessel, platelets can be activated via several pathways, resulting in changed shape, adherence to the injury site, aggregation to form a plug, degranulation to initiate activation in other nearby platelets, and acceleration of thrombin formation to convert fibrinogen to fibrin before contracting to strengthen the clot. Platelet function assays use agonists to induce and measure one or more of these processes to identify alterations in platelet function that increase the likelihood of bleeding or thrombotic events. In severe trauma, these assays have revealed that platelet dysfunction is strongly associated with poor clinical outcomes. However, to date, the mechanism(s) causing clinically significant platelet dysfunction remain poorly understood. We review the pros, cons, and evidence for use of many of the popular assays in trauma, discuss limitations of their use in this patient population, and present approaches that can be taken to develop improved functional assays capable of elucidating mechanisms of trauma-induced platelet dysfunction. Platelet dysfunction in trauma has been associated with need for transfusions and mortality; however, most of the current platelet function assays were not designed for evaluating trauma patients, and there are limited data regarding their use in this population. New or improved functional assays will help define the mechanisms by which platelet dysfunction occurs, as well as help optimize future treatment.

An infantile case of hereditary folate malabsorption with sudden development of pulmonary hemorrhage: a case report

BackgroundHereditary folate malabsorption—a rare disorder caused by impairment of the folate transporter—can develop into severe folate deficiency manifesting as megaloblastic anemia and occasionally thrombocytopenia. Reportedly, megaloblastic anemia can manifest with hemorrhagic episodes, possibly due to ineffective platelet production and platelet dysfunction. However, life-threatening hemorrhage events in hereditary folate malabsorption have not been well investigated.Case presentationA 3-month-old Japanese boy was transferred to our hospital due to thrombocytopenia and severe megaloblastic anemia. During a thorough examination of hematopoietic abnormalities, the patient suddenly went into cardiac arrest due to pulmonary hemorrhage. Although intravenous folate supplementation was started soon after the identification of folate deficiency, the patient died of circulatory defect and multiple organ failure. The cause of pulmonary hemorrhage, such as respiratory infection, could not be confirmed. Genetic investigation revealed a mutation in the SLC46A1 gene to be the cause of the hereditary folate malabsorption.ConclusionWe report an infantile case of hereditary folate malabsorption that progressed to lethal pulmonary hemorrhage before folate deficiency was identified. Clinicians should consider that megaloblastic anemia could lead to severe bleeding without warning, and that nutrient supplementation should be initiated as soon as possible.

Chronic Immune Platelet Activation Is Followed by Platelet Refractoriness and Impaired Contractility.

Autoimmune diseases, including systemic lupus erythematosus (SLE), have a high risk of thrombotic and hemorrhagic complications associated with altered platelet functionality. We studied platelets from the blood of SLE patients and their reactivity. The surface expression of phosphatidylserine, P-selectin, and active integrin αIIbβ3 were measured using flow cytometry before and after platelet stimulation. Soluble P-selectin was measured in plasma. The kinetics of platelet-driven clot contraction was studied, as well as scanning and transmission electron microscopy of unstimulated platelets. Elevated levels of membrane-associated phosphatidylserine and platelet-attached and soluble P-selectin correlated directly with the titers of IgG, anti-dsDNA-antibodies, and circulating immune complexes. Morphologically, platelets in SLE lost their resting discoid shape, formed membrane protrusions and aggregates, and had a rough plasma membrane. The signs of platelet activation were associated paradoxically with reduced reactivity to a physiological stimulus and impaired contractility that revealed platelet exhaustion and refractoriness. Platelet activation has multiple pro-coagulant effects, and the inability to fully contract (retract) blood clots can be either a hemorrhagic or pro-thrombotic mechanism related to altered clot permeability, sensitivity of clots to fibrinolysis, obstructiveness, and embologenicity. Therefore, chronic immune platelet activation followed by secondary platelet dysfunction comprise an understudied pathogenic mechanism that supports hemostatic disorders in autoimmune diseases, such as SLE.

Common Hematological Disorders in Patients with Schizophrenia: In-Patient Case — Control Study

INTRODUCTION: Although common hematological abnormalities (CHA) such as anemia, macrocytosis, and platelet dysfunction are often present in patients with schizophrenia, empirical data are limited. Thus far, such deviations have been mentioned either in reports or in a series of clinical cases.
 AIM: To study the incidence of CHA in patients with schizophrenia.
 MATERIALS AND METHODS: This study involved 791 patients with schizophrenia [including those who did not receive medical drugs (n = 115) and patients with chronic schizophrenia (n = 376)] and 504 healthy volunteers. From each participant, blood samples were taken and analyzed for CHA using an automatic Coulter counter. In the three groups, 2 tests and analysis of variance (ANOVA) were conducted to compare the variables.
 RESULTS: The incidence of macrocytosis was nearly the same in the schizophrenia group (patients not receiving medications, 10.5%; patients with chronic schizophrenia, 10.6%) and was significantly higher than that in the control group (4.2%). The platelet count was considerably higher in the chronic schizophrenia group ([282.5 87.9] 103/L) than in the group not receiving medical drugs ([277.0 92.8] 103/L) and control group ([249.6 85.2] 103/L), whereas the differences in the concentration of hemoglobin and leukocytes in the blood were insignificant.
 CONCLUSION: Patients with schizophrenia have a higher proportion of macrocytosis in combination with increased platelet count, which shows that the underlying diseases should be diagnosed and treated as early as possible. Moreover, prospective studies with a larger sample size are necessary to determine the etiology of these conditions in patients with schizophrenia.

Platelet dysfunction after trauma: From mechanisms to targeted treatment.

Platelet dysfunction after trauma: From mechanisms to targeted treatment.

Screening platelet function in blood donors.

BackgroundTransfusion of defective platelets could contribute to the inefficiency of platelet transfusion in preventing or stopping bleeding.Study Design and MethodsThis single‐center prospective study aimed to determine the prevalence of functional platelet abnormalities in a population of blood donors with a clinical history of bleeding diathesis or with history of hematoma (>4 cm) during blood donation. Donors with positive bleeding screening questionnaire were referred to the reference center for rare platelet diseases at La Timone University Hospital (Marseille) to confirm the bleeding tendency using a more extensive bleeding questionnaire (MCMDMscore) and to assess hemostasis, including a comprehensive platelet analysis.ResultsOne hundred and ninety‐five donors identified based on a history of hematoma and 2434 blood donors were included in the study. Eighty‐eight donors (3.6%) had a bleeding score indicating a potential bleeding disorder. Five donors with a history of hematoma (2.5%) and 15 (17%) donors with a confirmed bleeding score underwent hemostatic analysis, including two men and 18 women with average age of 33.9 years. Minor hemostatic abnormalities were observed in three donors. Two donors exhibited accelerated fibrinolysis with reduced euglobulin lysis time and increased D‐dimer levels in serum. Two donors had a platelet granule defect, without identification of genetic abnormality.ConclusionThe bleeding questionnaire proved to be a valuable tool to screen blood donors for potential platelet defects. Platelet dysfunction was rare in the blood donor population assessed. Additional studies are necessary to understand the clinical impact that the transfusion of platelets with qualitative defects has on recipients.

P1656: EVALUATION OF PLATELET FUNCTION IN RARE OR UNDIAGNOSED BLEEDING DISORDERS

Background: Qualitative and/or quantitative platelet defects promote bleeding and its identification requires a careful clinical evaluation and a rational use of diagnostic laboratory assays. Aims: To study platelet function by different methods in patients with hemorrhagic symptoms who are suspected of thrombopathy to compare results obtained with each system and validate usefulness of methods employed. Methods: We included 72 patients with bleeding suspected of thrombopathy, which in some cases was confirmed by genetic study (Table 1). Patients with coagulation disorders were excluded. We used the following methods to test platelet function: Light aggregometry in platelet-rich plasma (PRP) using ADP, collagen, epinephrine and arachidonic acid as stimulating agonists. Flow cytometry in PRP using TRAP and ADP to induce platelet activation, and PAC1 monoclonal antibody (mAb) to recognize activated fibrinogen receptor, and anti P- selectin and anti-CD63 mAbs to test, respectively, release from alpha and dense granules. PFA-100 ® in whole citrated blood with collagen +ADP and collagen+Epinephrine cartridges. Total Thrombus-formation Analysis System (T-TAS ® 01, Zarcos, Japan) with T-TAS ® PL-chip (capillaries covered with collagen / under flow) in blood samples drawn in BAPA, a potent synthetic anticoagulant which inhibits Factor Xa and thrombin. Results: Some bleeding due to platelet dysfunction was diagnosed by any of the methods used, but others can only be detected with some of the techniques tested (Table 2). This difference in the sensitivity of the methods may be due to the different experimental conditions used in each of them: type of sample used, platelets’ activators, and flow vs static conditions. Forty % of undiagnosed bleedings did not seem to be related to platelet dysfunction. Image:Summary/Conclusion: All methods are complementary and their sensitivity depends on the pathway evaluated by the technique used and the mechanism involved in platelet dysfunction.

P997: PROTEOMIC ANALYSIS ON PLATELETS OF ESSENTIAL THROMBOCYTHEMIA PATIENTS UNDERSCORES THE ROLE OF MITOCHONDRIA IN JAK2 V617F PLATELET REACTIVITY AND FUNCTION

Background: Essential thrombocythemia (ET) is a heterogeneous disease subdivided into five genetic groups according to WHO, based on the common MPN driver mutations (JAK2 V617F, MPL W515K/L, and CALR Type I&II). Current treatment strategies include anti-platelet (e.g. acetylsalicylic acid (ASA)) or cytoreductive agents (e.g. hydrea (HU)) and target mainly complications related to platelet dysfunction (i.e. hemorrhage/thrombosis). Platelet activation is an energy demanding process fueled mainly by a dynamic equilibrium between mitochondria oxidative phosphorylation and glycolysis1. Importantly, altering the platelet catabolic response to activation has been shown to prevent thrombus formation2. JAK2 V617F platelets have been reported to be more activated than CALR mutated platelets3, as well as JAK2 mutated patients have a greater thrombotic risk in comparison to other ET groups. However, the cause of this phenotype is not completely understood. Aims: In this study we aimed to analyze the proteome of ET platelets and to characterize their functional properties according to the mutational background and treatment regimens. Methods: 22 healthy donors (HD) and 67 ET patients have been included in the study. Most of the patients were treated with low dose aspirin (ASA), anagrelide (ANA) or hydrea (HU) or a combination of these. Specifically, 35 out of the 67 ET platelet samples and 8 out of 22 HD were subjected to label-free quantitation mass spectrometry (LFQ-MS). All HD and ET platelets were also analyzed for surface marker expression, degranulation and aggregation capacity by flow cytometry. Results: Hierarchical clustering of the mass spectrometry data revealed different proteomic profiles between HD and ET mutational groups and specifically between JAK2 V617F and CALR I and CALR Type II treated and/or untreated platelets. In general, HD platelets were more enriched for proteins related to platelet activation, and degranulation as compared to ET platelets and clustered next to JAK2 V617F ASA-treated platelet samples (Figure 1). In particular, the JAK2 V617F ASA-treated platelets presented significant enrichment in platelet activation metabolic and mitochondrial proteins in contrast to the CALR Type I and Type II ET platelets. Of note, no peptides corresponding to the mutant CALR were detected using label-free MS methods. Surface marker expression was variable among ET patients. However, CD49B and CD36 surface markers were the most affected among the JAK2V617F and CALR Type I and II platelets and their levels (mean fluorescence intensity-MFI-) were inversely correlated. With regards to platelet aggregation, JAK2 V617F platelets presented similar or lower levels when compared to HD platelets, in line with their proteomic profiles. Differences in aggregation and degranulation levels were also observed between CALR Type I and Type II platelets specifically in the untreated condition. Image:Summary/Conclusion: ET platelets are functional but they show different capacities to respond upon various stimuli and treatment regimens. JAK2 V61F platelets are more activated than any other ET group according to their proteome profile, which is not fully reflected by the functional assays. Mitochondrial activity arises as an important factor in the control of platelet reactivity and it could be critical in disease management and treatment strategies, specifically for the JAK2 V617F patients.

Practical management of the haemorrhagic complications of myeloproliferative neoplasms.

Myeloproliferative neoplasms can be associated with bleeding manifestations which can cause significant morbidities. Although haematologists are aware of the likelihood of this complication in the setting of myeloproliferative neoplasms, it may often be overlooked especially in patients with no extreme elevation of blood counts and those with myelofibrosis. Acquired von Willebrand syndrome and platelet dysfunction are the two common diagnoses to be considered in this regard. In this review article, we discuss the mechanisms for the development of these rare bleeding disorders, their diagnosis and practical management.

Platelet Dysfunction in Blood Donors Detected by Platelet Function Analyzer PFA-100™.

BackgroundPlatelet transfusions may be indicated to prevent and treat bleeding in patients with quantitative or qualitative platelet defects. Millions of platelet components are transfused worldwide. It is well known that platelet dysfunction predicts blood loss after surgery. Hence, the quality of the platelet donation and the resulting platelet concentrate are critical for the transfusion. The aim of this study is to assess platelet function in well-qualified blood donors.MethodologyBlood samples from 275 blood donors were collected in 0.129 M (3.8%) sodium citrate tubes prior to routine blood donation. Platelet function was assessed by measuring the closure time (CT) on the platelet function analyzer (PFA-100™; Siemens Health Diagnostics, Marburg, Germany) using collagen/epinephrine (CEPI) and collagen/ADP (CDP) cartridges.ResultsUsing the PFA-100™, 20.4% of donors had an abnormal platelet function test, of whom 9.4% had prolonged CT with two cartridges, 7% had only prolonged CEPI CTs consistent with aspirin-like defect, and 4% had prolonged CADP CTs only. We found no closure (>300 seconds) in 6.54% of donors, including 1.45% with the CEPI cartridge, 2.9% with the CADP cartridge, and 2.18% with CEPI and CADP cartridges. Level of von Willebrand factor ristocetin cofactor (vWF: RCo) activity was 112% (56-168%). Of the factors examined (age, sex, cigarette smoking, blood donation type, ABO, and Rhesus blood group), only blood group O was significantly linked with impaired platelet function test in qualified blood donors (p = 0.023; odds ratio = 1.981; 95% confidence interval (1.091-3.595)).ConclusionsSome qualified blood donors present abnormal platelet function results. More research is required to provide greater insight into the impact of platelet dysfunction in blood donors on the clinical efficacy of their platelet components. This study has confirmed that the influence of ABO blood group on the CT PFA-100™is not wholly dependent on vWF.

Efficacy of Ibuprofen Gargle for Postoperative Pain After Mandibular Third Molar Extraction: Protocol for a Phase II, Placebo-Controlled, Double-Blind, Randomized Crossover Trial.

BackgroundExtraction of mandibular third molars is one of the most commonly performed oral surgical procedures, and nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for pain management. Oral NSAIDs are associated with adverse events such as gastrointestinal disorders, renal and hepatic dysfunction, and platelet dysfunction. Topical analgesics have been proposed as alternatives to oral and injectable medications to safely improve postoperative pain relief. We will conduct a single-center, placebo-controlled, double-blind, randomized crossover trial to assess the pain-relieving effect of an ibuprofen-containing gargle in patients undergoing extraction of mandibular third molars when compared with a placebo gargle.ObjectiveThis will be the first clinical study to compare the efficacy of an ibuprofen gargle with that of a placebo for relieving postoperative pain in addition to loxoprofen after mandibular third molar extraction.MethodsThis study will be performed at Kobe University Hospital. Participants (N=40) will be randomized equally to 1 of 2 groups. The ibuprofen-placebo group will receive an ibuprofen gargle on postoperative day (POD) 1 and a placebo gargle on POD 2. The placebo-ibuprofen group will receive a placebo gargle on POD 1 and an ibuprofen gargle on POD 2. Both groups will receive ibuprofen gargles on PODs 3-5 at least once daily. The primary objective is to estimate the within-subject difference on a visual analog scale (VAS) before and 5 minutes after using the ibuprofen or placebo gargle on PODs 1 and 2. The secondary objectives are to estimate the within-subject differences in ΔVAS before and 15 minutes after using the ibuprofen or placebo gargle on PODs 1 and 2, ΔVAS before and 5 or 15 minutes after using the ibuprofen gargle on PODs 3-5, overall efficacy (self-completion, 5 scales) on PODs 1-5, daily frequency of use (ibuprofen or placebo gargle and analgesics) on PODs 1-7, and the occurrence of adverse events.ResultsThe Certified Review Board of Kobe University approved the study. The intervention was implemented in May 2021. For the primary analysis, we will calculate the mean and SD of ΔVAS5 on PODs 1 and 2 and the within-study difference in ΔVAS5. The treatment effect will be estimated by dividing the mean ΔVAS5 in the within-subject difference by 2 and calculating the P value using an unpaired t test. For the secondary analysis, we will calculate the mean and SD of ΔVAS15 on PODs 1 and 2 and the within-study difference in ΔVAS15. The treatment effect will be estimated as in the primary analysis.ConclusionsThis trial will provide exploratory evidence of the efficacy and safety of an ibuprofen gargle for pain reduction after mandibular third molar extraction.Trial RegistrationJapan Registry of Clinical Trials jRCTs051210022; https://tinyurl.com/39ej23zuInternational Registered Report Identifier (IRRID)DERR1-10.2196/35533

Multiplate Platelet Function Testing upon Emergency Room Admission Fails to Provide Useful Information in Major Trauma Patients Not on Platelet Inhibitors

Platelet dysfunction is a suggested driver of trauma-induced coagulopathy. However, there is still a paucity of data regarding the impact of injury pattern on platelet function and the association of platelet dysfunction on transfusion requirements and mortality. In this retrospective cohort study, patients were grouped into those with isolated severe traumatic brain injury (TBI group), those with major trauma without TBI (MT group), and a combination of both major trauma and traumatic brain injury (MT + TBI group). Platelet function was assessed by whole blood impedance aggregometry (Multiplate®, MP). Three different platelet activators were used: adenosine-diphosphate (ADP test), arachidonic acid (ASPI test), and thrombin activated peptide-6 (TRAP test). Blood transfusion requirements within 6 h and 24 h and the association of platelet dysfunction on mortality was investigated. A total of 328 predominantly male patients (75.3%) with a median age of 53 (37–68) years and a median ISS of 29 (22–38) were included. No significant difference between the TBI group, the MT group, and the MT + TBI group was detected for any of the investigated platelet function tests. Unadjusted and adjusted for platelet count, the investigated MP assays revealed no significant group differences upon ER admission and were not able to sufficiently predict massive transfusion, neither within the first 6 h nor for the first 24 h after hospital admission. No association between platelet dysfunction measured by MP upon ER admission and mortality was observed. Conclusion: Injury pattern did not specifically impact platelet function measurable by MP. Platelet dysfunction upon ER admission measurable by MP was not associated with transfusion requirements and mortality. The clinical relevance of platelet function testing by MP in trauma patients not on platelet inhibitors is questionable.

Platelet function testing: Current practice among clinical centres in Northern Europe.

IntroductionPlatelet function tests are used to screen and diagnose patients with possible inherited platelet function defects (IPFD). Some acquired platelet dysfunction may be caused by certain drugs or comorbidities, which need to be excluded before testing.AimsTo identify current practice among centres performing platelet function tests in Northern Europe.MethodsA total of 14 clinical centres from Sweden (six), Finland (two), Denmark (two), Norway (one), Estonia (two) and Iceland (one) completed the survey questionnaire, the population capture area of about 29.5 million.ResultsSix of the 14 (42.8%) centres providing platelet function assessment represent comprehensive treatment centres (EUHANET status). A Bleeding score (BS) or ISTH bleeding assessment tool (ISTH BAT score) is evaluated in 11/14 (78.6%) centres and family history in all. Five/14 centres (35.7%) use structured preanalytical patient instructions, and 10/14 (71.4%) recorded questionnaire on the preassessment of avoidance of any drugs or natural products affecting platelet functions. Preliminary investigations of screening tests of coagulation are performed in 10/14 (71.4%), while in 4/14 (28.6%), the diagnostic work‐up of IPFD and von Willebrand disease (VWD) is performed simultaneously. The work‐up of IPFD includes peripheral blood smear in 10/14 (71.4%), platelet aggregometry in all, flow cytometry in 10/14 (71.4%) and Platelet Function Analysis (PFA) in 3/11 (28.6%). Molecular genetic diagnosis is available in 7/14 (50%) centres.ConclusionsThe considerable variability in the current practice illustrates the need for harmonization between the Northern European centres according to the international registers (i.e. EUHASS) and IPFD guidelines (ISTH, EHA).

MO848: Platelet Thrombus Formation in Chronic Haemodialysis Patients Measured by the Total Thrombus-Formation Analysis System

Abstract BACKGROUND AND AIMS Patients with end-stage renal disease (ESRD) receiving haemodialysis (HD) often experience bleeding. However, mechanisms behind this bleeding tendency are incompletely understood but may involve platelet dysfunction. We therefore studied platelet-dependent thrombus formation in flowing whole blood inside a microchip coated with collagen, and its association with circulating von Willebrand factor (VWF). METHOD Blood samples were obtained in 22 patients before and after HD. The area under the 10 min flow pressure curve in a microchip (AUC10) reflecting total platelet thrombogenicity was measured, using the Total Thrombus-formation Analysis System (T-TAS01). AUC10 < 260 indicates platelet dysfunction. VWF-antigen and measures of VWF-activity, i.e. VWF-RCo, VWF-CBA and latex-particle based VWF activity were also assayed. RESULTS VWF levels were moderately elevated and increased further after HD (P < 0.01 or lower). In contrast, AUC10 before and after HD was < 260 in 17/22 patients and < 130 in 15/22 patients, with no statistically significant difference in pre- versus post-HD measurements (median AUC10 in all patients 10.2 versus 20.3, respectively), altogether indicating reduced platelet thrombogenicity, but with some variability (5/22 patients with normal platelet responsiveness). AUC10 before and after HD correlated fairly well (r = 0.77, P < 0.001), and all VWF-related parameters (before versus after HD) were also correlated (r = 0.74 or higher; P < 0.0001). In contrast, no significant correlations were found between absolute values of AUC10 and any VWF-related parameters or between changes in values (i.e delta-values for differences between pre versus post HD). CONCLUSION Most ESRD-patients display moderate to severe platelet dysfunction as assessed by shear-induced collagen-dependent platelet thrombus formation with T-TAS01.Platelet thrombus formation under high shear, as measured by the collagen-coated PL-chip, is not importantly influenced by a moderate HD-induced increase in VWF. T-TAS01 should be further evaluated as a tool in the assessment of bleeding risk in patients on HD.

The role of immature platelet count and immature platelet fraction in determining the need for transfusion in patients undergoing CABG.

Platelet dysfunction has been shown to play a role in postoperative bleeding, however it is not clear whether immature platelets (IP) can induce appropriate homeostasis to prevent excessive bleeding in patients undergoing coronary artery bypass grafting (CABG). The aim of this study was to evaluate the postoperative change in IP count (IPC), IP fraction (IPF) and mean platelet volume (MPV), and to examine their relationship with postoperative bleeding and blood transfusion. One hundred and forty-nine consecutive patients undergoing elective CABG were included in this prospective study. All CABGs were performed by the same surgical team in a standardised method, utilising the on-pump technique. IPC, MPV and IPF were measured pre-operatively, after the completion of surgery, and at the postoperative first, third and fifth days. The primary outcome measure of this study was whether the need for transfusion was associated with IP, IPF, MPV and platelet count. There was a significant decrease of 7.77% in IPC on the day of the operation. Pre-operative IPC and IPF were correlated with postoperative drainage (p < 0.001), intraoperative blood transfusion (p < 0.001) and intensive care unit blood transfusion (p < 0.001). Pre-operative haemoglobin levels were significantly correlated with length of hospital stay. However, neither pre-operative IPC nor IPF were associated with length of hospital stay. Postoperative IPC was however associated with the length of hospital and intensive care unit stay (p = 0.008 and p = 0.009, respectively). Pre-operative IPC and IPF were significantly correlated with postoperative drainage and blood transfusion frequency. In patients undergoing CABG, these can be seen as serious guiding parameters in the estimation of postoperative bleeding.

MicroRNA-26b Attenuates Platelet Adhesion and Aggregation in Mice.

Platelets are key regulators of haemostasis, making platelet dysfunction a major driver of thrombosis. Numerous processes that determine platelet function are influenced by microRNAs (miRs). MiR-26b is one of the highest-expressed miRs in healthy platelets, and its expression in platelets is changed in a diseased state. However, the exact effect of this miR on platelet function has not been studied yet. In this study, we made use of a whole-body knockout of miR-26b in ApoE-deficient mice in order to determine its impact on platelet function, thrombus formation and platelet signalling both ex vivo and in vivo. We show that a whole-body deficiency of miR-26b exacerbated platelet adhesion and aggregation ex vivo. Additionally, in vivo, platelets adhered faster, and larger thrombi were formed in mice lacking miR-26b. Moreover, isolated platelets from miR-26b-deficient mice showed a hyperactivated Src and EGFR signalling. Taken together, we show here for the first time that miR-26b attenuates platelet adhesion and aggregation, possibly through Src and EGFR signalling.