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The Beckman Coulter® DXH900 uses the impedance method to measure the total leukocytes count. In presence of platelet aggregates, the device identifies the structural changes and associates an alarm with the leukocytes result. The aim of this study was to evaluate the influence of platelet aggregates using the principle of flow cytometry as a second assessment of the white blood cell count. Total leukocytes count was evaluated in 49 specimens with presence of platelet aggregates and 32 without anomaly. The differences between total leukocyte count by the two automatic methods (impedance and flow cytometry) and the microscopic method were compared. Without platelet aggregates, the median values were 5.6 (microscopic cell count), 5.4 (impedance) and 5.4 (flow cytometry) and no discordance was observed. In presence of platelet aggregates, the median values were 5.6, 6.4 and 5.1 respectively. The graphical analysis with the allowable total error range of ± 25.7% showed substantial analytical discrepancies (15/49) using impedance method while the flow cytometry method revealed minor disagreements (3/49). Analytical discordances versus WBC reference ranges showed 88% agreement and a substantial Kappa coefficient of 0.70 by impedance, while the flow cytometry method had 94% agreement and a perfect Kappa coefficient of 0.83. The formation of platelet aggregates increased the total leukocyte count performed DXH900 impedance method. Our study has shown that DXH 900 flow cytometry method may be an alternative to exclude the presence of pseudoleukocytosis. In case flags are generated, the microscopic method may be needed for the confirmation of WBC count. [ABSTRACT FROM AUTHOR]

COVID-19 is characterised by a broad spectrum of clinical and pathological features. Natural killer (NK) cells play an important role in innate immune responses to viral infections. Here, we analysed the phenotype and activity of NK cells in the blood of COVID-19 patients using flow cytometry, single-cell RNA-sequencing (scRNA-seq), and a cytotoxic killing assay. In the plasma of patients, we quantified the main cytokines and chemokines. Our cohort comprises COVID-19 patients hospitalised in a low-care ward unit (WARD), patients with severe COVID-19 disease symptoms hospitalised in intensive care units (ICU), and post-COVID-19 patients, who were discharged from hospital six weeks earlier. NK cells from hospitalised COVID-19 patients displayed an activated phenotype with substantial differences between WARD and ICU patients and the timing when samples were taken post-onset of symptoms. While NK cells from COVID-19 patients at an early stage of infection showed increased expression of the cytotoxic molecules perforin and granzyme A and B, NK cells from patients at later stages of COVID-19 presented enhanced levels of IFN-γ and TNF-α which were measured ex vivo in the absence of usual in vitro stimulation. These activated NK cells were phenotyped as CD49a+CD69a+CD107a+ cells, and their emergence in patients correlated to the number of neutrophils, and plasma IL-15, a key cytokine in NK cell activation. Despite lower amounts of cytotoxic molecules in NK cells of patients with severe symptoms, majority of COVID-19 patients displayed a normal cytotoxic killing of Raji tumour target cells. In vitro stimulation of patients blood cells by IL-12+IL-18 revealed a defective IFN-γ production in NK cells of ICU patients only, indicative of an exhausted phenotype. ScRNA-seq revealed, predominantly in patients with severe COVID-19 disease symptoms, the emergence of an NK cell subset with a platelet gene signature that we identified by flow and imaging cytometry as aggregates of NK cells with CD42a+CD62P+ activated platelets. Post-COVID-19 patients show slow recovery of NK cell frequencies and phenotype. Our study points to substantial changes in NK cell phenotype during COVID-19 disease and forms a basis to explore the contribution of platelet-NK cell aggregates to antiviral immunity against SARS-CoV-2 and disease pathology.

During the last decade, significant progress has been made in understanding thrombus composition and organization in the setting of acute ischemic stroke (AIS). In particular, thrombus organization is now described as highly heterogeneous but with 2 preserved characteristics: the presence of (1) two distinct main types of areas in the core—red blood cell (RBC)-rich and platelet-rich areas in variable proportions in each thrombus—and (2) an external shell surrounding the core composed exclusively of platelet-rich areas. In contrast to RBC-rich areas, platelet-rich areas are highly complex and are mainly responsible for the thrombolysis resistance of these thrombi for the following reasons: the presence of platelet-derived fibrinolysis inhibitors in large amounts, modifications of the fibrin network structure resistant to the tissue plasminogen activator (tPA)-induced fibrinolysis, and the presence of non-fibrin extracellular components, such as von Willebrand factor (vWF) multimers and neutrophil extracellular traps. From these studies, new therapeutic avenues are in development to increase the fibrinolytic efficacy of intravenous (IV) tPA-based therapy or to target non-fibrin thrombus components, such as platelet aggregates, vWF multimers, or the extracellular DNA network.

Platelet clumps present in anticoagulant specimens may generate a falsely decreased platelet count and lead to an incorrect diagnosis. A clear understanding of the ability of a haematology analyser (HA) to detect platelet clumps is important for routine work in the clinical laboratory. Citrate-anticoagulated whole-blood samples were collected from various patients as a negative group. Adenosine diphosphate (ADP)-induced platelet aggregation was performed on those negative samples to mimic platelet-clump-containing (positive) samples. The 'platelet clumps' and 'platelet abnormal' flags generated by the Sysmex XN-10 instrument were used to assess the flagging performance of this HA and demonstrate its flagging features. The complete blood count (CBC) results of paired negative and positive samples were compared to evaluate the impact of platelet clumps on the CBC parameters. A total of 187 samples were eligible for this study. The total accuracy, sensitivity, and specificity of the platelet clumps flag were 0.786, 0.626, and 0.947, respectively. The total accuracy, sensitivity, and specificity of the platelet abnormal flag were 0.631, 0.348, and 0.914, respectively. A separate assessment focusing on the positive samples with low platelet counts showed that the total sensitivities of the platelet clumps and platelet abnormal flags were 0.801 and 1.000, respectively. Platelet clumps may interfere with the leukocyte count and with platelet and erythrocyte indices. Platelet clumps can influence not only platelet indices but also leukocyte and erythrocyte counts. The Sysmex XN-10 instrument is sensitive to positive samples with low platelet counts but insensitive to those with high platelet counts. [ABSTRACT FROM AUTHOR]

Platelet aggregates has been used in surgery for many years. The primary goal of these 'Autologous Preparation' was to aggregate platelets and their growth factors and to convey it to a surgical site, to improve healing only. The latest research work shows that the PRF also can be used for Protection of Graft, neo-angiogenesis, vascularization locally and release of various growth factors apart from healing. Platelet rich fibrin (PRF) is considered as the new generation of platelet concentrate. "Choukroun's PRF" or Leucocyte PRF (L-PRF) is the new development, which was first developed by Choukroun's et al. in 2001 as an 'Autologous biomaterial.' A systematic literature search was performed to identify relevant articles that describes the use of PRF, through PubMed and Scopus databases. The focus of this article is to explore the role of PRF in esthetic facial surgery. [ABSTRACT FROM AUTHOR]

Introduction: An apico-marginal defect is a combined endodontic periodontal lesion that poses a challenge to the healing outcome and therefore often leads to the decreased prognosis of periapical surgery. This systematic review aims to analyze clinical studies and case reports that show evidence of the effect of autologous platelet aggregates on the healing outcome of apico-marginal defects. Materials and Methods: Literature search strategy was performed to find relevant clinical studies and case reports according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. The question was “healing outcome of apico-marginal defects treated using autologous platelet aggregates.” The review involved a search of electronic databases of Pubmed, Scopus, Ebsco host, as well as manual search. Results: Five relevant literature published between 1990 and June 2019 were selected after thorough analysis and exclusion according to the strict criteria. The included studies were related to clinical and radiographic healing outcome of apico-marginal defects with autologous platelet aggregates. Conclusion: The collected data suggested that autologous platelet aggregates give a favorable healing outcome for the management of apico-marginal defects.

There are two types of fibrinoids within the placenta, fibrin-type and matrix-type. The clinical importance of these fibrinoids is poorly understood. Design: Fibrinoid deposits occurring in normal and complicated pregnancies were studies with H&E stain and CD42b as a marker for platelet aggregates. Results: Fibrin-like fibrinoid was associated with platelet aggregates positive by CD42b immunostaining in the subchorionic and basal plate areas, facing the maternal circulation and intervillous spaces. Matrix-type fibrinoid did not stain with CD42b, and it was found in the intervillous spaces, trophoblastic cysts, intravillous tissue areas, and vascular walls in decidual vasculopathy. Conclusion: Fibrin-type fibrinoid within the intervillous spaces are mostly from maternal circulation and these fibrinoids are likely the result of the laminar flow change at specific anatomic locations, leading to activation of coagulatory cascades. The pathogenesis of matrix-like fibrinoid is unclear. CD42b immunostaining is helpful in differentiation of the types of fibrinoid in difficult cases. [ABSTRACT FROM AUTHOR]

Inflammatory mechanisms are activated, and thrombotic complications occur during the initial months after coronary artery bypass grafting (CABG). Therefore, changes over time of platelet activation and platelet–leukocyte interactions after CABG are of interest. Whole-blood flow cytometry was performed before, and 4–6 days, one month, and three months after elective CABG in 54 men with stable coronary artery disease treated with acetylsalicylic acid (ASA). Single platelets and platelet–leukocyte aggregates (PLAs) among monocytes (P-Mon), neutrophils (P-Neu), and lymphocytes (P-Lym) were studied without and with stimulation by submaximal concentrations of ADP, thrombin, and the thromboxane analog U46619. White blood cell counts were increased during the initial postoperative course, and platelet counts were increased after one month. Platelet P-selectin expression was significantly enhanced at one month when stimulated by thrombin and U46619 and at three months with ADP and thrombin. All PLAs subtypes were increased at one month without stimulation in vitro. P-Mon and P-Neu stimulated by ADP, thrombin, or U46619 were significantly increased one month after the operation but decreased compared to baseline at three months. Agonist stimulated P-Lyms were increased at one month and remained increased at three months after ADP stimulation. There was significant platelet activation and formation of PLAs unstimulated and after agonist stimulation by ADP, thrombin, and a thromboxane analog after CABG in patients with stable coronary artery disease irrespective of ASA treatment. Changes observed up to three months after CABG support further studies of the clinical implications of protracted increases in platelet activation and platelet–leukocyte interactions.

Inflammatory mechanisms are activated, and thrombotic complications occur during the initial months after coronary artery bypass grafting (CABG). Therefore, changes over time of platelet activation and platelet–leukocyte interactions after CABG are of interest. Whole-blood flow cytometry was performed before, and 4–6 days, one month, and three months after elective CABG in 54 men with stable coronary artery disease treated with acetylsalicylic acid (ASA). Single platelets and platelet–leukocyte aggregates (PLAs) among monocytes (P-Mon), neutrophils (P-Neu), and lymphocytes (P-Lym) were studied without and with stimulation by submaximal concentrations of ADP, thrombin, and the thromboxane analog U46619. White blood cell counts were increased during the initial postoperative course, and platelet counts were increased after one month. Platelet P-selectin expression was significantly enhanced at one month when stimulated by thrombin and U46619 and at three months with ADP and thrombin. All PLAs subtypes were increased at one month without stimulation in vitro. P-Mon and P-Neu stimulated by ADP, thrombin, or U46619 were significantly increased one month after the operation but decreased compared to baseline at three months. Agonist stimulated P-Lyms were increased at one month and remained increased at three months after ADP stimulation. There was significant platelet activation and formation of PLAs unstimulated and after agonist stimulation by ADP, thrombin, and a thromboxane analog after CABG in patients with stable coronary artery disease irrespective of ASA treatment. Changes observed up to three months after CABG support further studies of the clinical implications of protracted increases in platelet activation and platelet–leukocyte interactions. [ABSTRACT FROM AUTHOR]

Background: Severe COVID-19 is associated with an excessive immunothrombotic response and thromboinflammatory complications. Vaccinations effectively reduce the risk of severe clinical outcomes in patients with COVID-19, but their impact on platelet activation and immunothrombosis during breakthrough infections is not known., Objectives: To investigate how preemptive vaccinations modify the platelet-immune crosstalk during COVID-19 infections., Methods: Cross-sectional flow cytometry study of the phenotype and interactions of platelets circulating in vaccinated ( n  = 21) and unvaccinated patients with COVID-19, either admitted to the intensive care unit (ICU, n  = 36) or not (non-ICU, n  = 38), in comparison to matched SARS-CoV-2-negative patients ( n  = 48), was performed., Results: In the circulation of unvaccinated non-ICU patients with COVID-19, we detected hyperactive and hyperresponsive platelets and platelet aggregates with adaptive and innate immune cells. In unvaccinated ICU patients with COVID-19, most of whom had severe acute respiratory distress syndrome, platelets had high P-selectin and phosphatidylserine exposure but low capacity to activate integrin αIIbβ3, dysfunctional mitochondria, and reduced surface glycoproteins. In addition, in the circulation of ICU patients, we detected microthrombi and platelet aggregates with innate, but not with adaptive, immune cells. In vaccinated patients with COVID-19, who had no acute respiratory distress syndrome, platelets had surface receptor levels comparable to those in controls and did not form microthrombi or platelet-granulocyte aggregates but aggregated avidly with adaptive immune cells., Conclusion: Our study provides evidence that vaccinated patients with COVID-19 are not associated with platelet hyperactivation and are characterized by platelet-leukocyte aggregates that foster immune protection but not excessive immunothrombosis. These findings advocate for the importance of vaccination in preventing severe COVID-19., (© 2023 The Author(s).)

Background Diverse variables are involved in apheresis platelet collection, processing and storage. This survey shows how these are realized in Spain. Method An analysis of collected data was performed in a questionnaire completed by ten Transfusion Centers (TC) which perform between 50 and 520 apheresis procedures per month. This information comprises the procedures used to collect, inspect and store apheresis platelet concentrates (PC), and quality control data. Results Macroscopic inspection of PC is performed in all TC, especially during the first few hours post-collection and before distribution. The type of processor, duration of post-collection resting periods and temperature from the time of collection until distribution are similar in all TC. In 80% of TC, PC with small and scarce aggregates are distributed to transfusion services. The presence of clumps is influenced by type of processor, female donor, cold ambient temperature and collection of hyperconcentrated platelets, and is often recurrent in the same donor, although some TC have not found any influential variables. Overall, no objective inspection methods are followed, although there are exceptions. The degree of compliance with quality control parameters, such as the number of units studied, mean platelet yield, residual leukocyte counts and pH at expiry date, is acceptable in all TC. Compliance in terms of number of microbiological culture samples is variable. Discussion The usual practice in Spanish TC with respect to the collection, post-collection handling and storage of apheresis PC can be considered uniform, although some specific aspects of analyses should follow more objective methods. [ABSTRACT FROM AUTHOR]

Objectives: to determine the association between organic alteration and pathological morphological findings in peripheral blood smears of patients with preeclampsia-eclampsia syndrome. Methods: It is framed in a quantitative, descriptive and transversal approach, which shows 54 patients from a study population of 137 patients admitted with diagnosis of preeclampsia at the Hospital Materno Infantil German Urquidi, between May and December Of 2016. It is consisted of a documented review through a checklist of the clinicallaboratory alterations of each one of the patients; as the microscopic visualization of the spread of peripheral blood smear in search of schistocytes, equinocytes and platelet aggregates, it was performed in a laboratory authorized by SEDES. Results: of 54 patients, 85% presented schistocytes, equinocytes and platelet aggregates, considered as a positive result; the remaining 15% did not present any of these alterations considering as a negative result. Taking these results and comparing with the clinical-laboratory alterations in this study group, it was possible to determine that there is an association between positive smear and organic alteration; The odds ratio (OR) being 66; Translated in probabilities is equal to 98.5% risk of organic alteration with a positive peripheral blood smear (Table 1). Conclusions: The search for schistocytes, equinocytes and platelet aggregates in smears of peripheral blood is a simple, economical and fast method to perform; which shows the probability of developing some organic alteration when the smear of peripheral blood is positive; thus anticipating the exacerbation of clinical and biochemical manifestations in patients with preeclampsia. [ABSTRACT FROM AUTHOR]

We have conducted a quantitative morphological evaluation of intravascular platelet activity and platelet aggregates in patients with diabetes mellitus type 2 with arterial hypertension under correction of arterial blood pressure with losartan and with considering of glycaemic control level and microalbuminuria. It is shown that in the patients with diabetes mellitus in a compensation with microalbuminuria observed significant degree violations of intravascular platelet activity, as a result of this is a significant increase in the relative content of bipolar and active forms with decreasing of disk cytes and rising of small platelet aggregates. Inclusion of losartan in the treatment makes it possible to reduce the degree of platelet hemostasis disorders from the 6th month of the treatment. The standard treatment for one year in the patients with diabetes mellitus in a subcompensation or decompensation is accompanied by increasing intravascular platelet activity and the continuing accumulation of small, medium and large platelet aggregates. Losartan usage in these patients limits the reduction of discocytes and formation of giant spherical platelets with pseudopodia and normalizes the contents of the bipolar forms since 6 month from starting treatment and significantly inhibits the formation of platelet aggregates in comparison with the initial level.

Pseudothrombocytopenia (PTP) is defined by falsely low platelet counts on automated analyzers caused by in vitro phenomena including large platelet aggregates in blood samples. Diagnosis and resolution of PTP is crucial as it can lead to unwarranted interventions. We discuss a case of PTP in a pre-surgical setting, which was resolved using 37°C incubation and Kanamycin.

Type 2B von Willebrand disease (VWD) is frequently associated with distinct platelet morphology. Here we present a familial case of type 2B VWD with a novel VWF mutation (p.R1308S), which caused neonatal thrombocytopenia. The mother had been treated for refractory immune thrombocytopenia (ITP) for more than 20 years. The most important hematological features of this case were large platelets and platelet aggregates detected on peripheral blood smears. Hemostatic tests showed enhanced ristocetin-induced platelet agglutination at low-ristocetin concentrations, absence of high-molecular weight von Willebrand factor (VWF) multimers, and low VWF cofactor activity/antigen ratio. In patients with intractable ITP, family history of ITP and consecutive neonatal thrombocytopenia, the differential diagnosis of congenital thrombocytopenia is mandatory. For this purpose, the identification of large platelets and platelet aggregates on peripheral blood smears is the key aspect of type 2B VWD diagnosis. [ABSTRACT FROM AUTHOR]

Pathogen reduction technology (PRT) is associated with increased blood safety through the inactivation of virus, bacteria and parasites. Dilution of platelet (PLT) concentrates in platelet additive solution (PAS) is a requirement for applying PRT, and that it is associated with various practical issues: increasing PLT target yields to compensate for loss of PLTs through PRT, extended apheresis donation time due to PAS addition at the end of the procedure, and the appearance of PLT aggregates. We proposed to program higher target PLT yields for plateletpheresis donations to compensate for PLTs lost due to PRT processing. To verify the feasibility of this approach, a paired study of the Amicus 3.11 and Trima 5.22 apheresis separators was performed using 196 procedures carried out on the same 98 donors. The Amicus 3.11 presented a higher collection efficiency (CE: 78.02 vs. 69.63; p < 0.0001) and collection rate (CR: 8.3 vs. 7.00; p < 0.0001); it was also faster (56.92 vs. 62.60; p < 0.0001) than the Trima 5.22 apheresis device. However, analysis of the donor group with higher pre-procedure PLT counts showed similar productivity results for the Amicus and Trima. The percentage of PLT aggregates detected was higher with the TA than the AM (8.62% vs. 3.88%, p = 0.04). Overall, both separators are entirely suitable for collecting hyper-concentrated PLTs that are subsequently diluted in PAS for PRT, without excessively increasing the donation time. PLT aggregation can occur after apheresis collection but most of them disappear by day 1. Further investigation is needed to study the clinical impact of PLT aggregation. [ABSTRACT FROM AUTHOR]

Background and Objectives Platelet ( PLT) aggregates can occur during or after PLT component processing. However, very few reports investigating the phenomenon and its clinical significance have been published. In this review, currently available information about aggregates in PLT products is summarized and possible causal factors as well as preventive strategies are discussed. Materials and Methods A review of the MEDLINE® database for relevant publications from 1960 to May 2013 was conducted. Results It is well known that PLT aggregates may occur during or after the PLT product preparation process. These aggregates normally dissipate with rest and agitation. However, in some rare cases, the aggregates do not dissipate within 24 h and can persist up to the end of storage. Exposure to low temperature, low p H, short resting period after collection, different collection systems, presence of bubbles or foam inside the PLT bag, PLT-container interactions, proper product mixing and donor-dependent variables may have an impact on the formation of PLT aggregates. Although publications are rare, the presence of small numbers of PLT aggregates appears to have only limited impact on PLT in vitro quality. Furthermore, data on the clinical impact of PLT aggregates are lacking. Conclusion Despite the fact that PLT aggregates occur in PLT products, published data on this topic remain scant. Considering the concern of clinicians about this phenomenon, more studies are needed which should focus on the possible clinical impact of such aggregates and precautions to avoid PLT aggregate formation in PLT products. [ABSTRACT FROM AUTHOR]

COVID-19 is characterised by a broad spectrum of clinical and pathological features. Natural killer (NK) cells play an important role in innate immune responses to viral infections. Here, we analysed the phenotype and activity of NK cells in the blood of COVID-19 patients using flow cytometry, single-cell RNA-sequencing (scRNA-seq), and a cytotoxic killing assay. In the plasma of patients, we quantified the main cytokines and chemokines. Our cohort comprises COVID-19 patients hospitalised in a low-care ward unit (WARD), patients with severe COVID-19 disease symptoms hospitalised in intensive care units (ICU), and post-COVID-19 patients, who were discharged from hospital six weeks earlier. NK cells from hospitalised COVID-19 patients displayed an activated phenotype with substantial differences between WARD and ICU patients and the timing when samples were taken post-onset of symptoms. While NK cells from COVID-19 patients at an early stage of infection showed increased expression of the cytotoxic molecules perforin and granzyme A and B, NK cells from patients at later stages of COVID-19 presented enhanced levels of IFN-γ and TNF-α which were measured ex vivo in the absence of usual in vitro stimulation. These activated NK cells were phenotyped as CD49a + CD69a + CD107a + cells, and their emergence in patients correlated to the number of neutrophils, and plasma IL-15, a key cytokine in NK cell activation. Despite lower amounts of cytotoxic molecules in NK cells of patients with severe symptoms, majority of COVID-19 patients displayed a normal cytotoxic killing of Raji tumour target cells. In vitro stimulation of patients blood cells by IL-12+IL-18 revealed a defective IFN-γ production in NK cells of ICU patients only, indicative of an exhausted phenotype. ScRNA-seq revealed, predominantly in patients with severe COVID-19 disease symptoms, the emergence of an NK cell subset with a platelet gene signature that we identified by flow and imaging cytometry as aggregates of NK cells with CD42a + CD62P + activated platelets. Post-COVID-19 patients show slow recovery of NK cell frequencies and phenotype. Our study points to substantial changes in NK cell phenotype during COVID-19 disease and forms a basis to explore the contribution of platelet-NK cell aggregates to antiviral immunity against SARS-CoV-2 and disease pathology., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Malengier-Devlies, Filtjens, Ahmadzadeh, Boeckx, Vandenhaute, De Visscher, Bernaerts, Mitera, Jacobs, Vanderbeke, Van Mol, Van Herck, Hermans, Meersseman, Wilmer, Gouwy, Garg, Humblet-Baron, De Smet, Martinod, Wauters, Proost, Wouters, Leclercq, Lambrechts, Wauters and Matthys.)

Assessment of platelet activation and/or function is important for primary and secondary prevention of vascular events. To test the hypothesis that determination of platelet aggregation in patients with chronic-stage cerebral infarction (CI) provides a simple measure of risk for ischemic stroke, we used a conventional hematology analyzer to detect aggregates and to assess the efficacy of antiplatelet agents in preventing spontaneous aggregate formation. Platelet aggregates were measured in citrated blood from 142 magnetic resonance imaging confirmed CI patients and 97 controls without CI (nonstroke). Aggregates were detected in 1 of 36 (2.8%) nonstroke subjects without risk factors, but in 24 of 52 (46.2%) nonstroke subjects with risk factors (odds ratio [OR], 3.32; 95% confidence interval [CI], 1.10-10.00), in 21 of 35 (60.0%) nonstroke subjects with a predictive factor (carotid artery intima-media thickness [IMT] >1.1 mm) (OR, 9.13; 95% CI, 2.70-30.48), and in 31 of 63 (49.2%) CI patients who had not received antiplatelet therapy (OR, 2.16; 95% CI, 1.12-4.17). After adjusting for other risk factors, the appearance of platelet aggregates was correlated only with IMT ≥1.1 mm. The rate of appearance of platelet aggregates was 0.33-fold lower in patients on antiplatelet therapy compared with those not on antiplatelet therapy (24.1%; 19 of 79 CI patients). Patients with platelet aggregates in the blood are considered at high risk for ischemic stroke, because the appearance of aggregates is associated with increased IMT. Our method is suitable for screening platelet function in high-risk patients and for examining the efficacy of antiplatelet agents. [Copyright &y& Elsevier]

The article presents a letter to the editor in response to a study which compared the performance of the low platelet count by two detection methods, the impedance method and the optical method, between a novel hematological analyzer Mindray and the used Sysmex XE-2100 analyzer.

Magnetic resonance imaging (MRI) of pulmonary emboli obtained ex vivo, verified by immunohistochemistry, showed that platelet layers display brighter signal intensity than areas containing predominantly red blood cells (RBC) in T 1-weighted MRI. These results were surprising since platelets do not contain paramagnetic haemoglobin that would enhance magnetic relaxation. Our assumption was that the fibrin meshwork areas with entrapped RBC retain abundant extracellular space filled with serum, whereas platelets regroup into tight aggregates lacking serum, essentially mimicking solid tissue structure, rich with cellular proteins that enhance T 1-relaxation. Our hypothesis was examined by MRI and NMR relaxometry of in vitro RBC suspensions and sedimented platelets, as well as by MRI of model clots and pulmonary emboli obtained ex vivo. Pure sedimented platelets exhibited shorter proton spin lattice relaxation times ( T 1 = 874 ± 310 ms) than those of venous blood of a healthy male with 40% haematocrit ( T 1 = 1277 ± 66 ms). T 1-values of RBC samples containing high haematocrit (≥80%) resembled T 1 of platelet samples. In T 1-weighted spin-echo MRI echo time and repetition time (TE/TR = 10/120 ms) the ratio of signal intensities between a non-retracted whole blood clot (with a haematocrit of 35%) and a pure platelet clot was 3.0, and the ratio between a retracted whole blood clot with an estimated haematocrit of about 58% and a pure platelet clot was 2.6. We conclude that T 1-weighted MRI can discriminate between platelet layers of thrombi and RBC-rich areas of thrombi that are not compacted to a haematocrit level of ≥80%. [ABSTRACT FROM AUTHOR]

Several hematological abnormalities associated with HIV have been documented, but the mechanisms responsible for the cytopenias in AIDS patients are complex and not always completely understood. Thrombocytopenia, which occurs in about 40% of patients with HIV infection, may be caused by increased peripheral platelet destruction, a defect in platelet production due to the impaired formation of platelets by HIV-infected magakaryocytes, or a combination of these. The aim of this study was to compare the morphology of the platelet aggregates in platelet-rich plasma (PRP) clots prepared from HIV patients with those of controls without HIV. These platelet aggregates were studied using the scanning electron microscope to determine the effect of the virus on platelet ultrastructure. The results showed that although the platelets do aggregate, the morphology was changed with membrane blebbing as well as torn cellular membranes. Membrane blebbing is typically associated with apoptosis. It is concluded that the altered morphology of platelet aggregates in HIV patients may be related to thrombocytopenia as a result of peripheral platelet destruction. [ABSTRACT FROM AUTHOR]

Abstract: Background: Laser light irradiation is assumed to have biostimulating effect in various cell types. However, there is still a lack of information concerning response of blood platelets to laser light irradiation. Methods: In our study we used flow cytometry to monitor the effect of a green Nd-YAG laser (532 nm, 30 mW) irradiation on platelet activation and the expression of activated GPIIbIIIa glycoprotein complex (fibrinogen receptor) of whole blood platelets stained with fluorolabelled monoclonal antibody PAC-1. Also the formation of platelet microparticles and aggregates in a population of whole blood platelets following such irradiation was evaluated. Results: Effects of laser light on platelet activation and reactivity were significant over a wide range of applied energies (p &#60;0.01). While low and medium laser light energies (18 and 54 J) increased platelet activation, the irradiation with a high-energy laser light (108 J) resulted in depressed platelet reactivity and attenuated platelet response to activators. In addition, laser light irradiation had significant influence on the formation of platelet microparticles in either resting (p &#60;0.05) or ADP-activated (p &#60;0.05) platelets, while no significant effect was observed in collagen-activated platelets. On the other hand, laser light irradiation significantly increased the formation of platelet aggregates both in resting (p &#60;0.01) and agonists-activated (p &#60;0.05) platelets. Conclusions: Our results clearly point that the laser light irradiation of blood platelets can trigger signal transduction, leading to platelet activation, as well as the gradual loss of natural platelet reactivity and platelets’ ability to respond to activating agents. [Copyright &y& Elsevier]

Abstract: Background: Although it is known that RBC concentrates may contain buffy coat and platelet concentrates may contain platelet aggregates, the circulation and distribution of these materials in the blood products have never been reported. Study design and methods: Baboon platelets were labeled with 111-In-oxine, aggregated with ADP and autotransfused without a filter. Baboon buffy coat was stored at 4°C, labeled with 111-In-oxine and autotransfused without a filter. The circulation of the radiolabeled platelets and buffy coat was measured and the distribution of the buffy coat and platelet aggregates was measured by external scanning of the baboon using a gamma camera. The effects of the infusion of aggregated platelets, buffy coat, and gelatin on the plasma fibronectin level also were evaluated. Results: The 111-In-oxine labeled platelet aggregates were initially sequestered in the lungs and released into the peripheral blood during the next 3h, during which time the cell associated radioactivity increased by about 25%. Following the autotransfusion of 111-In-oxine labeled buffy coat, the 111-In-oxine radioactivity over the lungs increased, but decreased during the 60-min post-transfusion period as the radioactivity over the liver increased. Cell-associated radioactivity increased by about 10% over the 3-h post-transfusion period. Fibronectin levels decreased by 3% following the autotransfusion of platelet aggregates, by 10% after the autotransfusion of buffy coat and by 50% after the infusion of gelatin. Conclusions: 111-In-oxine radioactivity in the platelet aggregates and buffy coat was initially sequestered in the lungs, and 10–25% of the 111-In-oxine cell-associated radioactivity was released into the circulation during the 24-h post-transfusion period. [Copyright &y& Elsevier]

Summary Laser-based flow cytometry and aperture-impedance methods are still the dominant technologies used for cell analysis in haematology, but both are limited to areas such as morphological analysis of red cell shape and high-sensitivity detection of platelet agglutinates and aggregates. Flow cytometry alone does not provide precise measurement of red cell volume without chemical pretreatment before detection and aperture-impedance is still considered the gold standard in the field of particle volume analysis. In the present study, an experimental prototype instrument called the imaging-combined flow cytometer (IFC) was evaluated. The IFC is equipped with an imaging device consisting of a pulse laser, lens units and a charge-coupled device (CCD) camera in addition to the flow-cytometric optical set-up. A personal computer was attached to the instrument to handle images derived from the imaging device. Laser illumination was triggered so that the image of an object was captured for each exposure of the CCD camera. Objects in the images were used to calculate size and shape information and to compute fractal texture features by image processing after each measurement. The advantage of the IFC is that it can capture images of selected cells of interest at the same time as flow-cytometric detection. Estimation of red cell volume, discrimination of red cells and platelets, and detection of platelet agglutinates and aggregates were attempted using the IFC in combination with image processing, It was found that image analysis on the IFC could provide a substitutional function for mean corpuscular volume (MCV) estimation and detection of platelet agglutinates and aggregates. The additional information generated by the IFC may be useful in diagnostic haematology. [ABSTRACT FROM AUTHOR]

Summary Platelet counts and automated detection of platelet clumps were evaluated by optical analysis with the Abbott CD4000 analyser (Abbott Diagnostics, Santa Clara, CA, USA) in this South African study of 828 samples referred for malaria investigations. Based on microscopy (Micro) and rapid tests (RT) for HRP2 protein and parasite-associated LDH, malaria negative samples (n = 417) were defined as Micro– , RT– . Convalescent cases (n = 64) were Micro– , RT+ and had a recent record of positive microscopy. Malaria positive cases were subdivided into Micro+ (n = 315) and Micro– , RT+ , PCR+ (polymerase chain reaction) (n = 32) subgroups. The mean platelet count for Micro+ cases (89.7 × 109 /l) was significantly lower than both the malaria negative (mean 212.6 × 109 /l) and convalescent malaria (mean 152.8 × 109 /l) groups; 89% of microscopy positive cases were thrombocytopenic (< 150 × 109 /l) and 30% had severe thrombocytopenia (< 50 × 109 /l). For comparison, 32% of the 417 malaria negative samples were thrombocytopenic and 6% of these were severe. Two thirds of samples with parasitaemia above 10% had platelet counts of < 50 × 109 /l while the counts were largely independent of parasite numbers when the parasitaemia was below 10%. Thirty percent of samples with microscopically detectable parasites had a PltClmp flag compared to 13% of the malaria negative group but, when the actual platelet count was taken into account, it became apparent that appearance of the flag was primarily associated with thrombocytopenia per se rather than malaria status. In most samples with a PltClmp flag, the CD4000 optical platelet clump ‘signature’ was indicative of small platelet aggregates and giant platelets. Morphological examination confirmed... [ABSTRACT FROM AUTHOR]

Endothelial cells that cover the lumen of all blood vessels have the inherent capacity to express both pro and anticoagulant molecules. However, under normal physiological condition, they generally function to maintain a non-thrombogenic surface for unobstructed blood flow. In response to injury, certain stimuli, or as a result of dysfunction, endothelial cells release a highly adhesive procoagulant protein, von Willebrand factor (VWF), which plays a central role in formation of platelet aggregates and thrombus generation. Since VWF expression is highly restricted to endothelial cells, regulation of its levels is among the most important functions of endothelial cells for maintaining hemostasis. However, with aging, there is a significant increase in VWF levels, which is concomitant with a significant rise in thrombotic events. It is not yet clear why and how aging results in increased VWF levels. In this review, we have aimed to discuss the age-related increase in VWF, its potential mechanisms, and associated coagulopathies as probable consequences. [ABSTRACT FROM AUTHOR]

The effects of Nd-YAG laser irradiation on platelet function in vitro were studied using platelet rich plasma obtained from the blood of healthy volunteers. Laser delivery was effected via the 'bare' optical fibre, thermal 'hot tip' fibre and spectraprobe and the effects of these probes on platelet function were compared. Fall in platelet count and mean platelet volume (MPV) were proportional to increasing energy delivery with all three probes, the effect being maximal with the spectraprobe, moderate with the 'hot tip' and least with the 'bare' optical fibre. A significant decrease in percentage aggregation of platelets in response to added ADP, collagen and ristocetin with increasing energy delivery was also observed with all three probes. The formation of preformed aggregates, however, showed an increase proportional to energy delivery with all three probes. The differential effects of the various probes used in this study on platelet function may enhance our understanding of the complex role played by platelets in the pathogenesis of complications such as arterial thrombosis and re-occlusion after laser angioplasty. [ABSTRACT FROM AUTHOR]

Thrombocytopenia is one of the adverse effects of extracorporeal circulation (ECC) but the mechanism of which has not been fully understood. Blood-gas interface, mechanical agitation, rough surface of extracorporeal circuit and sequestration in the liver have been considered to be a cuase of platelet loss. Extracorporeal circuit which provides large artificial surface for contact of blood has been blamed as the site of platelet destruction during oxygenation. However, the part of the oxygenator responsible for platelet loss has not been located. This study was designed to identify the sites of extracorporeal circuit responsible for platelet loss during ECC with scanning electron microscopy (SEM) of the post-perfusion circuit. The accumulation of platelet aggregates was most pronounced at the defoaming net and blood filter where a sudden changes in velocity of blood flow take place. The aggregates were considered to be formed locally at these sites. However, there were no accumulation and/or adherence of platelet aggregates of significant degree at the other parts of the circuit, namely venous and arterial tubings, venous colum and arterial reservoir. Platelets seem to be removed from the circulation during each passage by defoaming net and blood filter. However the other parts of the circuit seem to be less blamed for the platelet loss. It was not possible to conclude whether the formation and trapping of platelet microaggregates at the defoaming net and blood filter or the destruction by oxygen bubbles is mainly responsible for the plateletloss during ECC. [ABSTRACT FROM AUTHOR]

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Study objective – The aim of the study was to evaluate the effects of streptokinase, urokinase and recombinant tissue plasminogen activator (TPA) on platelet aggregability and metabolism and the stability of preformed platelet aggregates.Design – The experiments (n = 15 for each condition) were performed on citrated plasma or on platelet suspensions in phosphate buffered saline, both with a standardised platelet count of 250 × 109·litre−1.Subjects – were healthy volunteers.Measurements and main results – With both ADP (1 μmol·litre−1) and collagen (1 mg·litre−1) as aggregating agents, streptokinase at ≥105 units·litre−1 led to reduction in the rate of platelet aggregation. With collagen and in most instances with ADP, this was associated with a decreased extent of aggregation, though in five out of 30 cases with ADP as aggregating agent, a conversion from reversible to irreversible aggregation occurred with streptokinase. Urokinase inhibited platelet aggregation at ≥3 × 105 units·litre−1 with both aggregating agents. TPA inhibited aggregation at ≥1 mg·litre−1 with ADP and at ≥3.3 mg·litre−1 with collagen as aggregating agent. The inhibitory effect was still present when the platelets were suspended in saline. Platelet synthesis of thromboxane on stimulation with collagen, and of c-AMP on stimulation with prostaglandin E1, was markedly reduced by either agent. The stability of platelet aggregates, as assessed photometrically during a 90 min exposure to stirring stress, increased when streptokinase or urokinase was added to platelet rich plasma, but remained uninfluenced with TPA.Conclusions – Urokinase and TPA inhibited platelet aggregability uniformly and in a dose dependent manner. Streptokinase inhibited platelet aggregation in most instances, but led to a stimulation of aggregation in a minority of cases. These effects of the thrombolytic agents on platelets might have an influence on the occurrence of bleeding and of reocclusion after thrombolytic therapy. [ABSTRACT FROM PUBLISHER]

The present study was designed to examine the effects of a new organic nitrate, teopranitol, in acute myocardial ischaemia. Adult cats were subjected to 5 h of myocardial ischaemia by permanent ligation of the left anterior descending coronary artery (LAD). Teopranitol (10 mg kg × h) or physiological saline (vehicle) was infused i.v., beginning 30 min after LAD occlusion and continued until the end of the experiment. All animals subjected to myocardial ischaemia showed a significant elevation of the ST-segment within 20 min of LAD occlusion. In the LAD-vehicle group, the ST-segment elevation continued to increase; teopranitol attentuated this increase and significantly reduced the ST-segment elevation at 4 and 5 h (P<0.05). The loss of creatine phosphokinase-specific activity from the ischaemic myocardium was significantly reduced by teopranitol (P<0.05), indicating an improved preservation of myocardial tissue. There was a significant initial reduction in mean arterial blood pressure by teopranitol in sham-operated cats but no consistent change of this parameter, heart rate or the computed pressure-rate product in LAD-occluded cats. Teopranitol did completely reverse the ischaemia induced formation of platelet aggregates at 1 to 5 h (P<0.05). It is concluded that teopranitol exerts a significant protective effect in acute myocardial ischaemia in vivo that is independent of changes in systemic haemodynamics and might be associated with the generation of an antiplatelet activity in vivo. [ABSTRACT FROM PUBLISHER]

Platelet counts and aggregates have been measured in arterial, coronary sinus and peripheral venous blood in groups of patients with and without coronary artery disease, and under various conditions associated with myocardial ischaemia. No changes in platelet counts were observed. An increase in platelet aggregates across the coronary vascular bed was observed during spontaneous or ergometrine-induced ischaemia, but not with pacing-induced angina nor at the onset of coronary occlusion causing infarction. Platelet aggregates were high in systemic blood samples from patients with frequent episodes of spontaneous angina but not in samples from patients with stable effort angina, nor were they increased with exercise-induced angina or after myocardial infarction. The findings suggest that platelet aggregates are found in coronary sinus blood when there is very severe proximal narrowing (but not complete occlusion) of a coronary artery sufficient to cause cardiac pain at rest, but not when proximal constriction is less severe and the ischaemia is pacing-induced. Increased platelet aggregates in systemic blood samples may be a marker of recent episodes of rest pain. [ABSTRACT FROM PUBLISHER]

Platelets are essential mediators of inflammation and thrombosis. Chronic obstructive pulmonary disease (COPD) is a heterogeneous multisystem disease, causing significant morbidity and mortality worldwide. Recent evidence suggests that the lung is an important organ for platelet biogenesis. Cigarette smoking has been shown to induce platelet aggregation and decrease the capacity of mitochondrial electron transport system in platelets. Preclinical and clinical studies have suggested that platelets may contribute to the development of COPD through the breakdown of lung elastin by platelet factor 4, platelet activation and formation of platelet aggregates, and modulation of hypoxia signaling pathways. Recent large population studies have produced encouraging results indicating a potential role for aspirin in preventing exacerbations and delaying disease progression in patients with COPD. This review summarizes the information about the lung as an organ for platelet production, pathophysiological functions of platelets and platelet mediators in the development of COPD, and the most updated evidence on the utility of aspirin in patients with COPD., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Although antiplatelet drugs are widely used for the prevention and treatment of atherothrombosis, clinical tests capable of evaluating their efficacy have not been established. Focusing on platelet aggregates in blood, we announced the world's first basic technology, an intelligent Image-Activated Cell Sorter (iIACS), that can exhaustively and rapidly identify cells one-by-one using image analysis with high-speed imaging and deep learning to sort specific cells according to the analysis results. This technology has even enabled the detection of single platelets with a size of 2 µm in blood samples and the quantification of the proportion of platelet aggregates by size. Furthermore, by applying this technique, we discovered different morphological features of platelet aggregates formed by different types of agonists that activate platelets. Here, we discuss this application in the early diagnosis of thrombotic microangiopathy (TMA). In the early stage of TMA, consumptive thrombocytopenia is caused by excessive platelet activation. Therefore, the detection of excessive platelet aggregates can lead to early TMA diagnosis.

Hyperglycemia alone may not explain the increased risk of cardiovascular diseases (CVDs) in patients with type 1 diabetes (T1D) compared with type 2. This study emphases on the evaluation of some platelet activity markers in patients with T1D, with relevance to some metabolic disorders as hyperlipidemia and hyperglycemia. This study was performed on 35 patients with T1D and 20 healthy controls. All participants were subjected to full history taking, clinical examination and assay of glycated hemoglobin (HbA1c), and lipid profile. The expression of CD62P and CD36 on platelets and the frequency of platelet–monocyte, and platelet–neutrophil aggregates were assessed by flow cytometry. Patients showed significantly higher expression of CD62P and CD36 than the control group. Platelets aggregates with monocytes were also higher among patients than the control group. Levels of CD36+ platelets, CD62P+ platelets, and platelet–monocyte aggregates revealed significant correlations with the levels of HbA1c, total cholesterol, low-density lipoprotein, and triglycerides. Hyperlipidemia and hyperglycemia accompanying T1D have a stimulatory effect on platelet activation which probably makes those patients vulnerable to CVD than nondiabetics. [ABSTRACT FROM AUTHOR]

Intrapancreatic and intraabdominal accessory spleens (IPIASs) are rarely encountered in endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) biopsies. However, as incidentally discovered IPIAS can mimic a benign or malignant pancreatic neoplasm on imaging studies, a definitive diagnosis made by EUS-FNA can avert an unnecessary surgical intervention or additional radiologic follow-up. We report five cases of intrapancreatic splenules and one case of accessory spleen (AS) in which a definitive diagnosis was made on EUS-FNA. Previously recognized FNA cytomorphologic features of splenic tissue, including ASs and splenosis, are endothelial cells and polymorphous lymphocytes admixed with neutrophils, eosinophils, plasma cells, histiocytes, and lymphoglandular bodies. We describe the additional finding of abundant large platelet aggregates as another distinguishing feature of splenic tissue on FNA. In all six cases, large platelet aggregates were identified along with polymorphous lymphoid cells, lymphoglandular bodies, loose aggregates of endothelial cells and scattered or aggregated bland spindle cells. A review of 10 consecutive cases of EUS-FNA-sampled benign intraabdominal lymph nodes showed that the presence of large platelet aggregates, three-dimensional aggregates of lymphoid cells and of bland slender spindle cells and the absence of follicular germinal cell components (tingible body macrophages and lymphohistiocytic aggregates) are useful in differentiating IPIASs from reactive lymph nodes. Immunoperoxidase stains were useful to confirm a suspected IPIASs by showing CD31-positive acellular flocculent material, consistent with large platelet aggregates and a rich CD8-positive endothelial cell network between CD45-positive lymphoid cells and CD68-positive histiocytes in all six cases., (Copyright © 2011 Wiley Periodicals, Inc., a Wiley company.)