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Infection by SARS-CoV-2 is associated with a high risk of thrombosis. The laboratory documentation of hypercoagulability and impaired fibrinolysis remains a challenge. Our aim was to assess the potential usefulness of viscoelastometric testing (VET) to predict thrombotic events in COVID-19 patients according to the literature. We also (i) analyzed the impact of anticoagulation and the methods used to neutralize heparin, (ii) analyzed whether maximal clot mechanical strength brings more information than Clauss fibrinogen, and (iii) critically scrutinized the diagnosis of hypofibrinolysis. We performed a systematic search in PubMed and Scopus databases until 31st December 2020. VET methods and parameters, and patients' features and outcomes were extracted. VET was performed for 1063 patients (893 intensive care unit (ICU) and 170 non-ICU, 44 studies). There was extensive heterogeneity concerning study design, VET device used (ROTEM, TEG, Quantra and ClotPro) and reagents (with non-systematic use of heparin neutralization), timing of assay, and definition of hypercoagulable state. Notably, only 4 out of 25 studies using ROTEM reported data with heparinase (HEPTEM). The common findings were increased clot mechanical strength mainly due to excessive fibrinogen component and impaired to absent fibrinolysis, more conspicuous in the presence of an added plasminogen activator. Only 4 studies out of the 16 that addressed the point found an association of VETs with thrombotic events. So-called functional fibrinogen assessed by VETs showed a variable correlation with Clauss fibrinogen. Abnormal VET pattern, often evidenced despite standard prophylactic anticoagulation, tended to normalize after increased dosing. VET studies reported heterogeneity, and small sample sizes do not support an association between the poorly defined prothrombotic phenotype of COVID-19 and thrombotic events.

Reliable laboratory diagnosis of heparin-induced thrombocytopenia (HIT) remains a major clinical concern. Immunoassays are highly sensitive, while confirmatory functional tests (based on heparin-dependent platelet activation) lack standardization. We evaluated the diagnostic performance of a functional flow cytometric assay (FCA) based on the detection of heparin-dependent platelet activation with an anti-p-selectin. A total of 288 patients were included (131 HIT-positive and 157 HIT-negative) with a HIT diagnosis established by expert opinion adjudication (EOA) considering clinical data and local laboratory results. The FCA was centrally performed in a single laboratory on platelet-rich plasma, using a very simple four-color fluorometer. The results were standardized according to the Heparin Platelet Activation (HEPLA) index. The serotonin release assay (SRA) was performed in the four French reference laboratories. Based on the final HIT diagnosis established by EOA, the sensitivity and specificity of the FCA were 88 and 95%, respectively, values very similar to those of the SRA (88 and 97%, respectively). This study showed that the FCA, based on easily implementable technology, may be routinely used as a reliable confirmatory test for HIT diagnosis.

Lowe syndrome (LS) is an oculocerebrorenal syndrome of Lowe (OCRL1) genetic disorder resulting in a defect of the OCRL protein, a phosphatidylinositol-4,5-bisphosphate 5-phosphatase containing various domains including a Rho GTPase-activating protein (RhoGAP) homology domain catalytically inactive. We previously reported surgery-associated bleeding in patients with LS, suggestive of platelet dysfunction, accompanied with a mild thrombocytopenia in several patients. To decipher the role of OCRL in platelet functions and in megakaryocyte (MK) maturation, we conducted a case-control study on 15 patients with LS (NCT01314560). While all had a drastically reduced expression of OCRL, this deficiency did not affect platelet aggregability, but resulted in delayed thrombus formation on collagen under flow conditions, defective platelet spreading on fibrinogen and impaired clot retraction. We evidenced alterations of the myosin light chain phosphorylation (P-MLC), with defective Rac1 activity and, inversely, elevated active RhoA. Altered cytoskeleton dynamics was also observed in cultured patient MKs showing deficient proplatelet extension with increased P-MLC that was confirmed using control MKs transfected with OCRL-specific small interfering(si)RNA (siOCRL). Patients with LS also had an increased proportion of circulating barbell-shaped proplatelets. Our present study establishes that a deficiency of the OCRL protein results in a defective actomyosin cytoskeleton reorganisation in both MKs and platelets, altering both thrombopoiesis and some platelet responses to activation necessary to ensure haemostasis., (© 2021 British Society for Haematology and John Wiley & Sons Ltd.)

Background: Idarucizumab has been included in guidelines for the management of bleeding or surgical procedure in dabigatran-treated patients without need for biological monitoring. The aim of the study was to assess the prognostic value of dabigatran plasma level before reversal to test the hemostatic efficacy of idarucizumab. The secondary objectives were (i) to analyze plasma dabigatran level according to the risk of rebound and (ii) to evaluate the incidence of post-reversal non-favorable clinical outcomes (including thromboembolism, bleeding, antithrombotic, and death) and antithrombotic resumption. Methods and Results: This was an observational multicentric cohort study, which included all French patients who required idarucizumab for dabigatran reversal. Between May 2016 and April 2019, 87 patients from 21 French centers were enrolled. Patients received idarucizumab for overt bleeding ( n = 61), urgent procedures ( n = 24), or overdose without bleeding ( n = 2). Among patients with major bleeding ( n = 57), treatment with idarucizumab was considered effective in 44 (77.2%) of them. Patients who did not achieve effective hemostasis after reversal had a significantly higher mean level of plasma dabigatran at baseline (524.5 ± 386 vs. 252.8 ng/mL ± 235, p = 0.033). Furthermore, patients who did not achieve effective hemostasis after reversal had less favorable outcomes during follow-up (46.2 vs. 81.8%, p = 0.027). ROC curve identified a cutoff of 264 ng/mL for dabigatran level at admission to be predictive of ineffective hemostasis. No plasma dabigatran rebound was observed after reversal in patients with dabigatran plasma level < 264 ng/mL at baseline. Conclusion: This retrospective study shows that dabigatran level before reversal could predict hemostatic effectiveness and dabigatran plasma rebound after idarucizumab injection., Competing Interests: NG discloses consulting fees by Boehringer Ingelheim, Bayer, Bristol-Myers Squibb/Pfizer and LEO Pharma. RC reports consulting fees from Aspen. A-CM discloses consulting fees from Bayer and Boehringer Ingelheim, and consulting fees and grant from Bristol-Myers-Squibb/Pfizer. ALL discloses consulting fees by Boehringer Ingelheim and Bayer. LB reports personal fees and non-financial support from Aspen, Actelion, Bayer, LEO-pharma, Bristol-Myers Squibb/Pfizer, and MSD; non-financial support from Daiichi; and grants and personal fees from Sanofi outside the submitted work. DS declares consulting fees from Bayer, Bristol-Myers Squibb/Pfizer, Boehringer Ingelheim, Aspen, and LEO-Pharma. The remaining 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 © 2020 Gendron, Chocron, Billoir, Brunier, Camoin-Jau, Tuffigo, Faille, Teissandier, Gay, de Raucourt, Suner, Bonnet, Martin, Lasne, Ladhari, Lebreton, Bertoletti, Ajzenberg, Gaussem, Morange, Le Cam Duchez, Viallon, Roy, Lillo-le Louët and Smadja.)

The lack of quality control for patient point-of-care (POC) INR devices is an issue that has led the French health authorities to make recommendations: a laboratory INR (lab INR) has to be performed at the same time as the POC INR every 6 months. However, the differences observed between the two INRs, POC and lab INRs, are not necessarily due to a failure of the POC INR device. We present here a review of the different causes of discrepancies between INR results, which are the basis of the proposals of the Groupe français d'études sur l'hémostase et la thrombose (GFHT) on the management of lab and POC INR discrepancies. Pre-analytical conditions may account for discrepancies (sampling, transport and storage conditions), as well as analytical factors (mainly the nature of the thromboplastin used) and the clinical context (inflammatory or autoimmune diseases, polycythaemia...). The interpretation of INR discrepancies is not always easy and these proposals aim at standardizing the procedure to be followed in order to make the most appropriate decision for the patient.

Emicizumab, a bispecific humanised monoclonal antibody restoring to some extent the function of activated FVIII deficient in haemophilia A, represents a major therapeutic advance in the management of haemophilia A patients. No dosage adjustment is required, which leads to a major change for patients used to regular biological monitoring which is particularly burdensome in the case of substitution therapy. In some circumstances, such as before an invasive procedure or in case of bleeding, biological monitoring will be necessary and emicizumab's interference with haemostasis tests, particularly those based on an activated partial thromboplastin times (aPTT), must be known to best interpret the tests and to select the most appropriate methods to guide therapy. The normalisation of aPTT in patients treated with emicizumab is not sufficient to consider haemostasis as normalised. In the event of administration of FVIII to a patient receiving emicizumab, the determination of FVIII should use a chromogenic method using non-human reagents. Coagulation global tests have been proposed to evaluate the biological response when using bypassing agents in patients treated with emicizumab, but the usefulness must be confirmed. The French group BIMHO presents proposals for biological monitoring of a patient treated with emicizumab according to clinical situations., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Replacement therapy with plasma-derived or recombinant FVIII and FIX (pdFVIII/pdFIX or rFVIII/rFIX) concentrates is the standard of treatment in patients with haemophilia A and B, respectively. Measurement of factor VIII (FVIII:C) or factor IX (FIX:C) levels can be done by one-stage clotting assay (OSA) or chromogenic substrate assay (CSA). The French study group on the Biology of Hemorrhagic Diseases (a collaborative group of the GFHT and MHEMO network) presents a literature review and proposals for the monitoring of FVIII:C and FIX:C levels in treated haemophilia A and B patients, respectively. The use of CSA is recommended for the monitoring of patients treated with pdFVIII or rFVIII including extended half-life (EHL) rFVIII. Except for rFVIII-Fc, great caution is required when measuring FVIII:C levels by OSA in patients substituted by EHL-rFVIII. The OSA is recommended for the monitoring of patients treated with pdFIX or rFIX. Large discordances in the FIX:C levels measured for extended half-life rFIX (EHL-rFIX), depending on the method and reagents used, must lead to great attention when OSA is used for measuring FIX:C levels in patients substituted by EHL-rFIX. Data of most of recent studies, obtained with spiked plasmas, deserve to be confirmed in plasma samples of treated patients., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Correct diagnosis of the cause of thrombocytopenia is crucial for the appropriate management of patients. Hyposialylation/desialylation (characterized by abnormally high β-galactose exposure) accelerates platelet clearance and can lead to thrombocytopenia. However, the reference range for β-galactose exposure in healthy individuals has not been defined previously., Objective: The objective of the present study was to develop a standardized assay of platelet β-galactose exposure for implementation in a clinical laboratory., Methods: β-Galactose exposure was measured in platelet-rich plasma by using flow cytometry and Ricinus communis agglutinin (RCA). A population of 120 healthy adults was recruited to study variability., Results: We determined an optimal RCA concentration of 12.5 μg/mL. The measure was stable for up to 4 hours (mean fluorescence intensity [MFI]-RCA: 1233 ± 329 at 0 hour and 1480 ± 410 at 4 hours). The platelet count did not induce a variation of RCA and the measure of RCA was stable when tested up to 24 hours after blood collection (MFI-RCA: 1252 ± 434 at day 0 and 1140 ± 297 24 hours after blood sampling). To take into account the platelet size, results should be expressed as RCA/forward scatter ratio. We used the assay to study variability in 120 healthy adults, and we found that the ratio is independent of sex and blood group., Conclusion: We defined a normal range in a healthy population and several preanalytical and analytical variables were evaluated, together with positive and negative controls. This assay may assist in the diagnosis of thrombocytopenic diseases linked to changes in β-galactose exposure., (© 2020 The Authors. Research and Practice in Thrombosis and Haemostasis published by Wiley Periodicals LLC on behalf of International Society on Thrombosis and Haemostasis.)

Patients with type 2B von Willebrand disease (vWD) (caused by gain-of-function mutations in the gene coding for von Willebrand factor) display bleeding to a variable extent and, in some cases, thrombocytopenia. There are several underlying causes of thrombocytopenia in type 2B vWD. It was recently suggested that desialylation-mediated platelet clearance leads to thrombocytopenia in this disease. However, this hypothesis has not been tested in vivo The relationship between platelet desialylation and the platelet count was probed in 36 patients with type 2B von Willebrand disease (p.R1306Q, p.R1341Q, and p.V1316M mutations) and in a mouse model carrying the severe p.V1316M mutation (the 2B mouse). We observed abnormally high elevated levels of platelet desialylation in both patients with the p.V1316M mutation and the 2B mice. In vitro , we demonstrated that 2B p.V1316M/von Willebrand factor induced more desialylation of normal platelets than wild-type von Willebrand factor did. Furthermore, we found that N-glycans were desialylated and we identified αIIb and β3 as desialylation targets. Treatment of 2B mice with sialidase inhibitors (which correct platelet desialylation) was not associated with the recovery of a normal platelet count. Lastly, we demonstrated that a critical platelet desialylation threshold (not achieved in either 2B patients or 2B mice) was required to induce thrombocytopenia in vivo In conclusion, in type 2B vWD, platelet desialylation has a minor role and is not sufficient to mediate thrombocytopenia., (Copyright© 2019 Ferrata Storti Foundation.)

Deep vein thrombosis is a common disease associated with a variety of complications including post-thrombotic syndrome as a late complication. It is now clear that in addition to classical deep vein thrombosis triggers such as blood flow disturbance, hypercoagulability, and vessel wall changes, inflammation has a key role in the pathophysiology of deep vein thrombosis, and there is a close relationship between inflammation and coagulation. As attested by changes in several plasma biomarkers, inflammation may have a significant role in the development of post-thrombotic syndrome. Here, we review the link between inflammation and deep vein thrombosis and thus the potential value of anti-inflammatory and/or anticoagulant drugs in the treatment of deep vein thrombosis and the prevention of post-thrombotic syndrome.

Purpose: Viscoelastic tests (VETs), thromboelastography (TEG ® ) and thromboelastometry (ROTEM ® ) are global tests of coagulation performed on whole blood. They evaluate the mechanical strength of a clot as it builds and develops after coagulation itself. The time required to obtain haemostasis results remains a major problem for clinicians dealing with bleeding, although some teams have developed a rapid laboratory response strategy. Indeed, the value of rapid point-of-care diagnostic devices such as VETs has increased over the years. However, VETs are not standardised and there are few recommendations from the learned societies regarding their use. In 2014, the recommendations of the International Society of Thrombosis and Haemostasis (ISTH) only concerned haemophilia. The French Working Group on Perioperative haemostasis (GIHP) therefore proposes to summarise knowledge on the clinical use of these techniques in the setting of emergency and perioperative medicine., Methods: A review of the literature., Principal Findings: The role of the VETs seems established in the management of severe trauma and in cardiac surgery, both adult and paediatric. In other situations, their role remains to be defined: hepatic transplantation, postpartum haemorrhage, and non-cardiac surgery. They must be part of the global management of haemostasis based on algorithms defined in each centre and for each population of patients. Their position at the bedside or in the laboratory is a matter of discussion between clinicians and biologists., Conclusion: VETs must be included in algorithms. In consultation with the biology laboratory, these devices should be situated according to the way each centre functions., (Copyright © 2018 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Introduction: Emicizumab (Hemlibra ® ) recently became available and requires an adaptation for managing bleeding, suspected bleeding and emergency or scheduled invasive procedures in haemophilia A patients with inhibitor. This implicates a multidisciplinary approach and redaction of recommendations for care that must be regularly adapted to the available data., Aim: The following text aims to provide a guide for the management of people with haemophilia A with inhibitor treated with emicizumab in case of bleeding or invasives procedures., Methods: The French network on inherited bleeding disorders (MHEMO), the French Reference Centre on Haemophilia (CRH), in collaboration with the French Working Group on Perioperative Haemostasis (GIHP) have been working together to make proposals for the management of these situations., Results: Haemostatic treatment and other medications should be given stepwise, according to the severity and location of the bleeding or the risk of bleeding of the procedure as well as the haemostatic response obtained at each step in order to ensure an optimal benefit/risk ratio., Conclusion: The lack of data means that it is only possible to issue proposals rather than recommendations., (© 2019 John Wiley & Sons Ltd.)

Background: Extracorporeal circuit coating has been shown to improve coagulation derangements during pediatric cardiopulmonary bypass (CPB). This study compared platelet function and hemostasis activation in pediatric cardiac surgery conducted with nonheparin coating (Balance; Medtronic, Minneapolis, MN) versus heparin-based coating (Carmeda; Medtronic) circuits., Methods: A prospective, randomized, double-center trial was conducted in children older than 1 month undergoing congenital heart disease treatment. Blood samples were collected at baseline (T0), 15 minutes after the start of CPB (T1), and 15 minutes (T2) and 1 hour after the conclusion of CPB (T3). The primary end point of the study was to detect potential differences in β-thromboglobulin levels between the two groups at T2. Other coagulation and platelet function indicators were analyzed as secondary end points., Results: The concentration of β-thromboglobulin increased significantly at T2 in both groups. However, there was no significant difference between the groups across all time points. There was no difference in the secondary end points between the groups., Conclusions: The two circuits showed similar biological effects on platelet function and coagulation. This observation may be useful in optimizing the conduct of CPB and in rationalizing its cost for the treatment of congenital heart disease., (Copyright © 2019 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

The French Working Group on Perioperative Haemostasis (GIHP) and the French Study Group on Haemostasis and Thrombosis (GFHT), in collaboration with the French Society for Anaesthesia and Intensive Care (SFAR), drafted up-to-date proposals on the management of antiplatelet therapy for non-elective invasive procedures or bleeding complications. The proposals were discussed and validated by a vote; all proposals could be assigned with a high strength. Management of oral antiplatelet agents in emergency settings requires knowledge of their pharmacokinetic and pharmacodynamic parameters, evaluation of the degree of alteration of haemostatic competence and the associated bleeding risk. Platelet function testing may be considered. When antiplatelet agent-induced bleeding risk may worsen the prognosis, measures should be taken to neutralize antiplatelet therapy, by considering not only the efficacy of available means (which can be limited for prasugrel and even more for ticagrelor), but also the risks that these means expose the patient to. The measures include platelet transfusion at the appropriate dose and haemostatic agents (tranexamic acid; recombinant activated factor VII for ticagrelor). When possible, postponing non-elective invasive procedures at least for a few hours until the elimination of the active compound (which could compromise the effect of transfused platelets) or, if possible, for a few days (reduction of the effect of antiplatelet agents) should be considered., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Replacement therapy with plasma-derived or recombinant FIX (pdFIX or rFIX) concentrates is the standard of treatment in patients with hemophilia B. The method predominantly used for measuring factor IX (FIX:C) levels is the one-stage clotting assay (OSA) but this method depends on the activated partial thromboplastin time (APTT) reagent and the coagulation analyzer used, and wide variations in the measurements of FIX recovery have been reported with some factor concentrates. The French study group on the biology of hemorrhagic diseases (a collaborative group of the GFHT and MHEMO network), presents a review of the literature and proposals for the monitoring of FIX:C levels in treated hemophilia B patients. The use of OSA calibrated with a plasma reference tested against the current FIX WHO International Standard is recommended for the monitoring of patients treated with pdFIX or rFIX. Chromogenic substrate assays (CSA) are adequate for the monitoring of patients treated with Rixubis ® , but data available for Benefix ® are currently too limited. For extended half-life rFIX (EHL-rFIX), large discordances in the FIX:C levels measured were evidenced, depending on the method and reagents used. Great attention is therefore required for measuring FIX:C levels by OSA in patients substituted by EHL-rFIX. Commercial kits for CSA are not equivalent, and although potentially useful, they are not validated for all EHL-rFIX. Most of recent studies reported data obtained with spiked plasmas, which deserve to be confirmed on plasma samples collected in treated patients.

Replacement therapy with plasma-derived or recombinant FVIII (pdFVIII or rFVIII) concentrates is the standard of treatment in patients with hemophilia A. The reference method used for measuring factor VIII (FVIII:C) levels in patients treated by FVIII concentrates is the chromogenic substrate assay (CSA). However, the one-stage clotting assay (OSA) is predominantly used in current clinical practice, but this method depends on the activated partial thromboplastin time (APTT) reagent and the coagulation analyzer used, and wide variations in the measurements of FVIII recovery have been reported with some factor concentrates. The French study group on the biology of hemorrhagic diseases (a collaborative group of the GFHT and MHEMO network) presents a review of the literature and proposals for the monitoring of FVIII:C levels in treated hemophilia A patients. The use of CSA calibrated with a plasma reference tested against the current FVIII WHO (World Health Organization) International Standard is recommended for the monitoring of patients treated with pdFVIII or rFVIII including extended half-life (EHL) rFVIII. OSA are adequate for the monitoring of patients treated with pdFVIII or with most of rFVIII concentrates. However, preliminary comparison with CSA is mandatory before measuring FVIII:C by OSA in patients treated by Refacto AF ® . For rFVIII-EHL, OSA are only acceptable for Elocta®. Great caution is therefore required when measuring FVIII:C levels by OSA in patients substituted by other EHL-rFVIII. Indeed, most of recent studies reported data obtained with spiked plasmas, which deserve to be confirmed on plasma samples collected in treated patients.

The genetic causes of congenital hypothyroidism due to thyroid dysgenesis (TD) remain largely unknown. We identified three novel TUBB1 gene mutations that co-segregated with TD in three distinct families leading to 1.1% of TUBB1 mutations in TD study cohort. TUBB1 (Tubulin, Beta 1 Class VI) encodes for a member of the β-tubulin protein family. TUBB1 gene is expressed in the developing and adult thyroid in humans and mice. All three TUBB1 mutations lead to non-functional α/β-tubulin dimers that cannot be incorporated into microtubules. In mice, Tubb1 knock-out disrupted microtubule integrity by preventing β1-tubulin incorporation and impaired thyroid migration and thyroid hormone secretion. In addition, TUBB1 mutations caused the formation of macroplatelets and hyperaggregation of human platelets after stimulation by low doses of agonists. Our data highlight unexpected roles for β1-tubulin in thyroid development and in platelet physiology. Finally, these findings expand the spectrum of the rare paediatric diseases related to mutations in tubulin-coding genes and provide new insights into the genetic background and mechanisms involved in congenital hypothyroidism and thyroid dysgenesis., (© 2018 The Authors. Published under the terms of the CC BY 4.0 license.)

Enoxaparin is commonly used in the prevention of renal allograft vascular thrombosis but off-label in children, and no consensus exists regarding the optimal dosing and dose adjustment. In this retrospective study, 444 anti-Xa levels were obtained from 30 pediatric renal transplant recipients in order to investigate enoxaparin population pharmacokinetics. The main results were (1) 25% of children achieved the target anti-Xa activity 36 hours after initiation of treatment, (2) anti-Xa time courses were best described by a 1-compartment open model with first-order absorption, (3) body weight but not renal function was the sole covariate influencing clearance and volume of distribution, and (4) large between-subject and between-occasion variabilities in anti-Xa activity were observed. However, creatinine-based estimated glomerular filtration rate in the first post-renal transplantation hours may not reliably reflect the actual renal function of the children. Based on the final population model, a Bayesian-based program was developed in order to estimate the individual pharmacokinetic parameters on a single anti-Xa measurement, allowing determination of the next enoxaparin dose that will quickly achieve an appropriate anti-Xa activity (targeting 0.3-0.5 IU/mL) and anticoagulation. Finally, these results should help standardize practices that remain to date largely heterogeneous in pediatric intensive care units., (© 2018, The American College of Clinical Pharmacology.)

Background/objectives: Sickle cell disease (SCD) complications mostly result from vascular dysfunction, concerning systemic microvasculature and cerebral large vessels. The aim of this cohort study was to identify potential circulating biomarkers predictive for further vascular event occurrence in pediatric SCD., Methods: We consecutively enrolled 108 children with SCD at steady state, aged 3-18 years old (median 9.8 years). Hematology, coagulation, hemolysis, endothelial, platelet and vascular activation parameters were recorded at inclusion. Neurovascular and systemic vascular events were prospectively recorded during a mean follow-up period of 27 months., Results: Patients at steady state displayed significantly higher hemolysis and platelet activation markers, higher leukocyte, CD34+ hematopoietic stem cell and microvesicle counts, and a pro-coagulant profile compared to controls matched for age and ethnicity. Circulating endothelial cell or nucleosome level did not differ. During the follow-up period, 36 patients had at least one neurovascular (n = 12) or systemic vascular event (n = 25). In a multivariate model, high CD34+ cell count was the best predictor for the occurrence of a vascular event (OR 1.2 for 1000 cell/mL increase, 95% CI [1.049-1.4], p = 0.013, sensitivity 53%, specificity 84% for a threshold of 8675 cells/mL)., Conclusion: CD34+ cell count at steady state is a promising biomarker of further vascular event in children with SCD.

Point of care testing (POCT) must comply with regulatory requirements according to standard EN ISO 22870, which identify biologists as responsible for POCT. INR for vitamin K antagonists (VKAs) monitoring is a test frequently performed in haemostasis laboratories. Bedside INR is useful in emergency room, in particular in case of VKAs overdosage but also for specific populations of patients like paediatrics or geriatrics. INR POCT devices are widely used at home by the patients for self-testing, but their use in the hospital by the clinical staff for bedside measurement is growing, with devices which now comply with standard for POCT accreditation for hospital use. The majority of point of care devices for INR monitoring has shown a good precision and accuracy with results similar to those obtained in laboratory. With the aim to help the multidisciplinary groups for POCT supervision, the medical departments and the biologists to be in accordance with the standard, we present the guidelines of the GFHT (Groupe français d'étude sur l'hémostase et la thrombose, subcommittee "CEC et biologie délocalisée") for the certification of POCT INR. These guidelines are based on the SFBC guidelines for the certification of POCT and on the analysis of the literature to ascertain the justification of clinical need and assess the analytical performance of main analysers used in France, as well as on a survey conducted with biologists.

Background: The quality of life (QoL) of children receiving vitamin K antagonist (VKA) treatment has been scarcely studied., Aim: To assess QoL of children, and its evolution, throughout our non-selective international normalized ratio (INR) self-monitoring education programme., Methods: Children and parents completed QoL questionnaires (Qualin, PedsQL) during education sessions. Scores were compared with those from controls., Results: A total of 111 children (mean±standard deviation age 8.7±5.4 years) were included over a 3-year period. Indications for VKA treatment were congenital heart diseases (valve replacement [42.3%], total cavopulmonary connection [29.7%]), myocardiopathy (11.7%), coronary aneurysm (7.2%), venous/intracardiac thrombosis (4.5%), pulmonary artery hypertension (1.8%), arrhythmia (0.9%) and extra-cardiac disease (1.8%). Eighty children, 105 mothers and 74 fathers completed the QoL questionnaires. QoL was good among children aged 1-4 years and moderately impaired in those aged between 5 and 18 years. There was no significant relationship between self-reported QoL and patient's sex, type of VKA, number of group sessions attended, disease duration or time of diagnosis (prenatal or postnatal). QoL scores were significantly lower among children with congenital heart diseases compared with other diseases. There were few differences in QoL between children under transient VKA treatment and those treated for life. Parental proxy QoL scoring correlated well with but was significantly lower than child self-assessments. QoL reported by mothers increased throughout the education programme, independently of any improvement of the health condition., Conclusions: This QoL study provides original data from a large cohort of children and their parents participating in a formalized INR self-monitoring education programme for VKA treatment., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Microbial nucleic acid recognition serves as the major stimulus to an antiviral response, implying a requirement to limit the misrepresentation of self nucleic acids as non-self and the induction of autoinflammation. By systematic screening using a panel of interferon-stimulated genes we identify two siblings and a singleton variably demonstrating severe neonatal anemia, membranoproliferative glomerulonephritis, liver fibrosis, deforming arthropathy and increased anti-DNA antibodies. In both families we identify biallelic mutations in DNASE2, associated with a loss of DNase II endonuclease activity. We record increased interferon alpha protein levels using digital ELISA, enhanced interferon signaling by RNA-Seq analysis and constitutive upregulation of phosphorylated STAT1 and STAT3 in patient lymphocytes and monocytes. A hematological disease transcriptomic signature and increased numbers of erythroblasts are recorded in patient peripheral blood, suggesting that interferon might have a particular effect on hematopoiesis. These data define a type I interferonopathy due to DNase II deficiency in humans.

: Hemophilia A carriers have an abnormal X chromosome with a molecular abnormality of FVIII gene. These carriers, long considered to be free of bleeding risk, could have the same symptoms as mild hemophiliacs. This study aim to assess bleeding risk of hemophilia A carriers monitored at the Clinical Hematology Department of Dakar. This is a prospective study of a period of 6 months including 22 hemophilia A carriers aged between 8 and 48 years. Hemophilia carriers were recruited using the genealogical tree of hemophiliacs followed in the service. Their diagnosis was carried out by long range PCR and Sanger sequencing method searching the molecular abnormality responsible for hemophilia in their family. Bleeding risk was determined using a questionnaire consisting of different bleeding symptoms quoted from -1 to 4 according to the severity. Total of different values allow to determine the bleeding score which was pathological if it was greater than or equal to 1. Medium age was 22.5 years (8-48) (SD = 9.28). Four hemophilia A carriers (18.1%) presented bleeding symptoms and had a bleeding score at least 1 (P = 0.02). Menorrhagia was predominant (13.6%) followed by epistaxis (9%), gingivorrhagia (9%), and prolonged bleeding after tooth extraction (9%). Factor VIII level was lower in hemophilia carriers who presented bleeding (42 ± 8.61 UI/l) versus hemophilia carriers without bleeding (100 ± 50.95 UI/l) (P = 0.001). There was no significant correlation between bleeding occurrence and age (P = 0.81), activated patial thromboplastin time value (P = 0.97) and FVIII/Von Willebrand Factor ratio (P = 0.12). One in five hemophilia carriers presented bleeding and the questionnaire was effective to identify hemophilia carriers who had a risk of bleeding.

Pneumatic tube delivery system (PTS) enables to reduce considerably turnaround times. The aim of the study was to assess the influence of the PTS on the quality of routine biochemical and hematological tests in our laboratory. Blood samples from 6 hospitalized patients and 8 healthy volunteers were analyzed. Blood samples were delivered to the laboratory by a PTS and by a human courier. We performed the following analysis: ionized calcium, sodium, potassium, lactate deshydrogenase (LDH), aspartate aminotransferase (ASAT), arterial blood gas, complete blood count and coagulation test as prothrombin time, activated partial thromboplastin time, factors V and VIII. Results were compared between the both method of transport according to the recommendation of the Société française de biologie clinique and the French committee for accreditation (SH-GTA01, norme NF ISO 5275-6). The hemolysis index of plasma was similar between the groups and no morphological differences were found on blood cells. For three samples, when delivered by PTS, LDH levels (two samples) and neutrophil polynuclear count (one sample) were above the recommended guidelines compared to those delivered by courier. Conversely, LDH levels and FVIII were below in two samples delivered by PTS. LDH levels, PNN count or factor VIII can be affected by PTS without the clinical interpretation being modified. We concluded that the PTS can be used to transport blood samples for routine biochemical and hematological analysis in our hospital.

Introduction: The complex hemostatic changes associated with Berlin Heart (BH) implantation in children require a challenging antithrombotic treatment. The aim of this retrospective analysis was to evaluate the thromboelastography (TEG)-platelet mapping (PM) assay to monitor antiplatelet therapy in children implanted with a BH., Methods: TEG-PM was performed in 4 BH-implanted patients receiving dipyridamole and aspirin, and 9 healthy volunteers. Patients' antiplatelet therapy was adjusted to TEG-PM results. Light transmission aggregometry (LTA) was also available for 2 of these patients., Results: Between 2009 and 2014, 4 BH-implanted patients received a dual antiplatelet therapy monitored by TEG-PM. In 2 patients, 18 of 34 tracings were atypical, because the maximum amplitude due to fibrin never stabilized, which made difficult antiplatelet therapy adjustment as recommended by BH's guidelines. To overcome this difficulty, TEG-PM and LTA were next performed in parallel. However, both methods led to different decisions to adjust antiplatelet therapy in 57% of the cases. In order to better understand this atypical tracing, TEG-PM was also performed in 9 volunteers and surprisingly 3 of them had the same atypical tracing. This atypical tracing was corrected by adding apyrase, suggesting that adenosine diphosphate (ADP) participates to spontaneous platelet activation in heparinized samples. In addition, we evidenced a high variability in the responses of TEG-PM with ADP in volunteers., Conclusions: Antiplatelet therapy monitoring in BH-implanted children remains challenging, as TEG-PM is sensitive to several preanalytical and analytical conditions.

In the absence of specific antidote to fondaparinux, two modified forms of antithrombin (AT), one recombinant inactive (ri-AT) and the other chemically inactivated (chi-AT), were designed to antagonise AT-mediated anticoagulants, e. g. heparins or fondaparinux. These inactive ATs were previously proven to effectively neutralise anticoagulant activity associated with heparin derivatives in vitro and in vivo, as assessed by direct measurement of anti-FXa activity. This study was undertaken to evaluate in vitro the effectivity of inactive ATs to reverse anticoagulation by heparin derivatives and to compare them with non-specific fondaparinux reversal agents, like recombinant-activated factor VII (rFVIIa) or activated prothrombin-complex concentrate (aPCC), in a thrombin-generation assay (TGA). Addition of fondaparinux (3 µg/ml) to normal plasma inhibited thrombin generation by prolonging lag time (LT) as much as 244 % and lowering endogenous thrombin potential (ETP) to 17 % of their control (normal plasma) values. Fondaparinux-anticoagulant activity was reversed by ri-AT and chi-AT, as reflected by the corrections of LT up to 117 % and 114 % of its control value, and ETP recovery to 78 % and 63 %, respectively. Unlike ri-AT that had no effect on thrombin generation in normal plasma, chi-AT retained anticoagulant activity that minimises its reversal capacity. However, both ATs were more effective than rFVIIa or aPCC at neutralising fondaparinux and, unlike non-specific antidotes, inactive ATs specifically reversed AT-mediated anticoagulant activities, as suggested by their absence of procoagulant activity in anticoagulant-free plasma.

Understanding of developmental haemostasis is critical to ensure optimal prevention, diagnosis, and treatment of haemorrhagic and thrombotic diseases in children. As coagulation test results are known to be dependent on the reagents/analysers used, it is recommended for each laboratory to define the age-dependent reference ranges by using its own technical condition. That study was carried out in seven centers to establish age-specific reference ranges using the same reagents and analyser. Plasma samples were obtained from 1437 paediatric patients from the following age groups: 15 days-4 weeks (n=36), 1-5 months (n=320), 6-12 months (n=176), 1-5 years (n=507), 6-10 years (n=132) and 11-17 years (n=262). Indication of coagulation testing was pre-operative screening for non-acute diseases in most cases. PT values were similar in the different age groups to those in adults, whereas longer aPTTs were demonstrated in the younger children. Plasma levels of all clotting factors, except for FV, were significantly decreased (p<0.0001) in the youngest children, adult values being usually reached before the end of the first year. The same applied to antithrombin, protein C/S, and plasminogen. In contrast, FVIII and VWF levels were elevated in the youngest children and returned to adult values within six months. The same applied to D-dimer levels, which were found elevated, particularly until six months of life, until puberty. These data suggest that most coagulation test results are highly dependent on age, mainly during the first year of life, and that age-specific reference ranges must be used to ensure proper evaluation of coagulation in children.

Background: Systematic preoperative coagulation testing is still widely used in children scheduled for surgery, although current guidelines recommend that a bleeding history should be the first choice for hemostatic assessment. We performed a systematic review with meta-analysis to evaluate the pertinence of bleeding questionnaire and screening laboratory testing to detect bleeding disorders (BDs) in children and to predict abnormal surgical blood loss., Methods: A search was conducted in PubMed, EMBASE, MEDLINE(R), Cochrane Central Register of Controlled Trials, Health technology Assessment, and all EBM Reviews (Cochrane DSR, ACP Journal Club, DARE, CCTR, CMR, HTA, and NHSEED and EBM Reviews) up to October 22, 2013. Prospective trials containing 20 children or more and any tests evaluating either the ability of the test to detect a congenital BD or the ability of the test to predict increased surgical blood loss were retained. The quality of the study was judged with the Cochrane Collaboration Tool and two investigators extracted data independently. Data were combined to calculate the pooled diagnostic odds ratio (DOR) and their 95% confidence intervals (CI 95%). I(2) statistics were used to assess statistics heterogeneity., Results: Data could be extracted from 16 studies. Best results for detecting a congenital abnormality at potential risk for increased surgical blood loss were obtained with the PFA-100 (DOR = 113.0; 95% CI, 22.6-566.2; I(2) = 0%) in two studies, followed by the bleeding time in two other studies (DOR = 110.7; 95% CI, 24.4-502.3; I(2) = 0%). With a high amount of heterogeneity, questionnaires showed disappointing performances (DOR = 7.9; 95% CI: 3.5-17.5; I(2) = 72.6%)., Conclusion: Current evidence does not identify a tool that adequately predicts BDs and/or abnormal surgical blood loss in children. Questionnaires currently available do not perform well. In the setting of a pediatric coagulation clinic, the PFA-100 has the highest chance of detecting a BD. This meta-analysis highlights the weakness of the literature regarding the prediction of perioperative bleeding due to congenital hemostatic disorders in children., (© 2015 John Wiley & Sons Ltd.)

Point of care testing (POCT) must comply with regulatory requirements according to standard EN ISO 22870, which identify biologists as responsible for POCT. Activated clotting time (ACT) is mandatory to monitor on whole blood, anticoagulation achieved by unfractionated heparin during cardiopulmonary bypass (CPB) or cardiac catheterization. This test has no equivalent in the laboratory. With the aim to help the multidisciplinary groups for POCT supervision when they have to analyse the wish of medical departments to use ACT and to help the biologists to be in accordance with the standard, we present the guidelines of the GEHT (Groupe d'étude d'hémostase et thrombose) subcommittee "CEC et Biologie délocalisée" for the certification of ACT. These guidelines are based on the SFBC guidelines for the certification of POCT and on the analysis of the literature to ascertain the justification of clinical need and assess the analytical performance of main analyzers used in France, as well as on a survey conducted with French and Belgian biologists.

Clot retraction is an essential step during primary haemostasis, thereby promoting thrombus stability and wound healing. Integrin αIIbβ3 plays a critical role in clot retraction, by inducing acto-myosin interactions that allow platelet cytoskeleton reorganisation. However, the signalling pathways that lead to clot retraction are still misunderstood. In this study, we report the first data on the kinetics of myosin II light chain (MLC) phosphorylation during clot retraction. We found an early phosphorylation peak followed by a second peak. By using specific inhibitors of kinases and small G proteins, we showed that MLC kinase (MLCK), RhoA/ROCK, and Rac-1 were involved in clot retraction and in the early MLC phosphorylation peak. Only Rac-1 and actin polymerisation, controlled by outside-in signalling, were crucial to the second MLC phosphorylation peak.

Monitoring of the anticoagulant effect with the International normalized ratio (INR) is essential for patients receiving vitamin K antagonists (VKAs). The majority of point of care (POC) devices for INR monitoring has shown a good precision and accuracy with results similar to those obtained in a laboratory. In many countries, INR POC devices are widely used at home by the patients for self-testing. Their use in the hospital by the clinical staff (doctor or nurses) for bedside measurement is also growing. The INR POC testing is performed using fully automated devices. Capillary blood samples are easy to obtain. In the emergency room, POC INR devices are commonly used. This improves the quality of care for patient with suspicion of VKAs overdosage. INR measurement using bedside monitors is also of great interest in care units for specific populations of patients like paediatrics or geriatrics. Moreover, bedside INR monitoring may be useful in anticoagulant clinics or when the care unit is far from a laboratory. Although the bedside INR monitors are easy to use, their implementation requires adequate training and intermittent re-evaluation of any person performing the tests to ensure reliability of results. Such equipment must comply with EN ISO 22870 standard for POC testing accreditation, under the supervision of a biologist. In order to achieve these targets, connect the instrument to the laboratory's data management system is essential.

Adverse events related to vitamin K antagonist (VKA) therapy might be reduced by point-of-care international normalised ratio (POC INR) monitoring supported by an education program (EP). Our aim was to evaluate the efficacy of a non-selective VKA paediatric EP (regardless of the social, economic, educational or linguistic levels) by analysing the time spent in the therapeutic range (TTR), VKA adverse events and compliance to treatment, and INR control prescriptions. The EP was modified from the pediatric EP previously described but improved by a specifically devised child-focused game. One hundred four consecutive children (median age 8 years) receiving VKA were included in a standardised EP. Patients were in self-testing, and dose adjustments were made by a single physician for three tolerance ranges according to the underlying disease: [2.5-4], [1.8-3.2], and [1.5-2.5]. The median follow-up was 481 days [70-1,001]. The overall TTR was 81.4% [36-100]. The TTR were 74%, 85.6% and 89% for the ranges [2.5-4], [1.8-3.2], and [1.5-2.5], respectively. These results were sustainable during the study period. Only one serious VKA adverse event was recorded. The median number of POC INR tests was 2.5 [1.6-5.7] INR per patient and month. Patients/families performed POC INR when requested in 86.9% of the cases. More than 90% of the families found the EP supportive and wished to follow a long-term reinforcement program. In conclusion, this non-selective child-focused EP for VKA therapy, strongly supported by our dedicated game, is useful in maintaining efficacy, safety and compliance to anticoagulation and its monitoring.

Managing vitamin K antagonist (VKA) therapy is challenging in children because of a narrow therapeutic range and wide inter- and intra-individual variability in dose response. Only a few small studies have investigated the effect of nongenetic and genetic factors on the dose response to VKAs in children. In a cohort study including 118 children (median age 9 years; range, 3 months-18 years) mostly with cardiac disease, we evaluated by multivariate analysis the relative contribution of nongenetic factors and VKORC1/CYP2C9/CYP4F2 genotypes on warfarin (n = 83) or fluindione (n = 35) maintenance dose and the influence of these factors on the time spent within/above/below the range. The results showed that height, target international normalized ratio and VKORC1 and CYP2C9 genotypes were the main determinants of warfarin dose requirement, accounting for 48.1%, 4.4%, 18.2%, and 2.0% of variability, respectively, and explaining 69.7% of the variability. Our model predicted the warfarin dose within 7 mg/wk in 86.7% of patients. None of the covariates was associated with the time spent above or below the international normalized ratio range. Whether this model predicts accurately the effective maintenance dose is currently being investigated.

Lowe syndrome (LS) is a rare X-linked disorder caused by mutations in the oculocerebrorenal gene (OCRL), encoding OCRL, a phosphatidylinositol 5-phosphatase with a RhoGAP domain. An abnormal rate of haemorrhagic events was found in a retrospective clinical survey. Herein, we report the results of exploration of haemostasis in six LS patients. All patients had normal coagulation tests but prolonged closure times (CTs) in the PFA-100 system. Healthy donors' blood samples incubated with a RhoA kinase inhibitor had prolonged CTs. This suggests that an aberrant RhoA pathway in platelets contributes to CT prolongation and primary haemostasis disorders in LS.

The glycoprotein VI (GPVI)/FcRgamma complex is a key receptor for platelet activation by collagen. We describe, for the first time, 2 genetic abnormalities in one patient. This 10-year-old girl presented ecchymoses since infancy, a prolonged bleeding time despite a normal platelet count and no antiplatelet antibodies. Collagen-induced platelet activation was null, whereas GPVI quantification by flow cytometry evidenced an incomplete deficiency. Immunoblotting showed an abnormal migration of residual GPVI, and no FcRgamma defect. GPVI DNA sequencing revealed (1) an R38C mutation in exon 3 of one allele and (2) an insertion of 5 nucleotides in exon 4 of the other allele, leading to a premature nonsense codon and absence of the corresponding mRNA. Introduction of the R38C mutation into recombinant GPVI-Fc resulted in abnormal protein migration and a loss of collagen binding. Thus, this composite genetic GPVI deficiency and dysfunction cause absence of platelet responses to collagen and a mild bleeding phenotype.

Objective: To identify the mechanism of nodular regenerative hyperplasia in HIV-infected patients., Design: Case-control study., Setting: The hepatology and the infectious disease units of two tertiary care centers in France., Patients: We compared 13 consecutive HIV-positive patients with unexplained nodular regenerative hyperplasia to 16 consecutive HIV-positive patients without nodular regenerative hyperplasia, to eight HIV-negative patients with nodular regenerative hyperplasia from an identified cause and to 10 anonymous healthy blood donors., Main Outcome Measure: Patients and controls were screened for diminished protein S activity and antiprotein S immunoglobulin G (IgG) antibodies. The antiprotein S activity of purified IgG from patients and controls was assessed in a functional test of activation of protein C in which protein S serves as a cofactor. A full liver CT portography was realized on the liver explant of a case patient., Results: The CT portography disclosed diffuse obliterative portal venopathy. Levels of protein S activity were lower among patients with HIV-associated nodular regenerative hyperplasia when compared with HIV-positive patients without nodular regenerative hyperplasia and when compared with HIV-negative patients with nodular regenerative hyperplasia (P < 0.005 for all comparisons). HIV-positive patients with nodular regenerative hyperplasia had significantly higher levels of antiprotein S IgG than HIV-positive patients without nodular regenerative hyperplasia and healthy controls. Purified IgG from patients with HIV-associated nodular regenerative hyperplasia specifically inhibited the protein S-dependent protein C activation., Conclusion: Acquired autoimmune protein S paucity and secondary thrombophilia appear to be causes of obliterative portal venopathy and compensatory nodular regenerative hyperplasia in HIV-positive patients.

Fluorescence correlation spectroscopy (FCS) is a popular technique, complementary to cell imaging for the investigation of dynamic processes in living cells. Based on fluorescence, this single molecule method suffers from artifacts originating from the poor fluorophore photophysics: photobleaching, blinking, and saturation. To circumvent these limitations we present here a new correlation method called photothermal absorption correlation spectroscopy (PhACS) which relies on the absorption properties of tiny nano-objects. PhACS is based on the photothermal heterodyne detection technique and measures akin FCS, the time correlation function of the detected signals. Application of this technique to the precise determination of the hydrodynamic sizes of different functionalized gold nanoparticles are presented, highlighting the potential of this method.

The far-field optical imaging of mitochondria of live cells without the use of any label is demonstrated. It uses a highly sensitive photothermal method and has a resolution comparable to confocal fluorescence setups. The morphological states of mitochondria were followed under different physiological treatments, and the role of cytochrome c was ruled out as the main origin of the photothermal signals. This label free optical method provides a high contrast imaging of live mitochondria and should find many applications in biosciences.

Platelet dysfunction after cardiopulmonary bypass (CPB) can contribute to excessive post-operative bleeding. Most trials of the protective effect of aprotinin in this setting have involved hypothermic CPB, which is more deleterious for platelets than normothermic CPB. Here we investigated the effect of aprotinin on platelet function during normothermic CPB in pediatric patients. Twenty patients (9 newborns [<1 month old] and 11 infants [<36 month old]), weighting less than 15 kg and undergoing normothermic CPB (35-36 degrees C) were randomly assigned to two equal groups, one of which received high-dose aprotinin. Platelet function was assessed by flow cytometry just before CPB and 5 minutes after heparin neutralization. F1 + 2 fragments were measured by ELISA before and 5 minutes after CPB. Platelet activation marker expression (CD62P and activated alphaIIbbeta3) induced by ADP or TRAP was lower after CPB than before CPB, suggesting a deleterious effect of normothermic CPB on platelet function. Prothrombin fragment F1 + 2 levels increased after CPB. Aprotinin administration did not influence the level of prothrombin fragments or platelet marker expression measured in basal condition. However, after CPB, the capacity for platelet activation was higher in the aprotinin group, as shown by measuring CD62P expression after TRAP activation (p = 0.05). This study suggests that pediatric normothermic CPB causes platelet dysfunction, and that high-dose aprotinin has a protective effect.

Tracking individual nano-objects in live cells during arbitrary long times is a ubiquitous need in modern biology. We present here a method for tracking individual 5-nm gold nanoparticles on live cells. It relies on the photothermal effect and the detection of the Laser Induced Scattering around a NanoAbsorber (LISNA). The key point for recording trajectories at video rate is the use of a triangulation procedure. The effectiveness of the method is tested against single fluorescent molecule tracking in live COS7 cells on subsecond timescales. We further demonstrate recordings for several minutes of AMPA receptors trajectories on the plasma membrane of live neurons. Single Nanoparticle Photothermal Tracking has the unique potential to record arbitrary long trajectory of membrane proteins using nonfluorescent nanometer-sized labels.

Purpose: To review recent developments in the pathogenesis, clinical features, laboratory testing and treatment of heparin-induced thrombocytopenia (HIT)., Methods: Narrative review of the literature, including relevant papers published in English or French., Principal Findings: Although the prevalence of HIT has decreased with the widespread use of low molecular weight heparin in the past ten years, HIT remains a life-threatening prothrombotic state. This immune adverse event due to heparin-dependent antibodies that bind to chemokines (such as platelet factor 4) induces platelet activation and hypercoagulability. Heparin-induced thrombocytopenia can be complicated by thrombosis even after withdrawing heparin, explaining why substituting heparin with an alternative anticoagulant (danaparoid, lepirudin, argatroban) is always necessary. However, management of these alternative treatments is difficult, and in some patients there is the risk of withdrawing heparin without taking the time to diagnose HIT properly on the basis of clinical and laboratory findings (evolution of platelet count, laboratory testing such as antigen assays and platelet activation tests)., Conclusions: Management of HIT has become easier in recent years with the development of more specific and sensitive laboratory tests and new antithrombotic drugs. However, the diagnosis of HIT is often difficult, and it remains very important to investigate this adverse reaction systematically in every patient treated with heparin who develops thrombocytopenia.