Factors Influencing Anti-Xa Assays: A Multicenter Prospective Study in Critically Ill and Noncritically Ill Patients Receiving Unfractionated Heparin.

BACKGROUND: The presence of dextran sulfate (DS) in reagents and the type of blood collection tube (citrate/citrated-theophylline-adenosine-dipyridamole [CTAD]) can lead to discrepancies between unfractionated heparin (UFH) anti-Xa levels. OBJECTIVES: To evaluate the extent of the effect (1) of different reagents containing or not containing DS and (2) of the blood collection tubes, on UFH anti-Xa levels, in various clinical situations (NCT04700670). METHODS: We prospectively included patients from eight centers: group (G)1, cardiopulmonary bypass (CPB) after heparin neutralization (n = 39); G2, cardiothoracic intensive care unit (ICU) after CPB (n = 35); G3, medical ICU (n = 53); G4, other medical inpatients (n = 38). Blood was collected into citrated and CTAD tubes. Chromogenic anti-Xa assays were centrally performed, using seven reagent/analyzer combinations including two without DS. The association between anti-Xa levels and covariates was tested using a linear mixed-effects model. RESULTS: We analyzed 4,546 anti-Xa values from 165 patients. Median anti-Xa levels were systematically higher with reagents containing DS, whatever the patient group, with the greatest effect observed in G1 (0.32 vs. 0.05 IU/mL). Anti-Xa levels were slightly higher in CTAD than in citrate samples, irrespective of the assay. The model showed: (1) a significant dextran-patient group interaction (p < 0.0001), the effect of DS on anti-Xa levels varying from 30.9% in G4 to 296% in G1, and (2) a significant effect of CTAD, varying between patient groups (p = 0.0302). CONCLUSION: The variability of anti-Xa levels with a great overestimation of the values, using a reagent containing DS, can lead to different treatment decisions, especially after heparin neutralization by protamine. Clinical consequences of these differences remain to be demonstrated.

A focus on dominant negative variants in a series of 170 heterozygous FXI-deficient patients.

INTRODUCTION: Dominant-negative effects have been described for 10 F11 variants in the literature. AIM: The current study aimed at identifying putative dominant-negative F11 variants. MATERIAL AND METHODS: This research consisted in a retrospective analysis of routine laboratory data. RESULTS: In a series of 170 patients with moderate/mild factor XI (FXI) deficiencies, we identified heterozygous carriers of previously reported dominant-negative variants (p.Ser243Phe, p.Cys416Tyr, and p.Gly418Val) with FXI activities inconsistent with a dominant-negative effect. Our findings also do not support a dominant-negative effect of p.Gly418Ala. We also identified a set of patients carrying heterozygous variants, among which five out of 11 are novel, with FXI activities suggesting a dominant-negative effect (p.His53Tyr, p.Cys110Gly, p.Cys140Tyr, p.Glu245Lys, p.Trp246Cys, p.Glu315Lys, p.Ile421Thr, p.Trp425Cys, p.Glu565Lys, p.Thr593Met, and p.Trp617Ter). However, for all but two of these variants, individuals with close to half normal FXI coagulant activity (FXI:C) were identified, indicating an inconstant dominant effect. CONCLUSION: Our data show that for some F11 variants recognized has having dominant-negative effects, such effects actually do not occur in many individuals. The present data suggest that for these patients, the intracellular quality control mechanisms eliminate the variant monomeric polypeptide before homodimer assembly, thereby allowing only the wild-type homodimer to assemble and resulting in half normal activities. In contrast, in patients with markedly decreased activities, some mutant polypeptides might escape this first quality control. In turn, assembly of heterodimeric molecules as well as mutant homodimers would result in activities closer to 1:4 of FXI:C normal range.

Efficacy and safety of a recombinant Von Willebrand Factor treatment in patients with inherited Von Willebrand Disease requiring surgical procedures.

INTRODUCTION: Von Willebrand Disease is a common inherited haemorrhagic disorder due to a deficiency of Von Willebrand Factor (VWF). In case of surgical procedures in patients who are not responsive or have contraindications to desmopressin, replacement therapy with VWF concentrates is indicated. Until recently, only plasma-derived VWF concentrates were available. A new recombinant VWF (rVWF) concentrate that contains no Factor VIII (FVIII) but a high amount of high molecular weight VWF multimers has been available in France since 2018. AIM: Describe real-world experience of using rVWF in surgical procedures. METHODS: Sixty-three surgeries for 55 patients were retrospectively analysed in 7 French haemostasis centres. RESULTS: During minor surgeries, the median (range) number of infusions was 1 (1-8) with a preoperative loading dose of 35 (19-56) rVWF IU/kg and a total median dose of 37.5 IU (12-288). During major surgeries, the median (range) number of infusions was only 3 (1-14) with a median preoperative loading dose of 36 IU (12-51) rVWF IU/kg, and a total median dose of 108 IU (22-340) rVWF IU/kg. The overall clinical efficacy was qualified as excellent/good in 61 of the procedures (97%), moderate in 1 (1.5%) and poor in 1 (1.5%). There was no accumulation of VWF or FVIII during postoperative monitoring. No thromboembolic events, anti-VWF antibodies or adverse events were reported. CONCLUSION: This French 'real-world' experience shows that a few infusions and low doses of rVWF provided effective prevention of bleeding in major and minor surgeries in inherited VWD, with no clinically significant safety concerns.

Role of oculocerebrorenal syndrome of Lowe (OCRL) protein in megakaryocyte maturation, platelet production and functions: a study in patients with Lowe syndrome.

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.

Rapid screening of COVID-19 patients using white blood cell scattergrams, a study on 381 patients.

Complementary tools are warranted to increase the sensitivity of the initial testing for COVID-19. We identified a specific 'sandglass' aspect on the white blood cell scattergram of COVID-19 patients reflecting the presence of circulating plasmacytoid lymphocytes. Patients were dichotomized as COVID-19-positive or -negative based on reverse transcriptase polymerase chain reaction (RT-PCR) and chest computed tomography (CT) scan results. Sensitivity and specificity of the 'sandglass' aspect were 85·9% and 83·5% respectively. The positive predictive value was 94·3%. Our findings provide a non-invasive and simple tool to quickly categorize symptomatic patients as either COVID-19-probable or -improbable especially when RT-PCR and/or chest CT are not rapidly available.

First venous thromboembolism and hormonal contraceptives in young French women.

Information on the clinical and biological characteristics of combined hormonal contraceptives (CHC) users experiencing a venous thromboembolism (VTE) event is scarce. Better knowledge of factors determining the VTE risk in CHC users could help identify women at high risk.Data were obtained from a large cohort of consecutive women with the first documented VTE event. Cross-sectional analysis of clinical and biological characteristics of the women was performed.Of the 3009 women with the first VTE included, 31% were nonusers and 69% CHC users at time of VTE. CHC users were significantly younger (29.0 ±â€Š7.2) than nonusers (31.6 ±â€Š7.1) (P < .001). No difference in VTE familial history was observed between the 2 groups. Compared with nonusers, the CHC users experienced more frequently pulmonary embolism: odds ratio (OR) = 1.28 (1.06-1.55; 95% confidence interval [CI]), factor V Leiden mutations were more frequent in this group (OR = 1.41 [1.11-1.80; 95% CI]). Venous sclerotherapy and travel were associated with VTE in CHC users, whereas surgery and bed rest were significantly associated with VTE in nonusers. Finally, 2/3 of CHC users with VTE had additional VTE risk factors.CHC users experiencing the first VTE differ from nonusers with respect to clinical and genetic background. Better understanding of the characteristics of VTE and associated risk factors could allow more appropriate management of these women and contribute to more accurate benefit-risk assessment before prescribing a CHC.

Bleeding risk of surgery and its prevention in patients with inherited platelet disorders.

Excessive bleeding at surgery is a feared complication in patients with inherited platelet disorders. However, very few studies have evaluated the frequency of surgical bleeding in these hemorrhagic disorders. We performed a worldwide, multicentric, retrospective study to assess the bleeding complications of surgery, the preventive and therapeutic approaches adopted, and their efficacy in patients with inherited platelet disorders: the Surgery in Platelet disorders And Therapeutic Approach (SPATA) study. We rated the outcome of 829 surgical procedures carried out in 423 patients with well-defined forms of inherited platelet disorders: 238 inherited platelet function disorders and 185 inherited platelet number disorders. Frequency of surgical bleeding was high in patients with inherited platelet disorders (19.7%), with a significantly higher bleeding incidence in inherited platelet function disorders (24.8%) than in inherited platelet number disorders (13.4%). The frequency of bleeding varied according to the type of inherited platelet disorder, with biallelic Bernard Soulier syndrome having the highest occurrence (44.4%). Frequency of bleeding was predicted by a pre-operative World Health Organization bleeding score of 2 or higher. Some types of surgery were associated with a higher bleeding incidence, like cardiovascular and urological surgery. The use of pre-operative pro-hemostatic treatments was associated with a lower bleeding frequency in patients with inherited platelet function disorders but not in inherited platelet number disorders. Desmopressin, alone or with antifibrinolytic agents, was the preventive treatment associated with the lowest bleedings. Platelet transfusions were used more frequently in patients at higher bleeding risk. Surgical bleeding risk in inherited platelet disorders is substantial, especially in inherited platelet function disorders, and bleeding history, type of disorder, type of surgery and female sex are associated with higher bleeding frequency. Prophylactic pre-operative pro-hemostatic treatments appear to be required and are associated with a lower bleeding incidence.

Peri-procedural management of dabigatran and rivaroxaban: Duration of anticoagulant discontinuation and drug concentrations.

BACKGROUND: Peri-procedural management of direct oral anticoagulants (DOAC) is challenging. The optimal duration of pre-procedural discontinuation that guarantees a minimal DOAC concentration ([DOAC]) at surgery is unknown. The usual 48-hour discontinuation might not be sufficient for all patients. OBJECTIVES: To test the hypothesis that a 48-hour DOAC discontinuation is not sufficient to ensure a minimal per-procedural [DOAC], defined as [DOAC]<30ng/mL. To investigate the factors associated with per-procedural [DOAC]. To evaluate the ability of normal PT and aPTT to predict [DOAC]<30ng/mL. METHODS: Patients treated with dabigatran or rivaroxaban, and requiring any invasive procedure were included in this multicentre, prospective, observational study. [DOAC], PT and aPTT were measured during invasive procedure. RESULTS: Sixty-five patients were enrolled. Duration of DOAC discontinuation ranged from 1-168h. Per-procedural [DOAC] ranged from <30 to 466ng/mL. [DOAC]<30ng/mL occurred more frequently after 48-hour discontinuation than after a shorter delay. [DOAC] remained ≥30ng/mL in 36% and 14% of measurements performed 24-48h and 48h-120h after discontinuation, respectively. According to ROC curve, a cut-off value of 120hours for DOAC discontinuation had a better specificity than a cut-off value of 48hours to predict [DOAC]<30ng/mL. Normal PT and aPTT ratios had good specificity and positive predictive value, but limited sensitivity (74%) and negative predictive value (73%) to predict [DOAC]<30ng/mL. CONCLUSIONS: A 48-hour discontinuation does not guarantee a [DOAC]<30ng/mL in all patients. Normal PT and aPTT are flawed to predict this threshold and could not replace specific assays. Further studies are needed to define the relationship between per-procedural [DOAC] and clinical outcomes.

[Non-VKA oral anticoagulants: an update for the clinical biologists]. / Anticoagulants directs oraux : actualités pour les biologistes.

Non-VKA oral anticoagulants (NOACs), thanks to their ease of use and their similar or superior safety/efficacy profiles versus warfarin, have now widely reached the lucrative market of anticoagulation. However, while the marketing authorization holders always claim, in a quite unclear way that no monitoring is required, accumulative evidence and cases of major bleeding have been described in the literature and reported by spontaneous reporting systems at the regulator's level. These compounds are usually given at fixed doses without routine coagulation monitoring. However, new data suggests that an assessment of the response at the individual level could improve the benefit-risk ratio of, at least dabigatran. Therefore, in certain patient populations, i.e. acute or chronic renal impairment or multiple drug interactions, measurement of drug exposure may be useful to ensure an optimal treatment response. More specific circumstances such as patients experiencing a haemorrhagic or thromboembolic event during the treatment duration, patients who require urgent surgery or an invasive procedure, or patient with a suspected overdose could benefit from such a measurement. This article aims at providing guidance on how to best estimate the intensity of anticoagulation using laboratory assays in daily practice.

Duration of postoperative fibrinolysis after total hip or knee replacement: a laboratory follow-up study.

INTRODUCTION: Hyperfibrinolysis is observed during and immediately after major orthopedic surgery. The kinetics and duration of this phase should be defined to adjust the duration of antifibrinolytic treatment with tranexamic acid (TXA). OBJECTIVE: We aimed to quantify the duration of postoperative fibrinolysis and to assess the biological impact of TXA administration. MATERIALS AND METHODS: Fourteen patients undergoing total hip replacement (THR) and 10 patients undergoing total knee replacement (TKR) with tourniquet were included in an observational, prospective, single-center study. Among these patients, 7 THR patients and 5 TKR patients received TXA (15mg/kg IV intraoperatively, followed by continuous infusion of 15mg/kg/h until end of surgery, then every 4hours until 16±2hours after surgery). D-dimers, euglobulin lysis time (ELT), and thrombin generation time (TGT) were measured prior to surgery as well as 6, 18 and 24hours (H) after. RESULTS: No significant difference in ELT was observed between the groups. In contrast, D-dimers significantly increased postoperatively in patients not treated with TXA (p<0.001), while such an increase was prevented in patients receiving TXA, as measured at H0, H6, H18 and H24 after THR, and at H6 and H18 after TKR (p<0.001). No significant between-group change in TGT, was observed (peak thrombin and endogenous thrombin potential) all along the study. CONCLUSION: This study shows that fibrinolysis peaked 6hours after end of surgery and maintained about 18hours after surgery, as evidenced by an increase in D-dimers. When administered for up to 16±2hours after surgery, TXA reduced postoperative fibrinolysis.

Platelets and viruses: an ambivalent relationship.

Thrombocytopenia is a frequent complication of viral infections providing evidence that interaction of platelets with viruses is an important pathophysiological phenomenon. Multiple mechanisms are involved depending on the nature of the viruses involved. These include immunological platelet destruction, inappropriate platelet activation and consumption, and impaired megakaryopoiesis. Viruses bind platelets through specific receptors and identified ligands, which lead to mutual alterations of both the platelet host and the viral aggressor. We have shown that HIV-1 viruses are internalized specifically in platelets and megakaryocytes, where they can be either sheltered, unaltered (with potential transfer of the viruses into target organs), or come in contact with platelet secretory products leading to virus destruction and facilitated platelet clearance. In this issue, we have reviewed the various pathways that platelets use in order to interact with viruses, HIV and others. This review also shows that more work is still needed to precisely identify platelet roles in viral infections, and to answer the challenge of viral safety in platelet transfusion.