Thrombin generation test as a marker for high risk venous thrombosis pregnancies.

Pregnancy is a well-established risk factor for venous thromboembolism and is associated with a state of hypercoagulability. The use of sensitive and specific biological markers to predict risk factors for thrombosis is essential during pregnancy. Our objective was to investigate the usefulness of thrombin generation test (TGT) as a marker to predict the risk of thrombosis in high risk venous thrombosis (HRVT) pregnancies compared to normal pregnancies. This retrospective study enrolled 134 women with HRVT pregnancies, 78 of whom had monozygotic, spontaneous and untreated pregnancies and formed the study group. The control group comprised 106 women with normal pregnancies. Routine assessment of coagulation activation markers: fibrinogen, D-dimer, prothrombin fragments 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) was performed every 5 weeks in the study group to detect a possible pathological state of hypercoagulability. TGT was performed using platelet-free plasma, 1 and 5 pM tissue factor (TF), supplemented by phospholipids (PL) ± thrombomodulin. Fibrinogen, D-dimer, F1 + 2, and TAT, but not FMC, increased significantly throughout pregnancy in both groups but no difference was shown between the groups. TGT showed an early increase in thrombin generation in both groups, which stabilized during the second month of pregnancy. No correlation was demonstrated between thrombin generation parameters and coagulation activation markers. Based on our results, TGT did not prove conclusive as a marker to predict the risk of thrombosis in HRVT pregnancies. Finding a sensitive and specific biological marker to predict thrombosis risk requires further investigation.

Role of Toll-like receptors 2 and 4 in mediating endothelial dysfunction and arterial remodeling in primary arterial antiphospholipid syndrome.

OBJECTIVE: To assess the role of Toll-like receptors (TLRs) in antiphospholipid antibody (aPL)-mediated vascular abnormalities in patients with primary arterial antiphospholipid syndrome (APS). METHODS: Forty-eight subjects participated in the study. Arterial function and structure and TLR pathway activation were determined in patients with primary arterial APS and matched controls. The pathogenic effects of aPL isolated from patients were assessed in wild-type (WT) and TLR-knockout mice. RESULTS: APS patients had endothelial dysfunction, arterial stiffening, and hypertrophy, as evidenced by decreased brachial artery endothelium-dependent flow-mediated dilation (FMD) and increased aortic pulse wave velocity and carotid intima-media thickness (IMT), as compared with controls. Plasma samples from APS patients revealed decreased nitric oxide (NO) availability and a pro-oxidative, proinflammatory, and prothrombotic state illustrated by a decrease in nitrite and an increase in lipid peroxidation, tumor necrosis factor α levels, and tissue factor (TF) levels. Furthermore, TLR pathway activation was found in APS patients with increased TLR-2 and TLR-4 messenger RNA expression and increased protein levels of the activated TLR transduction protein interleukin-1 receptor-associated kinase 1 in peripheral blood mononuclear cells. Moreover, agonist-stimulated cell-surface expression of TLR-2 and TLR-4 in circulating monocytes was higher in APS patients than in controls. These changes were positively associated with IMT and negatively associated with FMD. Finally, aPL injection decreased mesenteric endothelium-dependent relaxation and increased TF expression in WT mice but not in TLR-2- or TLR-4-knockout mice. CONCLUSION: This translational study supports the notion that TLR-2 and TLR-4 play a role in mediating vascular abnormalities in patients with primary arterial APS. TLRs thus constitute a promising pharmacologic target for preventing cardiovascular complications in APS.

Analysis of 339 pregnancies in 181 women with 13 different forms of inherited thrombocytopenia.

Pregnancy in women with inherited thrombocytopenias is a major matter of concern as both the mothers and the newborns are potentially at risk of bleeding. However, medical management of this condition cannot be based on evidence because of the lack of consistent information in the literature. To advance knowledge on this matter, we performed a multicentric, retrospective study evaluating 339 pregnancies in 181 women with 13 different forms of inherited thrombocytopenia. Neither the degree of thrombocytopenia nor the severity of bleeding tendency worsened during pregnancy and the course of pregnancy did not differ from that of healthy subjects in terms of miscarriages, fetal bleeding and pre-term births. The degree of thrombocytopenia in the babies was similar to that in the mother. Only 7 of 156 affected newborns had delivery-related bleeding, but 2 of them died of cerebral hemorrhage. The frequency of delivery-related maternal bleeding ranged from 6.8% to 14.2% depending on the definition of abnormal blood loss, suggesting that the risk of abnormal blood loss was increased with respect to the general population. However, no mother died or had to undergo hysterectomy to arrest bleeding. The search for parameters predicting delivery-related bleeding in the mother suggested that hemorrhages requiring blood transfusion were more frequent in women with history of severe bleedings before pregnancy and with platelet count at delivery below 50 × 10(9)/L.

[Comparison between the centrifugation on MPA C10 (Roche Diagnostics) and the centrifugation according recommendations of GEHT (Groupe d'étude de l'hémostase et de la thrombose) for the daily hemostasis assays]. / Comparaison de la centrifugation sur MPA C10 (Roche Diagnostics) et de la centrifugation selon les préconisations du Groupe d'étude de l'hémostase et de la thrombose pour les analyses d'hémostase du quotidien.

Actually, many laboratories tend to acquire pre analytic automates to prepare specimens for analysis. For haemostasis, these pre analytical modules are not always in agreement with the recommendations from the Groupe d'étude de l'hémostase et de la thrombose (GEHT). For example in the MPA C10 module (Roche Diagnostics) the speed of centrifugation was not rather fast compared with the GEHT recommandations. Then, to be able to use this automate for routine coagulation assays, we compared results of Quick time, activated partial prothombin time, fibrinogen, factor II, factor V, factor VII, factor X and antithrombin levels and unfractioned heparin anti-Xa activity measurement after MPA (1,885 g - 999 sec) or GEHT (2,500 g - 900 sec) protocol of centrifugation. First, we verified platelet counts: in 82% of specimens, the platelet counts were under 10.10(9)/L after centrifugation on MPA module. Moreover, a good correlation was observed in all comparisons. Then we concluded the MPA C10 module was usable for routine coagulation tests.

New combinational assay using soluble fibrin and d-dimer determinations: a promising strategy for identifying patients with suspected venous thromboembolism.

AIM: To establish a new and reliable assay for quantification of the soluble fibrin (SF) in combination with that of D-dimer for early diagnosis of venous thromboembolism. METHODS AND SAMPLES: The SF assay is based on D-dimer generated after incubation of plasma with tissue-type plasminogen activator (t-PA). SF and standard D-dimer assays, run in blind, were used to test 119 untreated outpatients with clinically suspected deep-vein thrombosis (DVT, 49 patients) or pulmonary embolism (PE, 70 patients) consulting at the emergency unit of the hospital. Thromboses were confirmed by current imaging methods such as ultrasonography, scintigraphy, computed tomographic pulmonary angiography (CTPA) and ventilation/perfusion scan. RESULTS: SF assay was validated in 270 healthy volunteers [51.8% males; mean age years ± SD: 41±13; age range 19 to 65]. Among these normal plasmas, SF levels were ≤200 ng/mL in 97.8% of them, and 200-250 ng/mL in the remainder [26-46 years old; 50% males]. ROC curves were used to determine the SF cut-off value for plasma SF positivity, which was found to be 300 ng/mL. In patients with suspected venous thromboembolism, SF sensitivities for DVT and PE (92% and 94%, respectively) were comparable to those of D-dimer (96% and 94%), whereas SF specificities (86% and 95%) were higher than those of D-dimer (50% and 54%). Positive-predictive values for SF (89% and 94%) were again higher than those of D-dimer (70% and 65%) in DVT and PE. The amount of circulating SF normalized rapidly after anticoagulant therapy. CONCLUSION: Results from this small group of patients suggest that the evaluation of plasma SF, in combination with that of D-dimer, represents a potentially useful tool for the early diagnosis of venous thromboembolism, provided that the patients have not been treated previously by anticoagulants.

Comparison of markers of coagulation activation and thrombin generation test in uncomplicated pregnancies.

INTRODUCTION: Pregnancy is a well-established risk factor for venous thromboembolism, and is associated with a state of hypercoagulability or parameters of thrombin generation. Currently, there is a lack of consensual data on thrombin generation during pregnancy. This study aimed to find a sensitive and specific biological marker of coagulation activation and to identify parameters of thrombin generation. PATIENTS AND METHODS: The population included 101 women with uncomplicated pregnancies. The objective of this study was to correlate thrombin generation test (measured at 5pM tissue factor, 4µM lipids and without thrombomodulin), with fibrinogen and markers of blood coagulation activation: D-dimer, prothrombin fragments 1+2 (F1+2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) in these women. Internal quality control was performed in each set of experiments. RESULTS: Fibrinogen, D-dimer, F1+2, and TAT concentrations increased significantly throughout pregnancy, and were correlated with term of pregnancy. In our study, thrombin generation seemed to increase early on, and then remained stable throughout normal pregnancy, in contrast with other markers of blood coagulation activation, excepting FMC. The latter are subject to large inter-individual variations, especially during second trimester. No correlation was demonstrated between thrombin generation parameters and other activation markers. CONCLUSION: While markers of coagulation activation significantly increased during pregnancy, thrombin generation increased only early on and remains stable during pregnancy. Finding a sensitive and specific biological marker for vascular pregnancy complications, such as FMC and thrombin generation levels, requires further investigation.

Proteolytic antibodies activate factor IX in patients with acquired hemophilia.

Acquired hemophilia is a rare bleeding disorder characterized by the spontaneous occurrence of inhibitory antibodies against endogenous factor VIII (FVIII). IgG from some patients with acquired hemophilia hydrolyze FVIII. Because of the complex etiology of the disease, no clinical parameter, including the presence of FVIII-hydrolyzing IgG, has been associated with patient's survival or death. Here, we demonstrate the presence of anti-FIX antibodies in acquired hemophilia patients. IgG from some patients were found to hydrolyze FIX. In most cases, IgG-mediated FIX-hydrolysis resulted in FIX activation. IgG-mediated hydrolysis of FIX thus led to the significant generation of activated FIX in 25 of 65 patients. Based on the estimated kinetic parameters, patients' IgG activated up to 0.3nM FIX in 24 hours, an amount that restored thrombin generation in vitro provided the presence of more than or equal to 3% residual FVIII activity in plasma. This work identifies proteolytic IgG as novel molecules able to activate FIX under pathologic conditions. IgG-mediated FIX activation is a prevalent phenomenon among acquired hemophilia patients. The presence of FIX-activating IgG may partly compensate for the antibody-mediated inhibition of endogenous FVIII in restoring thrombin generation. This clinical trial was registered at www.clinicaltrials.gov as #NCT00213473.

Population pharmacokinetics of fondaparinux administered at prophylactic doses after major orthopaedic surgery in everyday practice.

Fondaparinux is a synthetic antithrombotic agent with specific anti-factor Xa activity. A population pharmacokinetic model of fondaparinux, based on data obtained in patients included in phase II/III trials, has been described. However, the validity of this model in everyday practice needed to be confirmed. This study was a multicenter, prospective cohort study in consecutive orthopaedic patients treated with 2.5 mg of fondaparinux. Anti-Xa activities were recorded in 809 patients. Population parameters and inter-individual variability were estimated using NONMEM VI software. A two-compartment model with first-order absorption best described fondaparinux pharmacokinetics. Covariates partly explaining inter-individual variability were body weight, age and creatinine clearance estimated by the simplified Modification of Diet in Renal Disease formula (MDRD). A body weight less than 50 kg and moderate renal failure increased drug exposure. Although the population pharmacokinetic model of fondaparinux was described, this one requires to be validated in everyday practice.

Hereditary thrombophilia and recurrence of ischemic placental disease.

OBJECTIVE: We sought to evaluate whether testing for hereditary thrombophilia alone or in combination with second-trimester uterine artery Doppler (UAD) is useful in predicting recurrent complications in patients with previous preeclampsia, placental abruption, or stillbirth. STUDY DESIGN: Between 2001 and 2005, 110 consecutive women were included in the study and received 100 mg of aspirin daily. Adjustment was made for several maternal confounding factors using a logistic regression model. RESULTS: After multivariable logistic regression analyses, only abnormal UAD assessment was significantly associated with recurrent complications (odds ratio, 11.2; 95% confidence interval, 3.8-32.6) Combining the results of UAD and the presence of laboratory markers of thrombophilia failed to improve the accuracy of UAD to predict recurrent complications. CONCLUSION: Hereditary thrombophilia testing is not useful in predicting recurrent complications in subsequent pregnancy.

Rare genotypes of protein Z gene are a risk factor for premature myocardial infarction but not protein Z plasma level.

Protein Z (PZ) is the cofactor of PZ dependent inhibitor (ZPI) that inhibits activated coagulation factor X. PZ was expected to play a role in coronary artery disease (CAD) but with inconsistent clinical findings. We therefore evaluated whether PZ plasma level and/or three genetic variants encoding for low PZ plasma level were associated with premature CAD in stable young post-myocardial infarction (MI) patients. PZ plasma level and three polymorphisms A-13G, G-103A and G79A were determined in 176 young stable post-MI patients and in 176 sex- and age-matched controls (FITE-NAT population). Moreover the genotypes, resulting from the combination of the three polymorphisms (A-13G/G-103A/G79A), were studied. PZ plasma level and the number of patients disclosing a PZ deficiency did not differ between post-MI patients and controls. The presence of the mutated allele for each polymorphism was associated with a significantly reduced level of PZ. The A-13G polymorphism was associated with premature CAD only in univariate analysis. Whereas, the presence of rare genotypes of PZ gene was an independent risk factor for premature CAD. In conclusion, PZ plasma level is not a key player in the pathophysiology of premature coronary artery disease. But, rare genotypes of PZ gene were found to be associated with premature CAD.

Factor VIII-hydrolyzing IgG in acquired and congenital hemophilia.

Anti-factor VIII (FVIII) inhibitory IgG may arise as alloantibodies to therapeutic FVIII in patients with congenital hemophilia A, or as autoantibodies to endogenous FVIII in individuals with acquired hemophilia. We have described FVIII-hydrolyzing IgG both in hemophilia A patients with anti-FVIII IgG and in acquired hemophilia patients. Here, we compared the properties of proteolytic auto- and allo-antibodies. Rates of FVIII hydrolysis differed significantly between the two groups of antibodies. Proline-phenylalanine-arginine-methylcoumarinamide was a surrogate substrate for FVIII-hydrolyzing autoantibodies. Our data suggest that populations of proteolytic anti-FVIII IgG in acquired hemophilia patients are different from that of inhibitor-positive hemophilia A patients.

Risk factors of vitamin K antagonist overcoagulation. A case-control study in unselected patients referred to an emergency department.

The aims of this case-control study were to identify in vitamin K antagonist (VKA)-treated unselected patients, factors associated with international normalised ratio (INR) values: (i) greater than 6.0.; and (ii) ranging from 4.0 to 6.0 complicated with bleeding. We also assessed VKA-related morbidity in these patients. During a two-month period, 4,188 consecutive and unselected patients were referred to our Emergency Department. At admission, the medical records of each patient and two age- and sex-matched controls were reviewed for: both duration and indication of VKA therapy, previous medical history of VKA-related haemorrhage, underlying co-morbidities, concomitant medications other than VKA, duration of hospitalization and deaths' causes. Of these 4,188 subjects, 50 case-patients (1.19%) were identified; both case-patients and controls did not differ as regards indications and patterns of VKA therapy. Interestingly, two-thirds of case-patients were women, suggesting that female gender may be a risk factor of VKA over-coagulation onset. We identified the following risk factors of VKA over-coagulation: previous medical history of INR levels over therapeutic range, therapy with antibiotics, amiodarone and proton pump inhibitors, as well as fever. A total of 88% of case-patients were hospitalized; mean duration of patients' hospitalization was seven days [range: 1-56 days]; no patient died from major bleeding. Our study underscores that it is of utmost importance to consider the strength of indication before starting VKA therapy, as this therapy has been responsible for as high as 1.19% of admissions in unselected subjects referred to an Emergency Department. Our data therefore suggest that internists should be aware of VKA-related high morbidity, particularly in situations at risk of VKA over-coagulation.

An unusual clinical presentation of factor XIII deficiency and issues relating to the monitoring of factor XIII replacement therapy.

Congenital factor XIII deficiency is a very rare bleeding disorder. Patients with severe FXIII deficiency usually exhibit severe bleeding diatheses. Factor XIII is also involved in maintaining pregnancy, and women with factor XIII deficiency have a high risk of spontaneous abortions. We report here the case of a patient with a mild bleeding history before her pregnancy but who had three spontaneous haemorrhagic miscarriages. The patient was homozygous for G 501 R mutation of the factor XIII A subunit gene. We also detected a coinherited heterozygous factor V Leiden mutation, probably leading to a milder bleeding tendency. The patient had successful factor XIII replacement therapy throughout her fourth pregnancy. The efficacy of the factor XIII infusions was monitored using thromboelastometry and routine factor XIII measurements. This case report shows that factor XIII deficiency should be ruled out in patients with recurrent fetal loss but with a normal miscarriage workup, even in the absence of a history of severe bleeding since childhood. We also showed that thromboelastometry could be a valuable tool for the monitoring of factor XIII replacement therapy.

Factor VIII hydrolysis mediated by anti-factor VIII autoantibodies in acquired hemophilia.

Acquired hemophilia is a rare hemorrhagic disorder caused by the spontaneous appearance of inhibitory autoantibodies directed against endogenous coagulation factor VIII (FVIII). Inhibitory Abs also arise in patients with congenital hemophilia A as alloantibodies directed to therapeutic FVIII. Both autoimmune and alloimmune inhibitors neutralize FVIII by steric hindrance. We have described FVIII-hydrolyzing IgG in 50% of inhibitor-positive patients with severe hemophilia A that inactivate therapeutic FVIII. In this study, we investigated the presence of autoimmune FVIII-hydrolyzing IgG in patients with acquired hemophilia. Pooled IgG from healthy donors demonstrated moderate FVIII-hydrolyzing activity (56 +/- 26 micromol/min/mol). Purified IgG from 21 of 45 patients with acquired hemophilia demonstrated FVIII hydrolysis rates (mean 219 +/- 94 micromol/min/mol) significantly greater than that of control IgG. Three of four patients followed over the course of the disease had rates of FVIII hydrolysis that co-evolved with inhibitory titers in plasma, suggesting that IgG-mediated FVIII hydrolysis participates, in part, in FVIII inactivation. The present work extends the scope of the diseases associated with FVIII proteolysis and points toward the importance of FVIII as a key target substrate for hydrolytic immunoglobulins. Our data suggest that elevated levels of FVIII-hydrolyzing IgG in acquired hemophilia result from the exacerbation of a physiological catalytic immune response.

Multicenter evaluation of a bilayer polymer blood collection tube for coagulation testing: effect on routine hemostasis test results and on plasma levels of coagulation activation markers.

We compared the results of different hemostasis tests obtained in an evacuated bilayer polymer tubes (Vacuette, Greiner Bio-One) and in a siliconized glass tubes containing the same citrate concentrations (0.109 M and 0.129 M). For that purpose, blood was collected in five centers from 60 untreated patients and from patients on oral anticoagulant (n = 168), unfractionated heparin (n = 111) or a low molecular weight derivative (n = 108). Test results obtained in polymer tubes were not significantly different from those in glass tubes, except for INR when a high ISI thromboplastin was used (p < 0.0001 for tubes containing 0.129 M sodium citrate) and for APTT (p < 0.05 for both citrate concentrations). However, these differences had no clinical relevance (Bland-Altman analysis). In addition, no effect of aging of the polymer tubes on the test results could be demonstrated. The plasma levels of F1+2 and TAT, measured in a subset of 30 untreated patients, were significantly lower when blood was collected in polymer than in glass tubes, for both citrate concentrations. These results suggest that samples collected into the Vacuette polymer tubes allow accurate routine hemostasis testing both in untreated patients and in patients on traditional anticoagulant treatment during the whole shelf-life indicated by the manufacturer.

Prevention of postoperative venous thromboembolism. Risk assessment and methods of prophylaxis.

PURPOSE: To describe risk assessment models that have been developed to stratify patients into different risk levels of postoperative venous thromboembolism (VTE) and then to review the different methods of prophylaxis and to outline the evidence supporting their effectiveness and safety. SOURCE: Our review of the literature is focused on consensus documents, recent large randomized trials and meta-analyses. PRINCIPAL FINDINGS: The risk of VTE is determined by the type of surgery and underlying patient factors. Risk assessment models are useful in stratifying patients into different VTE risk levels. However, multiple risk factors are often present in the same patient and in practice the evaluation of their relative contribution to the overall risk remains difficult. A variety of prophylactic strategies including physical and pharmacological methods have been shown to be effective in different patient groups. Patients with a moderate or high risk of VTE should receive prophylaxis consisting of an antithrombotic agent, unless contraindicated, used alone or in combination with a mechanical method. Recommendations concerning which prophylaxis to use and how intensive it should be are based mainly on data from trials using surrogate endpoints, and do not translate easily into practical decisions aiming to reduce the incidence of symptomatic events. CONCLUSION: Although risk assessment models and recommendations provided by consensus documents are of practical assistance, a decision concerning any patient is best made by combining recommendations of the literature with clinical judgment, including individual patient risk factors for thrombosis and bleeding.

Catastrophic antiphospholipid syndrome and pulmonary embolism in a 3-year-old child.

We report a rare example of catastrophic antiphospholipid syndrome (CAPS) in a young child. A 3-year-old girl with no previous medical history presented with extensive and recurrent thromboses. The diagnosis of CAPS was based on the occurrence of cardiopulmonary embolism in the child with a high titre of autoantibodies directed against phospholipids and beta-2-glycoprotein 1. In spite of a relatively rapid diagnosis and multiple treatments, the outcome was unfavourable. Multimodality imaging, including both ultrasonography and spiral CT, allowed close follow-up of the thromboses.