Showing papers in "Thrombosis and Haemostasis in 2000"

Derivation of a Simple Clinical Model to Categorize Patients Probability of Pulmonary Embolism: Increasing the Models Utility with the SimpliRED D-dimer

Abstract: We have previously demonstrated that a clinical model can be safely used in a management strategy in patients with suspected pulmonary embolism (PE). We sought to simplify the clinical model and determine a scoring system, that when combined with D-dimer results, would safely exclude PE without the need for other tests, in a large proportion of patients. We used a randomly selected sample of 80% of the patients that participated in a prospective cohort study of patients with suspected PE to perform a logistic regression analysis on 40 clinical variables to create a simple clinical prediction rule. Cut points on the new rule were determined to create two scoring systems. In the first scoring system patients were classified as having low, moderate and high probability of PE with the proportions being similar to those determined in our original study. The second system was designed to create two categories, PE likely and unlikely. The goal in the latter was that PE unlikely patients with a negative D-dimer result would have PE in less than 2% of cases. The proportion of patients with PE in each category was determined overall and according to a positive or negative SimpliRED D-dimer result. After these determinations we applied the models to the remaining 20% of patients as a validation of the results. The following seven variables and assigned scores (in brackets) were included in the clinical prediction rule: Clinical symptoms of DVT (3.0), no alternative diagnosis (3.0), heart rate >100 (1.5), immobilization or surgery in the previous four weeks (1.5), previous DVT/PE (1.5), hemoptysis (1.0) and malignancy (1.0). Patients were considered low probability if the score was 4.0. 7.8% of patients with scores of less than or equal to 4 had PE but if the D-dimer was negative in these patients the rate of PE was only 2.2% (95% CI = 1.0% to 4.0%) in the derivation set and 1.7% in the validation set. Importantly this combination occurred in 46% of our study patients. A score of

Incidence of venous thromboembolism: a community-based study in Western France. EPI-GETBP Study Group. Groupe d'Etude de la Thrombose de Bretagne Occidentale.

Abstract: The incidence of venous thromboembolism has been studied during one year in a defined population of 342,000 inhabitants. The overall incidence (95% confidence interval) of venous thromboembolism was found to be 1.83 per thousand per year (1.69 to 1.98). The incidences of deep venous thrombosis and pulmonary embolism were 1.24 per thousand per year (1.12 to 1.36) and 0.60 per thousand per year (0.52 to 0.69), respectively. The incidence of venous thromboembolism rose markedly with increasing age for both sexes; over the age of 75, the annual incidence reached 1 per 100. Sixty three percent of the patients were at home when venous thromboembolism occurred. Of these, sixteen percent had been previously hospitalised within three months. These results raise concerns on identification of medical patients at high risk and effective prophylaxis.

Identification and biological activity of the active metabolite of clopidogrel.

Abstract: Like ticlopidine, the ADP receptor antagonist clopidogrel is inactive in vitro and must be administered i.v. or orally to exhibit antiaggregatory and antithrombotic activities. We have previously shown that hepatic metabolism is necessary for activity. This study demonstrates that an active metabolite can be generated from human liver microsomes incubated with clopidogrel. Using several analytical methodologies (LC/MS, NMR, chiral supercritical fluid chromatography), we have identified its structure. In vitro, this highly unstable compound, different from that formed from ticlopidine, exhibited all the biological activities of clopidogrel observed ex vivo: Irreversible inhibition of the binding of 33P-2MeS-ADP to washed human platelets (IC50 = 0.53 µM), selective inhibition of ADP-induced platelet aggregation (IC50 = 1.8 µM) and ADP-induced adenylyl cyclase down-regulation. The irreversible modification of the ADP-receptor site which is responsible for the biological activity could be explained by the formation of a disulfide bridge between the reactive thiol group of the active metabolite and a cysteine residue of the platelet ADP receptor. Abbreviations: ADP: adenosine 5’diphosphate; 2-MeS-ADP: 2-methylthioadenosine-5’-diphosphate; Bmax: maximum binding capacity; IC50: concentration which inhibits 50% of the activity; Kd: dissociation constant; LC/MS: Liquid chromatography coupled to mass spectrometry; NMR: Nuclear magnetic resonance

Impact, Diagnosis and Treatment of von Willebrand Disease*

Abstract: Von Willebrand disease (VWD) is one of the most common inherited bleeding diseases. Based on a conservative estimate of prevalence (at least 100 per million persons) (1-7) and a population of 5.8 billion, there are at least 580,000 persons with symptomatic VWD worldwide who could benefit from appropriate diagnosis followed by replacement or pharmacological therapy. Approximately 80% of these persons live in the developing world. Because severe menorrhagia is common in VWD, the disease tends to cause greater morbidity in women of childbearing age. Consequently, VWD impairs the health of a critical segment of the population during a time of life when the demands of work and family are the greatest.

High plasma concentration of factor viiic is a major risk factor for venous thromboembolism

Abstract: Established risk factors, including deficiencies of protein C, protein S or antithrombin and the factor V Leiden and prothrombin mutation, are present in about one third of unselected patients with venous thromboembolism. In addition to these inherited thrombophilic defects, elevated plasma levels of factor VIIIc have been suggested to be important in the pathogenesis of (recurrent) venous thromboembolism. The objective of this study was to assess the relevance of factor VIIIc plasma concentration in consecutive patients with venous thromboembolism. We studied the prevalence of elevated plasma levels of factor VIIIc in 65 patients with a proven single episode and in 60 matched patients with documented recurrent venous thromboembolism. The reference group consisted of 60 ageand sex-matched patients who were referred for suspected venous thromboembolism, which was refuted by objective testing and longterm clinical follow-up. To minimalize the influence of the acute phase, blood was obtained at least 6 months after the thromboembolic event and results were adjusted for fibrinogen and C-reactive protein. Factor VIIIc was re-determined several years after the first measurement in a subset of patients to evaluate the variability over time. To study a possible genetic cause, a family study was done. In the control, single and recurrent episode group, the prevalences of plasma levels of factor VIIIc above 175 IU/dl (90th percentile of controls) were 10% (95% CI: 4 to 21%), 19% (95% CI: 10 to 30%) and 33% (95% CI: 22 to 47%), respectively. For each 10 IU/dl increment of factor VIIIc, the risk for a single and recurrent episode of venous thrombosis increased by 10% (95% CI: 0.9 to 21%) and 24% (95% CI: 11 to 38%), respectively. Both low and high plasma levels of factor VIIIc were consistent over time (R = 0.80, p = 0.01). A family study indicated a high concordance for elevated factor VIIIc plasma concentrations among first degree family members. Adjustment for fibrinogen, C-reactive protein and known thrombophilic risk factors did not change the observed association of elevated factor VIIIc with thrombosis. Elevated plasma levels of factor VIIIc are a significant, prevalent, independent and dose-dependent risk factor for venous thromboembolism. It also predisposes to recurrent venous thromboembolism.

Acute Exacerbations of Chronic Obstructive Pulmonary Disease Are Accompanied by Elevations of Plasma Fibrinogen and Serum IL-6 Levels

Abstract: Background. Respiratory tract infections may acutely increase risk from coronary heart disease (CHD), though the mechanisms have not been defined. Patients with chronic obstructive pulmonary disease (COPD) are prone to repeated exacerbations that are often associated with respiratory infections. These patients also have increased cardiovascular morbidity and mortality. We hypothesized that transient acute increases in plasma fibrinogen, an independent risk factor for CHD, could occur at COPD exacerbation (mediated through a rise in IL6) and thereby provide a mechanism linking respiratory infection to risk of coronary heart disease. Methods. 93 COPD patients [mean (SD) age 66.8 (8.1) years] were followed regularly over one year, with daily diary card monitoring of respiratory symptoms and peak expiratory flow rate (PEFR); 67 patients [mean FEV1 1.06 (0.44) l, FVC 2.43 (0.79) l] were seen during 120 exacerbations. At each visit spirometry was measured and blood samples taken for plasma fibrinogen and Interleukin-6 (IL-6) levels. Result. At baseline, the mean (SD) plasma fibrinogen was elevated at 3.9 (0.67) g/l in the 67 patients with exacerbations during the study and the median (IQR) IL-6 at 4.3 (2.4 to 6.8) pg/ml. Plasma fibrinogen increased by 0.36 (0.74) g/l at exacerbation (p

Prevention of Venous Thromboembolism in Internal Medicine with Unfractionated or Low-molecular-weight Heparins: A Meta-analysis of Randomised Clinical Trials

Abstract: Background. The prevention of venous thromboembolic disease is less studied in medical patients than in surgery. Methods. We performed a meta-analysis of randomised trials studying prophylactic unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) in internal medicine, excluding acute myocardial infarction or ischaemic stroke. Deepvein thrombosis (DVT) systematically detected at the end of the treatment period, clinical pulmonary embolism (PE), death and major bleeding were recorded. Results. Seven trials comparing a prophylactic heparin treatment to a control (15,095 patients) were selected. A significant decrease in DVT and in clinical PE were observed with heparins as compared to control (risk reductions = 56% and 58% respectively, p 0.001 in both cases), without significant difference in the incidence of major bleedings or deaths. Nine trials comparing LMWH to UFH (4,669 patients) were also included. No significant effect was observed on either DVT, clinical PE or mortality. However LMWH reduced by 52% the risk of major haemorrhage (p = 0.049). Conclusions. This meta-analysis, based on the pooling of data available for several heparins, shows that heparins are beneficial in the prevention of venous thromboembolism in internal medicine.

Predicting Adverse Outcome in Patients with Acute Pulmonary Embolism: A Risk Score

Abstract: Reliable prediction of adverse outcomes in acute pulmonary embolism may help choose between in-hospital and ambulatory treatment. We aimed to identify predictors of adverse events in patients with pulmonary embolism and to generate a simple risk score for use in clinical settings. We prospectively followed 296 consecutive patients with pulmonary embolism admitted through the emergency ward. Logistic regression was used to predict death, recurrent thromboembolic event, or major bleeding at 3 months. Thirty patients (10.1%) had one or more adverse events during the 3-month follow-up period: 25 patients (8.4%) died, thromboembolic events recurred in 10 patients (3.4%), and major bleeding occurred in 5 patients (1.7%). Factors associated with an adverse outcome in multivariate analysis were cancer, heart failure, previous deep vein thrombosis, systolic blood pressure

Acquired von Willebrand syndrome: data from an international registry.

Abstract: The acquired von Willebrand syndrome (AvWS) is a rare bleeding disorder with laboratory findings similar to those of congenital von Willebrand disease (vWD). Despite the numerous cases reported in the literature until 1999 (n = 266), large studies on AvWS are not available. Moreover, diagnosis of AvWS has been difficult and treatment empirical. These considerations prompted us to organize an international registry. A questionnaire, devised to collect specific information on AvWS, was sent to all the members of the International Society on Thrombosis and Haemostasis (ISTH), who were invited to respond if they had diagnosed cases with the AvWS cases. 156 members answered the questionnaire and 54 of them sent information on 211 AvWS cases from 50 centers. Data were compared with those already published in the literature and 25 cases already described or not correctly diagnosed were excluded. The 186 AvWS cases that qualified for the registry were associated with lymphoproliferative (48%) and myeloproliferative disorders (15%), neoplasia (5%), immunological (2%), cardiovascular (21%) and miscellaneous disorders (9%). Ristocetin cofactor activity (vWF:RCo) or collagen binding activity (vWF:CBA) were usually low in AvWS (median values 20 U/dL, range 3-150), while factor VIII coagulant activity was sometimes normal (median 25 U/dL, range 3-191). FVIII/vWF inhibiting activities were present in only a minority of cases (16%). Bleeding episodes in AvWS were mostly of mucocutaneous type (68%) and were managed by DDAVP (32%), FVIII/vWF concentrates (37%), intravenous immunoglobulins (33%), plasmapheresis (19%), corticosteroids (19%) and immunosuppressive or chemotherapic agents (35%). Based upon the data of this international registry, it appears that AvWS is especially frequent in lympho- or myeloproliferative and cardiovascular diseases. Therefore, AvWS should be suspected and searched with the appropriate laboratory tests especially when excessive bleeding occurs in patients with these disorders. On the basis of the information provided by this registry guidelines for diagnosis and management of the AvWS are given.

The thrombogram: monitoring thrombin generation in platelet-rich plasma

Abstract: A method is described in which thrombin activity in clotting plasma can be monitored through the continuous measurement of the fluorescent split-product of the substrate Z-Gly-Gly-Arg-AMC. The signal is not impaired by turbidity; therefore proper measurement is not disturbed by the occurrence of a clot or the presence of platelets and direct measurement in platelet rich plasma is possible.

Increased risk of recurrent venous thromboembolism during hormone replacement therapy--results of the randomized, double-blind, placebo-controlled estrogen in venous thromboembolism trial (EVTET).

Abstract: Recent observational studies suggest a 2-4 fold increased risk of venous thromboembolism (VTE) in women taking hormone replacement therapy (HRT). The present study was started before publication of these studies, and the aim was to determine if HRT alters the risk of VTE in high risk women. The study was a randomized, double-blind, and placebo-controlled clinical trial with a doubletriangular sequential design. Females with previously verified VTE were randomized to 2 mg estradiol plus 1 mg norethisterone acetate, 1 tablet daily (n = 71) or placebo (n = 69). The primary outcome was recurrent deep venous thrombosis (DVT) or pulmonary embolism (PE). Between 1996 and 1998 a total of 140 women were included. The study was terminated prematurely based on the results of circumstantial evidence emerging during the trial. Eight women in the HRT group and one woman in the placebo group developed VTE. The incidence of VTE was 10.7% in the HRT group and 2.3% in the placebo group. In the HRT group, all events happened within 261 days after inclusion. The sequential design did not stop the study, but strongly indicated a difference between the two groups. Our data strongly suggests that women who have previously suffered a VTE have an increased risk of recurrence on HRT. This treatment should therefore be avoided in this patient group if possible. The results also support those of recent epidemiological studies, which also indicate increased risk of VTE in non-selected female populations during HRT.

Gestational Outcome in Thrombophilic Women with Recurrent Pregnancy Loss Treated by Enoxaparin

Abstract: Inherited and acquired thrombophilia are associated with recurrent pregnancy loss (RPL). We have evaluated the efficacy and safety of the low molecular weight heparin enoxaparin in 50 women, (mean age 26 ± 3 years) with RPL (3 losses in 1st , 2 losses in 2nd and 1 loss in 3rd trimester) who were found to harbor thrombophilia. Twenty-seven had a solitary thrombophilic defect, and twenty-three women had combined thrombophilic defects: 17 - two defects and 6 - three defects. Following diagnosis of thrombophilia, sixty-one subsequent pregnancies were treated with the low molecular weight heparin enoxaparin throughout gestation until 4 weeks after delivery. Dosage was 40 mg/day in women with solitary defect and 80 mg/day in combined defects. Aspirin, 75 mg daily was given in addition to enoxaparin to women with antiphospholipid syndrome. Forty-six out of 61 (75%) gestations treated by enoxaparin resulted in live birth compared to only 38/193 (20%) of the untreated pregnancies in these 50 women prior to diagnosis of thrombophilia (p 0.00001). In 23 women without a single living child following 82 untreated gestations, antithrombotic therapy resulted in 26/31 (84%) successful deliveries (p 0.0001). In 20 women with a prior living child, antithrombotic therapy improved successful delivery from 33/86 (38%) to 20/21 (95%) (p 0.0001). Enoxaparin dose of 40 mg/day resulted in live birth in 24/35 (69%) of gestations, compared to 19/23 (83%) gestations in women treated with 80 mg/day (p = 0.37). Only one thrombotic episode and one mildbleeding episode were noticed during enoxaparin therapy. Enoxaparin is safe and effective in prevention of pregnancy loss in women with inherited and acquired thrombophilia.

The endothelial cell protein C receptor.

Abstract: The Protein C Pathway before EPCR The protein C anticoagulant pathway is recognized as a major control mechanism of blood coagulation [reviewed in]. Defects in protein C, protein S and thrombomodulin have all been implicated as predisposing factors for the development of venous thrombosis (2-5) and, under some circumstances, contributing to arterial thrombosis (6-8). The pathway is initiated when thrombin binds to thrombomodulin (TM), an integral membrane receptor found primarily on endothelium, but also on a variety of other cells including monocytes. The thrombin-TM complex activates protein C rapidly and can also activate a procarboxypeptidase B, often referred to as TAFI, thrombin activatable fibrinolysis inhibitor. Once activated protein C (APC) is generated, it binds to protein S and can then inactivate either factor Va or factor VIIIa on the surface of negatively charged phospholipids or on the membranes of activated cells. The thrombin-TM complex is inhibited by either antithrombin or protein C inhibitor. The estimated half life of the complex at plasma levels of these inhibitors is only a few seconds. Since EPCR is among the newest proteins in the coagulation/anticoagulation area to be identified, I have included references to abstracts in this review that are yet to be published in full.

Genetic modulation of oral anticoagulation with warfarin.

Abstract: Cytochrome P450 CYP2C9 gene variants have been associated with hyperresponsiveness to small doses of warfarin and a higher bleeding complication rate. The aim of this study was to investigate whether CYP2C9 gene variants affect doses of drug prescribed to acquire the target anticoagulation intensity and the occurence of bleeding complications. In a cohort of 180 patients followed up at one specialized clinic from the start of the anticoagulation with warfarin, we have investigated whether CYP2C9 gene variants have affected doses of drug prescribed to acquire the target anticoagulation intensity and the incidence of bleeding complications. The adjusted dose required of warfarin was higher among patients with the CYP2C9*1 haplotype (5.6 mg) than those of patients carrying the CYP2C9*2 (4.7 mg; p = 0.007, Scheffe’s test) or the CYP2C9*3 haplotype (4.0 mg; p

A Comparison of the Safety and Efficacy of Oral Antiocoagulation for the Treatment of Venous Thromboembolic Disease in Patients with or without Malignancy

Abstract: The optimal long-term treatment of acute venous thromboembolism (VTE) in patients with malignancy remains undefined. In particular, based on current evidence, it is uncertain whether secondary prophylaxis using standard intensity oral anticoagulant therapy is associated with higher risks of bleeding and recurrent thrombosis in patients with cancer than in those without cancer. This study compared the outcome of anticoagulation courses in 95 patients with malignancy with those of 733 patients without malignancy. All patients were participants in a large, nation-wide population study and were prospectively followed from the initiation of their oral anticoagulant therapy. Based on 744 patient-years of treatment and follow-up, the rates of major (5.4% vs 0.9%), minor (16.2% vs 3.6%) and total (21.6% vs 4.5%) bleeding were statistically significantly higher in cancer patients compared with patients without cancer. Bleeding was also a more frequent cause of early anticoagulation withdrawal in patients with malignancy (4.2% vs. 0.7%; p

Monitoring of aspirin (ASA) pharmacodynamics with the platelet function analyzer PFA-100

Abstract: Background. Anti-platelet drug therapy is currently performed without monitoring, because the established method of platelet aggregomet-ry is cumbersome. The recently developed platelet function analyzer PFA-100 ® measures shear stress dependent, collagen epinephrine (CEPI) and collagen adenosine diphosphate (CADP) induced platelet plug formation. As the PFA-100 provides a valuable tool to detect patients with platelet dysfunction more efficiently and cost-effectively than aggregometry, we investigated its potential to monitor the efficacy of aspirin treatment. Methods. All healthy volunteers (n = 10) received a fractionated infusion of L-aspirin to establish individual dose-response curves. Fur-ther, in a randomized, double-blind, placebo controlled two-way cross over study the same volunteers received either 50 or 100 mg aspirin/day p.o. for a period of 11 days to determine the day-to-day variability CEPI induced closure time (CT) under constant intake of low dose aspirin, and to compare the efficacy of those two doses. Results. Intra- and intersubject variability of CEPI-CT averaged 9% and 22%, respectively. Seven volunteers exceeded the maximum of CEPI-CT (>300 s) already after infusion of 100 mg L-aspirin. Intake of 100 mg of aspirin elicited a more rapid onset of effect than 50 mg, which was only significant on days 3 and 4 of aspirin intake. The aspirin induced CEPI-CT prolongation correlated positively with basal CEPI-CT values (r = 0.86; p = 0.001) and were strongly dependent on von Willebrand Factor levels (r = -0.9; p = 0.001). Conclusion. Thus, the PFA-100 system appears suitable to demonstrate an aspirin-induced platelet effect in a longitudinal study, and may be adequate to monitor a patient’s compliance. However, prospective trials have to be conducted to demonstrate whether the EPI-CT

Blood Rheology, Cardiovascular Risk Factors, and Cardiovascular Disease: The West of Scotland Coronary Prevention Study

Abstract: The West of Scotland Coronary Prevention Study (WOSCOPS) showed that pravastatin reduced the risk of coronary heart disease (CHD) events in 6,595 middle-aged hypercholesterolaemic men aged 45-64 years without prior myocardial infarction followed for an average of 4.9 years. We hypothesised prospectively (a) that baseline levels of haemorheological variables were related to baseline and incident CHD and to mortality; and (b) that reduction in lipoproteins by pravastatin would lower plasma and blood viscosity, a potential contributory mechanism to CHD events. We therefore studied plasma and blood viscosity, fibrinogen, haematocrit, and blood cell counts at baseline and 1 year. At baseline, plasma and blood viscosity were related to risk factors, CHD measures, and claudication. On univariate analysis, baseline levels of all rheological variables (except platelet count) were related to incident CHD; CHD mortality; and total mortality. On multivariate analysis including baseline CHD and risk factors, plasma and blood viscosity, haematocrit and white cell count each remained significantly associated with incident CHD; while fibrinogen remained an independent predictor of mortality (all p < 0.03). After one year, lipoprotein reduction by pravastatin was associated with significant reductions (about one quarter of a standard deviation) in plasma viscosity (mean difference 0.02 mPa.s, p <0.001) and in blood viscosity (mean difference 0.06 mPa.s, p<0.001), but was not associated with significant changes in other rheological variables. We therefore suggest that pravastatin therapy, which reduces elevated lipoproteins in hypercholesterolaemic men, may lower risks of CHD and mortality partly by lowering plasma and blood viscosity. Further studies are required to test this hypothesis.

Outpatient treatment of pulmonary embolism with dalteparin.

Abstract: Background: Pulmonary embolism is a common complication of deep vein thrombosis. It has been established that low molecular weight heparin may be used to treat deep vein thrombosis or pulmonary embolism and randomized studies have established that outpatient management of deep vein thrombosis with low molecular weight heparin is at least as effective as in-hospital management with unfractionated heparin. Methods: This was a prospective cohort study of eligible patients with pulmonary embolism managed as outpatients using dalteparin (200 U/kg s/c daily) for a minimum of five days and warfarin for 3 months. Outpatients included those managed exclusively out of hospital and those managed initially for 1-3 days as inpatients who then completed therapy out of hospital. Reasons for admission included hemo-dynamic instability; hypoxia requiring oxygen therapy; admission for another medical reason; severe pain requiring parenteral analgesia or high risk of major bleeding. Patients were followed for three months for clinically apparent recurrent venous thromboembolism and bleeding. Results: Between three teaching hospitals, a total of 158 patients with pulmonary embolism were identified. Fifty patients were managed as inpatients and 108 as outpatients. Of the outpatients, 27 were managed for an average of 2.5 days as inpatients and then completed dalteparin therapy as outpatients. The remaining 81 patients were managed exclusively as outpatients with dalteparin. For all outpatients the overall symptomatic recurrence rate of venous thromboembolism was 5.6% (6/108) with only 1.9% (2/108) major bleeds. There were a total of four deaths with none due to pulmonary embolism or major bleed. Conclusions: This prospective study suggests that outpatient management of pulmonary embolism is feasible and safe for the majority of patients.

Elevation of FVIII : C in Venous Thromboembolism Is Persistent and Independent of the Acute Phase Response

Abstract: Recent literature has suggested a role for elevated FVIII:C in venous thromboembolic disease (VTED). However since FVIII:C is known to rise in response to an acute phase reaction, it is difficult to determine whether the increased FVIII:C precedes the thrombosis or represents a secondary reactive phenomenon. In an attempt to address this question, we followed 35 patients with confirmed VTED, raised FVIII:C level (>1.5 iu/ml) and no other thrombotic tendency. Serial measurements of FVIII:C, vWF:Ag, C-reactive protein and fibrinogen were performed. We hypothesized that a persistent increase in FVIII:C in the absence of any other measures of ongoing acute phase response, would support the idea that elevation of FVIII:C is a constitutional phenomenon. Of this initial group, 94% continued to have an elevated FVIII:C level throughout the period of follow up (median 8 months; range 3 to 39 months), with no significant difference between the FVIII:C levels determined at first estimation and those obtained during follow up (p = 0.58). Conversely, only 18% had evidence of an acute phase reaction when first assessed, and nonparametric ranking analysis demonstrated no correlation between FVIII:C and either C-reactive protein or fibrinogen (p = 0.315 and 0.425 respectively).We conclude that increased FVIII:C levels following VTED are persistent, independent of the acute phase reaction, and thus may represent a constitutional risk factor for VTED.

Effects on Coagulation of Levonorgestrel- and Desogestrel-containing Low Dose Oral Contraceptives: a Cross-over Study

Abstract: Combined oral contraceptives (OC) are known to increase the risk of venous thromboembolism. The aim of this randomized, cycle-controlled, cross-over study in 28 healthy volunteers was to assess potential differences between the effects of an OC containing 150 microg levonorgestrel (as representative of the so-called second generation OC) and an OC containing 150 microg desogestrel (as representative of the third generation OC) in combination with 30 microg ethinylestradiol on several coagulation factors and markers of thrombin formation. All participants used each OC for two cycles, and were switched to the other OC after a washout period of two menstrual cycles. The plasma concentrations of factors II, VII, X, and fibrinogen significantly increased during use of both the levonorgestrel- and desogestrel-containing OC's. The plasma concentrations of factor VIII increased, and of factor V decreased, changes which only reached statistical significance during the use of the desogestrel-containing OC. During exposure to the desogestrel-containing OC, as compared with the levonorgestrel-containing OC, both factor VII and factor II showed a greater increase (FVII: 32% and 12% respectively; p <0.0001; FII: 16% and 12% respectively; p = 0.048), whereas factor V showed a greater decrease (-11% and -3% respectively; p = 0.010). Only one of the markers for ongoing coagulation (prothrombin fragment 1+2) showed a significant increase during OC use, whereas concentrations of thrombin-antithrombin complexes and soluble fibrin remained unchanged. For these markers, there was no difference between the tested OC's. We conclude that there are differences between the effects of levonorgestrel and desogestrel-containing OC's on some coagulation factors. Whether these changes provide a biological explanation for the reported differences in venous thromboembolic risk is as yet unclear. The real challenge now becomes to define a pattern of changes in the various systems which, if affected simultaneously, may tip the hemostatic balance towards a prethrombotic state and may lead to overt clinical venous thromboembolism.

Exclusion of deep venous thrombosis with D-dimer testing--comparison of 13 D-dimer methods in 99 outpatients suspected of deep venous thrombosis using venography as reference standard.

Abstract: In a direct assay comparison we evaluated the diagnostic performance of 10 novel D-Dimer assays for the exclusion of deep venous thrombosis (DVT). In addition, 3 conventional ELISA D-Dimer assays were included as reference tests. The study was performed in 99 consecutive outpatients referred to the emergency department for clinical suspicion of DVT. Venography was used as reference standard and demonstrated the presence of DVT in 50 patients (6 patients with isolated distal DVT and 44 patients with proximal DVT). The qualitative D-Dimer assays Minutex and SimpliRED and the quantitative BC DD showed overall sensitivities (for proximal and distal DVT) of only 80-83% with specificities that ranged from 87 to 94%. Overall sensitivity was 94% for the qualitative INSTANT I.A. and 98% for the quantitative Turbiquant at a cut-off level equal to the detection limit. Using different cut-off levels a sensitivity of 100% for proximal DVT and for proximal as well as distal DVT could be obtained for NycoCard, IL DD, Liatest, Tinaquant and VIDAS D-Dimer assays with specificities that ranged from 31% (NycoCard) to 71% (VIDAS) for proximal DVT and from 12% (NycoCard) to 47% (IL DD) for overall DVT. At a cut-off level equal to the upper limit of the reference range only Tinaquant and VIDAS showed a sensitivity of 100% for proximal as well as for distal DVT with a specificity of 39% and 41% respectively. The results of this study suggest that the VIDAS and Tinaquant D-Dimer assays have the highest sensitivity for the exclusion of DVT in outpatients. In outpatients that have a low or moderate pretest probability for DVT, these tests may be used in management studies where anticoagulation is withheld on the basis of D-Dimer testing alone.

A Randomized Cross-over Study on the Effects of Levonorgestrel- and Desogestrel-containing Oral Contraceptives on the Anticoagulant Pathways

Abstract: The use of oral contraceptives (OC) causes disturbances of the procoagulant, anticoagulant and fibrinolytic pathways of blood coagulation which may contribute to the increased risk of venous thrombosis associated with OC therapy. Here we report the results of a cycle-controlled randomized cross-over study, in which we determined the effects of so-called second and third generation OC's on a number of anticoagulant parameters. In this study, 28 non-OC using women were randomly prescribed either a second generation (150 microg levonorgestrel/30 microg ethinylestradiol) or a third generation OC (150 microg desogestrel/30 microg ethinylestradiol) and who switched to the other OC after a two month wash out period. The anticoagulant parameters determined were: antithrombin (AT), alpha2-macroglobulin (alpha2-M), alpha1-antitrypsin, protein C inhibitor (PCI), protein C, total and free protein S and activated protein C sensitivity ratios (APC-sr) measured with two functional APC resistance tests which quantify the effect of APC on either the activated partial thromboplastin time (aPTT) or on the endogenous thrombin potential (ETP). During the use of desogestrel-containing OC the plasma levels of alpha2-M, alpha1-antitrypsin, PCI and protein C significantly increased, whereas AT and protein S significantly decreased. Similar trends were observed with levonorgestrel-containing OC, although on this kind of OC the changes in AT, PCI and protein S (which was even slightly increased) did not reach significance. Compared with levonorgestrel, desogestrel-containing OC caused a significant decrease of total (p <0.005) as well as free protein S (p <0.0001) and more pronounced APC resistance in both the aPTT (p = 0.02) and ETP-based (p <0.0001) APC resistance tests. These observations indicate that the activity of the anticoagulant pathways in plasma from users of desogestrel-containing OC is more extensively impaired than in plasma from users of levonorgestrel-containing OC.

Plasma procarboxypeptidase U in men with symptomatic coronary artery disease.

Abstract: Procarboxypeptidase U (proCPU) is the plasma precursor of carboxypeptidase U (CPU, carboxypeptidase R. plasma carboxypeptidase B or activated thrombin-activatable fibrinolysis inhibitor, TAFIa). CPU removes C-terminal lysine residues that act as plasminogen binding sites from partially degraded fibrin, thereby down-regulating plasminogen activation and fibrinolysis. The present study was carried out as a pilot study to examine whether the plasma proCPU concentration is related to the presence of coronary artery disease (CAD) and/or to levels of established risk indicators for CAD, in a case-control study of 110 men requiring coronary artery bypass grafting (CABG) because of stable angina pectoris. The preoperative plasma proCPU level in the CABG patients was significantly higher than in population-based controls (1029 +/- 154 vs. 974 +/- 140 U/L, p <0.05). In addition, in a subset of the patients (n = 31 ) the proCPU concentration, which was significantly lower on the third postoperative day (-17 +/- 10%), had increased significantly on the sixth day (+14 +/- 12%) after surgery, compared with the preoperative level. In both patients and controls, proCPU concentration was strongly and positively associated with factor VII amidolytic activity and protein C activity, suggesting a common mechanism modulating the plasma levels of these proteins. Otherwise, statistically significant correlations with proCPU were group-specific. In the patients, proCPU correlated significantly with plasma fibrinogen and protein S. In the controls, proCPU correlated significantly with concentrations of cholesterol in plasma. VLDL and LDL. In addition, proCPU correlated significantly with C-reactive protein and haptoglobin levels in the controls only, indicating that also inflammatory mechanisms are involved in the regulation of plasma proCPU. These results suggest that a mechanism exists by which fibrinolytic function is impaired in a manner that is likely to result in more stable fibrin deposits and increase the risk of precocious CAD as well as early occlusion of venous bypass grafts.

Phenotyping the Clotting System

Abstract: The combined research efforts in our field over the last hundred years made that we now recognise dozens of plasma proteins with a function in the clotting system and a set of platelet components that is of the same order. Progress in molecular biology is such as to have identified some one hundred genes that may influence haemostasis and thrombosis and a new one comes about every month. Nevertheless the phenotype of the clotting system cannot be adequately established. There is no simple method that gives us a clear picture of the net result of the activity of all those genes, together with non-genetic influences (e. g. drugs), on the over-all clotting function of blood at a given moment. For over a century we make do with clotting times that we know to be marginally - if at all - sensitive to hypercoagulability and mild bleeding disorders. We are used to employing different variants for the control of oral anticoagulants and of heparin. Some anticoagulants do not significantly influence any type of clotting time and for convenience are assumed not to require control. Standardisation is a constant problem. But we are so used to clotting times as to almost forget that they do not actually serve the purpose of a simple adequate indicator of clotting function, that we lack a test that is equivalent to blood sugar in diabetes or blood pressure in hypertension.

Occurrence of amphoterin (HMG1) as an endogenous protein of human platelets that is exported to the cell surface upon platelet activation.

Abstract: Amphoterin (HMG1) is a 30-kD heparin-binding protein which is functionally associated with the outgrowth of cytoplasmic processes in developing neurones. Amphoterin has been shown to mediate adhesive and proteolytic interactions at the leading edge of motile cells. Recently it was shown that inhibition of amphoterin interactions with its cell surface receptor (RAGE) suppresses tumour growth and metastasis. In this work we have identified amphoterin polypeptide and its mRNA in human platelets. Amphoterin had a cytoplasmic localisation in resting platelets according to subcellular fractionation studies and immunogold electronmicroscopy. After platelet activation, part of amphoterin was associated with the external surface of plasma membrane. Externalisation of amphoterin during platelet activation was also detected in immunofluorescence studies. Amphoterin was detectable in human serum (0.2 ng/ml) but not in plasma. Resting platelets treated with PGI 2 and forskolin bound to immobilised recombinant amphoterin independently of divalent cations. The binding induced a spicular morphology in platelets, and was effectively inhibited by heparin. Amphoterinbinding protein components on the platelet surface were not identified, but amphoterin bound to phosphatidylserine and sulfatide in lipid binding assays. Our results suggest that amphoterin is an endogenous protein in human platelets, which is exported to the cell surface during platelet activation. Interaction of amphoterin with the platelet surface may be mediated by sulfoglycolipids and phospholipids.

Thrombotic variables and risk of idiopathic venous thromboembolism in women aged 45-64 years. Relationships to hormone replacement therapy.

Abstract: Hormone replacement therapy (HRT) has been shown to increase the relative risk of idiopathic venous thromboembolism (VTE) about threefold in several observational studies and one randomised controlled trial. Whether or not this relative risk is higher in women with underlying thrombophilia phenotypes, such as activated protein C (APC) resistance, is unknown. We therefore restudied the participants in a case-control study of the relationship between the use of HRT and the occurrence of idiopathic VTE in women aged 45-64 years. After protocol exclusions, 66 of the cases in the original study and 163 of the controls were studied. Twenty haematological variables relevant to risk of VTE were analysed, including thrombotic states defined from the literature. The relative risk of VTE showed significant associations with APC resistance (OR 4.06; 95% CI 1.62, 10.21); low antithrombin (3.33; 1.15, 9.65) or protein C (2.93; 1.06, 8.14); and high coagulation factor IX (2.34; 1.26, 4.35), or fibrin D-dimer (3.84; 1.99, 7.42). HRT use increased the risk of VTE in women without any of these thrombotic states (OR 4.09; 95% CI 1.26, 13.30). A similar effect of HRT use on the relative risk of VTE was also found in women with prothrombotic states. Thus for example, the combination of HRT use and APC resistance increased the risk of VTE about 13-fold compared with women of similar age without either APC resistance or HRT use (OR 13.27; 95% CI 4.30, 40.97). We conclude that the combination of HRT use and thrombophilias (especially if multiple) increases the relative risk of VTE substantially; hence women known to have thrombophilias (especially if multiple) should be counselled about this increased risk prior to prescription of HRT. However, HRT increases the risk of VTE about fourfold even in women without any thrombotic abnormalities: possible causes are discussed.

Blood coagulation factor X deficiency causes partial embryonic lethality and fatal neonatal bleeding in mice.

Abstract: Mice with a total deficiency in blood coagulation Factor X (FX) were generated by targeted replacement of an 18-kb fragment of the FX gene, comprising all exons encoding the mature FX protein, with a neor cassette. The genotype distribution among the offspring from heterozygous breeding pairs suggested that FX deficiency resulted in partial embryonic lethality, with approximately one-third of the FX −/− embryos dying around embryonic day (E) 11.5-12.5. Two of 44 non-resorbed FX −/− embryos analyzed at these stages showed signs of massive bleeding, one of which into the brain ventricles, but no histological defects in the vasculature of these embryos or their yolk sac were observed. The remainder of the FX −/− embryos appeared normal and survived to term, but the majority of neonates (90%) died within 5 days, most frequently from intraabdominal bleeding. The remaining FX −/− animals succumbed between postnatal day (P)5 and P20 with intraabdominal, subcutaneous, or intracranial bleeding or a combination thereof. The lethal phenotype of the FX −/− mice illustrates the importance of FX function in embryonic and postnatal survival and demonstrates that these mice serve as effective models of the bleeding disorders observed in severe FX deficiency in humans.

Protein S deficiency: a database of mutations--summary of the first update.

Abstract: Protein S is a vitamin K dependent protein whose inherited deficiency is a well recognized risk factor for venous thrombosis. Its role is to act as activated protein C cofactor in factor Va and VIIIa proteolysis, thus restricting thrombin generation. Its gene lies on chromosome 3, at position 3p11.1-q11.2, and its structural organization has been described. Elucidation of the gene defects responsible for protein S deficiency is proceeding rapidly. A first record of identified mutations was undertaken in 1996 under the auspices of the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee (ISTH SSC) and was published in 1997 (Thromb Haemost 1997; 77: 1201-14). This first database reported mutations identified in 126 protein S-deficient subjects postulated to be detrimental, and 19 mutations that were considered as neutral polymorphisms. The classification proposed by Bertina at the subcommittee meeting in 1991 was used to classify the mutations according to the phenotype observed in deficient subjects, that is type I when both free and total PS antigen levels were decreased, type III when free PS levels were decreased with normal total PS antigen levels, and type II when cofactor activity of PS was decreased while total and free antigen levels were within the normal ranges.

Increased fibrinolytic activity during use of oral contraceptives is counteracted by an enhanced factor XI-independent down regulation of fibrinolysis: a randomized cross-over study of two low-dose oral contraceptives.

Abstract: The effect of oral contraceptives (OC) on fibrinolytic parameters was investigated in a cycle-controlled cross-over study in which 28 non-OC using women were randomly prescribed either a representative of the so-called second (30 µg ethinylestradiol, 150 µg levonorgestrel) or third generation OC (30 µg ethinylestradiol, 150 µg desogestrel) and who switched OC after a two month wash out period. During the use of OC, the levels of tissue-type plasminogen activator (tPA) activity, plasminogen, plasmin-α2-antiplasmin complexes and D-dimer significantly increased (by 30 to 80%), while the levels of plasminogen activator inhibitor-1 (PAI-1) antigen, PAI-1 activity and tPA antigen significantly decreased (25 to 50%), suggesting an increase in endogenous fibrinolytic activity. These OC-induced changes were not different between the two contraceptive pills. TAFI (thrombin-activatable fibrinolysis inhibitor) levels increased on levonorgestrel, and even further increased on desogestrel. A clot lysis assay that probes both fibrinolytic activity and the efficacy of the coagulation system to generate thrombin necessary to down regulate fibrinolysis via TAFI showed no change of the clot lysis time during OC use. This finding suggests that the OC-induced increase in endogenous fibrinolytic activity is counteracted by an increased capacity of the coagulation system to down regulate fibrinolysis via TAFI. Indeed we observed that during OC use there was a significant increase of F1+2 generation during clot formation. When these assays were performed in the presence of an antibody against factor XI, we observed that the clot lysis time was significantly increased during OC use and that the increase in F1+2 generation during OC therapy was due to a factor XI-independent process, which was significantly higher on desogestrel than on levonorgestrel. These data indicate that the OC-induced inhibition of endogenous fibrinolysis takes place in a factor XI-independent way and is more pronounced on desogestrel than on levonorgestrel-containing OC.

Modulation of the binding of matrix Gla protein (MGP) to bone morphogenetic protein-2 (BMP-2)

Abstract: Matrix Gla protein (MGP) is an inhibitor of calcification of the arterial wall but the mechanism of inhibition has not been resolved. Since chondrogenesis has been identified in calcified arteries from MPG null mice, we hypothesized that locally produced MGP might inhibit calcification by neutralizing the known effect of bone morphogenetic proteins (BMPs) as promotors of chondrogenesis and bone formation. As the first step to test this hypothesis, we demonstrate that MGP is a binding protein for 125I-BMP-2. Optimal binding is dependent on metals which suggests that the metal binding Gla region in MGP is involved. MGP is shown to undergo a Ca++ induced conformational change despite the presence of the γ-carboxylase binding site being part of the mature protein sequence. The data propose that MGP matures earlier in the secretory pathway than other vitamin K-dependent proteins. Antibodies were used in an attempt to identify MGP in bovine serum. Conformational specific MGP antibodies were shown to also recognize the Gla region in prothrombin and factor X but did not identify MGP in serum. This finding is supported by electrophoresis data which demonstrate the absence of MGP among Ba-citrate absorbed vitamin K-dependent serum proteins. We conclude that MGP does not exist in normal bovine serum.