Reduced plasma fibrinolytic potential is a risk factor for venous thrombosis

Effect of fibrinolysis on bleeding phenotype in moderate and severe von Willebrand disease

Patients with von Willebrand disease (VWD), the most common inherited bleeding disorder, display large variation in bleeding tendency, which is not completely related to VWF levels. The cause of variability in clinical expression is largely unknown. The effect of plasma fibrinolytic capacity on bleeding tendency in VWD patients has not been investigated. We hypothesized that enhanced fibrinolysis may result in a more severe bleeding phenotype. Therefore, we measured the fibrinolytic potential in patients with moderate or severe VWD to investigate the contribution of fibrinolysis to the bleeding tendency. Fibrinolytic potential was measured as plasma clot lysis time (CLT) with and without addition of potato carboxypeptidase inhibitor (PCI) in 638 patients with moderate or severe VWD who participated in a nationwide multicentre cross-sectional study. Bleeding severity was measured using the Bleeding Score (BS).The CLTs were significantly longer, indicative of hypofibrinolysis, in men compared to women with VWD [106.2 (IQR 95.7-118.1) vs. 101.9 (IQR 92.8-114.0) min]. The CLTs prolonged with increasing age. No association was found between VWF or FVIII levels and CLT, or between VWF or FVIII levels and CLT(+PCI) . No association was observed for BS in a model with 10log-transformed CLT, adjusted for age, gender, VWF:Act and FVIII [b = 6.5 (95%CI -0.3 to 13.4)]. Our study showed that the plasma fibrinolytic potential does not influence bleeding tendency in VWD patients and therefore does not explain the variability in bleeding phenotype in VWD.

Alterations in coagulation and fibrinolysis after levothyroxine exposure in healthy volunteers: a controlled randomized crossover study

BACKGROUND

Several hemostatic abnormalities have been reported in hyperthyroidism, but the overall effect of thyroid hormone excess on coagulation and fibrinolysis is unclear.

OBJECTIVE

Our aim was to assess whether the use of supraphysiological doses of levothyroxine leads to coagulation activation and inhibition of fibrinolysis.

PATIENTS AND METHODS

Healthy volunteers were randomized to receive levothyroxine or no medication for 14 days with a washout period of at least 28 days in a crossover design. To study the effects of different degrees of thyroid hormone excess, 16 participants received levothyroxine in a dose of 0.3 mg per day, and 12 received levothyroxine 0.45 or 0.6 mg per day depending on body weight. Several variables of coagulation and fibrinolysis were measured.

RESULTS

Levels of von Willebrand factor activity (VWF:RiCo) and antigen (VWF:Ag), factor (F) VIII, plasminogen activator inhibitor-1 (PAI-1) and clot-lysis time were slightly higher after levothyroxine 0.3 mg per day than after the control situation, but only levels of VWF showed a significant increase from baseline. After levothyroxine 0.45 or 0.6 mg per day, levels of fibrinogen increased by 17%, VWF activity by 24%, VWF antigen by 26%, FVIII by 19%, FIX by 14%, FX by 7%, PAI-1 by 116% and clot-lysis time by 14%, and activated partial thromboplastin time decreased by 3%; all were significant changes compared with the control situation. We did not observe clear evidence of coagulation activation.

CONCLUSIONS

Our data suggest that thyroid hormone excess increases coagulation factor levels and inhibits fibrinolysis in a dose-dependent fashion. This implies an increased risk of venous thrombosis during hyperthyroidism.

Fibrin clot structure and function: a role in the pathophysiology of arterial and venous thromboembolic diseases

The formation of fibrin clots that are relatively resistant to lysis represents the final step in blood coagulation. We discuss the genetic and environmental regulators of fibrin structure in relation to thrombotic disease. In addition, we discuss the implications of fibrin structure for treatment of thrombosis. Fibrin clots composed of compact, highly branched networks with thin fibers are resistant to lysis. Altered fibrin structure has consistently been reported in patients with several diseases complicated by thromboembolic events, including patients with acute or prior myocardial infarction, ischemic stroke, and venous thromboembolism. Relatives of patients with myocardial infarction or venous thromboembolism display similar fibrin abnormalities. Low-dose aspirin, statins, lowering of homocysteine, better diabetes control, smoking cessation, and suppression of inflammatory response increase clot permeability and susceptibility to lysis. Growing evidence indicates that abnormal fibrin properties represent a novel risk factor for arterial and venous thrombotic events, particularly of unknown etiology in young and middle-aged patients.

Clot lysis time in platelet-rich plasma: method assessment, comparison with assays in platelet-free and platelet-poor plasmas, and response to tranexamic acid

Fibrinolysis dysfunctions cause bleeding or predisposition to thrombosis. Platelets contain several factors of the fibrinolytic system, which could up or down regulate this process. However, the temporal relationship and relative contributions of plasma and platelet components in clot lysis are mostly unknown. We developed a clot lysis time (CLT) assay in platelet-rich plasma (PRP-CLT, with and without stimulation) and compared it to a similar one in platelet-free plasma (PFP) and to another previously reported test in platelet-poor plasma (PPP). We also studied the differential effects of a single dose of tranexamic acid (TXA) on these tests in healthy subjects. PFP- and PPP-CLT were significantly shorter than PRP-CLT, and the three assays were highly correlated (p < 0.0001). PFP- and PPP-, but more significantly PRP-CLT, were positively correlated with age and plasma PAI-1, von Willebrand factor, fibrinogen, LDL-cholesterol, and triglycerides (p < 0.001). All these CLT assays had no significant correlations with platelet aggregation/secretion, platelet counts, and pro-coagulant tests to explore factor X activation by platelets, PRP clotting time, and thrombin generation in PRP. Among all the studied variables, PFP-CLT was independently associated with plasma PAI-1, LDL-cholesterol, and triglycerides and, additionally, stimulated PRP-CLT was also independently associated with plasma fibrinogen. A single 1 g dose of TXA strikingly prolonged all three CLTs, but in contrast to the results without the drug, the lysis times were substantially shorter in non-stimulated or stimulated PRP than in PFP and PPP. This standardized PRP-CLT may become a useful tool to study the role of platelets in clot resistance and lysis. Our results suggest that initially, the platelets enmeshed in the clot slow down the fibrinolysis process. However, the increased clot resistance to lysis induced by TXA is overcome earlier in platelet-rich clots than in PFP or PPP clots. This is likely explained by the display of platelet pro-fibrinolytic effects. Focused research is needed to disclose the mechanisms for the relationship between CLT and plasma cholesterol and its potential pathophysiologic and clinical relevance.

Asymmetric dimethylarginine impairs fibrinolytic activity in human umbilical vein endothelial cells via p38 MAPK and NF-κB pathways

INTRODUCTION

Asymmetric dimethylarginine (ADMA) is a potent endogenous inhibitor of nitric oxide (NO) synthase. An increased synthesis and/or a reduced catabolism of ADMA might contribute to the onset and progression of thrombosis. The present study was designed to evaluate the effect of ADMA on fibrinolytic factors in endothelial cells, and to investigate the cellular mechanisms.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with different concentrations of ADMA for various periods; Then HUVECs were preincubated with NO precursor (L-arginine), MAPK inhibitors, or NF-κB inhibitor (PDTC) before ADMA treatment to repeat the experiment. Protein levels of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1), and NF-κB activity were measured by ELISA; mRNA levels of tPA and PAI-1 were assayed by qRT-PCR; The activation of MAPK was characterized by western blot analysis.

RESULTS

(1) ADMA decreased tPA antigen levels in time- and concentration-dependent manners, with the maximum effect of 30 μmol/L ADMA for 48h (control 109.01 ± 4.15 ng/ml vs ADMA 86.76 ± 5.95 ng/ml, p<0.01); (2) 30 μmol/L ADMA elevated antigen levels of PAI-1 in a time-dependent manner, with the maximum effect of 30 μmol/L ADMA for 48 h (control 2721.12 ± 278.02 ng/ml vs. ADMA 3435.78 ± 22.33ng/ml, p<0.05); (3) ADMA reduced tPA mRNA levels and increased PAI-1 mRNA levels; (4) L-arginine, SB203580 (p38 MAPK inhibitor) and PDTC attenuated the effects of ADMA on tPA and PAI-1 significantly. (5) ADMA induced a rapid phosphorylation of p38 MAPK, and stimulated NF-κB activity greatly.

CONCLUSIONS

ADMA may accelerate thrombosis development by impairing fibrinolytic activity in vascular via inhibiting nitric oxide production and then activating its downstream p38 MAPK and NF-κB pathways.

Genome scan of clot lysis time and its association with thrombosis in a protein C-deficient kindred

BACKGROUND

 Previously, we found increased clot-lysis time (CLT), as measured with a plasma-based assay, to increase the risk of venous thrombosis in two population-based case-control studies. The genes influencing CLT are as yet unknown.

PATIENTS/METHODS

 We tested CLT as risk factor for venous thrombosis in Kindred Vermont II (n = 346), a pedigree suffering from a high thrombosis risk, partially attributable to a type I protein C deficiency. Furthermore, we tested for quantitative trait loci (QTLs) for CLT, using variance component linkage analysis.

RESULTS

 Protein C-deficient family members had shorter CLTs than non-deficient members (median CLT 67 min vs. 75 min). One standard deviation increase in CLT increased the risk of venous thrombosis 2.4-fold in non-deficient family members. Protein C deficiency without elevated CLT increased the risk 6.9-fold. Combining both risk factors yielded a 27.8-fold increased risk. The heritability of CLT was 42-52%. We found suggestive evidence of linkage on chromosome 11 (62 cM), partly explained by the prothrombin 20210A mutation, and on chromosome 13 (52 cM). Thrombin-activatable fibrinolysis inhibitor genotypes did not explain the variation in CLT.

CONCLUSION

Hypofibrinolysis appears to increase thrombosis risk in this family, especially in combination with protein C deficiency. Protein C deficiency is associated with short CLT. CLT is partly genetically regulated. Suggestive QTLs were found on chromosomes 11 and 13.

Causal relationship between hyperfibrinogenemia, thrombosis, and resistance to thrombolysis in mice

Epidemiologic studies have correlated elevated plasma fibrinogen (hyperfibrinogenemia) with risk of cardiovascular disease and arterial and venous thrombosis. However, it is unknown whether hyperfibrinogenemia is merely a biomarker of the proinflammatory disease state or is a causative mechanism in the etiology. We raised plasma fibrinogen levels in mice via intravenous infusion and induced thrombosis by ferric chloride application to the carotid artery (high shear) or saphenous vein (lower shear); hyperfibrinogenemia significantly shortened the time to occlusion in both models. Using immunohistochemistry, turbidity, confocal microscopy, and elastometry of clots produced in cell and tissue factor-initiated models of thrombosis, we show that hyperfibrinogenemia increased thrombus fibrin content, promoted faster fibrin formation, and increased fibrin network density, strength, and stability. Hyperfibrinogenemia also increased thrombus resistance to tenecteplase-induced thrombolysis in vivo. These data indicate that hyperfibrinogenemia directly promotes thrombosis and thrombolysis resistance and does so via enhanced fibrin formation and stability. These findings strongly suggest a causative role for hyperfibrinogenemia in acute thrombosis and have significant implications for thrombolytic therapy. Plasma fibrinogen levels may be used to identify patients at risk for thrombosis and inform thrombolytic administration for treating acute thrombosis/thromboembolism.

Reduced plasma fibrinolytic potential in patients with recurrent implantation failure after IVF and embryo transfer

BACKGROUND

Recurrent implantation failure (RIF) following embryo transfer (ET) is a major continuing problem in IVF. Women with haemostatic defects may be at increased risk of miscarriage and preclinical pregnancy loss. The fibrinolytic system is considered, at present, the key to new thrombotic pathogenic mechanisms. Patients with unexplained recurrent miscarriage have an impairment of fibrinolysis, as demonstrated by prolonged clot lysis time (CLT) in association with increased plasma levels of thrombin-activatable fibrinolysis inhibitor (TAFI). In this study, we investigated fibrinolytic potential in patients with RIF.

METHODS

Three groups of patients were studied: 30 women with RIF (RIF group), 60 patients undergoing a first successful IVF-ET cycle (IVF group) and 60 healthy fertile women (FER group). Plasma CLT was measured using a global fibrinolysis assay. TAFI antigen plasma levels and polymorphisms in the TAFI gene (+505A/G and +1542C/G) were analysed using enzyme-linked immunosorbent assay and allele-specific PCR, respectively.

RESULTS

CLT was significantly longer (P < 0.0001 and P < 0.0009, respectively) and TAFI antigen levels were significantly higher (both P < 0.0001) in the RIF versus the IVF and FER groups. A direct relationship between CLT and TAFI antigen levels (r = 0.40; P = 0.001) was detected in the whole study population. There were no differences in distribution of TAFI polymorphisms between groups.

CONCLUSIONS

Patients with RIF have reduced plasma fibrinolytic potential, as shown by a prolonged CLT, and this may be explained, at least in part, by increased TAFI antigen levels.

Failure to lyse venous thrombi because of elevated plasminogen activator Inhibitor 1 (PAI-1) and 4G polymorphism of its promotor genome (The PAI-1/4G Syndrome)

Plasminogen activator Inhibitor 1 (PAI-1) inhibits plasminogen activators leading to decreased fibrinolysis and increased risk of thromboembolic disease (TED). Shifts in PAI-1 promoter genome from normal 5G>5G to 4G>5G or 4G>4G alleles are associated with overexpression of PAI-1. In this study patients with residual venous thrombi were observed to have increased PAI-1 levels and more frequent shifts to 4G alleles. Of the 26, 20 (76.9%) patients with unresolved thrombus had elevated PAI-1 values. 4G genomic shifts were found in 92.9% patients studied. Normal PAI-1 levels were found in 5 patients with 4G polymorphisms. Thus, PAI-1 is often elevated among patients with residual thrombus, with an unexpectedly high prevalence of the 4G polymorphism of the promoter genome. Patients with persistent thrombus should be considered at risk of having constituently increased PAI-1 due to genomic changes in the PAI-1 promoter genome. Hypotheses are proposed to explain those with normal PAI-1, despite having 4G polymorphisms.

Adenosine potentiates human lung mast cell tissue plasminogen activator activity

We investigated whether adenosine, a potent contributor to the regulation of pulmonary function, can modulate human lung mast cell (HLMC) fibrinolytic activity. Tissue plasminogen activator (tPA) activity and tPA transcript expression levels from a human mast cell line (HMC-1) and HLMC were monitored following adenosine application. Adenosine potentiated mast cell tPA activity and tPA gene expression in a dose-dependent manner. Adenosine effects were abolished in the presence of adenosine deaminase. HMC-1 cells and HLMC predominantly expressed adenosine A(2A) and A(2B) receptor transcripts (A(2B) ≈ A(2A) > A(3) >> A(1)). Pharmacological and signaling studies suggest that the A(2A) receptor is the major subtype accounting for adenosine-induced mast cell tPA activity. Finally, the supernatant from HMC-1 cells and HLMC treated with adenosine (for 24 h) significantly increased fibrin clot lysis, whereas ZM241385, an A(2A) receptor antagonist, abolished this effect. To our knowledge, this study provides the first data to demonstrate the potentiating effect of adenosine on mast cell tPA activity and fibrin clot lysis.

Venous thrombosis risk associated with plasma hypofibrinolysis is explained by elevated plasma levels of TAFI and PAI-1

Elevated plasma clot lysis time (CLT) increases risk of venous and arterial thrombosis. It is unclear which fibrinolytic factors contribute to thrombosis risk. In 743 healthy control subjects we investigated determinants of CLT. By comparison with 770 thrombosis patients, we assessed plasma levels of fibrinolytic proteins as risk factors for a first thrombosis. Plasminogen activator inhibitor-1 (PAI-1) levels were the main determinants of CLT, followed by plasminogen, thrombin-activatable fibrinolysis inhibitor (TAFI), prothrombin, and α2-antiplasmin. Fibrinogen, factor VII, X, and XI contributed minimally. These proteins explained 77% of variation in CLT. Levels of the fibrinolytic factors were associated with thrombosis risk (odds ratios, highest quartile vs lowest, adjusted for age, sex, and body mass index: 1.6 for plasminogen, 1.2 for α2-antiplasmin, 1.6 for TAFI, 1.6 for PAI-1, and 1.8 for tissue plasminogen activator [t-PA]). Adjusting for acute-phase proteins attenuated the risk associated with elevated plasminogen levels. The risk associated with increased t-PA nearly disappeared after adjusting for acute-phase proteins and endothelial activation. TAFI and PAI-1 remained associated with thrombosis after extensive adjustment. In conclusion, CLT reflects levels of all fibrinolytic factors except t-PA. Plasminogen, TAFI, PAI-1, and t-PA are associated with venous thrombosis. However, plasminogen and t-PA levels may reflect underlying risk factors.

Impaired fibrinolysis as a risk factor for Budd-Chiari syndrome

In Budd-Chiari syndrome (BCS), thrombosis develops in the hepatic veins or inferior vena cava. To study the relationship between hypofibrinolysis and BCS, we measured plasma levels of fibrinolysis proteins in 101 BCS patients and 101 healthy controls and performed a plasma-based clot lysis assay. In BCS patients, plasminogen activator inhibitor 1 (PAI-1) levels were significantly higher than in controls (median, 6.3 vs 1.4 IU/mL, P < .001). Thrombin-activatable fibrinolysis inhibitor and plasmin inhibitor levels were lower than in controls (13.8 vs 16.9 μg/mL and 0.91 vs 1.02 U/L, both P < .001). Median plasma clot lysis time (CLT) was 73.9 minutes in cases and 73.0 minutes in controls (P = .329). A subgroup of cases displayed clearly elevated CLTs. A CLT above the 90th or 95th percentile of controls was associated with an increased risk of BCS, with odds ratios of 2.4 (95% confidence interval, 1.1-5.5) and 3.4 (95% confidence interval, 1.2-9.7), respectively. In controls, only PAI-1 activity was significantly associated with CLT. Analysis of single nucleotide polymorphisms of fibrinolysis proteins revealed no significant differences between cases and controls. This case-control study provides the first evidence that an impaired fibrinolytic potential, at least partially caused by elevated PAI-1 levels, is related to the presence of BCS.

Fibrin clot properties in acute ischemic stroke: relation to neurological deficit

INTRODUCTION

Hypercoagulable state occurs in patients with acute vascular events. We wondered whether clot structure/function is altered in acute ischemic stroke (AIS), like in acute myocardial infarction.

PATIENTS AND METHODS

In 45 consecutive patients with AIS (24M, 21F), aged 67.4+/-10.9 years, and 45 healthy controls matched for age and sex, we investigated plasma fibrin clot structure/function by permeation, turbidity, and efficiency of fibrinolysis.

RESULTS

Compared to controls, AIS patients produced clots that had 30.5% less porous network (p<0.0001), were less susceptible to fibrinolysis (10.8% longer lysis time, p=0.001), were 20.5% more compact (p<0.0001), had 17.1% higher clot mass (p<0.0001), and showed increased (by 10.2%) overall fiber thickness (p<0.0001) with 8% shorter lag phase of fibrin formation (p=0.0002). Maximum rate of D-dimer release from clots was similar. Multiple regression analyses for all subjects (n=90) showed that being a stroke patient (p<0.0001), fibrinogen (p<0.0001) and lipoprotein(a) (p=0.0075) were independent predictors of clot permeability (model R2 0.79). Only fibrinogen (p<0.0001) and lipoprotein(a) (p=0.0026) predicted lysis time. All other fibrin parameters were predicted only by being a stroke patient. Clot compaction was associated with neurological deficit on admission (r=-0.81; p<0.0001) and at discharge (r=-0.69; p<0.0001). Patients with 0 or 1 point in the modified Rankin scale (n=19) had 13.3% higher clot permeability compared to the remainder (p=0.02).

CONCLUSIONS

This study is the first to show that AIS is associated with unfavorably altered fibrin clot properties that might correlate with neurological deficit.

Chronic kidney disease and venous thromboembolism: epidemiology and mechanisms

PURPOSE OF REVIEW

An estimated 13% of Americans have kidney disease. We sought to describe the association of kidney disease with risk of venous thromboembolism and discuss possible mechanisms explaining this association.

RECENT FINDINGS

All severities of kidney disease appear to increase the risk of venous thromboembolism. In the general population the risk associated with mild to moderate kidney disease is 1.3-2-fold increased, and present even for microalbuminuria, although stage 1 chronic kidney disease itself has not been studied. End-stage renal disease is also associated with a 2.3-fold increased risk, compared to the general population. Although data are limited, risk increases after kidney transplant and with nephrotic syndrome as well.

SUMMARY

Rates of kidney disease are increasing rapidly in the population and kidney disease is a risk factor for venous thromboembolism. An improved understanding of mechanisms linking kidney disease with venous thromboembolism will allow further study of best prevention efforts.

Altered fibrin clot structure/function in patients with idiopathic venous thromboembolism and in their relatives

We tested the hypothesis that fibrin structure/function is unfavorably altered in patients after idiopathic venous thromboembolism (VTE) and their relatives. Ex vivo plasma fibrin clot permeability, turbidimetry, and efficiency of fibrinolysis were investigated in 100 patients with first-ever VTE, including 34 with pulmonary embolism (PE), 100 first-degree relatives, and 100 asymptomatic controls with no history of thrombotic events. Known thrombophilia, cancer, trauma, and surgery were exclusion criteria. VTE patients and their relatives were characterized by lower clot permeability (P < .001), lower compaction (P < .001), higher maximum clot absorbancy (P < .001), and prolonged clot lysis time (P < .001) than controls, with more pronounced abnormalities, except maximum clot absorbance, in the patients versus relatives (all P < .01). Fibrin clots obtained for PE patients were more permeable, less compact, and were lysed more efficiently compared with deep-vein thrombosis patients (all P < .05) with no differences in their relatives. Being VTE relative, fibrinogen, and C-reactive protein were independent predictors of clot permeability and fibrinolysis time in combined analysis of controls and relatives. We conclude that altered fibrin clot features are associated with idiopathic VTE with a different profile of fibrin variables in PE. Similar features can be detected in VTE relatives. Fibrin properties might represent novel risk factors for thrombosis.

Contributions of extravascular and intravascular cells to fibrin network formation, structure, and stability

Fibrin is essential for hemostasis; however, abnormal fibrin formation is hypothesized to increase thrombotic risk. We previously showed that in situ thrombin generation on a cell's surface modulates the 3-dimensional structure and stability of the fibrin network. Currently, we compared the abilities of extravascular and intravascular cells to support fibrin formation, structure, and stability. Extravascular cells (fibroblasts, smooth muscle) supported formation of dense fibrin networks that resisted fibrinolysis, whereas unstimulated intravascular (endothelial) cells produced coarse networks that were susceptible to fibrinolysis. All 3 cell types produced a fibrin structural gradient, with a denser network near, versus distal to, the cell surface. Although fibrin structure depended on cellular procoagulant activity, it did not reflect interactions between integrins and fibrin. These findings contrasted with those on platelets, which influenced fibrin structure via interactions between beta3 integrins and fibrin. Inflammatory cytokines that induced prothrombotic activity on endothelial cells caused the production of abnormally dense fibrin networks that resisted fibrinolysis. Blocking tissue factor activity significantly reduced the density and stability of fibrin networks produced by cytokine-stimulated endothelial cells. Together, these findings indicate fibrin structure and stability reflect the procoagulant phenotype of the endogenous cells, and suggest abnormal fibrin structure is a novel link between inflammation and thrombosis.

Thrombophilic conditions in the adolescent: the gynecologic impact

As Virchow's triad suggests, a fine balance exists between the vascular wall, intravascular contents, and dynamic blood flow, such that a shift in this balance predisposes to thrombosis. Although thromboembolic events (TEs) are relatively infrequent in adolescents, the morbidity and mortality associated with TEs can be significant. Over the past 15 years, TEs and inherited and acquired thrombophilic conditions underlying them have become increasingly recognized in teens at risk, with combined hormonal contraception constituting one of the most significant of these risk factors. Therefore, managing gynecologic problems in teens who have thrombophilic conditions can be challenging. It is important to have a clear understanding about safe options available to help address adolescent gynecologic concerns in this setting and to manage situations collaboratively with a hematologist.

An age-adapted approach for the use of D-dimers in the exclusion of deep venous thrombosis

A normal D-dimer (DD) concentration for the exclusion of deep venous thrombosis (DVT) has a low specificity in older patients and compression ultrasonography is often required. Three D-dimer assays, STA Liatest, Tina-quant, and Innovance, are evaluated in symptomatic outpatients suspected for DVT with emphasis on its performance in older patients by using different cut-off levels. This study includes 466 outpatients suspected for having DVT. The diagnostic accuracy, measured as sensitivity and area under the curve of the receiver operation characteristic curve is good for all DD assays. The specificity of the DD assays combined with a low pretest probability varies from 42.6 to 51.5%. The specificity of the three DD assays in patients > or = 60 years varies, however, between 24.6 and 40.9%. Several cut-off values in different age-subgroups are studied. For patients < 60 years, the most accurate cut-off value is 500 microg/L for all DD assays. For patients > or = 60 years, a threshold of 750 microg/L has the best results with NPV of 100% for all assays and specificity of 48.5% (STA Liatest), 60.6% (Tina-quant), and 49.2% (Innovance), respectively. For the three assays, the number needed to test (NNT) decreases in both subgroups of patients compared to the standard algorithm. A cut-off level of 750 microg/L for patients > or = 60 years improves the clinical performance of DD assays in combination with the PTP score without the loss of NPV. The NNT improves substantially with an age-adapted algorithm.

Annexin A2 is involved in antiphospholipid antibody-mediated pathogenic effects in vitro and in vivo

Antiphospholipid (aPL) antibodies recognize receptor-bound beta(2) glycoprotein I (beta(2)GPI) on target cells, and induce an intracellular signaling and a procoagulant/proinflammatory phenotype that leads to thrombosis. Evidence indicates that annexin A2 (A2), a receptor for tissue plasminogen activator and plasminogen, binds beta(2)GPI on target cells. However, whether A2 mediates pathogenic effects of aPL antibodies in vivo is unknown. In this work, we studied the effects of human aPL antibodies in A2-deficient (A2(-/-)) mice. A2(-/-) and A2(+/+) mice were injected with immunoglobulin G (IgG) isolated from either a patient with antiphospholipid syndrome (IgG-APS), a healthy control subject (IgG-normal human serum), a monoclonal anti-beta(2)GPI antibody (4C5), an anti-A2 monoclonal antibody, or monoclonal antibody of irrelevant specificity as control. We found that, after IgG-APS or 4C5 injections and vascular injury, mean thrombus size was significantly smaller and tissue factor activity was significantly less in A2(-/-) mice compared with A2(+/+) mice. The expression of vascular cell adhesion molecule-1 induced by IgG-APS or 4C5 in explanted A2(-/-) aorta was also significantly reduced compared with A2(+/+) mice. Interestingly, anti-A2 monoclonal antibody significantly decreased aPL-induced expression of intercellular cell adhesion molecule-1, E-selectin, and tissue factor activity on cultured endothelial cells. Together, these data indicate for the first time that A2 mediates the pathogenic effects of aPL antibodies in vivo and in vitro APS.

Antiphospholipid antibodies may impair factor XIIa-dependent activation of fibrinolysis in pregnancy: in vitro evidence with human endothelial cells in culture and monoclonal anticardiolipin antibodies

OBJECTIVE

The purpose of this study was to analyze the in vitro activation of the contact complex with the use of human umbilical vein endothelial cells (HUVEC) in culture and monoclonal anticardiolipin antibodies (MaCL).

STUDY DESIGN

Cultured HUVECs were incubated with pooled plasma from third-trimester pregnant women with the addition (20 mg/mL) of MaCL with anti-beta-2 glycoprotein I activity that was obtained from patients with antiphospholipid syndrome (APS), MaCL from an individual without APS, or from a control patient with immunoglobulin M without aCL activity. Supernatants were evaluated. Activated factors XII and VII, prothrombin-fragment 1 + 2, urokinase-type plasminogen activator (UPA), and differentiating 2 chain UPA were determined.

RESULTS

In the cultured HUVEC supernatants, the addition of MaCL increased activated factor VII and prothrombin-fragment 1 + 2, did not modify UPA, and decreased activated factor XII and differentiating 2 chain UPA, in comparison with samples with control immunoglobulin M added. The MaCL without APS activity did not change any parameter that was evaluated.

CONCLUSION

MaCL with anti-beta-2 activity that was obtained from patients with APS may interfere in the activation of the contact complex during pregnancy.

Does an active sun exposure habit lower the risk of venous thrombotic events? A D-lightful hypothesis

BACKGROUND

Venous and arterial thrombotic complications exhibit a seasonal variation, with risk peaking in winter and dropping to a nadir in summer. We sought a possible correlation between sun exposure habits and venous thromboembolism (VTE) events.

METHODS

This was a cohort study comprising 40,000 women (1000 per year of age from 25 to 64 years) who were drawn from the southern Swedish population registry for 1990 and followed for a mean of 11 years. Seventy-four per cent answered an inquiry at the inception of the study (n=29,518), and provided detailed information on their sun exposure habits. Cox regression analysis was used with the presence of VTE as a dependent variable and selected demographics as independent variables. The main outcome was the relationship between VTE and sun exposure habits.

RESULTS

Swedish women who sunbathed during the summer, on winter vacations, or when abroad, or used a tanning bed, were at 30% lower risk of VTE than those who did not. Risk estimates did not change substantially after adjustment for demographic variables. The risk of VTE increased by 50% in winter as compared to the other seasons; the lowest risk was found in the summer.

CONCLUSIONS

Women with more active sun exposure habits were at a significantly lower risk of VTE. We speculate that greater ultraviolet B light exposure improves a person's vitamin D status, which in turn enhances anticoagulant properties and enhances the cytokine profile.

Identification of quantitative trait loci for fibrin clot phenotypes: the EuroCLOT study

OBJECTIVE

Fibrin makes up the structural basis of an occlusive arterial thrombus, and variability in fibrin phenotype relates to cardiovascular risk. The aims of the current study from the EU consortium EuroCLOT were to (1) determine the heritability of fibrin phenotypes and (2) identify QTLs associated with fibrin phenotypes.

METHODS AND RESULTS

447 dizygotic (DZ) and 460 monozygotic (MZ) pairs of healthy UK white female twins and 199 DZ twin pairs from Denmark were studied. D-dimer, an indicator of fibrin turnover, was measured by ELISA and measures of clot formation, morphology, and lysis were determined by turbidimetric assays. Heritability estimates and genome-wide linkage analysis were performed. Estimates of heritability for d-dimer and turbidometric variables were in the range 17% to 46%, with highest levels for maximal absorbance which provides an estimate of clot density. Genome-wide linkage analysis revealed 6 significant regions with LOD >3 on 5 chromosomes (5, 6, 9, 16, and 17).

CONCLUSIONS

The results indicate a significant genetic contribution to variability in fibrin phenotypes and highlight regions in the human genome which warrant further investigation in relation to ischemic cardiovascular disorders and their therapy.

Hypofibrinolysis is a risk factor for arterial thrombosis at young age

The relationship between defective fibrinolysis and arterial thrombosis is uncertain. The evaluation of the plasma fibrinolytic potential might provide stronger evidence linking fibrinolysis to arterial thrombosis than the evaluation of the individual fibrinolytic factors. We determined the plasma fibrinolytic potential of 335 young survivors of a first arterial thrombosis, including coronary artery disease (n = 198), ischaemic stroke (n = 103) and peripheral artery disease (n = 34), enrolled in a population-based case-control study and of 330 healthy individuals. Patients had significantly higher clot lysis times (CLTs) than the controls. Odds ratios (ORs) were calculated as a measure of relative risk. The OR for arterial thrombosis was determined in these subjects who had a CLT above the 60th, 70th, 80th, 90th and 95th percentiles of the values found in the control subjects. We found a progressive increase in risk of arterial thrombosis in subjects with hypofibrinolysis (OR: 1.7, 2.0, 2.3, 2.3 and 2.9, respectively). Relative risk estimates obtained in the whole group were comparable those obtained in the event-subgroups. In conclusion, a low plasma fibrinolytic potential, found in 10% of the population, increases the relative risk of arterial thrombosis twofold. This points to an important contribution of hypofibrinolysis to the burden of arterial thrombosis.

Reduced plasma fibrinolytic capacity as a potential risk factor for a first myocardial infarction in young men

Studies on the relationship between fibrinolysis and arterial thrombosis have been conflicting. Previously, we demonstrated that hypofibrinolysis, as measured by a plasma-based assay, increased the risk of venous thrombosis. The present study investigated increased clot lysis time (CLT) measured with the same assay as a risk factor for myocardial infarction in a case-control study including 421 men with a first myocardial infarction and 642 controls below 70 years. CLT was strongly associated with body-mass index, lipid levels, blood pressure and C-reactive protein. Overall, risk of myocardial infarction was 1.4-fold (95% confidence interval (CI) 1.0-1.9) increased for CLT in the fourth quartile (longest CLT) compared with the first quartile. After adjusting for cardiovascular risk factors this risk disappeared (OR 1.0, 95%CI 0.6-1.5). In men aged <50 years the association was pronounced (OR 3.2, 95%CI 1.5-6.7). After adjustment for cardiovascular risk factors the risk was nearly twofold increased (OR 1.8, 95%CI 0.7-4.8). In men aged > or = 50 years, no clear association between CLT and risk of myocardial infarction was found. Our study suggests that hypofibrinolysis increases the risk of a first myocardial infarction in young men, although the causality of this association remains to be determined.

Assessment of fibrinolytic activity by measuring the lysis time of a tissue-factor-induced clot: a feasibility evaluation

A clot lysis time assay in which a tissue factor-induced fibrin clot is lysed by exogenously added tissue plasminogen activator has been recently reported. We evaluated the feasibility of clot lysis time in a routine hemostasis laboratory, and its correlation with thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 levels and changes with aging in 185 healthy participants. Clot lysis time was assessed by monitoring changes in turbidity during clot formation and subsequent lysis using a computerized kinetic spectrophotometric microtiter plate. After preliminary experiments, 100 and 160 ng/mL tissue plasminogen activator concentrations were chosen for the study. Clot lysis time was calculated by a new mathematical analysis of the lysis curve based on discrete derivative. Clot lysis time, thrombin activatable fibrinolysis inhibitor, and plasminogen activator inhibitor-1 plasma levels showed a normal distribution. For both concentrations of tissue plasminogen activator, clot lysis time progressively increased with increase in age (P < .0001) and was significantly correlated with thrombin activatable fibrinolysis inhibitor antigen, thrombin activatable fibrinolysis inhibitor activity, and plasminogen activator inhibitor-1 antigen (at least P < .01). During linear regression analysis, thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 antigen were found to significantly influence clot lysis time (at least P < .01). Clot lysis time determination has a good laboratory performance. Our new method of calculation is independent of the time of reading and allows a more accurate and consistent detection of both short and prolonged lysis times. Our data suggest the feasibility of the use of this test in the work of routine hemostasis laboratory.

The relationship between lifestyle factors and venous thromboembolism among women: a report from the MISS study

There has been a great advance in our knowledge of the role that thrombophilic factors play in the risk of venous thromboembolic events (VTE). However, the effect of lifestyle factors on VTE has been inadequately explored in large scale studies of women. This cohort study comprised one thousand native Swedish women for each age year between 25 and 64 inclusive (total = 40,000) drawn from the South Swedish population registry for 1990 (n = 40,000), who were followed for a mean of eleven years. Seventy-four percent completed a questionnaire at the inception of the study (n = 29,518) and 24,098 women responded to a follow-up inquiry between the years 2000-2002. The main outcome was the relationship between VTE and physical exercise, smoking habits, and alcohol consumption. Moderate drinkers of alcohol (10-15 g/d) and women engaged in strenuous exercise were at half the risk of VTE compared to those who consumed little or no alcohol or lived a sedentary life. Heavy smoking was associated with a 30% increased risk of VTE. Lifestyle factors have a major impact on the risk of VTE. Women non-smokers who were physically active and who consumed alcohol in moderation were at a lower risk of VTE.

Mechanisms of the Factor V Leiden Paradox

Objective— Carriers of the factor V Leiden mutation (FVL-carriers) have a substantially increased risk of deep venous thrombosis (DVT), whereas the risk of pulmonary embolism (PE) is only mildly increased compared with noncarriers. So far few studies have investigated possible mechanisms for this so-called FVL paradox.

Methods and Results— Consecutive patients with a first DVT or PE were included in a large population-based case-control study (MEGA study). Patients, aged 18 to 70 years, provided a questionnaire, DNA (n=3313), or plasma (n=1474). Surgery, injury, and travel were considered thrombosis-provocative. Of 2063 patients with isolated DVT, 20% were FVL-carrier, as were 8% of the 885 patients with isolated PE. Among DVT patients, FVL-carriers had their thrombi more often proximal and a higher number of affected veins than noncarriers. No differences were observed between FVL-carriers and noncarriers in time between provocation and diagnosis, in vitro coagulation time, and thrombus density. Compared with patients with both DVT and PE, isolated DVT patients more often had thrombi located distally and had a similar number of affected veins. Compared with isolated PE patients, isolated DVT patients had a similar time between provocation and diagnosis, and similar in vitro coagulation time and thrombus density.

Conclusion— Although some effects were differential for FVL-carriers and noncarriers, and some were differential for PE and DVT patients, none of the potential mechanisms offered a clear explanation.

Synergistic effects of hypofibrinolysis and genetic and acquired risk factors on the risk of a first venous thrombosis

BACKGROUND

Previously, we demonstrated that hypofibrinolysis, a decreased capacity to dissolve a blood clot as measured with an overall clot lysis assay, increases the risk of venous thrombosis. Here, we investigated the combined effect of hypofibrinolysis with established risk factors associated with hypercoagulability.

METHODS AND FINDINGS

Fibrinolytic potential was determined with a plasma-based clot lysis assay in 2,090 patients with venous thrombosis and 2,564 control participants between 18 and 70 y of age enrolled in the Multiple Environmental and Genetic Assessment (MEGA) of risk factors for venous thrombosis study, a population-based case-control study on venous thrombosis. Participants completed a standardized questionnaire on acquired risk factors. Hypofibrinolysis alone, i.e., clot lysis time (CLT) in the fourth quartile (longest CLT) (in absence of the other risk factor of interest) increased thrombosis risk about 2-fold relative to individuals with CLT in the first quartile (shortest CLT). Oral contraceptive use in women with CLT in the first quartile gave an odds ratio (OR) of 2.6 (95% confidence interval [CI] 1.6 to 4.0), while women with hypofibrinolysis who used oral contraceptives had an over 20-fold increased risk of venous thrombosis (OR 21.8, 95% CI 10.2 to 46.7). For immobilization alone the OR was 4.3 (95% CI 3.2 to 5.8) and immobilization with hypofibrinolysis increased the risk 10.3-fold (95% CI 7.7 to 13.8). Factor V Leiden alone increased the risk 3.5-fold (95% CI 2.3 to 5.5), and hypofibrinolysis in factor V Leiden carriers gave an OR of 8.1 (95% CI 5.3 to 12.3). The combination of hypofibrinolysis and the prothrombin 20210A mutation did not synergistically increase the risk. All ORs and 95% CIs presented are relative to individuals with CLT in the first quartile and without the other risk factor of interest.

CONCLUSIONS

The combination of hypofibrinolysis with oral contraceptive use, immobilization, or factor V Leiden results in a risk of venous thrombosis that exceeds the sum of the individual risks.

Development of a new test for the global fibrinolytic capacity in whole blood

BACKGROUND

The development of global tests for the fibrinolytic capacity in blood is hampered by the low base-line fibrinolytic activity in blood, by the involvement of both plasmatic components and blood cells in the fibrinolytic system and by the loss of fibrinolytic activity as a result of the action of plasminogen activator inhibitor-1 (PAI-1).

OBJECTIVE

To develop a new test for the global fibrinolytic capacity (GFC) of whole blood samples.

METHODS AND RESULTS

Collection of blood in thrombin increased the subsequent generation of fibrin degradation products. This was ascribed to rapid clot formation and concomitant reduction of in vitro neutralization of tissue-type plasminogen activator (tPA) by PAI-1. On the basis of this observation, the following test was designed: blood samples were collected in thrombin with and without aprotinin and clots were incubated for 3 h at 37 degrees C. The GFC was assessed from the difference between the fibrin degradation products in the two sera. The assay was applied to blood samples from patients and healthy subjects. Other hemostasis parameters were determined in plasma samples taken simultaneously. The GFC varied considerably (normal range 0.13-13.6 microg mL(-1)); physical exercise strongly increased the GFC. Statistically significant correlations were found with tPA activity, PAI-1 activity and fibrinogen level. A mixture of antibodies against tPA and urokinase-type plasminogen activator (uPA) completely inhibited the GFC. An inhibitor of activated thrombin-activatable fibrinolysis inhibitor (TAFI) accelerated fibrinolysis 8-fold.

CONCLUSION

The new test represents a global assessment of the main fibrinolytic factors in plasma and potentially those associated with blood cells.

Heritability of Clot Formation, Morphology, and Lysis

Objective— The relative balance between clot formation and fibrinolysis is considered to reflect thrombotic potential following vascular injury. The aims of the present study were to (1) to determine the contribution of genetic and environmental factors to variance in measures of clot structure/function in the Leeds Family Study, and (2) to determine the relationship between measures of clot structure/function and cardiovascular risk.

Methods and Results— Using high throughput turbidimetric assays, heritabilities of measures of clot formation, clot structure, and clot lysis were ≈0.30. Fibrinogen contributed to variance in all measures and plasminogen activator inhibitor-1 to variance in lysis variables. Subjects at increased cardiovascular risk due to the presence of the metabolic syndrome (MetS) had increased clot density (MaxAbs C : 0.358 [0.340, 0.375]au) and prolonged lysis times (Lys T : 510 [6569, 7939]s) compared with those without MetS (MaxAbs C : 0.319 [0.310, 0.328]au, P =0.003; Lys T : 7221 [4884, 5328]s, P <0.001). Furthermore, measures of clot structure/function increased progressively with increasing number of MetS components.

Conclusions— This study indicates that genetic factors contribute modestly to variance in clot structure/function and that clot structure/function is related to presence of the MetS and number of MetS components. Identification of the genetic and environmental factors influencing clot structure/function may further our understanding of the underlying factors predisposing to cardiovascular disease.

Influence of factor VIII on overall coagulability and fibrinolytic potential of haemophilic plasma as measured by global assay: monitoring in haemophilia A

The objectives of the present study were to evaluate the analytical sensitivity of the recently developed Clot Formation and Lysis (CloFAL) global assay for factor VIII (FVIII) deficiency, both in vitro and ex vivo, to determine whether this global assay is influenced by FVIII inhibitors, and to investigate the coagulative response to FVIII replacement in haemophilia A patients using the CloFAL assay in comparison with FVIII activity. Among adults and children alike, the CloFAL assay coagulation index (CI) was significantly decreased in FVIII-deficient vs. healthy subjects (adults median CI: 2% vs. 94% respectively; children median CI: 3% vs. 63%; P < 0.001 for each), and correlated significantly with activated partial thromboplastin time-based FVIII activity across all individuals (r = 0.78; P < 0.001). The CloFAL assay was analytically sensitive to deficient FVIII activity and also influenced by the presence of von Willebrand factor. Severe haemophilia A patients without inhibitory antibodies to FVIII showed considerable heterogeneity in CloFAL assay waveforms, despite a uniformly diminished CI of 0-1%. During FVIII infusion half-life studies in patients with severe haemophilia A, the CloFAL assay demonstrated a marked rise in coagulability 30 min following infusion, with progressive decrease in coagulability towards baseline over the ensuing 48-h period. In each case, the profile of coagulative response to FVIII infusion as determined by CloFAL assay CI differed qualitatively from that measured by FVIII activity. These findings indicate that the CloFAL assay may be useful as an adjunctive test to FVIII activity measurements in the therapeutic monitoring of haemophilia A.

Fibrinolysis and the risk of venous and arterial thrombosis

PURPOSE OF REVIEW

The fibrinolytic system is often regarded as just an innocent bystander in the pathogenesis of venous and arterial thrombosis, while (hyper)coagulation as a risk factor has been studied extensively. In this review, we evaluated studies that investigated the association between fibrinolysis and thrombosis.

RECENT FINDINGS

There is some evidence for an association between impaired overall fibrinolytic activity and increased risk of venous or arterial thrombosis. Plasminogen levels were found not to be related to thrombosis. Plasma levels of tissue-type plasminogen activator were related to arterial thrombosis in a number of studies but not to venous thrombosis. Thrombin activatable fibrinolysis inhibitor levels appeared to be associated with venous thrombosis. Studies on the association between thrombin activatable fibrinolysis inhibitor or plasminogen activator inhibitor-1 and arterial thrombosis had conflicting results.

SUMMARY

Current evidence on an association between fibrinolysis and thrombosis is inconclusive. Although overall assays point to an association, not all individual factors have an association with thrombosis. Most importantly, plasminogen deficiency is not related to thrombosis, which suggests that the fibrinolytic system as a whole is unimportant in the occurrence of thrombosis. Certain components of the fibrinolytic system, however, appear to be involved in processes unrelated to fibrin degradation but related to other processes important in the development of thrombosis.

Evaluation of pre-analytical, demographic, behavioural and metabolic variables on fibrinolysis and haemostasis activation markers utilised to assess hypercoagulability

BACKGROUND

Measurement of some haemostatic factors and products formed during activation of haemostasis seems to be promising in the determination of hypercoagulability.

METHODS

The fibrinolytic variables euglobulin clot lysis time, tissue-type plasminogen activator, plasminogen activator inhibitor-1 and the haemostasis activation markers prothrombin fragment 1+2, thrombin-antithrombin complex and D-dimer were determined in 101 apparently healthy men and women aged 20-92 years (58+/-18 years, mean+/-SD) to establish variability due to several demographic, behavioural and metabolic factors.

RESULTS

None of the fibrinolytic variables were affected by smoking, while tissue-type plasminogen activator antigen was significantly lower in women compared to men. Multiple regression analysis revealed several independent associations between tissue-type plasminogen activator, plasminogen activator inhibitor, body mass index and lipid levels, describing up to 40% of the variance in fibrinolytic variables. For haemostasis activation markers, no gender difference or effect of smoking was observed. Only D-dimer was independently associated with age. The haemostasis activation markers determined proved to be extremely sensitive to blood sampling procedure and were significantly higher in samples obtained by an untrained nurse compared to a trained nurse.

CONCLUSIONS

Fibrinolytic variables are predominantly modulated by age, body mass index and blood lipids, while haemostasis activation markers are mainly un-influenced by these factors.

Thrombophilia: common questions on laboratory assessment and management

Thrombophilia is an inherited or acquired predisposition to thrombosis. This article reviews the clinical manifestations of thrombophilia and addresses common questions on laboratory assessment and management: what are the potential indications for thrombophilia testing, who should be tested, what tests should be requested, when should testing be performed, and how should the test results affect primary prevention, acute therapy, and secondary prophylaxis of thrombosis.

The effect of genetic variants in the thrombin activatable fibrinolysis inhibitor (TAFI) gene on TAFI-antigen levels, clot lysis time and the risk of venous thrombosis

Thrombin activatable fibrinolysis inhibitor (TAFI) is an important inhibitor of fibrinolysis. High TAFI antigen levels are associated with an increased risk of deep venous thrombosis (DVT). Because TAFI levels are partly determined genetically, we assessed the association between three TAFI gene polymorphisms (-438 G/A, 505 A/G and 1040 C/T), TAFI antigen levels and clot lysis times and the risk of DVT. Carriers of the 505G allele, which is associated with lower TAFI antigen levels than the 505A allele, showed an increased risk of DVT. This indicates that the relationship between TAFI and venous thrombosis is more complex than previously suggested.

The epidemiology of venous thromboembolism in the community: implications for prevention and management

The epidemiology of venous thromboembolism (VTE) in the community has important implications for VTE prevention and management. This review describes the incidence, survival, recurrence, complications and risk factors for deep vein thrombosis and pulmonary embolism occurring in the community. VTE incidence among whites of European origin exceeds 1 per 1000; the incidence among persons of African and Asian origin may be higher and lower, respectively. VTE incidence over recent time remains unchanged. Survival after VTE is worse than expected, especially for pulmonary embolism where one-quarter of patients present as sudden death. Of those patients who survive, 30% develop VTE recurrence and venous stasis syndrome within 10 and 20 years, respectively. Common independent VTE risk factors include surgery, hospitalization for acute medical illness, nursing home confinement, trauma, active cancer, neurologic disease with extremity paresis, superficial vein thrombosis, central venous catheter/transvenous pacemaker, and among women, oral contraceptives, pregnancy and the puerperium, and hormone and SERM therapy. Exposures can identify populations at risk but have a low predictive value for the individual person. An acquired or familial thrombophilia may predict the subset of exposed persons who actually develop symptomatic VTE. In conclusion, VTE is a common, lethal disease that recurs frequently and causes serious long-term complications. To improve survival and prevent complications, VTE occurrence must be reduced. Better individual risk stratification is needed in order to modify exposures and target primary and secondary prophylaxis to the person who would benefit most.

Obesity and risk of venous thromboembolism among postmenopausal women: differential impact of hormone therapy by route of estrogen administration. The ESTHER Study

BACKGROUND

Oral estrogen use and elevated body mass index (BMI) increase the risk of venous thromboembolism (VTE). Recent data suggest that transdermal estrogen might be safe with respect to thrombotic risk. However, the impact of transdermal estrogen on the association between overweight (25 kg m(-2) < BMI < or = 30 kg m(-2)) or obesity (BMI >30 kg m(-2)) and VTE risk has not been investigated.

METHODS

We carried a multicenter case-control study of VTE among postmenopausal women aged 45-70 years, between 1999 and 2005, in France. Case population consisted of women with a first documented idiopathic VTE. We recruited 191 hospital cases matched with 416 hospital controls and 62 outpatient cases matched with 181 community controls.

RESULTS

The odds ratio (OR) for VTE was 2.5 [95% confidence interval (CI):1.7-3.7] for overweight and 3.9 (95% CI: 2.2-6.9) for obesity. Oral, not transdermal, estrogen was associated with an increased VTE risk (OR = 4.5; 95% CI: 2.6-7.7 and OR = 1.1; 95% CI: 0.7-1.7, respectively). Compared with non-users with normal weight, the combination of oral estrogen use and overweight or obesity further enhanced VTE risk (OR = 10.2; 95% CI: 3.5-30.2 and OR = 20.6; 95% CI: 4.8-88.1, respectively). However, transdermal users with increased BMI had similar risk as non-users with increased BMI (OR = 2.9; 95% CI: 1.5-5.8 and OR = 2.7; 95% CI: 1.7-4.5 respectively for overweight; OR = 5.4; 95% CI: 2.1-14.1 and OR = 4.0; 95% CI: 2.1-7.8 respectively for obesity).

CONCLUSIONS

In contrast to oral estrogen, transdermal estrogen does not confer an additional risk of idiopathic VTE in women with increased BMI. The safety of transdermal estrogen on thrombotic risk has to be confirmed.

Autoantibodies against the fibrinolytic receptor, annexin 2, in antiphospholipid syndrome

The association of thrombosis and gestational morbidity with antiphospholipid antibodies is termed antiphospholipid syndrome (APS). Annexin 2 (A2) is a profibrinolytic endothelial cell surface receptor that binds plasminogen, its tissue activator (tPA), and beta(2)-glycoprotein I (beta2GPI), the main antigen for antiphospholipid antibodies. Here, we evaluate A2 as a target antigen in APS. Serum samples from 434 individuals (206 patients with systemic lupus erythematosus without thrombosis, 62 with APS, 21 with nonautoimmune thrombosis, and 145 healthy individuals) were analyzed by enzyme-linked immunosorbent assay (ELISA) and immunoblot for antiphospholipid and A2 antibodies. Anti-A2 antibodies (titer > 3 SDs) were significantly more prevalent in patients with APS (22.6%; venous, 17.5%; arterial, 34.3%; and mixed thrombosis, 40.4%) than in healthy individuals (2.1%, P < .001), patients with nonautoimmune thrombosis (0%, P = .017), or patients with lupus without thrombosis (6.3%, P < .001). Anti-A2 IgG enhanced the expression of tissue factor on endothelial cells (6.4-fold +/- 0.13-fold SE), blocked A2-supported plasmin generation in a tPA-dependent generation assay (19%-71%) independently of beta2GPI, and inhibited cell surface plasmin generation on human umbilical vein endothelial cells (HUVECs) by 34% to 83%. We propose that anti-A2 antibodies contribute to the prothrombotic diathesis in antiphospholipid syndrome.