Activated protein C resistance (FV(Leiden)) and thrombosis: factor V mutations causing hypercoagulable states

Thrombophilia Screening: Not So Straightforward

Although inherited thrombophilias are lifelong risk factors for a first thrombotic episode, progression to thrombosis is multifactorial and not all individuals with inherited thrombophilia develop thrombosis in their lifetimes. Consequently, indiscriminate screening in patients with idiopathic thrombosis is not recommended, since presence of a thrombophilia does not necessarily predict recurrence or influence management, and testing should be selective. It follows that a decision to undertake laboratory detection of thrombophilia should be aligned with a concerted effort to identify any significant abnormalities, because it will inform patient management. Deficiencies of antithrombin and protein C are rare and usually determined using phenotypic assays assessing biological activities, whereas protein S deficiency (also rare) is commonly detected with antigenic assays for the free form of protein S since available activity assays are considered to lack specificity. In each case, no single phenotypic assay is capable of detecting every deficiency, because the various mutations express different molecular characteristics, rendering thrombophilia screening repertoires employing one assay per potential deficiency, of limited effectiveness. Activated protein C resistance (APCR) is more common than discrete deficiencies of antithrombin, protein C, and protein S and also often detected initially with phenotypic assays; however, some centres perform only genetic analysis for factor V Leiden, as this is responsible for most cases of hereditary APCR, accepting that acquired APCR and rare F5 mutations conferring APCR will go undetected if only factor V Leiden is evaluated. All phenotypic assays have interferences and limitations, which must be factored into decisions about if, and when, to test, and be given consideration in the laboratory during assay performance and interpretation. This review looks in detail at performance and limitations of routine phenotypic thrombophilia assays.

Patients with severe coronavirus disease 2019 have high frequency of factor 5 Leiden and prothrombin gene mutations

We investigated the frequency of factor 5 Leiden (FVL) and prothrombin gene (PTG) mutations in patients with severe coronavirus disease 2019 (COVID-19). Our primary aim is to reveal whether these mutations are associated with severity of disease and mortality. A total of 249 patients were included in this cross-sectional study. Severe COVID-19 cases (with oxygen saturation of less than 90 mmHg and who received ventilation support invasively or noninvasively) were included. FVL and PTG mutations were identified by real time- PCR technique. Frequency of mutations for FVL was 11.7%, whereas for PTG was 3.5%. The frequency of FVL and PTG's mutations in our patient group was found to be significantly higher than the normal population ( P  < 0.0001, 0.004, respectively). There was no difference in the frequency of mutations of FVL and PTG between the patients ventilated - invasively and noninvasively. There was also no difference in D-dimer, ferritin, fibrinogen, ex status, and entubational status between the groups of FVL and PTG mutated and wild-type. To the best of our knowledge, it is the first time that we have examined the frequencies of FVL and PGM's mutations in severe COVID-19 disease on such a large scale. The frequencies of both mutations in severe COVID-19 patients were higher than in the healthy population. We believe that studies prospectively designed, including asymptomatic and mild COVID-19 patients, will provide more comprehensive information on the subject.

Jejunal Varices Bleeding in a Patient with Extensive Portomesenteric Thrombosis Secondary to Factor V Leiden Mutation: A Management Dilemma

Ectopic varices are portosystemic collaterals that occur away from the gastroesophageal junction and account for 1-5% of all variceal bleeding. Its occurrence in the jejunum is rare. Most common cause of ectopic jejunal varices is portal hypertension especially in those patients who have undergone prior abdominal surgery. Portomesenteric thrombosis is a rare cause of ectopic jejunal varices. Ectopic varices are rare cause of obscure GI bleeding and hence should be always suspected in patients with history of portal hypertension who present with GI bleeding and have negative upper and lower GI endoscopies. Management of patients with ectopic varices is often very challenging and requires multidisciplinary approach. Therapeutic options include endoscopic therapy, interventional radiologic procedures, surgically creating shunting, or surgical resection. We present the case of a 52-year-old patient who was on anticoagulation for extensive portomesenteric thrombosis secondary to factor V Leiden heterozygous mutation and presented with melena and symptomatic anemia. Investigations showed bleeding jejunal varices as the cause of anemia. We discuss the therapeutic options and dilemma in the management of such cases.

The structure-function relationship of activated protein C

Protein C is the central enzyme of the natural anticoagulant pathway and its activated form APC (activated protein C) is able to proteolyse non-active as well as active coagulation factors V and VIII. Proteolysis renders these cofactors inactive, resulting in an attenuation of thrombin formation and overall down-regulation of coagulation. Presences of the APC cofactor, protein S, thrombomodulin, endothelial protein C receptor and a phospholipid surface are important for the expression of anticoagulant APC activity. Notably, APC also has direct cytoprotective effects on cells: APC is able to protect the endothelial barrier function and expresses anti-inflammatory and anti-apoptotic activities. Exact molecular mechanisms have thus far not been completely described but it has been shown that both the protease activated receptor 1 and EPCR are essential for the cytoprotective activity of APC. Recently it was shown that also other receptors like sphingosine 1 phosphate receptor 1, Cd11b/CD18 and tyrosine kinase with immunoglobulin-like and EGFlike domains 2 are likewise important for APC signalling. Mutagenesis studies are being performed to map the various APC functions and interactions onto its 3D structure and to dissect anticoagulant and cytoprotective properties. The results of these studies have provided a wealth of structure-function information. With this review we describe the state-of-the-art of the intricate structure-function relationships of APC, a protein that harbours several important functions for the maintenance of both humoral and tissue homeostasis.

Lessons from natural and engineered mutations

To determine the frequency of Factor V Leiden in cases of Deep Vein Thrombosis and Healthy controls

Objective:

To determine the frequency of Factor V Leiden in cases of Deep Vein Thrombosis and Healthy controls.

Methods:

This case control study was performed in Armed Forces Institute of Pathology Rawalpindi, From 21^st March to 25^th September 2013. One hundred patients with diagnostic evidence of Deep vein thrombosis on Doppler ultrasound/Magnetic resonance imaging (MRI) scan were included in the study through non probability convenient sampling and compared with 100 matched healthy controls. DNA was extracted from the blood sample by kit method. In order to identify Factor V Leiden mutation, the polymerase chain reaction (PCR) method was utilized combined with the Amplification refractory mutation system. Data was analyzed using statistical package for social sciences (SPSS) version 17.

Results:

In 100 patients of Deep Vein Thrombosis (DVT), frequency of Factor V Leiden (FVL) was 13% and it is was 2% in healthy control group. A significant association was found between FVL and DVT with odds ratio of 7.32 and with P value (P = 0.003).

Conclusion:

FVL was found to be highly prevalent among patients of DVT, Signifying strong association between the two.

Effects of exogenous recombinant APC in mouse models of ischemia reperfusion injury and of atherosclerosis

Activated protein C (APC) is a serine protease that has both anticoagulant and cytoprotective properties. The cytoprotective effects are protease activated receptor 1 (PAR-1) and endothelial protein C receptor (EPCR) dependent and likely underlie protective effects of APC in animal models of sepsis, myocardial infarction and ischemic stroke. S360A-(A)PC, a variant (A)PC that has no catalytic activity, binds EPCR and shifts pro-inflammatory signaling of the thrombin-PAR-1 complex to anti-inflammatory signaling. In this study we investigated effects of human (h)wt-PC, hS360A-PC, hwt-APC and hS360A-APC in acute (mouse model of acute myocardial ischemia/reperfusion (I/R) injury) and chronic inflammation (apoE-/- mouse model of atherosclerosis). All h(A)PC variants significantly reduced myocardial infarct area (p<0.05) following I/R injury. IL-6 levels in heart homogenates did not differ significantly between sham, placebo and treatment groups in I/R injury. None of the h(A)PC variants decreased number and size of atherosclerotic plaques in apoE-/- mice. Only hS360A-APC slightly affected phenotype of plaques. IL-6 levels in plasma were significantly (p<0.001) decreased in hwt-APC and hS360A-PC treated mice. In the last group levels of monocyte chemotactic protein 1 (MCP-1) were significantly increased (p<0.05). In this study we show that both hwt and hS360A-(A)PC protect against acute myocardial I/R injury, which implies that protection from I/R injury is independent of the proteolytic activity of APC. However, in the chronic atherosclerosis model hwt and hS360-(A)PC had only minor effects. When the dose, species and mode of (A)PC administration will be adjusted, we believe that (A)PC will have potential to influence development of chronic inflammation as occurring during atherosclerosis as well.

Factor V-Leiden Mutation: A Common Risk Factor for Venous Thrombosis among Lebanese Patients

Aim. Lebanon exhibits one of the highest prevalences of factor V-Leiden (FVL) in the world (14.4%). The aim of this study is to evaluate the incidence of FVL mutation among Lebanese patients with lower extremity venous thrombosis. Material and Methods. From January 2003 to January 2011, 283 consecutive Lebanese patients, diagnosed with deep venous thrombosis (DVT) by duplex scan, were retrospectively reviewed. FVL mutation was tested among patients with conditions highly suggestive of hypercoagulation states (65 patients). Results. FVL mutation was detected among 56.9% of patients, 68.6% of patients younger than 50 years, and 43.4% of patients older than 50 years (P = 0.041). FVL mutation was commonly reported in young adults, in patients with pregnancy, estrogen drugs, recurrent DVT, and resistance to anticoagulation. Conclusion. The high rate of FVL mutation observed among Lebanese patients with venous thrombosis is related to the high prevalence of this mutation in the Lebanese population. Thrombophilia screening should be tailored to accommodate a population's risk factor. In countries with high prevalence of FVL, this mutation should be screened among patients younger than 50 years and patients with situations highly suggestive of hypercoagulation states.

Hypercoagulable states

Hypercoagulable states can be inherited or acquired. Inherited hypercoagulable states can be caused by a loss of function of natural anticoagulant pathways or a gain of function in procoagulant pathways. Acquired hypercoagulable risk factors include a prior history of thrombosis, obesity, pregnancy, cancer and its treatment, antiphospholipid antibody syndrome, heparin-induced thrombocytopenia, and myeloproliferative disorders. Inherited hypercoagulable states combine with acquired risk factors to establish the intrinsic risk of venous thromboembolism for each individual. Venous thromboembolism occurs when the risk exceeds a critical threshold. Often a triggering factor, such as surgery, pregnancy, or estrogen therapy, is required to increase the risk above this critical threshold.

Hypercoagulable states

Hypercoagulable states can be inherited or acquired. Inherited hypercoagulable states can be caused by a loss of function of natural anticoagulant pathways or a gain of function in procoagulant pathways. Acquired hypercoagulable risk factors include a prior history of thrombosis, obesity, pregnancy, cancer and its treatment, antiphospholipid antibody syndrome, heparin-induced thrombocytopenia, and myeloproliferative disorders. Inherited hypercoagulable states combine with acquired risk factors to establish the intrinsic risk of venous thromboembolism for each individual. Venous thromboembolism occurs when the risk exceeds a critical threshold. Often a triggering factor, such as surgery, pregnancy, or estrogen therapy, is required to increase the risk above this critical threshold.

Venous thromboembolism and oral contraception

Introduction. Because of their safety and efficacy, oral contraceptives are available without prescription in many countries. Monophasic combined oral contraceptives are a combination of estrogen and progestin taken in constant amounts. Venous thromboembolism. Combined oral contraceptives slightly increase the risk of venous thromboemolism, but this event is very rare among non-pregnant women of reproductive age. The absolute risk rises with age, obesity, recent surgery and certain forms of thrombophilia. The estrogen component of combined oral contraceptives increases the synthesis of several coagulation factors in a dose-dependent manner. Changes of most of these parameters are very small and there is no evidence that they have any effect upon the clinical risk of developing venous thrombosis. If a woman has an inherited coagulation disorder that increases her risk of developing thrombosis, the risk is increased several fold if she ingests estrogen containing oral contraception. Conclusion. The increased risk of venous thromboembolism associated with combined oral contraceptives should have little impact on healthy women, but may have substantial impact on women with a history of thromboembolism. Combined oral contraceptive use increases the risk of venous thromboembolosm in a dose-dependent manner. The absolute risk of venous thromboembolism rises with age, obesity, recent surgery and certain forms of thrombophilia, as well.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Thrombin generation in acute coronary syndrome and stable coronary artery disease: dependence on plasma factor composition

BACKGROUND

Acute coronary syndrome (ACS) is associated with thrombin formation, triggered by ruptured or eroded coronary atheroma. We investigated whether thrombin generation based on circulating coagulation protein levels, could distinguish between acute and stable coronary artery disease (CAD).

METHODS AND RESULTS

Plasma coagulation factor (F) compositions from 28 patients with ACS were obtained after onset of chest pain. Similar data were obtained from 25 age- and sex-matched patients with stable CAD. All individuals took aspirin. Patients on anticoagulant therapy were excluded. The groups were similar in demographic characteristics, comorbidities and concomitant treatment. Using each individual's coagulation protein composition, tissue factor (TF) initiated thrombin generation was assessed both computationally and empirically. TF pathway inhibitor (TFPI), antithrombin (AT), factor II (FII) and FVIII differed significantly (P < 0.01) between the groups, with levels of FII, FVIII and TFPI higher and AT lower in ACS patients. When thrombin generation profiles from individuals in each group were compared, simulated maximum thrombin levels (P < 0.01) and rates (P < 0.01) were 50% higher with ACS while the initiation phases of thrombin generation were shorter. Empirical reconstructions of the populations reproduced the thrombin generation profiles generated by the computational model. The differences between the thrombin generation profiles for each population were primarily dependent upon the collective contribution of AT, FII and FVIII.

CONCLUSION

Simulations of thrombin formation based on plasma composition can discriminate between acute and stable CAD.

The genetic predisposition to adverse outcome after trauma

Technological advances and shorter rescue times have allowed early and effective resuscitation after trauma and brought attention to the host response to injury. Trauma patients are at risk of progressive organ dysfunction from what appears to be an uncontrolled immune response. The availability of improved techniques of molecular diagnosis has allowed investigation of the role of genetic variations in the inflammatory response to post-traumatic complications and particularly to sepsis.

This review examines the current evidence for the genetic predisposition to adverse outcome after trauma. While there is evidence supporting the involvement of different polymorphic variants of genes in determining the post-traumatic course and the development of complications, larger-scale studies are needed to improve the understanding of how genetic variability influences the responses to post-traumatic complications and pharmacotherapy.

A case report of a new pulmonary embolism occurring in a patient receiving continuous infusion of recombinant activated protein C

BACKGROUND

There are no guidelines governing the concomitant use of recombinant human activated protein C (rhAPC) and deep venous thrombosis/pulmonary embolism (DVT/PE) prophylaxis in critically ill patients. It is unknown if rhAPC provides any protection against DVT/PE in this population of patients.

METHODS

Case report.

RESULTS

This report describes the first case of a radiographically demonstrated pulmonary embolism occurring in a patient receiving continuous therapeutic infusion of rhAPC.

CONCLUSION

The administration of rhAPC alone may not be sufficient DVT/PE prophylaxis in high risk patients. The risks associated with concomitant anticoagulation and rhAPC therapy are unknown. Further research is necessary to determine the safest and most effective regimen for DVT/PE prophylaxis in patients receiving rhAPC.

Elevated coagulation factor VIII, postoperative thrombosis and flap failure in late breast reconstruction with a free TRAM flap: a case report

Only a few studies have sought to establish whether an underlying coagulation disorder might predispose a patient to thrombosis or coincide with flap failure in the context of free flap surgery. Here, we report a case of both intra- and postoperative arterial anastomotic thromboses and late flap failure due to venous thrombosis after late breast reconstruction with a TRAM flap, in which laboratory evaluation revealed elevated levels of coagulation factor VIII (FVIII). High FVIII concentrations have recently been cited as an independent and dose-dependent risk factor for thromboembolism.

Models of blood coagulation

Our research aims to provide quantitatively transparent, biologically realistic descriptions of the processes involved in hemostasis which will permit predictions of the behavior of the coagulation system in normal and pathologic states. We use four models of coagulation: (1) numerical approximations of the tissue factor (Tf) pathway of thrombin generation based upon mechanism and dynamics; (2) Tf activation of the "blood coagulation proteome" from isolated cells and proteins; (3) Tf activated contact pathway inhibited whole blood in vitro; and (4) blood shed from standardized microvascular wounds in vivo. The results from these models are integrated in interactive assessments aimed at achieving convergence of biochemical rigor and biological authenticity. Microvascular injury is the most biologically secure but least accessible to mechanistic study. Numerical models while quantitatively transparent are biologically limited. By the integrated analyses of all four models, we establish observations which require inclusion or discovery of new parameters to achieve mechanistically interpretable biological reality. Discoveries made in this fashion have included thrombin's role in the initiation phase, TFPI/ATIII/APC synergy interactions, rfVIIa in fVII deficiency, the roles of fVIII and fIX in the Tf reaction, and the cleavage of fIX by fXa membrane. Ideally, our results will provide descriptions which predict the behavior of the biological blood coagulation system under normal and pathologic conditions.

Thrombin generation profiles in deep venous thrombosis

BACKGROUND

Reliable markers and methods to predict risk for thrombosis are essential to clinical management.

OBJECTIVE

Using an integrated approach that defines an individual's comprehensive coagulation phenotype might prove valuable in identifying individuals at risk for experiencing a thrombotic event.

METHODS

Using a numerical simulation model, we generated tissue factor (TF) initiated thrombin curves using coagulation factor levels from the Leiden Thrombophilia Study population and evaluated thrombotic risk, by sex, age, smoking, alcohol consumption, body mass index (BMI) and oral contraceptive (OC) use. We quantitated the initiation, propagation and termination phases of each individuals' comprehensive TF-initiated thrombin generation curve by the parameters: time to 10 nm of thrombin, maximum time, level and rate (MaxR) of thrombin generated and total thrombin.

RESULTS

The greatest risk association was obtained using MaxR; with a 2.6-fold increased risk at MaxR exceeding the 90th percentile. The odds ratio (OR) for MaxR was 3.9 in men, 2.1 in women, and 2.9 in women on OCs. The association of risk with thrombin generation did not differ by age (OR:2.8 OR:2.5), BMI (OR:2.9 OR:2.3) or alcohol use. In both numerical simulations and empirical synthetic plasma, OC use created extreme shifts in thrombin generation in both control women and women with a prior thrombosis, with a larger shift in thrombin generation in control women. This suggests an interaction of OC use with underlying prothrombotic abnormalities.

CONCLUSIONS

Thrombin generation based upon the individual's blood composition is associated with the risk for thrombosis and may be useful as a predictive marker for evaluating thrombosis on an individual basis.

GENETIC POLYMORPHISMS AND SEPSIS

Sepsis is a polygenic and complex syndrome that is initiated by infection and is characterized by a systemic inflammatory response. Genetic polymorphisms in the immune response to infection have been shown to be associated with clinical outcomes. Functional and association studies involving genetic polymorphisms in essential genes, including Toll-like receptors, cytokines, and coagulation factors, have provided important insights into the mechanisms involved in the pathogenesis of sepsis-induced organ dysfunction. The advancement of high-throughput single nucleotide polymorphism (SNP) genotyping will provide valuable information on the interaction of multiple allelic variants and clinical outcome. More precise categorization of patients based on genetic background is likely to lead to individualized targeted treatment. Future therapeutic trials as well as actual treatment regimens for patients with sepsis are likely to be designed to target specific genotypes and associated cellular responses, maximizing clinical response and patient safety.

Antithrombotic Therapy for Stroke in Young Adults

Stroke in young adults is a markedly heterogeneous disease, and remains an understudied phenomenon. While advances are being made in our understanding of the pathophysiology of its underlying conditions, treatment concerns are controversial, and clinical trials are sorely lacking. This review presents an overview of some of the relevant management issues in hypercoagulable states, migraine, patent foramen ovale, vascular dissection and venous sinus thrombosis.

The plasma hemostatic proteome: thrombin generation in healthy individuals

BACKGROUND AND OBJECTIVES

The range of plasma concentrations of hemostatic analytes in the population is wide. In this study these components of blood coagulation phenotype are integrated in an attempt to predict clinical risk.

METHODS

We modeled tissue factor (TF)-induced thrombin generation in the control population (N = 473) from the Leiden Thrombophilia Study utilizing a numerical simulation model. Hypothetical thrombin generation curves were established by modeling pro- and anticoagulant factor levels for each individual. These curves were evaluated using parameters which describe the initiation, propagation and termination phases of thrombin generation, i.e. time to 10 nm thrombin (approximate clot time), total thrombin and the maximum rates and levels of thrombin generated.

RESULTS AND CONCLUSIONS

The time to 10 nm thrombin varied over a 3-fold range (2.9-9.5 min), maximum levels varied over a approximately 4-fold range (200-800 nm), maximum rates varied approximately 4.8-fold (90-435 nm min(-1)) and total thrombin varied approximately 4.5-fold (39-177 microm s(-1)) within this control population. Thrombin generation curves, defined by the clotting factor concentrations, were distinguished by sex, age, alcohol consumption, body mass index (BMI) and oral contraceptive (OC) use (OC > sex > BMI > age). Our results show that the capacity for thrombin generation in response to a TF challenge may represent a method to identify an individual's propensity for developing thrombosis.

Blood coagulation and its regulation by anticoagulant pathways: genetic pathogenesis of bleeding and thrombotic diseases

Blood coagulation and its regulation by anticoagulant pathways: genetic pathogenesis Platelet-mediated primary haemostasis and blood coagulation have evolved as important defence mechanisms against bleeding. The formation of the platelet plug provides the initial occlusion of the vascular lesion. This is temporally co-ordinated with the activation of the coagulation system, which occurs in response to the rupture of endothelium and the exposure of blood to the extravascular tissue. The reactions of blood coagulation are carefully controlled by several anticoagulant mechanisms and under normal conditions they prevail over the procoagulant forces. Genetic or acquired disturbances of the natural balance between the pro- and anticoagulant systems may result in bleeding or thrombotic diseases.

Genetic thrombophilia

The genetic thrombophilias are an important cause of venous thrombotic events. Much has been learned about the natural history of these disorders, their genetics, and, to a lesser degree, their treatment. This article provides an overview of the genetics of thrombophilia. Specific information on the factor V Leiden mutation;the prothrombin G20210A mutation; and protein C, proteinS, and antithrombin deficiency is reviewed. Current testing and treatment options for the genetic thrombophilias also are discussed.

Anticoagulation in Hypercoagulable Conditions: Special Considerations in the Treatment and Prevention of Venous Thromboembolism

Patients with hypercoagulable conditions, including malignancy, are at increased risk of recurrent venous thromboembolic events (VTE). The general approach to treatment and prevention of VTE in patients with thrombophilia is similar to that of patients who present with VTE associated with transient risk factors, including immobility, trauma, and surgery. However, several important issues must be considered in the initial management of acute VTE, in the long-term prevention of VTE following an initial event, and in VTE prophylaxis in patients with hypercoagulable conditions. Patients with antithrombin deficiency are prone to heparin resistance and may require concurrent antithrombin concentrates or anticoagulation with direct thrombin inhibitors for adequate treatment of acute VTE. In patients with malignancy, low-molecular-weight heparins have been found to be more effective than unfractionated heparin for the initial treatment of VTE. Long-term prevention is preferred for most patients with hypercoagulable conditions, and the latest trials show that low-intensity warfarin is not as effective as typical moderate-intensity therapy for chronic therapy. Primary prophylaxis of asymptomatic carriers is not warranted unless they are exposed to additional risk factors, including surgery, trauma, immobilization, and pregnancy. Prolonged prophylaxis may be appropriate in patients with malignancy who undergo surgical procedures.

Importance of hemostatic gene polymorphisms for susceptibility to and outcome of severe sepsis

Individuals vary considerably in their susceptibility to infection and in their ability to recover from apparently similar infectious processes. These differences can be partially explained by polymorphisms of the genes encoding proteins involved in mediating and controlling the innate immune response, the inflammatory cascade, coagulation, and fibrinolysis. It is evident from experimental studies that dysregulation of the coagulation system, which is characteristic of the pathophysiology of septic shock (a procoagulant and antifibrinolytic state), contributes to systemic inflammation and death in sepsis. Several genetic variations in proteins that increase coagulation or impair anticoagulation and fibrinolysis have been described. Thus, polymorphisms have been reported in prothrombin, fibrinogen, factor V, tissue factor, endothelial protein C receptor, and plasminogen activator inhibitor-1 genes. Some of them are associated with an increased risk of pulmonary emboli, acute myocardial infarction, stroke, and severe sepsis. Hence, the deletion polymorphism (4G) within the promoter region of the plasminogen activator inhibitor-1 gene leads to impaired fibrinolysis and influences the severity and outcome of meningococcal disease and the susceptibility to severe sepsis and multiple organ failure after trauma. The factor V Leiden mutation is associated with thrombotic events and has been reported to exacerbate purpura fulminans in meningococcal infection. Surprisingly, this genetic variant seems to provide a survival advantage in severe sepsis, underlying the extreme complexity of the interaction between inflammation and coagulation. The study of genetic polymorphisms might provide important insights into the pathogenesis of severe sepsis and could make it possible to identify individuals who are at risk of developing or dying of severe infections. As genetic associations are discovered, medical practice can become more preemptive, using the predictive ability of genetics to anticipate disease and recommend therapy.

Thrombin generation: phenotypic quantitation

An individual's ability to generate thrombin following tissue factor stimulus was evaluated in 13 healthy male donors in a 6-month study. Thrombin generation in whole blood collected by phlebotomy, contact pathway suppressed by the presence of 100 micro g mL-1 corn trypsin inhibitor, was initiated by the addition of 5 pm tissue factor/10 nm phospholipid. Reactions were quenched at 20 min by the addition of an ethylenediaminetetraacetic acid (EDTA), benzamidine, FPRck cocktail. Thrombin generation was determined by an ELISA for thrombin-antithrombin III (TAT) complex formation. Results showed that the levels of TAT observed varied from 245 to 775 nm. Thrombin production was consistent within each individual, CVi = 11.6%, but varied significantly within the group, CVg = 25.2%, and correlated inversely with an individual's clotting time (r = - 0.54, P = 0.07). No correlations were individually observed between TAT and C-reactive protein, antithrombin III, factors II, V, VII, VIII, IX and X, fibrinogen and prothrombin time. However, computer simulations, which integrated each individual's coagulation factor levels using the Speed Rx method (Hockin et al., J Biol Chem 2002; 277: 18322), predicted maximum active thrombin levels (ranging from calculated values of 220-500 nm) consistent with the empirically determined values. Overall, these data suggest that thrombin generated in whole blood exclusively by tissue factor stimulation can be used as an integrative phenotypic marker to determine an individual's response to a tissue factor challenge.

Coagulation inhibitors in preeclamptic pregnant women

OBJECTIVE

Our objective was to detect clinical evaluation of coagulation inhibitors in preeclamptic and normotensive pregnant women and to determine their important role in pathogenesis of preeclampsia.

METHODS

A total of 20 mild, 20 severe preeclamptic and 45 normotensive pregnant women were included in this study. The plasma value of antithrombin III (AT-III) activity, proteins C and S activity, PT, PTT, fibrinogen and platelet counts were determined.

RESULTS

The values AT-III were lower in women with severe preeclampsia than in controls (p<0.05). In all groups, there was no significantly difference in the concentration of protein C activity, protein S and fibrinogen (p>0.05). The plasma thrombocyte counts were significantly lower in severe preeclamptic women than in normotensive women (p<0.05). There was no significant difference in the prothrombin time value in all groups, but a significantly difference with regard to partial thromboplastin time between severe preeclamptic and the control group (p<0.0001). It was longer than the control.

CONCLUSION

The markers of hemostasis activation such as protein S, protein C activity together with fibrinogen levels are not useful tools but the reduction of AT-III and platelet counts would seem useful in different pathological situations in pregnancy to predict and monitor the severity of the condition.