Showing papers in "Seminars in Thrombosis and Hemostasis in 1998"
TL;DR: The data suggest that the PFA-100 system is highly accurate in discriminating normal from abnormal platelet function and the ease of operation of the instrument makes it a useful tool to use in screening patients for platelet-related hemostasis defects.
Abstract: The PFA-100 system is a platelet function analyzer designed to measure platelet-related primary hemostasis. The instrument uses two disposable cartridges: a collagen/epinephrine (CEPI) and a collagen/ADP (CADP) cartridge. Previous experience has shown that CEPI cartridges detect qualitative platelet defects, including acetylsalicylic acid (ASA)-induced abnormalities, while CADP cartridges detect only thrombocytopathies and not ASA use. In this seven-center trial, 206 healthy subjects and 176 persons with various platelet-related defects, including 127 ASA users, were studied. The platelet function status was determined by a platelet function test panel. Comparisons were made as to how well the defects were identified by the PFA-100 system and by platelet aggregometry. The reference intervals for both cartridges, testing the 206 healthy subjects, were similar to values described in smaller studies in the literature [mean closure time (CT) 132 s for CEPI and 93 s for CADP]. The use of different lot numbers of cartridges or duplicate versus singleton testing revealed no differences. Compared with the platelet function status, the PFA-100 system had a clinical sensitivity of 94.9% and a specificity of 88.8%. For aggregometry, a sensitivity of 94.3% and a specificity of 88.3% were obtained. These values are based on all 382 specimens. A separate analysis of sensitivity by type of platelet defect, ASA use versus congenital thrombocytopathies, revealed for the PFA-100 system a 94.5% sensitivity in identifying ASA users and a 95.9% sensitivity in identifying the other defects. For aggregometry, the values were 100% for ASA users and 79.6% for congenital defects. Analysis of concordance between the PFA-100 system and aggregometry revealed no difference in clinical sensitivity and specificity between the systems (p > 0.9999). The overall agreement was 87.5%, with a Kappa index of 0.751. The two tests are thus equivalent in their ability to identify normal and abnormal platelet defects. Testing 126 subjects who took 325 mg ASA revealed that the PFA-100 system (CEPI) was able to detect 71.7% of ASA-induced defects with a positive predictive value of 97.8%. The overall clinical accuracy of the system, calculated from the area under the ROC curve, was 0.977. The data suggest that the PFA-100 system is highly accurate in discriminating normal from abnormal platelet function. The ease of operation of the instrument makes it a useful tool to use in screening patients for platelet-related hemostasis defects.
419 citations
TL;DR: Until data are available to address the magnitude of any increase inThrombotic risk induced by HRT for women with thrombophilia, physicians probably serve their patients best by providing information about the benefits of HRT, emphasizing that the risk of VTE is unknown, and encouraging patients to take an active role in decisions about their healthcare.
Abstract: Women with inherited or acquired thrombophilia are at increased risk for venous thromboembolism (VTE) when they use oral contraceptives (OCs) of either the second or third generation. For women who are heterozygous for Factor V Leiden, the risk is probably 28 to 50 of 10,000 women-years compared to 2 to 5 of 10,000 years for those not known to have thrombophilia. The thrombotic risk is highest during the first year that OCs are used. Whether women with thrombophilia are at increased risk for VTE when they use hormone replacement therapy (HRT) has not been assessed in any study. For women without thrombophilia, the risk for VTE associated with HRT is probably 2 to 3 of 10,000 years. The benefits of HRT include reduced risk for myocardial infarction and Alzheimer's disease, and increased bone density. The physiological changes induced by HRT are not the same as those induced by OCs. Small studies have suggested that for women who have additional risks of thrombosis (i.e., perioperative setting, underlying systemic lupus erythematosus), HRT does not confer the same increased risk of thrombosis, as does the use of OCs. Until data are available to address the magnitude of any increase in thrombotic risk induced by HRT for women with thrombophilia, physicians probably serve their patients best by providing information about the benefits of HRT, emphasizing that the risk of VTE is unknown, and encouraging patients to take an active role in decisions about their healthcare.
287 citations
TL;DR: Screening for factor V Leiden is suggested for all Caucasian individuals with previous venous thrombosis and inclusion criteria for the screening should not be stringent because clinical manifestations associated with the mutant genotype can be also mild or secondary to circumstantial risk factors or manifesting at advanced age.
Abstract: Inherited resistance to activated protein C (APC) has been recently recognized as a novel cause underlying venous thrombophilia. In most cases APC resistance is due to a single point mutation in the factor V gene leading to a replacement of Arg506 with Gln (factor V Leiden). Factor V Leiden allele is present in about 5% of the Caucasian individuals (Europeans, Jews, Israeli Arabs, and Indians) and is virtually absent in Africans, Asians, and races with Asian ancestry such as Amerindians, Eskimos, and Polynesians; this suggests a single origin of the mutation, which has been proven by haplotype analysis. A low prevalence of the mutation (1%) was noticed in African-Americans for recent racial admixture. Factor V Leiden presents not a major role as risk factor for arterial thrombosis, while it is present in 18% of Caucasian patients with venous thrombosis. This high incidence prevalence mirrors the incidence in the corresponding general populations and can be even higher in some areas according to the ethnic background. Conversely, factor V Leiden is usually not found in non-Caucasian thrombotic patients; this could give reason of the lower incidence of venous thrombotic disease in Africa and Asia in comparison with Europe. Therefore, screening for factor V Leiden is suggested for all Caucasian individuals with previous venous thrombosis; inclusion criteria for the screening should not be stringent because clinical manifestations associated with the mutant genotype can be also mild or secondary to circumstantial risk factors or manifesting at advanced age. Factor V Leiden can act also as concurrent risk factor in individuals with deficiency of natural inhibitors or mild hyperhomocysteinemia. So far, screening for the mutation in individuals with no history of thrombosis is recommended only for relatives of proband patients identified as carriers; the available data do not justify indiscriminate screening before risk situations such as oral contraceptives intake, pregnancy, or high-risk surgery.
212 citations
TL;DR: Current concepts of the many complex pathophysiological mechanisms and clinical and laboratory manifestations of disseminated intravascular coagulation (DIC) are presented and significant attention has been devoted to interrelationships within the hemostasis system.
Abstract: Current concepts of the many complex pathophysiological mechanisms and clinical and laboratory manifestations of disseminated intravascular coagulation (DIC) are presented. Considerable attention has been devoted to interrelationships within the hemostasis system. Only by clearly understanding these extraordinarily complex pathophysiological interrelationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. Many therapeutic decisions are controversial and will remain so until more is published about specific therapeutic modalities and survival patterns. The future holds promise for not only newer antithrombotic agents, but also agents which will block, blunt or modify cytokine activity and the activity of vasoactive substances. Also, therapy must be highly individualized depending on the nature of DIC, age, etiology of DIC, site and severity of hemorrhage or thrombosis and hemodynamic and other clinical parameters.
131 citations
TL;DR: There is considerable evidence that the hemostatic system is involved in the growth and spread of malignant disease, and intravascular coagulation activation and peritumor fibrin deposition seem to be important.
Abstract: There is considerable evidence that the hemostatic system is involved in the growth and spread of malignant disease. There is an increased incidence of thromboembolic disease in patients with cancers and hemostatic abnormalities are extremely common in such patients. Antihemostatic agents have been successfully used to treat a variety of experimental tumors, and several clinical trials in humans have been initiated. Although metastasis is undoubtedly multifactorial, intravascular coagulation activation and peritumor fibrin deposition seem to be important. The mechanisms by which hemostatic activation facilitates the malignant process remain to be completely elucidated. Of central importance may be the presence on malignant cells of tissue factor and urokinase receptor. Recent studies have suggested that these proteins, and others, may be involved at several stages of metastasis, including the key event of neovascularization. Tissue factor, the principal initiator of coagulation, may have additional roles, outside of fibrin formation, that are central to the biology of some solid tumors.
122 citations
TL;DR: The important role of AT in DIC and sepsis is the basis for considering antithrombin concentrates as an additional therapeutic modality.
Abstract: Antithrombin (AT) is a single-chain glycoprotein in plasma and belongs to the family of the serpins. It is synthesized in liver parenchymal cells, and its plasma concentration is between 112-140 mg/L. AT is a unique inhibitor of the clotting system and neutralizes most of the enzymes generated during activation of the clotting cascade, especially thrombin, factors Xa and IXa. Equimolar, irreversible complexes are formed between AT and the enzymes. The interaction between AT and the activated clotting factors is at least 1,000-fold increased in the presence of heparins. Heparins bind to multiple sites of the AT molecule resulting in a steric reconfiguration. Heparins contain a specific pentasaccharide unit which is the minimum requirement for AT binding. The glycosaminoglycan (GAG) heparan sulfate found on endothelial cell surfaces also contains this pentasaccharide and can thus "activate" AT. It is believed that much of the physiological inactivation of enzymes by AT occurs on the endothelium, mediated by heparan sulfate. The binding of AT to the GAGs also releases prostacyclin which possesses strong antiinflammatory properties. Deficiencies of AT are inherited or acquired. Only acquired defects due to increased consumption are discussed, most notably AT in DIC, especially DIC in sepsis. During acute DIC, clotting factors and inhibitors are consumed faster than they can be reproduced. This consumption of AT is of great significance in DIC and sepsis, and plasma AT levels predict outcome. AT levels drop early in sepsis and laboratory signs of DIC can already be found in patients with SIRS and early sepsis. The important role of AT in DIC and sepsis is the basis for considering antithrombin concentrates as an additional therapeutic modality.
113 citations
TL;DR: Antiinflammatory activity of AT III may be useful for the treatment of organ failure such as in ischemia/reperfusion-induced organ dysfunction, in which activated leukocytes play a critical role.
Abstract: Antithrombin III (AT III) supplementation has proven to be effective in the treatment of disseminated intravascular coagulation. Administration of AT III is also useful for prevention of organ failure in animals challenged with endotoxin or bacteria and it increases the survival rate of such animals. Since inhibition of coagulation abnormalities failed to prevent organ failure in animals given bacteria, AT III may exert a therapeutic effect independent of its anticoagulant effect. This therapeutic mechanism of AT III has been explored using an animal model of septicemia. AT III prevented pulmonary vascular injury by inhibiting leukocyte activation in rats given endotoxin. This effect is mediated by the promotion of endothelial release of prostacyclin which inhibits leukocyte activation. Interaction of AT III with heparin-like glycosaminoglycans (GAGs) on the endothelial cell surface appears to be important for this effect. Heparin inhibits these therapeutic effects of AT III by preventing AT III from interacting with the cell surface heparin-like GAGs. This activity of AT III may explain why AT III prevents organ failure as well as coagulation abnormalities in patients with sepsis. This antiinflammatory activity of AT III may be useful for the treatment of organ failure such as in ischemia/reperfusion-induced organ dysfunction, in which activated leukocytes play a critical role.
110 citations
TL;DR: Immunogold and cytochemical techniques have expanded the horizon of electron microscopy in the evaluation of platelet disorders and have assured its continued use for this purpose in the future.
Abstract: The electron microscope is generally regarded as a sophisticated instrument used almost exclusively for basic research. However, ultrastructural methods can be just as valuable for the clinical diagnosis of inherited platelet disorders, as for more fundamental studies. This report describes several instances in which electron microscopy has been critical for identifying and characterizing genetic problems. For example, platelet storage pool deficiency (SPD) is due to a marked decrease or absence of the organelles storing adenine nucleotides, serotonin, and calcium destined for secretion during the platelet release reaction. The organelles are referred to as dense bodies because they are inherently electron opaque. As a result, platelet SPD is more rapidly and reliably diagnosed in the electron microscope than by any other technique. Giant platelet disorders have presented a bewildering array. The electron microscope has made it possible to separate the various types into distinct conditions based on the nature of platelet structural defects and inclusions found in leukocytes. Immunogold and cytochemical techniques have expanded the horizon of electron microscopy in the evaluation of platelet disorders and have assured its continued use for this purpose in the future.
76 citations
Journal Article•
TL;DR: The focus has shifted from rare deficiencies associated with high probability for events to relatively common aberrations that produce high risk only in combination.
Abstract: Substantial progress has been made in the study of inherited abnormalities that predispose to venous thrombosis. With new discoveries, the focus has shifted from rare deficiencies associated with high probability for events to relatively common aberrations that produce high risk only in combination. Interactions between inherited and acquired disorders are also attracting much attention. The challenge for the future is how to best discover new risk factors and understand their contributions to multifactorial events.
73 citations
TL;DR: Besides recombinant hirudins, Argatroban (Novastan) and Bivalirudin (Hirulog) are promising thrombin-directed inhibitors for antithrombotic intervention.
Abstract: From injury through healing, thrombin has several important functions in blood clotting, subsequent clot lysis, and tissue repair. These include edema, inflammation, cell recruitment, cellular releases, transformations, mitogenesis, and angiogenesis. Thrombin also participates in disease states, such as venous thrombosis, coronary thrombosis, stroke, and pulmonary emboli, among others and is implicated in atherosclerosis, the growth and metastasis of certain cancers, Alzheimer's disease, and perhaps other conditions. Thrombin must be continually generated to sustain normal and pathogenic processes. This is because of a variety of consumptive mechanisms. Unlike other activated factors in thrombotic and fibrinolytic pathways, and because thrombin promotes its own generation (feedback and cellular activation), thrombin is a primary target for therapeutics. Besides recombinant hirudins, Argatroban (Novastan) and Bivalirudin (Hirulog) are promising thrombin-directed inhibitors for antithrombotic intervention.
72 citations
TL;DR: Evidence from clinical and preclinical studies now suggests to adjust the AT III plasma levels to about 200%, i.e., doubling the normal value, which suggests, that AT III substitution reduces morbidity and mortality in the diseased animals.
Abstract: Antithrombin III (AT III) is the physiological inhibitor of thrombin and other serine proteases of the clotting cascade. In the development of sepsis, septic shock and organ failure, the plasma levels of AT III decrease considerably, suggesting the concept of a substitution therapy with the inhibitor. A decrease of AT III plasma levels might also be associated with other pathological disorders like trauma, burns, pancreatitis or preclampsia. Activation of coagulation and consumption of AT III is the consequence of a generalized inflammation called SIRS (systemic inflammatory response syndrome). The clotting cascade is also frequently activated after organ transplantation, especially if organs are grafted between different species (xenotransplantation). During the past years AT III has been investigated in numerous corresponding disease models in different animal species which will be reviewed here. The bulk of evidence suggests, that AT III substitution reduces morbidity and mortality in the diseased animals. While gaining more experience with AT III, the concept of substitution therapy to maximal baseline plasma levels (100%) appears to become insufficient. Evidence from clinical and preclinical studies now suggests to adjust the AT III plasma levels to about 200%, i.e., doubling the normal value. During the last few years several authors proposed that AT III might not only be an anti-thrombotic agent, but to have in addition an anti-inflammatory effect.
TL;DR: The doses of Sulodexide required for antithrombotic efficacy suggest that the combination of heparin and dermatan sulfate in SulodExide provides a more effective antithROMbotic mechanism than hepar in/low-Mr heparins or dermatan sulphate/ low-Mr dermatAn sulfate (which catalyze thrombin inhibition byHeparin cofactor II).
Abstract: This report summarizes the results of some of the studies that have evaluated the pharmacokinetic, pharmacodynamic, anticoagulant, and antithrombotic properties of Sulodexide, which consists of a mixture of electrophoretically fast moving heparin (80% of the mass) and dermatan sulfate (the balance), with an average product (Mr) <8000. The low molecular weight (Mr) of the constituents of Sulodexide would predict that the product has the high bioavailability associated with low-Mr heparin and low-Mr dermatan sulfate. Given orally, subcutaneously, or by intravenous injection, Sulodexide exhibits antithrombotic and profibrinolytic properties in several animal models of venous and arterial thrombosis and has relatively high affinity for endothelial (and possibly other) cells. Additionally, in a large multicenter clinical trial involving 3986 patients who had recovered from acute myocardial infarction, oral Sulodexide was associated with a 32% reduction in death and a significant reduction of left ventricular thrombus formation. Compared with heparin, low-Mr heparin, and unfractionated and low-Mr dermatan sulfates, the doses of Sulodexide required for antithrombotic efficacy suggest that the combination of heparin and dermatan sulfate in Sulodexide provides a more effective antithrombotic mechanism than heparin/low-Mr heparins (which catalyze the antiprotease actions of antithrombin III) or dermatan sulfate/low-Mr dermatan sulfate (which catalyze thrombin inhibition by heparin cofactor II).
TL;DR: The PAI-2 inhibitor is produced by placental trophoblasts and by macrophages and is involved in the processes of invasion and remodeling of fetal and uterine tissues as discussed by the authors.
Abstract: Marked changes in the hemostasis system, especially increases in PAI-2, are observed during pregnancy and at delivery. This inhibitor is produced by placental trophoblasts and by macrophages. PAI-2 occurs in two forms, a LMW and a HMW form. LMW PAI-2 is intracellular, HMW PAI-2 is secreted. PAI-2 inhibits both u-PA and two-chain t-PA. PAI-2 seems to be involved in the processes of invasion and remodeling of fetal and uterine tissues. It may protect against premature placental separation and secure hemostasis at parturition. Excess levels of PAI-2 in amniotic fluid may protect membranes from premature rupture. An imbalance between fibrinolytic activators and inhibitors may also be related to intracranial hemorrhage in premature infants. During preeclampsia t-PA and PAI-1 levels are markedly increased in plasma, and in cases of intrauterine growth retardation, u-PA and PAI-2 levels are decreased. While elevated PAI-1 concentrations might be helpful markers of severity of preeclampsia, decreased PAI-2 levels seem to indicate decreased placental function and intrauterine growth retardation.
TL;DR: It is demonstrated that neonatal platelets are less reactive than adult platelets to physiological agonists in whole blood, as determined by the activation-induced increase in the platelet surface expression of P-selectin and the glycoprotein (GP) IIb-IIIa complex and by theactivation-induced decrease in the Platelet surfaceexpression of the GPIb-IX complex.
Abstract: Whole blood flow cytometry, an important new method for the assessment of platelet function, is particularly advantageous for neonatal studies because only minuscule volumes (approximately 2 microL) of blood are required. By this method, we have demonstrated that neonatal platelets are less reactive than adult platelets to physiological agonists in whole blood, as determined by the activation-induced increase in the platelet surface expression of P-selectin and the glycoprotein (GP) IIb-IIIa complex and by the activation-induced decrease in the platelet surface expression of the GPIb-IX complex. Our data suggest that the mechanism of neonatal platelet hyporeactivity is, at least in part, a relative defect in a common signal transduction pathway. We have further demonstrated that the platelets of very low birth weight (VLBW) preterm neonates are maximally hyporeactive on days 3 to 4 of life but return to almost the adult range by days 10 to 14. Given that intraventricular hemorrhage (IVH) is also maximal on days 3 to 4, these defects may contribute to the propensity of VLBW preterm neonates to IVH.
TL;DR: It is concluded that both TKH-2 immunostaining and serum STN assay are sensitive methods to diagnose patients with AFE.
Abstract: The purpose of this study was to evaluate whether serological assays and immunohistochemical staining, employing antibody TKH-2, are sensitive methods for the serological and histologic diagnosis of amniotic fluid embolism (AFE) TKH-2 is a sensitive antibody directed to sialyl Tn (STN), NeuAcalpha2-6GalNAc Nineteen samples of maternal sera with clinical AFE and 120 control sera and 15 specimen of formalin-fixed, paraffin-embedded lung tissue sections were examined in this study Tissue sections were stained using the streptavidin-biotin-immunoperoxidase method The concentration of STN in serum was measured by an immunoradiometric competitive inhibition assay using the monoclonal antibody TKH-2 in a one-step procedure Remarkable positive TKH-2 stainings were easily seen within the pulmonary vasculature in 14 of the 15 (93%) patients with AFE The serum STN levels (mean+/-SD) in patients with AFE (1108+/-481 U/ml) showed significantly higher concentrations compared with those of patients with non-AFE (173+/-26 U/ml) (p <001) Seventeen of 19 sera (89%) were diagnosed as AFE by serum TRH-2 level We conclude that both TKH-2 immunostaining and serum STN assay are sensitive methods to diagnose patients with AFE
TL;DR: The role that autocrine growth factors play in alpha-thrombin-induced proliferation will be discussed in this review.
Abstract: Alpha-thrombin is a multifunctional serine proteinase that is concentrated at sites of vascular injury and has been implicated in vascular healing responses following balloon injury. In addition to its well-known hemostatic effects, thrombin stimulates smooth muscle cell (SMC) proliferation via binding of protease activated receptor-1 (PAR-1), a seven transmembrane, G-protein-coupled cell surface receptor. Following activation of this receptor, SMC produce and secrete various autocrine growth factors, including platelet-derived growth factor-AA (PDGF-AA), basic fibroblast growth factor (bFGF), heparin binding epidermal growth factor (HBEGF), and transforming growth factor-beta (TGFbeta). The role that autocrine growth factors play in alpha-thrombin-induced proliferation will be discussed in this review.
TL;DR: Fibrinogen is a complex multifunctional protein, which contains constitutive association sites (gammaXL, D:D, Da, Db) as well as cryptic sites that become exposed as a result of fibr inogen proteolysis by thrombin, which together result in the mature fibrin network.
Abstract: Fibrinogen is a complex multifunctional protein, which contains constitutive association sites (gammaXL, D:D, Da, Db) as well as cryptic sites that become exposed as a result of fibrinogen proteolysis by thrombin (EA, EB). Utilization of these sites by self-association (gammaXL or D:D) or by association with exposed complementary fibrin sites (Da:EA, Db:EB) produces an orderly process of molecular assembly to form linear and branched fibrils, concomitant with lateral fibril associations and factor XIIIa-mediated fibrin crosslinking that together result in the mature fibrin network.
TL;DR: This article discusses the issue of hyperhomocysteinemia, in general, the known causes of hyper homocysteineemia and the association with venous thrombosis, and therapeutic options to treat.
Abstract: In recent years hyperhomocysteinemia has been established as a new risk factor for neural tube defects, arterial cardiovascular disease, and venous thrombosis. Concerning vascular problems, it first became clear that hyperhomocysteinemia might be (though not proven) a risk factor for arterial disease as observed in case-control studies, as well as in prospective analysis. More recently, the subject of hyperhomocysteinemia and venous thrombosis has received much attention. In this article, we discuss the issue of hyperhomocysteinemia, in general, the known causes of hyperhomocysteinemia and the association with venous thrombosis. Special attention is given to the value of the methionine loading test to diagnose hyperhomocysteinemia. An association of venous thrombosis and hyperhomocysteinemia has now been documented in several case control studies, but only in one prospective analysis. Thus far, there is limited evidence for a causal relationship for mild hyperhomocysteinemia in venous thrombosis. Briefly, the possible mechanisms of how hyperhomocysteinemia can lead to venous thrombosis are discussed. The article ends with therapeutic options to treat hyperhomocysteinemia (hyperhomocysteinemia can easily be treated with vitamins) and the description of a study that is presently being undertaken in an international multicenter design. This placebo-controlled study might resolve the question of whether lowering of homocysteine levels is of any clinical relevance in preventing recurrent venous thrombosis.
TL;DR: Results show that low concentrations of plasma DD measured by especially SimpliRed or VIDAS DD, might be used to reliably rule out DVT or PE in clinically suspected patients, and should be assessed for clinical usefulness in management trials under routine conditions.
Abstract: Studies measuring the fibrin degradation product D-Dimer (DD) using enzyme-linked immunosorbent assays (ELISA) in patients suspected of deep venous thrombosis (DVT) or pulmonary embolism (PE) suggest that it is possible to exclude DVT/PE when the DD level is below a certain cut-off value. However, ELISA methods are time-consuming, bare high costs, and are only available in experienced laboratories. For this reason several rapid and less costly DD assays have been recently developed. This article reviews the current literature about rapid latex and ELISA DD assays in the diagnostic approach of DVT and PE. Two new latex assays seem suitable in clinical practice. The most extensively studied assay is the so-called SimpliRed DD, an autologous red cell agglutination test that can be performed on fresh whole blood. For DVT a sensitivity (Sens) and a negative predictive value (NPV) of 89-100% and 95-100%, respectively, have been reported, for PE 94-100% and 98-100%, respectively. The second test, Tinaquant, is a quantitative latex assay. Sens and NPV for DVT of 99% and 93% have been reported in one study. Two rapid ELISA assays have been investigated. The most extensively studied is the VIDAS DD assay, a fully automated quantitative ELISA method. Sens and NPV of 94-100% and 92-100% for DVT and both 100% for PE have been reported. For the other rapid ELISA, Instant IA DD, Sens and NPV of 92-93% and 76-77% have been reported for DVT. The last one is a qualitative assay giving only positive or negative results. These results show that low concentrations of plasma DD measured by especially SimpliRed or VIDAS DD, might be used to reliably rule out DVT or PE in clinically suspected patients. Tinaquant seems promising and has to be evaluated further. As for standard ELISA, increased DD concentrations are of no use because of the low specificity of the assays. Future studies should assess the clinical usefulness of both assays in management trials under routine conditions, in the frame of clinical decision-making diagnostic processes to prove that withholding further noninvasive testing and/or anticoagulants in patients with a low or negative DD is safe. Strategies to identify patients with false-negative results should be developed.
TL;DR: A combined clinical and laboratory approach taking into account the history of the patient and his family, the prevalence of the defects, and also the accuracy of the tests should allow tailoring a laboratory testing program to each individual patient.
Abstract: In the past two decades, several mechanisms leading to thrombophilia have been elucidated, and corresponding laboratory tests developed. At a time of financial constraints, it is crucial to distinguish between the tests of proven value (which can modify the therapeutic attitude toward the patient and/or his family) from those of unproven value. We have listed in the first category determination or measurement of factor V Leiden, factor II G20210A, antithrombin, protein C, protein S, as well as antiphospholipid antibodies and hyperhomocysteinemia. A combined clinical and laboratory approach taking into account the history of the patient and his family, the prevalence of the defects, and also the accuracy of the tests should allow tailoring a laboratory testing program to each individual patient. It is essential to keep in mind that the more difficult task is not to perform the tests, but to consider who will benefit from testing both for prevention and therapy of venous thromboembolism. The present review provides answers to some of these issues. These answers should, however, be considered as provisional because new findings and study results will certainly modify them in the future.
TL;DR: Preliminary results indicate that the PFA-100 will be useful in the evaluation of primary hemostasis in children, as well as in adults, and reproducibility between duplicate samples is excellent.
Abstract: The platelet function analyzer, PFA-100, has been designed to provide an in vitro measure of primary hemostasis simply, quickly, quantitatively, and accurately to aid in the routine screening of patients with potential hemorrhagic risk due to abnormal platelet plug formation. The system measures the closure time (CT), or the time taken for platelets in a sample of anticoagulated blood to form a plug that occludes a microscopic aperture cut into a membrane coated with collagen and either epinephrine or ADP. The high shear stresses produced in the analyzer lead to platelet plug formation that is greatly dependent on von Willebrand's factor (vWF). In this article, we detail the system itself and describe our initial studies using the PFA-100 to assess primary hemostasis in pediatric populations. Normal ranges have been established for healthy children and neonates. CTs for healthy children are independent of the needle gauge (21G or 23G) used for blood sampling. They are similar to CTs for healthy adults, but neonates have significantly shorter CTs, likely due to increased levels of vWF. Children with hemophilia have normal CTs, whereas seven out of eight patients with von Willebrand's disease (vWD) have abnormally long CTs. CT reproducibility between duplicate samples is excellent. Our preliminary results indicate that the PFA-100 will be useful in the evaluation of primary hemostasis in children, as well as in adults.
TL;DR: Several hemostatic parameters were assayed in venous umbilical cord blood of 93 infants, 58 of which suffered from asphyxia due to abruptio placentae, breech delivery, preeclampsia, dead twin, and amniotic fluid embolism, suggesting the presence of DIC in the high-risk group of infants.
Abstract: Asphyxiated newborns have evidence of disseminated intravascular coagulation (DIC). Several hemostatic parameters were assayed in venous umbilical cord blood of 93 infants, 58 of which suffered from asphyxia due to abruptio placentae, breech delivery, preeclampsia, dead twin, and amniotic fluid embolism. Levels of factor XIII were markedly lower in the high-risk infants; the lowest values coincided with lowest Apgar scores. Plasma levels of thrombin-antithrombin (TAT) complexes, D-dimer, fibrin(ogen) degradation products (FDP), and soluble fibrin monomer complexes (SFMC) were markedly higher in the asphyxiated newborns with good correlations to DIC scores. DIC scores for infants were explained. A significant negative correlation was found between plasma levels of SFMC and Apgar scores. Also primary hemostasis measurements by a Thrombostat 4000 revealed defects in the asphyxiated infants. The data strongly suggest the presence of DIC in the high-risk group of infants.
TL;DR: The modified APC-resistance tests claim a separation between heterozygotes and homozygotes for factor V Leiden in the normal population, asymptomatic subjects, and thrombosis patients, which points to the need to perform the more time consuming and expensive DNA test to identify heterozygote from the more clinically significant homozygote.
Abstract: Genetic defects of antithrombin (AT) or one of the components of the protein C pathway are associated with hereditary thrombophilia. Laboratory assays are currently available to diagnose and type hereditary thrombophilia due to deficiency or dysfunction of one of the anticoagulant factors antithrombin (AT), protein C (PC) and protein S (PS), and APC resistance without the need of DNA analysis. There are no functional tests for the prothrombin mutant G20210A and thrombomodulin mutations, which can be diagnosed by a PCR-based test or by gene analysis, respectively. Hereditary AT deficiency is classified in a quantitative type I and three functional type II deficiencies affecting the reactive site (RS), heparin binding site (HBS), or pleiomorphic site of the AT protein. All four types of hereditary AT deficiencies can be diagnosed by a heparin cofactor assay and one immune assay in combination with crossed immunoelectrophoresis of the AT protein. The combination of an enzyme-linked immunoadsorbent assay (ELISA) and a functional Protac-APTT-based assay for PC will detect quantitative type I and dysfunctional type II PC deficiencies. There is a significant overlap in PC antigen and functional levels between heterozygotes of PC deficiency and normals leaving a gray zone of uncertainty in differentiating congenital PC deficiency and normal individuals. Accurate diagnosis of hereditary PS deficiency should be a combination of tests aimed to measure free PS activity and antigen and total PS antigen levels. APTT-, Xa-, and RVVT-based APC-resistance tests, when test plasmas are diluted in factor V deficient plasma, have increased in sensitivity and specificity to 100% for the discrimination of normal individuals from heterozygotes and homozygotes for factor V Leiden. The RVVT-based APC-resistance test provides better separation of factor V Leiden and normals in the various clinical settings, lupus anticoagulant in particular. The modified APC-resistance tests also claim a separation between heterozygotes and homozygotes for factor V Leiden in the normal population, asymptomatic subjects, and thrombosis patients. Below a certain cut-off level, a minor overlap of normalized APC ratios between heterozygotes and homozygotes for factor V Leiden of thrombosis patients has been shown in one study, which still points to the need to perform the more time consuming and expensive DNA test to identify heterozygotes from the more clinically significant homozygotes. The prothrombin-based APC-resistance test, which measures thrombin activated factor Va in highly diluted test plasma, appears to be the most sensitive and specific of all APC-resistance tests and separates normal individuals from heterozygotes and heterozygotes from homozygotes for factor V Leiden without the need of confirmation by a DNA test.
TL;DR: Evidence has been accumulating that there is an additional anti-inflammatory potential of Antithrombin III and there are several clinical trials ongoing to investigate whether this effect is of clinical relevance in the treatment of patients with severe sepsis.
Abstract: Despite improvements in critical care medicine and the development and aggressive use of potent broad-spectrum anti-microbial agents, mortality due to severe sepsis has not changed during the recent years and still comes to 35% to 45%. For quite a long time our understanding of the pathophysiology of sepsis was mainly focused on endotoxin and proinflammatory cytokines like tumor necrosis factor or interleukin-1. Now it is generally accepted that many signs and symptoms of sepsis are not directly mediated by cytokines but are transmitted through other mediator systems. The coagulation system comes into play especially when the septic process progresses to malperfusion and organ failure. Antithrombin III is an important inhibitor of the intrinsic, extrinsic and common pathway of coagulation. Recently, evidence has been accumulating that there is an additional anti-inflammatory potential of the drug. Currently there are several clinical trials ongoing to investigate whether this effect is of clinical relevance in the treatment of patients with severe sepsis.
TL;DR: The aggregation and release reaction by collagen were diminished in the specimens from newborns and beyond the postnatal period and during childhood, no remarkable differences from the adult norm were found.
Abstract: Blood samples from 42 newborns, 78 infants and schoolchildren, and 81 healthy adults were tested for the parameters of primary hemostasis. Only whole blood techniques were used. Agonist-induced aggregation and release-reaction studies were performed in a whole blood lumi-aggregometer simultaneously. The release of adenosine triphosphate (ATP) was detected by the luciferin-luciferase method. The in vitro bleeding time was measured by the PFA 100 system. The results of these studies were ostensibly influenced by blood cells. Many aggregation phenomena were correlated with the platelet count. Aggregation and release reaction by collagen were inversely correlated with the hematocrit. In the PFA 100, hematocrit and leukocyte count were also inversely correlated with the closure time and the maximal blood flow velocity. Both parameters were diminished in newborns. The aggregation response to adenosine diphosphate (ADP) was similar in the three groups. The same was true for the aggregation and release reaction by arachidonic acid and for the agglutination by ristocetin. The aggregation and release reaction by collagen were diminished in the specimens from newborns. For the explanation of this transient hypofunction, only theoretical considerations exist. Beyond the postnatal period and during childhood, no remarkable differences from the adult norm were found.
TL;DR: These findings further support the hypothesis that the coagulation and fibrinolysis systems can play an essential role in the initiation and progression of atherosclerosis through fibrin deposition both in atherosclerotic plaques and on the arterial surface by neointimal hypercoagulability and a hypofibrinlytic state.
Abstract: Tissue factor (TF) protein was overexpressed by macrophages and smooth muscle cells (SMCs) and deposited in the extracellular matrix of atherosclerotic intimas, probably resulting in enhanced procoagulant activity and the intimate participation in either thrombus formation or intimal fibrin deposition after the exposure of flowing blood and permeated fibrinogen to TF in atherosclerotic lesions. On the other hand, APO(a) was localized both in the stroma and within some macrophages. Fibrin deposition, which was more frequently detected in the matrix of advanced lesions than in that of early lesions, occasionally colocated with cell- and matrix-associated TF and APO(a) deposited in the matrix. These findings further support the hypothesis that the coagulation and fibrinolysis systems can play an essential role in the initiation and progression of atherosclerosis through fibrin deposition both in atherosclerotic plaques and on the arterial surface by neointimal hypercoagulability and a hypofibrinolytic state, which can also participate in SMC proliferation due to the decreased activation of TGF-beta by embedded and deposited APO(a). The clinical implications of these phenomena may thus contribute to future investigations in the prevention and treatment of atherosclerotic diseases.
TL;DR: The recent findings on the association between coronary artery disease (CAD) and polymorphisms in platelet membrane glycoproteins are shown and it is found that the genotypes having at least one 4-repeat allele (4R) are more frequently found in patients than in controls.
Abstract: The fact that certain ethnic groups and specific populations residing in certain geographic areas carry an increased risk for thrombosis and that thrombosis occurs in young patients without established risk factors indicates the presence of new, previously unrecognized inherited conditions predisposing to thrombosis. We are now aware that interindividual variations within the loci coding for proteins relevant to lipid and vascular metabolisms as well as blood coagulation are universally found. Platelets play central roles in cerebrovascular diseases and acute coronary syndromes, as demonstrated by histopathological findings and clinical observations showing the efficacy of antiplatelet therapies for these disorders. In this article, we show our recent findings on the association between coronary artery disease (CAD) and polymorphisms in platelet membrane glycoproteins. The glycoprotein (GP) Ib/IX complex is a receptor for von Willebrand factor, which mediates shear stress-dependent platelet activation. It has recently been implicated in the pathogenesis of acute coronary syndromes. We have determined genotypes of the "size-polymorphism" of GPIb alpha--i.e., the variable number (1-4) of a 13 amino acid sequence (399-411)--in angiographically proven Japanese CAD patients with myocardial infarction or angina pectoris as well as in individuals from the general population with no history of angina or other heart diseases and normal resting electrocardiograms (ECG). We have found that the genotypes having at least one 4-repeat allele (4R) are more frequently found in patients than in controls. Logistic regression analyses for the adjustment of age, sex, and other acquired coronary risk factors provided an odds ratio of 7.94 (p=0.0043) for those with 4R vs. those without 4R, suggesting that the presence of 4R is an independent risk factor for CAD. The molecular mechanisms underlying this association are currently under investigation. Relationships between arterial thrombosis and polymorphisms in other platelet GPs (collagen receptor and fibrinogen receptor), blood coagulation factors, fibrinolytic factors, vasoactive substances, and factors relevant for lipid metabolisms are also discussed.
TL;DR: Improved, user-friendly assays for plasma AT levels would permit more rapid turnaround time for AT results and could help fine-tune the use of AT concentrate to the specific needs of each patient.
Abstract: Sepsis and its associated complications of disseminated intravascular coagulation (DIC) and multiple organ dysfunction syndrome (MODS) continue to be a major cause of morbidity and mortality. Improved detection of all forms of DIC is essential to assure earlier diagnosis. Studies already indicate that the therapeutic use of antithrombin (AT) concentrate may produce a more positive outcome for sepsis-associated DIC. If DIC could be identified earlier and AT concentrate could then be given earlier in the sepsis continuum, study results for the use of AT concentrate in humans might reveal a statistically significant difference versus placebo, and the efficacy of AT concentrate for this syndrome is more likely to be proved. Fixed-bolus doses of AT concentrate based on body weight are currently preferred, but improved, user-friendly assays for plasma AT levels would permit more rapid turnaround time for AT results and could help fine-tune the use of AT concentrate to the specific needs of each patient. Clinical trials involving the therapeutic use of AT concentrate in sepsis should continue, and it can be hoped that their design will reflect the concepts and conclusions offered by this panel of investigators.
TL;DR: The effect of TF as an angiogenic factor might be useful as an antitumor therapy against hypervascular tumors or as a novel agent against delayed wound healing in a diabetic mouse wound-healing model.
Abstract: We report a novel function of tissue factor (TF) as an angiogenic factor in malignant and non-malignant cells and tissue. When methylcholanthrene A-induced murine fibrosarcoma (Meth-A sarcoma) was stably transfected with mouse TF (mTF) cDNA (pXT1 expression vector), its vascularization in vivo was significantly enhanced, whereas TF-antisense suppressed the vascularization and tumor growth. In vitro expression of vascular endothelial growth factor (VEGF) was enhanced with stable transfection of mTF (pcDNA3 expression vector) into a mouse fibroblast cell line (NIH3T3). Moreover, in vivo topical transfection of mTF (pcDNA3) showed an enhanced vascularization and healing in a diabetic mouse wound-healing model. This effect of TF as an angiogenic factor might be useful as an antitumor therapy against hypervascular tumors or as a novel agent against delayed wound healing.
TL;DR: The availability of new drugs such as activated protein C, tissue factor pathway inhibitor, hirudin, or synthetic serine protease inhibitors, and the upcoming trials investigating the role of these and older treatment options will help to more clearly recommend therapy in DIC of different etiology.
Abstract: Current concepts of etiology and pathophysiology resulting in disseminated intravascular coagulation (DIC) form the basis of treatment of this hemostatic disorder. Due to the heterogeneous triggering diseases and different kinds of DIC, clinical symptoms such as predominant bleeding, thromboembolic complications or organ failure, clinical experience together with the profile of laboratory test results and their development over time provide the basis for the individually tailored treatment strategy. The guiding principle of therapy is to identify and vigorously treat the underlying cause of DIC without delay. Treatment options to correct the hemostatic defect and to dampen the intravascular clotting/fibrinolytic process include transfusion of blood products, heparin, antithrombin III, and antifibrinolytic agents. The availability of new drugs such as activated protein C, tissue factor pathway inhibitor, hirudin, or synthetic serine protease inhibitors, and the upcoming trials investigating the role of these and older treatment options will help us to more clearly recommend therapy in DIC of different etiology.