Showing papers in "Seminars in Thrombosis and Hemostasis in 2012"

Non-O Blood Type Is the Commonest Genetic Risk Factor for VTE: Results from a Meta-Analysis of the Literature

Abstract: It is well known that the ABO blood group exerts a major influence on hemostasis, as O blood group individuals have lower von Willebrand factor and factor VIII levels than non-O blood group subjects. To evaluate the possible clinical implication of the different ABO blood groups on the risk of developing venous thromboembolism (VTE), we conducted a meta-analysis of the existing literature. After an electronic search strategy using Medline and Embase and a manual review of abstract books of the International Society on Thrombosis and Haemostasis and of reference lists of all retrieved articles, we included in the systematic review 38 studies with 10,305 VTE cases. The prevalence of non-O blood group was significantly higher in VTE patients compared with controls with a resulting pooled odds ratio (OR) of 2.09 (95% confidence interval [CI], 1.83, 2.38; p < 0.00001). Similar findings were obtained when the genotypes A1O/BO/A2B (OR 1.73, 95% CI, 1.47, 2.05; p < 0.00001) and A1B/A1A1/BB (OR 1.87, 95% CI, 1.84, 2.44; p < 0.00001) were analyzed. The maximum VTE risk was observed in non-O-factor V Leiden patients (OR 7.60, 95% CI, 3.21, 17.99), while for G20210A prothrombin mutation it was not possible to perform a pooled analysis due to a paucity of published studies. Finally, the association between non-O blood group and VTE was weaker when provoked VTE cases were considered (OR 1.33, 95% CI, 1.18, 1.50), while it was substantially unchanged when unprovoked VTE cases were analyzed (OR 1.88, 95% CI, 1.42, 2.50). In conclusion, considering its prevalence, non-O blood group is a candidate to be one of the most important genetic risk factors for venous thrombosis.

Quality standards for sample collection in coagulation testing.

Abstract: Preanalytical activities, especially those directly connected with blood sample collection and handling, are the most vulnerable steps throughout the testing process. The receipt of unsuitable samples is commonplace in laboratory practice and represents a serious problem, given the reliability of test results can be adversely compromised following analysis of these specimens. The basic criteria for an appropriate and safe venipuncture are nearly identical to those used for collecting blood for clinical chemistry and immunochemistry testing, and entail proper patient identification, use of the correct technique, as well as appropriate devices and needles. There are, however, some peculiar aspects, which are deemed to be particularly critical when collecting quality specimens for clot-based tests, and these require clearer recognition. These include prevention of prolonged venous stasis, collection of nonhemolyzed specimens, order of draw, and appropriate filling and mixing of the primary collection tubes. All of these important preanalytical issues are discussed in this article, and evidence-based suggestions as well as recommendations on how to obtain a high-quality sample for coagulation testing are also illustrated. We have also performed an investigation aimed to identify variation of test results due to underfilling of primary blood tubes, and have identified a clinically significant bias in test results when tubes are drawn at less than 89% of total fill for activated partial thromboplastin time, less than 78% for fibrinogen, and less than 67% for coagulation factor VIII, whereas prothrombin time and activated protein C resistance remain relatively reliable even in tubes drawn at 67% of the nominal volume.

Platelet-derived microvesicles: multitalented participants in intercellular communication.

Abstract: Platelets can release a heterogeneous pool of vesicles which include plasma membrane-derived microparticles (PMPs) and multivesicular body-derived exosomes. As both vesicle types are generated upon activation and their distinction is complicated due to an overlap in their molecular properties and sizes, they are best discussed as an entity, the platelet-derived microvesicles (PMVs). PMPs can be formed through several induction pathways, which determine their different molecular profiles and facilitate tailor-made participation in intercellular communication. This dynamic variability may lie behind the multifaceted and sometimes very different observations of the PMPs in physiological and pathological settings. Currently, little is known of platelet-derived exosomes. In all, PMVs not only participate in several homeostatic multicellular processes, such as hemostasis, maintenance of vascular health, and immunity, but they also play a role in thrombotic and inflammatory diseases and cancer progression. In the past few years, the number of original articles and reviews on microvesicles has dramatically increased, but the data simultaneously raise further questions, the answers to which depend on forthcoming analytical improvements. In this article, the differential activation pathways and the molecular and functional properties of PMVs are reviewed in context with their sometimes paradoxical role in health and in disease. Also, the methodological issues of PMV detection and analysis are discussed in the light of recent advances within the field.

Quality standards for sample processing, transportation, and storage in hemostasis testing.

Abstract: Samples for hemostasis testing drawn into sodium citrate anticoagulant are vulnerable to the effects of preanalytical variables associated with sample processing, transportation, and storage. These variables include the temperature at which samples are transported and stored; the stability of the samples once processed; whether maintained at room temperature, refrigerated, or frozen; methods of centrifugation; as well as the potential impact of using an automated line. Acknowledgment of these variables, as well as understanding their potential impact on assay results, is imperative to the reporting of high quality and accurate results. This article discusses the preanalytical issues associated with sample processing, transportation, and storage and also presents the ideal conditions for sample handling.

Drugs that affect platelet function.

Abstract: Drugs represent the most common cause of platelet dysfunction in our overmedicated society. While acetylsalicylic acid (aspirin), adenosine diphosphate receptor antagonists (clopidogrel and prasugrel), and integrin αIIbβ3 (GPIIb-IIIa) receptor blockers (abciximab, eptifibatide, and tirofiban) are well-known prototypes of antiplatelet drugs, other widely used agents such as nonsteroidal anti-inflammatory drugs, antibiotics, cardiovascular and lipid-lowering drugs, selective serotonin reuptake inhibitors, and volume expanders can also impair platelet function and thus cause or aggravate hemorrhages in certain clinical settings. Therefore, induction of a bleeding diathesis remains a significant concern. This is especially relevant in patients with preexisting hemostatic defects of any kind, which may remain compensated as long as platelet function (and/or coagulation) is not inhibited pharmacologically. Identification of individual patients with preexisting hemostatic defects remains crucial (1) to prevent otherwise unexpected bleeding complications, (2) to manage hemorrhagic symptoms adequately, (3) to minimize the risk from invasive procedures, and (4) to avoid unnecessary patient exposure to blood products. This article provides a review of the large variety of agents that have not been designed for antiplatelet therapy but nevertheless interfere with platelet reactivity or induce platelet inhibition. In particular, drug interactions and mechanisms by which these agents can trigger or cause platelet dysfunction are detailed.

Interference in coagulation testing: focus on spurious hemolysis, icterus, and lipemia.

Abstract: The chance that errors might jeopardize the quality of testing is inherently present throughout the total testing process, especially in the preanalytical phase. In the coagulation laboratory, as well as in other areas of diagnostic testing, spurious hemolysis, icteria, and lipemia in test samples represent by far the leading diagnostic challenges. Interference in hemostasis testing due to spurious hemolysis is attributed to both analytical and biologic elements, namely high absorbance of cell-free hemoglobin at wavelengths used by optical instrumentation and release of both cytoplasmatic and plasma membrane molecules (e.g., tissue factor, proteases, phospholipids, and ADP) that can spuriously activate blood coagulation and platelets. The interference attributable to hyperbilirubinemia is mostly due to spectral overlap, whereas that of hypertriglyceridemia mainly reflects elements of light scatter and volume displacement as well as direct interference of lipid particles with hemostasis. In practical terms, spurious hemolysis reflects a more generalized process of endothelial and blood cell damage, so that test results on spuriously hemolyzed specimens should be systematically suppressed. The bias attributable to hyperbilirubinemia is less significant using modern coagulometers equipped with dedicated wavelengths (i.e., with readings at 650 nm or above), so that test results in samples with a bilirubin concentration up to 20 mg/dL can still be analytically reliable. The interference observed in lipemic samples is most evident with readings using wavelengths lower than 500 nm and can hence be prevented with readings at 650 nm or above, and/or using higher dilutions of the test sample, or can be abated in high hypertriglyceridemic specimens (i.e., > 1,000 mg/dL) using high speed microcentrifugation or lipid extraction with organic solvents such as fluorine-chlorinated hydrocarbon, or lipid-clearing agents such as LipoClear (StatSpin Inc., Norwood, MA) and n-hexane.

D-dimer assays in diagnosis and management of thrombotic and bleeding disorders.

Abstract: D-dimer is a global indicator of coagulation activation and fibrinolysis and, therefore, an indirect marker of thrombotic activity. The utility of D-dimer measurement has been evaluated in several clinical situations including the exclusion of venous thromboembolism (VTE), prediction of future risk of VTE, and the diagnosis and monitoring of disseminated intravascular coagulation (DIC). Assay standardization remains problematic and clinicians need to be aware of variability in D-dimer assay performance and the characteristics of their institution's test when making clinical decisions. This article will review the available evidence for the utilization of D-dimer antigen measurement in the management of thrombotic and bleeding disorders.

Exposure to high altitude: a risk factor for venous thromboembolism?

Abstract: There are several genetic and acquired risk factors for venous thromboembolism. Exposure to high altitude (HA), either during air travel, ascension of mountains, or while engaging in sports activities, has been observed to result in a hypercoagulable state, thus predisposing to thromboembolic events. Although several previous studies have suggested that conditions present at HAs contribute to establish a prothrombotic milieu, published reports are contradictory and the exact underlying mechanism remains poorly understood. Results from HA studies also show that environmental conditions at HA such as hypoxia, dehydration, hemoconcentration, low temperature, use of constrictive clothing as well as enforced stasis due to severe weather, would support the occurrence of thrombotic disorders. The three leading factors of Virchow triad, that is, venous stasis, hypercoagulability, and vessel-wall injury, all appear to be present at HA. In synthesis, the large list of environmental variables suggests that a single cause of HA-induced thromboembolic disorders (TED) may not exist, so that this peculiar phenomenon should be seen as a complex or multifactorial trait. Further investigation is needed to understand the risk of TED at HA as well as the possible underlying mechanisms.

Immune thrombocytopenia: pathophysiologic and clinical update.

Abstract: Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by both reduced platelet survival and suppression of megakaryocyte and platelet development. It can either be primary or secondary to other autoimmune disorders, infections, vaccines, lymphoproliferative disorders, and drugs. Antibodies reacting against platelet glycoproteins are typical of ITP; these antibodies can mediate destruction of platelets by the monocyte–macrophage system as well as suppress megakaryocyte proliferation and maturation. Abnormalities of cell-mediated immunity are known to contribute to the pathologic process. Like many other autoimmune diseases, ITP has a T helper cell type 1 bias and a reduced activity of T-regulatory cells. Cytotoxic T cells may directly lyse platelets and possibly suppress megakaryopoiesis. Recent studies suggest that mesenchymal stem cells are dysfunctional in ITP and may contribute to an aberrant amplification of the autoimmune response. Significant advances in the treatment of chronic ITP have been witnessed in the past decade, first with the introduction of rituximab and more recently with the thrombopoietin-receptor agonists. While splenectomy is still considered the gold standard in this setting, effective medical therapy is now available for patients in whom surgery is not an option.

Infection and inflammation as risk factors for thrombosis and atherosclerosis.

Abstract: Severe infection and inflammation almost invariably lead to hemostatic abnormalities, ranging from insignificant laboratory changes to gross activation of coagulation that may result in localized thrombotic complications or systemic intravascular fibrin deposition. Systemic inflammation results in activation of coagulation, due to tissue factor-mediated thrombin generation, downregulation of physiological anticoagulant mechanisms, and inhibition of fibrinolysis. Proinflammatory cytokines, immune cells, and the endothelium play a central role in the differential effects on the coagulation and fibrinolysis pathways. Vice-versa, activation of the coagulation system may importantly affect inflammatory responses by direct and indirect mechanisms. Similar mechanisms appear to play a role in the development of atherosclerosis and related arterial thrombosis. Apart from the general coagulation response to inflammation associated with severe infection, specific infections may cause distinct features, such as hemorrhagic fever or thrombotic microangiopathy.

Acquired Inhibitors of Coagulation Factors: Part I—Acquired Hemophilia A

Abstract: Acquired hemophilia A (AHA) is a rare, but often severe, bleeding disorder caused by autoantibodies against clotting factor VIII (FVIII). AHA occurs more frequently in the elderly and in association with several conditions, such as malignancies, autoimmune diseases, postpartum, or drug exposure; however, about half of the cases remain idiopathic. At variance with congenital hemophilia, where hemarthroses are the most common bleeding symptoms, hemorrhages in AHA involving soft tissues (muscle, skin) are more frequently reported. AHA is diagnosed in patients: with negative personal or family bleeding history; in which prolonged activated partial thromboplastin time is not corrected after mixing and incubating equal volumes of patient and normal plasma for ~2 hours at 37°C; FVIII levels are reduced; and a specific FVIII-inhibiting activity is detected. Prompt recognition and treatment of AHA are mandatory, as inadequate management and complications of the disease are associated with high mortality rates. Therapeutic approaches should aim to control acute bleeds, eradicate FVIII-autoantibody production, treat associated diseases, and when possible, eliminate them. Present knowledge about this often overlooked and challenging condition has significantly increased following establishment of recent national and international studies, as will also be reviewed in this article.

The Diagnosis and Management of Congenital Hemophilia

Abstract: Hemophilia is the most common, severe, inherited bleeding disorder recognized in humans and makes up the largest proportion of patients followed in most bleeding disorders' clinics. Persons with hemophilia have a life-long bleeding tendency that roughly correlates to their endogenous coagulant factor VIII (FVIII) or factor IX (FIX) level (FVIII:C and FIX:C). The hallmark of bleeding in severe hemophilia is musculoskeletal bleeds (soft tissue, muscle and joint bleeds) but persons with hemophilia are also prone to other bleeds including intracranial bleeds. The neonatal period is a particularly vulnerable period for persons with severe hemophilia. Diagnosing hemophilia is mainly based on measuring FVIII:C and FIX:C levels and on distinguishing hemophilia from other conditions that can cause a low FVIII:C or FIX:C level. Management involves preventing bleeds and rapidly treating those that occur. Bleed prevention in severe hemophilia can be accomplished by avoiding high-risk activities, taking appropriate precautions and early commencement of life-long prophylaxis. With proper management, persons with severe hemophilia can now live an essentially normal life. The development of an inhibitor does however complicate management. This review will summarize the very complex and multifaceted aspects of diagnosing and managing persons with hemophilia.

Update on the catastrophic antiphospholipid syndrome and the "CAPS Registry".

Abstract: Although less than 1% of patients with the antiphospholipid syndrome (APS) develop the catastrophic variant known as catastrophic antiphospholipid syndrome (CAPS), its potentially lethal outcome emphasizes its importance in clinical medicine today. However, the rarity of this variant makes it extraordinarily difficult to study in any systematic way. To collate all the published case reports as well as the newly diagnosed cases from all over the world, an international registry of patients with CAPS (“CAPS Registry”) was created in 2000 by the European Forum on Antiphospholipid Antibodies ( www.med.ub.es/MIMMUN/FORUM/CAPS.HTM ). Currently, this database documents the entire clinical, laboratory, and therapeutic data of more than 350 fully registered patients.

Ticlopidine-, clopidogrel-, and prasugrel-associated thrombotic thrombocytopenic purpura: a 20-year review from the Southern Network on Adverse Reactions (SONAR).

Abstract: Thienopyridine-derivatives (ticlopidine, clopidogrel, and prasugrel) are the primary antiplatelet agents. Thrombotic thrombocytopenic purpura (TTP) is a rare drug-associated syndrome, with the thienopyridines being the most common drugs implicated in this syndrome. We reviewed 20 years of information on clinical, epidemiologic, and laboratory findings for thienopyridine-associated TTP. Four, 11, and 11 cases of thienopyridine-associated TTP were reported in the first year of marketing of ticlopidine (1989), clopidogrel (1998), and prasugrel (2010), respectively. As of 2011, the FDA received reports of 97 ticlopidine-, 197 clopidogrel-, and 14 prasugrel-associated TTP cases. Severe deficiency of ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) was present in 80% and antibodies to 100% of these TTP patients on ticlopidine, 0% of the patients with clopidogrel-associated TTP (p < 0.05), and an unknown percentage of patients with prasugrel-associated TTP. TTP is associated with use of each of the three thienopyridines, although the mechanistic pathways may differ.

Fibrinogen as a hemostatic agent.

Abstract: Coagulation factor I (fibrinogen) plays an essential role in the hemostatic system by bridging activated platelets and being the key substrate for thrombin in establishing a consolidating fibrin network. Fibrinogen is synthesized in the liver and the plasma concentration is 1 to 5-4.0 g/L. During recent 10 years, fibrinogen has been recognized to play an important role in controlling hemorrhage. Dilutional coagulopathy induced by colloid plasma expanders is characterized by fibrinogen deficiency and dysfunctional fibrin polymerization. Trauma and use of extracorporeal circulation is also known to reduce levels of fibrinogen. A series of laboratory experiments and experimental animal studies have suggested fibrinogen as a potent hemostatic agent. These data are supported by retrospective surveys as well as a series of prospective proof of principal clinical trials. This article provides a description of the biochemistry and mechanisms of fibrinogen as well as the etiology for developing fibrinogen deficiency. Furthermore, it summarizes laboratory and experimental data on the role of fibrinogen in dilutional coagulopathy and addresses laboratory monitoring issues. Finally, it lists retrospective and prospective studies, which have been designed to assess the clinical efficacy and safety of hemostatic intervention with fibrinogen concentrate.

Pathogenesis of the antiphospholipid syndrome.

Abstract: The presence of pathogenic antiphospholipid antibodies (aPL) is the characterizing feature of the antiphospholipid syndrome (APS), mediating the recurrent pregnancy loss and thrombosis typical of the disease, through their action on various antigenic targets. Despite the available knowledge regarding the mechanisms by which aPL induce a procoagulant phenotype in the vasculature and abnormal cellular proliferation and differentiation in placental tissues to cause the typical clinical features, these processes still remain incompletely understood. It is also known that inflammation serves as a necessary link between the observed procoagulant phenotype and actual thrombus development, and is an important mediator of the placental injury in APS patients. Even less well understood are the processes underlying the ontogeny of these pathogenic antibodies. This review seeks to highlight what is known about the mechanisms that contribute to the origin of pathogenic aPL and to the action of these antibodies on target antigens that produce the pathological features of APS. We will also examine the feasibility of classifying patients in clinical phenotypes related to underlying pathophysiological mechanisms, and how this could impact the management of patients with novel "targeted" therapeutic strategies.

Vitamin D, thrombosis, and hemostasis: more than skin deep.

Abstract: Vitamin D(3) deficiency is a highly prevalent condition worldwide. Clinically, vitamin D(3) has a key role in calcium homeostasis and bone mineralization and has recently been implicated in the pathogenesis and/or progression of several acute and chronic illnesses, including cardiovascular disease (CVD). Accumulating evidence from observational, prospective studies suggests that low levels of serum 25-hydroxyvitamin D(3) are independently associated with an increased risk of CVD events and death. The molecular mechanisms of this association remain incompletely understood. A variety of biologically plausible mechanisms may mediate a cardiovascular role for the active metabolite of vitamin D(3). 1-α,25-dihydroxyvitamin D(3) regulates the renin-angiotensin system, suppresses proliferation of vascular cell smooth muscle, improves insulin resistance and endothelial cell-dependent vasodilation, inhibits myocardial cell hypertrophy, exerts anticoagulant and antifibrotic activity, and modulates macrophage activity and cytokine generation. Overall, the high prevalence of vitamin D(3) deficiency and the plausible biological mechanisms linking this to CVD risk suggest that the treatment of vitamin D(3) deficiency to prevent CVD is a promising field to explore. Large placebo-controlled randomized clinical trials are urgently needed to determine whether vitamin D supplementation could have any potential benefit in reducing future CVD events and mortality risk.

Prophylaxis in children with hemophilia: evidence-based achievements, old and new challenges.

Abstract: Recurrent joint bleeding leading to progressive musculoskeletal damage (hemophilic arthropathy), in spite of on-demand replacement with deficient factor concentrates, is the clinical hallmark of severe hemophilia A and B (i.e., the congenital deficiencies of coagulation factors VIII and IX with circulating levels

Thrombin and cancer: From molecular basis to therapeutic implications

Abstract: The relationship between cancer and thrombosis has been recognized for nearly 150 years. Although the mechanisms underlying this association are not completely understood, there are increasing evidences suggesting a pivotal role of thrombin in cancer biology. This review will focus on the most important pathways by which thrombin may affect cancer growth and dissemination. In addition, the potential role of congenital (i.e., hemophilia) and pharmaceutical (i.e., antithrombotic agents) anticoagulation in cancer incidence and survival will be investigated through the analysis of the published experimental and clinical studies.

Thrombotic microangiopathies, thrombotic thrombocytopenic purpura, and ADAMTS-13.

Abstract: Thrombotic microangiopathy (TMA) is a term used to describe a group of disorders characterized by hemolytic anemia (with prominent red blood cell fragmentation), thrombocytopenia, and thrombosis in the microvasculature It may be used when describing patients with thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome, atypical hemolytic uremic syndrome, as well as a myriad of other disorders in which the TMA may be secondary to another disease or disorder While limited information exists as to the exact cause of microthrombosis in many TMA, recent advances have been made in the understanding of TTP and its pathophysiology This progress can be attributed to discovery of the von Willebrand factor cleaving protease ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13), whose absence in TTP has given the disorder a distinct molecular identity The discovery of this metalloprotease has prompted a significant amount of research relating to its role in TTP as well as its general function in hemostasis The exact mechanisms by which this metalloprotease achieves its role are slowly being understood and these now provide other avenues by which TMA may occur

Determination of dabigatran in human plasma samples.

Abstract: The oral direct thrombin inhibitor dabigatran effectively prevents arterial and venous thromboembolism using fixed doses without the need for adjustment according to laboratory results. Dabigatran is eliminated from the circulation by ∼80% through the kidneys. However, the in vitro anticoagulant effect of dabigatran may be necessary to determine in special patient populations such as in the elderly, for renal impairment, before operations, bleeding or thrombotic episodes, and to monitor self-compliance. Several clotting and thrombin-specific chromogenic substrate assays are available to analyze the biological activity of dabigatran. All of them are prolonged in the presence of dabigatran. This article reports the effects of dabigatran on clinical routine assays and the potential usefulness for determination in special risk groups of patients when overdose or lack of compliance are suspected.

Determination of rivaroxaban in human plasma samples.

Abstract: Rivaroxaban is one of the novel oral direct factor Xa inhibitors, which is effective in preventing thromboembolic complications at fixed doses (i.e., once daily), without the need for dose adjustment according to laboratory monitoring. Nearly 60% of rivaroxaban is cleared from circulation by glomerular filtration, 30% of which is excreted as active drug. Therefore, as renal elimination plays a pivotal role in the metabolism of this drug, impairment of renal function may be important during anticoagulation with rivaroxaban over long periods of time. The assessment of the anticoagulant effect/concentration of rivaroxaban may thus be useful in special patient populations such as in the elderly and eldest, during acute diseases with concurrent dehydration, before surgery, during bleeding or thrombotic episodes, or to verify adherence to therapy. Rivaroxaban prolongs prothrombin time in a dose-dependent, linear fashion. Activated partial thromboplastin time (APTT) is also prolonged, but in an exponential manner. Substantial differences in test results might be generated by different thromboplastin and APTT reagents. One-step prothrombin-induced clotting time assay is sensitive to low concentrations of rivaroxaban. Chromogenic substrate assays specific for factor Xa are also sensitive to rivaroxaban. Several initiatives are currently ongoing to standardize the various methods to determine rivaroxaban in human plasma samples, some of which will be summarized in this article along with the dose-dependent effects of rivaroxaban on relevant coagulation parameters. Therefore, although rivaroxaban prolongs all coagulation assays used to assess the anticoagulant effects of most anticoagulants, the most specific assay cannot be identified at present. Moreover, clinical trials are needed to determine the relationship of assay results with bleeding or thrombotic complications.

Effect of genetic variants, especially CYP2C9 and VKORC1, on the pharmacology of warfarin.

Abstract: The genes encoding the cytochrome P450 2C9 enzyme (CYP2C9) and vitamin K-epoxide reductase complex unit 1 (VKORC1) are major determinants of anticoagulant response to warfarin. Together with patient demographics and clinical information, they account for approximately one-half of the warfarin dose variance in individuals of European descent. Recent prospective and randomized controlled trial data support pharmacogenetic guidance with their use in warfarin dose initiation and titration. Benefits from pharmacogenetics-guided warfarin dosing have been reported to extend beyond the period of initial dosing, with supportive data indicating benefits to at least 3 months. The genetic effects of VKORC1 and CYP2C9 in African and Asian populations are concordant with those in individuals of European ancestry; however, frequency distribution of allelic variants can vary considerably between major populations. Future randomized controlled trials in multiethnic settings using population-specific dosing algorithms will allow us to further ascertain the generalizability and cost-effectiveness of pharmacogenetics-guided warfarin therapy. Additional genome-wide association studies may help us to improve and refine dosing algorithms and potentially identify novel biological pathways.

What have we learned about antiphospholipid syndrome from patients and antiphospholipid carrier cohorts

Abstract: Venous or arterial thrombosis or pregnancy morbidity in the presence of circulating antiphospholipid antibodies (aPL) define the antiphospholipid syndrome (APS). In terms of accepted APS criteria, aPL are detected by one coagulation test (lupus anticoagulant; LAC) and two immunoassays (anticardiolipin antibodies and anti-β2-glycoptrotein I antibodies). In patients with APS, a single positive test carries a much lower risk of thrombosis recurrence or new pregnancy loss than does multiple (or triple) positivity. The same holds true for aPL carriers, namely subjects with laboratory tests but without clinical criteria for APS. Thus, very different risk categories exist among patients with APS as well as in carriers of aPL. Triple positivity apparently identifies the pathogenic autoantibody (antidomain I-II of β2-glycoptrotein I); it is in this category of patients that trials on new therapeutic strategies should focus.

Cardiovascular risk in rheumatic patients: the link between inflammation and atherothrombosis.

Abstract: In addition to a high prevalence of the metabolic syndrome and a significant under-diagnosis of vascular risk factors (VRFs), the effect of chronic inflammation also represents the cornerstone of the raised cardiovascular (CV) risk in patients with rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis. Moreover, the finding that among current anti-inflammatory treatments, the use of tumor necrosis factor (TNF)-α blockers is associated with optimal rheumatologic and CV outcomes further supports the impact of inflammation on the CV risk. However, up-to-date treatment guidelines suggest that TNF-α blockers should be used only after the failure of traditional disease-modifying antirheumatic drugs (DMARDs). Early predictors of the therapeutic efficacy of traditional DMARDs are needed to identify candidates for TNF-α blocker treatment. Furthermore, whether the CV risk should be taken into account while choosing antirheumatic treatments is an emerging issue to be addressed. Common educational programs for specialists and general practitioners and appropriate CV prevention programs, taking into consideration traditional VRFs as well as the inflammatory status, should be planned to prevent ischemic events and to achieve optimal inflammation control in rheumatic patients.

Novel and emerging therapies: thrombus-targeted fibrinolysis.

Abstract: Thrombolytic therapy by infusion of analogs of tissue plasminogen activator (tPA), other recombinant-based plasminogen activators (e.g., alteplase, reteplase, and tenecteplase), streptokinase, and urokinase (uPA) aims to clear blood clots and restore blood flow in occluded blood vessels. Thrombolytic therapy is thereby frequently used in patients with myocardial infarction, stroke, peripheral arterial disease, and massive pulmonary embolism. The leading drawbacks of thrombolysis and associated therapy are represented by a significant burden of inefficacy combined with a high risk of bleeding complications. Recent advances in understanding the complex pathophysiology of vascular occlusions, combined with important technological innovations, are notably improving the therapeutic armamentarium against thrombotic and occlusive disorders. Most of the past and ongoing research in this area have entailed thrombus-targeted fibrinolytic therapy with either tissue- and fibrin-specific immunoconjugates, fibrinolytic-bearing erythrocytes, or fibrinolytic-bearing nanoparticles. The greatest advantages of thrombus-targeted fibrinolysis, especially with biocompatible nanoparticles, are represented by their preferential localization within developing clots, effectual thrombolysis and enhanced safety due to substantial reduction of the dosage of fibrinolytic agents, and reduced onstream adverse effects. These positive biological features, coupled with minimal extravasation and favorable clearance from the circulation, appear advantageous for obtaining more efficacious and durable thrombolytic effects while concomitantly lowering or even eliminating the risk of systemic bleeding complications that typically accompany the injection of free or soluble plasminogen activators. Although an ideal technique has not been definitely established so far, tPA-bearing nanoparticles exhibiting affinity for clot-specific cells and biomolecules coupled with low-frequency ultrasound seem to bear the greatest advantages for prevention and therapy of acute thrombosis, with the possibility to specifically guide and concentrate the thrombolytic agent at the site of pathologic thrombi and clear preexisting clots by a series of mechanisms combining mechanical stress and increased penetration and effectiveness of the drugs employed.

Bleeding complications in patients with hematologic malignancies.

Abstract: Abnormalities of hemostasis are frequently encountered in patients with hematologic malignancies leading to both hemorrhagic and thrombotic adverse events. The prompt recognition and management of such complications, which have a negative impact on the morbidity and mortality of these patients, represents a major challenge for hematologists. This review describes the most important changes of hemostasis associated with hemorrhage in hematologic malignancies with particular emphasis on their contributory etiologic factors, complex pathogenic mechanisms, clinical manifestations, and therapeutic strategies. In particular, platelet and acquired coagulation abnormalities, bleeding complications in acute leukemia, and hematopoietic stem cell transplantation are discussed.