Type 1 VWD classification revisited: novel insights from combined analysis of the LoVIC and WiN studies

ABSTRACT

There is significant ongoing debate regarding type 1 von Willebrand disease (VWD) defintion. Previous guidelines recommended patients with von Willebrand factor (VWF) levels <30 IU/dL be diagnosed type 1 VWD, whereas patients with significant bleeding and VWF levels from 30 to 50 IU/dL be diagnosed with low VWF. To elucidate the relationship between type 1 VWD and low VWF in the context of age-induced increases in VWF levels, we combined data sets from 2 national cohort studies: 162 patients with low VWF from the Low VWF in Ireland Cohort (LoVIC) and 403 patients with type 1 VWD from the Willebrand in The Netherlands (WiN) studies. In 47% of type 1 VWD participants, VWF levels remained <30 IU/dL despite increasing age. Conversely, VWF levels increased to the low VWF range (30-50 IU/dL) in 30% and normalized (>50 IU/dL) in 23% of type 1 VWD cases. Crucially, absolute VWF antigen (VWF:Ag) levels and increase of VWF:Ag per year overlapped between low VWF and normalized type 1 VWD participants. Moreover, multiple regression analysis demonstrated that VWF:Ag levels in low VWF and normalized type 1 VWD patients would not have been different had they been diagnosed at the same age (β = 0.00; 95% confidence interval, -0.03 to 0.04). Consistently, no difference was found in the prevalence of VWF sequence variants; factor VIII activity/VWF:Ag or VWF propeptide/VWF:Ag ratios; or desmopressin responses between low VWF and normalized type 1 VWD patients. In conclusion, our findings demonstrate that low VWF does not constitute a discrete clinical or pathological entity. Rather, it is part of an age-dependent type 1 VWD evolving phenotype. Collectively, these data have important implications for future VWD classification criteria.

Standardization of definition and management for bleeding disorder of unknown cause: communication from the SSC of the ISTH

In many patients referred with significant bleeding phenotype, laboratory testing fails to define any hemostatic abnormalities. Clinical practice with respect to diagnosis and management of this patient cohort poses significant clinical challenges. We recommend that bleeding history in these patients should be objectively assessed using the International Society on Thrombosis and Haemostasis (ISTH) bleeding assessment tool. Patients with increased bleeding assessment tool scores should progress to hemostasis laboratory testing. To diagnose bleeding disorder of unknown cause (BDUC), normal complete blood count, prothrombin time, activated partial thromboplastin time, thrombin time, von Willebrand factor antigen, von Willebrand factor function, coagulation factors VIII, IX, and XI, and platelet light transmission aggregometry should be the minimum laboratory assessment. In some laboratories, additional specialized hemostasis testing may be performed to identify other rare causes of bleeding. We recommend that patients with a significant bleeding phenotype but normal laboratory investigations should be registered with a diagnosis of BDUC in preference to other terminology. Global hemostatic tests and markers of fibrinolysis demonstrate variable abnormalities, and their clinical significance remains uncertain. Targeted genomic sequencing examining candidate hemostatic genes has a low diagnostic yield. Underlying BDUC should be considered in patients with heavy menstrual bleeding since delays in diagnosis often extend to many years and negatively impact quality of life. Treatment options for BDUC patients include tranexamic acid, desmopressin, and platelet transfusions.

VWF-ADAMTS13 axis dysfunction in children with sickle cell disease treated with hydroxycarbamide vs blood transfusion

Previous studies have reported elevated von Willebrand factor (VWF) levels in patients with sickle cell disease (SCD) and demonstrated a key role for the VWF-ADAMTS13 axis in the pathobiology of SCD vaso-occlusion. Although blood transfusion is the gold standard for stroke prevention in SCD, the biological mechanisms underpinning its improved efficacy compared with hydroxycarbamide are not fully understood. We hypothesized that the improved efficacy of blood transfusion might relate to differences in VWF-ADAMTS13 axis dysfunction. In total, 180 children with a confirmed diagnosis of SCD (hemoglobin SS) on hydroxycarbamide (n = 96) or blood transfusion (n = 84) were included. Despite disease-modifying treatment, plasma VWF and VWF propeptide were elevated in a significant proportion of children with SCD (33% and 47%, respectively). Crucially, all VWF parameters were significantly higher in the hydroxycarbamide compared with the blood transfusion cohort (P < .05). Additionally, increased levels of other Weibel-Palade body-stored proteins, including factor VIII (FVIII), angiopoietin-2, and osteoprotegerin were observed, indicated ongoing endothelial cell activation. Children treated with hydroxycarbamide also had higher FVIII activity and enhanced thrombin generation compared with those in the blood transfusion cohort (P < .001). Finally, hemolysis markers strongly correlated with VWF levels (P < .001) and were significantly reduced in the blood transfusion cohort (P < .001). Cumulatively, to our knowledge, our findings demonstrate for the first time that despite treatment, ongoing dysfunction of the VWF-ADAMTS13 axis is present in a significant subgroup of pediatric patients with SCD, especially those treated with hydroxycarbamide.

Direct oral anticoagulants or vitamin K antagonists in emergencies: comparison of management in an observational study

Background

Restoring hemostasis in patients on oral anticoagulants presenting with major hemorrhage (MH) or before surgical intervention has changed, with the replacement of vitamin K antagonist (VKA) with direct oral anticoagulants (DOACs).

Objectives

To observe the difference in urgent hemostatic management between patients on VKA and those on DOACs.

Methods

A multicenter observational study evaluated the variation in laboratory testing, hemostatic management, mortality, and hospital length of stay (LOS) in patients on VKA or DOACs presenting with MH or urgent hemostatic restoration.

Results

Of the 1194 patients analyzed, 783 had MH (61% VKA) and 411 required urgent hemostatic restoration before surgery (56% VKA). Compared to the international normalized ratio (97.6%), plasma DOAC levels were measured less frequently (<45%), and the time taken from admission for the coagulation sample to reach the laboratory varied widely (median, 52.3 minutes; IQR, 24.8-206.7). No significant plasma DOAC level (<50 ng/mL) was found in up to 19% of patients. There was a poor relationship between plasma DOAC level and the usage of a hemostatic agent. When compared with patients receiving VKA (96.5%) or dabigatran (93.7%), fewer patients prescribed a factor Xa inhibitor (75.5%) received a prohemostatic reversal agent. The overall 30-day mortality for MH (mean: 17.8%) and length of stay (LOS) (median: 8.7 days) was similar between VKA and DOAC patients.

Conclusion

In DOAC patients, when compared to those receiving VKA, plasma DOAC levels were measured less frequently than the international normalized ratio and had a poor relationship with administering a hemostatic reversal agent. In addition, following MH, mortality and LOS were similar between VKA and DOAC patients.

Endothelial cell activation, Weibel-Palade body secretion, and enhanced angiogenesis in severe COVID-19

Background

Severe COVID-19 is associated with marked endothelial cell (EC) activation that plays a key role in immunothrombosis and pulmonary microvascular occlusion. However, the biological mechanisms through which SARS-CoV-2 causes EC activation and damage remain poorly defined.

Objectives

We investigated EC activation in patients with acute COVID-19, and specifically focused on how proteins stored within Weibel-Palade bodies may impact key aspects of disease pathogenesis.

Methods

Thirty-nine patients with confirmed COVID-19 were recruited. Weibel-Palade body biomarkers (von Willebrand factor [VWF], angiopoietin-2 [Angpt-2], and osteoprotegerin) and soluble thrombomodulin (sTM) levels were determined. In addition, EC activation and angiogenesis were assessed in the presence or absence of COVID-19 plasma incubation.

Results

Markedly elevated plasma VWF antigen, Angpt-2, osteoprotegerin, and sTM levels were observed in patients with acute COVID-19. The increased levels of both sTM and Weibel-Palade body components (VWF, osteoprotegerin, and Angpt-2) correlated with COVID-19 severity. Incubation of COVID-19 plasma with ECs triggered enhanced VWF secretion and increased Angpt-2 expression, as well as significantly enhanced in vitro EC tube formation and angiogenesis.

Conclusion

We propose that acute SARS-CoV-2 infection leads to a complex and multifactorial EC activation, progressive loss of thrombomodulin, and increased Angpt-2 expression, which collectively serve to promote a local proangiogenic state.

Low von Willebrand Disease: A Bleeding Disorder of Unknown Cause?

von Willebrand disease (VWD) represents the most common inherited bleeding disorder. The majority of VWD cases are characterized by partial quantitative reductions in plasma von Willebrand factor (VWF) levels. Management of patients with mild to moderate VWF reductions in the range of 30 to 50 IU/dL poses a common clinical challenge. Some of these low VWF patients present with significant bleeding problems. In particular, heavy menstrual bleeding and postpartum hemorrhage can cause significant morbidity. Conversely, however, many individuals with mild plasma VWF:Ag reductions do not have any bleeding sequelae. In contrast to type 1 VWD, most patients with low VWF do not have detectable pathogenic VWF sequence variants, and bleeding phenotype correlates poorly with residual VWF levels. These observations suggest that low VWF is a complex disorder caused by variants in other genes beyond VWF. With respect to low VWF pathobiology, recent studies have shown that reduced VWF biosynthesis within endothelial cells likely plays a key role. However, pathological enhanced VWF clearance from plasma has also been described in approximately 20% of low VWF cases. For low VWF patients who require hemostatic treatment prior to elective procedures, tranexamic acid and desmopressin have both been shown to be efficacious. In this article, we review the current state of the art regarding low VWF. In addition, we consider how low VWF represents an entity that appears to fall between type 1 VWD on the one hand and bleeding disorders of unknown cause on the other.

Adenosine 2A Receptor Activation Amplifies Ibrutinib Antiplatelet Effect; Implications in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia patients have an increased bleeding risk with the introduction of Bruton tyrosine kinase (BTK) inhibitors. BTK is a signaling effector downstream of the platelet GPVI receptor. Innate platelet dysfunction in CLL patients and the contribution of the leukemia microenvironment to the anti-platelet effect of BTK inhibitors are still not well defined. Herein, we investigated platelet function in stable, untreated CLL patients in comparison to age-matched healthy subjects as control. Secondly, we proposed a novel mechanism of platelet dysfunction via the adenosinergic pathway during BTK inhibitor therapy. Our data indicate that the nucleotidase that produces adenosine, CD73, was expressed on one-third of B-cells in CLL patients. Inhibition of CD73 improved platelet response to ADP in the blood of CLL patients ex vivo. Using healthy platelets, we show that adenosine 2A (A2A) receptor activation amplifies the anti-platelet effect of ibrutinib (10 nM). Ibrutinib plus an A2A agonist-but not ibrutinib as a single agent-significantly inhibited collagen (10 µg/mL)-induced platelet aggregation. Mechanistically, A2A activation attenuated collagen-mediated inhibition of p-VASP and synergized with ibrutinib to inhibit the phosphorylation of AKT, ERK and SYK kinases. This manuscript highlights the potential role of adenosine generated by the microenvironment in ibrutinib-associated bleeding in CLL patients.

Sustained VWF-ADAMTS-13 axis imbalance and endotheliopathy in long COVID syndrome is related to immune dysfunction

BACKGROUND

Prolonged recovery is common after acute SARS-CoV-2 infection; however, the pathophysiological mechanisms underpinning Long COVID syndrome remain unknown. VWF/ADAMTS-13 imbalance, dysregulated angiogenesis, and immunothrombosis are hallmarks of acute COVID-19. We hypothesized that VWF/ADAMTS-13 imbalance persists in convalescence together with endothelial cell (EC) activation and angiogenic disturbance. Additionally, we postulate that ongoing immune cell dysfunction may be linked to sustained EC and coagulation activation.

PATIENTS AND METHODS

Fifty patients were reviewed at a minimum of 6 weeks following acute COVID-19. ADAMTS-13, Weibel Palade Body (WPB) proteins, and angiogenesis-related proteins were assessed and clinical evaluation and immunophenotyping performed. Comparisons were made with healthy controls (n = 20) and acute COVID-19 patients (n = 36).

RESULTS

ADAMTS-13 levels were reduced (p = 0.009) and the VWF-ADAMTS-13 ratio was increased in convalescence (p = 0.0004). Levels of platelet factor 4 (PF4), a putative protector of VWF, were also elevated (p = 0.0001). A non-significant increase in WPB proteins Angiopoietin-2 (Ang-2) and Osteoprotegerin (OPG) was observed in convalescent patients and WPB markers correlated with EC parameters. Enhanced expression of 21 angiogenesis-related proteins was observed in convalescent COVID-19. Finally, immunophenotyping revealed significantly elevated intermediate monocytes and activated CD4+ and CD8+ T cells in convalescence, which correlated with thrombin generation and endotheliopathy markers, respectively.

CONCLUSION

Our data provide insights into sustained EC activation, dysregulated angiogenesis, and VWF/ADAMTS-13 axis imbalance in convalescent COVID-19. In keeping with the pivotal role of immunothrombosis in acute COVID-19, our findings support the hypothesis that abnormal T cell and monocyte populations may be important in the context of persistent EC activation and hemostatic dysfunction during convalescence.

Subcutaneous daratumumab (DARA SC) versus active monitoring in patients (pts) with high-risk smoldering multiple myeloma (SMM): Randomized, open-label, phase 3 AQUILA study

TPS8075

Background: Standard of care for SMM includes active monitoring until progression to multiple myeloma (MM); however, recent evidence suggests pts with high-risk features may benefit from early treatment. DARA is a human IgGκ monoclonal antibody targeting CD38 that is approved as monotherapy for relapsed/refractory MM (RRMM) or in combination with standard of care for RRMM or newly diagnosed MM. Results from the phase 3 COLUMBA study showed that DARA SC demonstrated similar efficacy to intravenous (IV) DARA but with a lower rate of infusion-related reactions and shorter administration time. Based on the promising single-agent activity observed with IV DARA in intermediate- or high-risk SMM pts during the phase 2 CENTAURUS study, we hypothesized that DARA SC may delay progression to MM versus active monitoring in pts with high-risk SMM. Methods: AQUILA is an ongoing, randomized, open-label, multicenter phase 3 study of DARA SC versus active monitoring in pts with high-risk SMM. DARA SC (DARA 1,800 mg + recombinant human hyaluronidase PH20 [rHuPH20; 2,000 U/mL; Halozyme]) is administered by manual injection over approximately 5 minutes at alternating locations on the abdomen weekly in Cycles 1 and 2, every 2 weeks in Cycles 3-6, and every 4 weeks thereafter until 39 cycles (28 days/cycle), up to 36 months, or until disease progression. Eligibility criteria include confirmed diagnosis of SMM for ≤5 years, factors indicating high risk of progression to MM (clonal bone marrow plasma cells [BMPCs] ≥10% and ≥1 of the following: serum M protein ≥30 g/L, IgA SMM, immunoparesis with reduction of 2 uninvolved Ig isotypes, serum involved:uninvolved free light chain ratio ≥8 to < 100, or clonal BMPCs > 50% to < 60% with measurable disease), and ECOG performance status ≤1. The primary endpoint is progression-free survival (PFS), assessed by an independent review committee, with disease progression defined according to International Myeloma Working Group diagnostic criteria for MM. Secondary endpoints include time to biochemical or diagnostic (SLiM-CRAB) progression, overall response rate, complete response rate, duration of response, time to response, time to first-line treatment for MM, PFS on first-line treatment for MM (PFS2), overall survival, and incidence of MM with adverse prognostic features. The study completed enrollment on May 6, 2019; 390 pts have been randomly assigned to DARA SC or active monitoring. The primary efficacy analysis will be performed after approximately 165 PFS events have been observed. Clinical trial information: NCT03301220.

Examining international practices in the management of pregnant women with von Willebrand disease

BACKGROUND

The management of pregnant women with von Willebrand disease (VWD) is complex as physiological pregnancy-induced increases in plasma von Willebrand factor (VWF) may be blunted or absent. Women with VWD experience a heightened risk of postpartum hemorrhage (PPH) and special consideration must be given regarding neuraxial anesthesia (NA) and the need for prophylaxis at time of delivery. These challenges are compounded by a lack of robust evidence to guide clinical decision-making.

OBJECTIVES AND METHODS

To determine the current international clinical practices in the management of pregnancy for women with VWD, the International Society on Thrombosis and Haemostasis (ISTH) conducted an international survey of health-care providers (HCP).

RESULTS

One hundred thirty-two respondents from 39 countries were included in the final analysis. Variations in clinical practice were identified in antenatal (monitoring of plasma VWF and ferritin levels), peripartum (optimal plasma VWF target at delivery) and postpartum management (definitions used for PPH and postpartum monitoring). A key area of divergence was suitability for NA for women with type 2 and type 3 VWD, with many respondents advising against the use of NA even with VWF supplementation (29% type 2 VWD, 37% type 3 VWD) but others advising use once plasma VWF activity was >50 IU/dL (57% type 2 VWD; 50% type 3 VWD).

CONCLUSIONS

This survey highlighted areas of uncertainty surrounding common management issues for pregnant women with VWD. These data underscore the need for international collaborative research efforts focused on peripartum management to improve care for pregnant women with VWD.

Fc Binding by FcγRIIa Is Essential for Cellular Activation by the Anti-FcγRIIa mAbs 8.26 and 8.2

FcγR activity underpins the role of antibodies in both protective immunity and auto-immunity and importantly, the therapeutic activity of many monoclonal antibody therapies. Some monoclonal anti-FcγR antibodies activate their receptors, but the properties required for cell activation are not well defined. Here we examined activation of the most widely expressed human FcγR; FcγRIIa, by two non-blocking, mAbs, 8.26 and 8.2. Crosslinking of FcγRIIa by the mAb F(ab’)₂ regions alone was insufficient for activation, indicating activation also required receptor engagement by the Fc region. Similarly, when mutant receptors were inactivated in the Fc binding site, so that intact mAb was only able to engage receptors via its two Fab regions, again activation did not occur. Mutation of FcγRIIa in the epitope recognized by the agonist mAbs, completely abrogated the activity of mAb 8.26, but mAb 8.2 activity was only partially inhibited indicating differences in receptor recognition by these mAbs. FcγRIIa inactivated in the Fc binding site was next co-expressed with the FcγRIIa mutated in the epitope recognized by the Fab so that each mAb 8.26 molecule can contribute only three interactions, each with separate receptors, one via the Fc and two via the Fab regions. When the Fab and Fc binding were thus segregated onto different receptor molecules receptor activation by intact mAb did not occur. Thus, receptor activation requires mAb 8.26 Fab and Fc interaction simultaneously with the same receptor molecules. Establishing the molecular nature of FcγR engagement required for cell activation may inform the optimal design of therapeutic mAbs.

Persistent endotheliopathy in the pathogenesis of long COVID syndrome

BACKGROUND

Persistent symptoms including breathlessness, fatigue, and decreased exercise tolerance have been reported in patients after acute SARS-CoV-2 infection. The biological mechanisms underlying this "long COVID" syndrome remain unknown. However, autopsy studies have highlighted the key roles played by pulmonary endotheliopathy and microvascular immunothrombosis in acute COVID-19.

OBJECTIVES

To assess whether endothelial cell activation may be sustained in convalescent COVID-19 patients and contribute to long COVID pathogenesis.

PATIENTS AND METHODS

Fifty patients were reviewed at a median of 68 days following SARS-CoV-2 infection. In addition to clinical workup, acute phase markers, endothelial cell (EC) activation and NETosis parameters and thrombin generation were assessed.

RESULTS

Thrombin generation assays revealed significantly shorter lag times (p < .0001, 95% CI -2.57 to -1.02 min), increased endogenous thrombin potential (p = .04, 95% CI 15-416 nM/min), and peak thrombin (p < .0001, 95% CI 39-93 nM) in convalescent COVID-19 patients. These prothrombotic changes were independent of ongoing acute phase response or active NETosis. Importantly, EC biomarkers including von Willebrand factor antigen (VWF:Ag), VWF propeptide (VWFpp), and factor VIII were significantly elevated in convalescent COVID-19 compared with controls (p = .004, 95% CI 0.09-0.57 IU/ml; p = .009, 95% CI 0.06-0.5 IU/ml; p = .04, 95% CI 0.03-0.44 IU/ml, respectively). In addition, plasma soluble thrombomodulin levels were significantly elevated in convalescent COVID-19 (p = .02, 95% CI 0.01-2.7 ng/ml). Sustained endotheliopathy was more frequent in older, comorbid patients, and those requiring hospitalization. Finally, both plasma VWF:Ag and VWFpp levels correlated inversely with 6-min walk tests.

CONCLUSIONS

Collectively, our findings demonstrate that sustained endotheliopathy is common in convalescent COVID-19 and raise the intriguing possibility that this may contribute to long COVID pathogenesis.

ADAMTS13 regulation of VWF multimer distribution in severe COVID-19

BACKGROUND

Consistent with fulminant endothelial cell activation, elevated plasma von Willebrand factor (VWF) antigen levels have been reported in patients with COVID-19. The multimeric size and function of VWF are normally regulated through A Disintegrin And Metalloprotease with ThrombSpondin Motif type 1 motif, member 13 (ADAMTS-13)--mediated proteolysis.

OBJECTIVES

This study investigated the hypothesis that ADAMTS-13 regulation of VWF multimer distribution may be impaired in severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection contributing to the observed microvascular thrombosis.

PATIENTS AND METHODS

Patients with COVID-19 (n = 23) were recruited from the Beaumont Hospital Intensive Care Unit (ICU) in Dublin. Plasma VWF antigen, multimer distribution, ADAMTS-13 activity, and known inhibitors thereof were assessed.

RESULTS

We observed markedly increased VWF collagen-binding activity in patients with severe COVID-19 compared to controls (median 509.1 versus 94.3 IU/dl). Conversely, plasma ADAMTS-13 activity was significantly reduced (median 68.2 IU/dl). In keeping with an increase in VWF:ADAMTS-13 ratio, abnormalities in VWF multimer distribution were common in patients with COVID-19, with reductions in high molecular weight VWF multimers. Terminal sialylation regulates VWF susceptibility to proteolysis by ADAMTS-13 and other proteases. We observed that both N- and O-linked sialylation were altered in severe COVID-19. Furthermore, plasma levels of the ADAMTS-13 inhibitors interleukin-6, thrombospondin-1, and platelet factor 4 were significantly elevated.

CONCLUSIONS

These findings support the hypothesis that SARS-CoV-2 is associated with profound quantitative and qualitative increases in plasma VWF levels, and a multifactorial down-regulation in ADAMTS-13 function. Further studies will be required to determine whether therapeutic interventions to correct ADAMTS-13-VWF multimer dysfunction may be useful in COVID-microvascular thrombosis and angiopathy.

Estradiol-Responsive miR-365a-3p Interacts with Tissue Factor 3'UTR to Modulate Tissue Factor-Initiated Thrombin Generation

BACKGROUND

 High estradiol (E₂) levels are linked to an increased risk of venous thromboembolism; however, the underlying molecular mechanism(s) remain poorly understood. We previously identified an E₂-responsive microRNA (miR), miR-494-3p, that downregulates protein S expression, and posited additional coagulation factors, such as tissue factor, may be regulated in a similar manner via miRs.

OBJECTIVES

 To evaluate the coagulation capacity of cohorts with high physiological E₂, and to further characterize novel E₂-responsive miR and miR regulation on tissue factor in E₂-related hypercoagulability.

METHODS

 Ceveron Alpha thrombin generation assay (TGA) was used to assess plasma coagulation profile of three cohorts. The effect of physiological levels of E₂, 10 nM, on miR expression in HuH-7 cells was compared using NanoString nCounter and validated with independent assays. The effect of tissue factor-interacting miR was confirmed by dual-luciferase reporter assays, immunoblotting, flow cytometry, biochemistry assays, and TGA.

RESULTS

 Plasma samples from pregnant women and women on the contraceptive pill were confirmed to be hypercoagulable (compared with sex-matched controls). At equivalent and high physiological levels of E₂, miR-365a-3p displayed concordant E₂ downregulation in two independent miR quantification platforms, and tissue factor protein was upregulated by E₂ treatment. Direct interaction between miR-365a-3p and F3-3'UTR was confirmed and overexpression of miR-365a-3p led to a decrease of (1) tissue factor mRNA transcripts, (2) protein levels, (3) activity, and (4) tissue factor-initiated thrombin generation.

CONCLUSION

 miR-365a-3p is a novel tissue factor regulator. High E₂ concentrations induce a hypercoagulable state via a miR network specific for coagulation factors.

Prognostic utility of ADAMTS13 activity for the atypical hemolytic uremic syndrome (aHUS) and comparison of complement serology between aHUS and thrombotic thrombocytopenic purpura

Background

Atypical hemolytic uremic syndrome (aHUS) involves dysregulation of the complement system, but whether this also occurs in thrombotic thrombocytopenic purpura (TTP) remains unclear. Although these conditions are difficult to differentiate clinically, TTP can be distinguished by low (<10%) ADAMTS13 activity. The aim was to identify the differences in complement activation products between TTP and aHUS and investigate ADAMTS13 activity as a prognostic factor in aHUS.

Methods

We analyzed patients with thrombotic microangiopathy diagnosed as TTP (N=48) or aHUS (N=50), selected from a Korean registry (N=551). Complement activation products in the plasma samples collected from the patients prior to treatment and in 40 healthy controls were measured by ELISA.

Results

The levels of generalized (C3a), alternate (factor Bb), and terminal (C5a and C5b-9) markers were significantly higher (all P<0.01) in the patients than in the healthy controls. Only the factor Bb levels significantly differed (P=0.008) between the two disease groups. In aHUS patients, high normal ADAMTS13 activity (≥77%) was associated with improved treatment response (OR, 6.769; 95% CI, 1.605-28.542; P=0.005), remission (OR, 6.000; 95% CI, 1.693-21.262; P=0.004), exacerbation (OR, 0.242; 95% CI, 0.064-0.916; P=0.031), and disease-associated mortality rates (OR, 0.155; 95% CI, 0.029-0.813; P=0.017).

Conclusion

These data suggest that complement biomarkers, except factor Bb, are similarly activated in TTP and aHUS patients, and ADAMTS13 activity can predict the treatment response and outcome in aHUS patients.

A Multicenter Trial of Vena Cava Filters in Severely Injured Patients

BACKGROUND

Whether early placement of an inferior vena cava filter reduces the risk of pulmonary embolism or death in severely injured patients who have a contraindication to prophylactic anticoagulation is not known.

METHODS

In this multicenter, randomized, controlled trial, we assigned 240 severely injured patients (Injury Severity Score >15 [scores range from 0 to 75, with higher scores indicating more severe injury]) who had a contraindication to anticoagulant agents to have a vena cava filter placed within the first 72 hours after admission for the injury or to have no filter placed. The primary end point was a composite of symptomatic pulmonary embolism or death from any cause at 90 days after enrollment; a secondary end point was symptomatic pulmonary embolism between day 8 and day 90 in the subgroup of patients who survived at least 7 days and did not receive prophylactic anticoagulation within 7 days after injury. All patients underwent ultrasonography of the legs at 2 weeks; patients also underwent mandatory computed tomographic pulmonary angiography when prespecified criteria were met.

RESULTS

The median age of the patients was 39 years, and the median Injury Severity Score was 27. Early placement of a vena cava filter did not result in a significantly lower incidence of symptomatic pulmonary embolism or death than no placement of a filter (13.9% in the vena cava filter group and 14.4% in the control group; hazard ratio, 0.99; 95% confidence interval [CI], 0.51 to 1.94; P = 0.98). Among the 46 patients in the vena cava filter group and the 34 patients in the control group who did not receive prophylactic anticoagulation within 7 days after injury, pulmonary embolism developed in none of those in the vena cava filter group and in 5 (14.7%) in the control group, including 1 patient who died (relative risk of pulmonary embolism, 0; 95% CI, 0.00 to 0.55). An entrapped thrombus was found in the filter in 6 patients.

CONCLUSIONS

Early prophylactic placement of a vena cava filter after major trauma did not result in a lower incidence of symptomatic pulmonary embolism or death at 90 days than no placement of a filter. (Funded by the Medical Research Foundation of Royal Perth Hospital and others; Australian New Zealand Clinical Trials Registry number, ACTRN12614000963628.).

Construction of a Bivalent Thrombin Binding Aptamer and Its Antidote with Improved Properties

Aptamers are short synthetic DNA or RNA oligonucleotides that adopt secondary and tertiary conformations based on Watson–Crick base-pairing interactions and can be used to target a range of different molecules. Two aptamers, HD1 and HD22, that bind to exosites I and II of the human thrombin molecule, respectively, have been extensively studied due to their anticoagulant potentials. However, a fundamental issue preventing the clinical translation of many aptamers is degradation by nucleases and reduced pharmacokinetic properties requiring higher dosing regimens more often. In this study, we have chemically modified the design of previously described thrombin binding aptamers targeting exosites I, HD1, and exosite II, HD22. The individual aptamers were first modified with an inverted deoxythymidine nucleotide, and then constructed bivalent aptamers by connecting the HD1 and HD22 aptamers either through a triethylene glycol (TEG) linkage or four consecutive deoxythymidines together with an inverted deoxythymidine nucleotide at the 3′-end. The anticoagulation potential, the reversal of coagulation with different antidote sequences, and the nuclease stability of the aptamers were then investigated. The results showed that a bivalent aptamer RNV220 containing an inverted deoxythymidine and a TEG linkage chemistry significantly enhanced the anticoagulation properties in blood plasma and nuclease stability compared to the existing aptamer designs. Furthermore, a bivalent antidote sequence RNV220AD efficiently reversed the anticoagulation effect of RNV220 in blood plasma. Based on our results, we believe that RNV220 could be developed as a potential anticoagulant therapeutic molecule.

Identification of reference miRNAs in plasma useful for the study of oestrogen-responsive miRNAs associated with acquired Protein S deficiency in pregnancy

Background

Accumulating evidence indicate that circulating microRNAs (miRNAs) are useful independent non-invasive biomarkers, with unique miRNA signatures defined for various pathophysiological conditions. However, there are no established universal housekeeping miRNAs for the normalisation of miRNAs in body fluids. We have previously identified an oestrogen-responsive miRNA, miR-494, in regulating the anticoagulant, Protein S, in HuH-7 liver cells. Moreover, increased thrombotic risk associated with elevated circulating oestrogen levels is frequently observed in pregnant women and oral contraceptive users. In order to identify other oestrogen-responsive miRNAs, including miR-494, that may be indicative of increased thrombotic risk in plasma, we used nanoString analysis to identify robust and stable endogenous reference miRNAs for the study of oestrogen-responsive miRNAs in plasma.

Results

We compared the plasma miRNA expression profile of individuals with: (1) Low circulating oestrogens (healthy men and non-pregnant women not taking oral contraceptives), (2) High circulating synthetic oestrogens, (women taking oral contraceptives) and (3) High circulating natural oestrogens (pregnant females >14 weeks gestation). From the nanoString analyses, 11 candidate reference miRNAs which exhibited high counts and not significantly differentially expressed between groups were selected for validation using realtime quantitative polymerase chain reaction (RT-qPCR) and digital droplet PCR (DDPCR) in pooled plasma samples, and the stability of their expression evaluated using NormFinder and BestKeeper algorithms. Four miRNAs (miR-25-5p, miR-188-5p, miR-222-3p and miR-520f) demonstrated detectable stable expression between groups and were further analysed by RT-qPCR in individual plasma samples, where miR-188-5p and miR-222-3p expression were identified as a stable pair of reference genes. The miRNA reference panel consisting of synthetic spike-ins cel-miR-39 and ath-miR159a, and reference miRNAs, miR-188-5p and miR-222-3p was useful in evaluating fold-change of the pregnancy-associated miRNA, miR-141-3p, between groups.

Conclusion

The miRNA reference panel will be useful for normalising qPCR data comparing miRNA expression between men and women, non-pregnant and pregnant females, and the potential effects of endogenous and synthetic oestrogens on plasma miRNA expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2636-3) contains supplementary material, which is available to authorized users.

Long-term safety and efficacy of extended-interval prophylaxis with recombinant factor IX Fc fusion protein (rFIXFc) in subjects with haemophilia B

The safety, efficacy, and prolonged half-life of recombinant factor IX Fc fusion protein (rFIXFc) were demonstrated in the Phase 3 B-LONG (adults/adolescents ≥12 years) and Kids B-LONG (children <12 years) studies of subjects with haemophilia B (≤2 IU/dl). Here, we report interim, long-term safety and efficacy data from B-YOND, the rFIXFc extension study. Eligible subjects who completed B-LONG or Kids B-LONG could enrol in B-YOND. There were four treatment groups: weekly prophylaxis (20-100 IU/kg every 7 days), individualised prophylaxis (100 IU/kg every 8-16 days), modified prophylaxis (further dosing personalisation to optimise prophylaxis), and episodic (on-demand) treatment. Subjects could change treatment groups at any point. Primary endpoint was inhibitor development. One hundred sixteen subjects enrolled in B-YOND. From the start of the parent studies to the B-YOND interim data cut, median duration of rFIXFc treatment was 39.5 months and 21.9 months among adults/adolescents and children, respectively; 68/93 (73.1 %) adults/adolescents and 9/23 (39.1 %) children had ≥100 cumulative rFIXFc exposure days. No inhibitors were observed. Median annualised bleeding rates (ABRs) were low in all prophylaxis regimens: weekly (≥12 years: 2.3; <6 years: 0.0; 6 to <12 years: 2.7), individualised (≥12 years: 2.3; 6 to <12 years: 2.4), and modified (≥12 years: 2.4). One or two infusions were sufficient to control 97 % (adults/adolescents) and 95 % (children) of bleeding episodes. Interim data from B-YOND are consistent with data from B-LONG and Kids B-LONG, and confirm the long-term safety of rFIXFc, absence of inhibitors, and maintenance of low ABRs with prophylactic dosing every 1 to 2 weeks.

The platelet Fc receptor, FcγRIIa

Human platelets express FcγRIIa, the low-affinity receptor for the constant fragment (Fc) of immunoglobulin (Ig) G that is also found on neutrophils, monocytes, and macrophages. Engagement of this receptor on platelets by immune complexes triggers intracellular signaling events that lead to platelet activation and aggregation. Importantly these events occur in vivo, particularly in response to pathological immune complexes, and engagement of this receptor on platelets has been causally linked to disease pathology. In this review, we will highlight some of the key features of this receptor in the context of the platelet surface, and examine the functions of platelet FcγRIIa in normal hemostasis and in response to injury and infection. This review will also highlight pathological consequences of engagement of this receptor in platelet-based autoimmune disorders. Finally, we present some new data investigating whether levels of the extracellular ligand-binding region of platelet glycoprotein VI which is rapidly shed upon engagement of platelet FcγRIIa by autoantibodies, can report on the presence of pathological anti-heparin/platelet factor 4 immune complexes and thus identify patients with pathological autoantibodies who are at the greatest risk of developing life-threatening thrombosis in the setting of heparin-induced thrombocytopenia.

Current state and novel approaches of antiplatelet therapy

An unresolved problem with clinical use of antiplatelet therapy is that a significant number of individuals either still get thrombosis or run the risk of life-threatening bleeding. Antiplatelet drugs are widely used clinically, either chronically for people at risk of athero/thrombotic disease or to prevent thrombus formation during surgery. However, a subpopulation may be resistant to standard doses, while the platelet targets of these drugs are also critical for the normal hemostatic function of platelets. In this review, we will briefly examine current antiplatelet therapy and existing targets while focusing on new potential approaches for antiplatelet therapy and improved monitoring of effects on platelet reactivity in individuals, ultimately to improve antithrombosis with minimal bleeding. Primary platelet adhesion-signaling receptors, glycoprotein (GP)Ib-IX-V and GPVI, that bind von Willebrand factor/collagen and other prothrombotic factors are not targeted by drugs in clinical use, but they are of particular interest because of their key role in thrombus formation at pathological shear.

Phase 3 study of recombinant factor IX Fc fusion protein in hemophilia B

BACKGROUND

Prophylactic factor replacement in patients with hemophilia B improves outcomes but requires frequent injections. A recombinant factor IX Fc fusion protein (rFIXFc) with a prolonged half-life was developed to reduce the frequency of injections required.

METHODS

We conducted a phase 3, nonrandomized, open-label study of the safety, efficacy, and pharmacokinetics of rFIXFc for prophylaxis, treatment of bleeding, and perioperative hemostasis in 123 previously treated male patients. All participants were 12 years of age or older and had severe hemophilia B (endogenous factor IX level of ≤2 IU per deciliter, or ≤2% of normal levels). The study included four treatment groups: group 1 received weekly dose-adjusted prophylaxis (50 IU of rFIXFc per kilogram of body weight to start), group 2 received interval-adjusted prophylaxis (100 IU per kilogram every 10 days to start), group 3 received treatment as needed for bleeding episodes (20 to 100 IU per kilogram), and group 4 received treatment in the perioperative period. A subgroup of group 1 underwent comparative sequential pharmacokinetic assessments of recombinant factor IX and rFIXFc. The primary efficacy end point was the annualized bleeding rate, and safety end points included the development of inhibitors and adverse events.

RESULTS

As compared with recombinant factor IX, rFIXFc exhibited a prolonged terminal half-life (82.1 hours) (P<0.001). The median annualized bleeding rates in groups 1, 2, and 3 were 3.0, 1.4, and 17.7, respectively. In group 2, 53.8% of participants had dosing intervals of 14 days or more during the last 3 months of the study. In groups 1, 2 and 3, 90.4% of bleeding episodes resolved after one injection. Hemostasis was rated as excellent or good during all major surgeries. No inhibitors were detected in any participants receiving rFIXFc; in groups 1, 2, and 3, 73.9% of participants had at least one adverse event, and serious adverse events occurred in 10.9% of participants. These events were mostly consistent with those expected in the general population of patients with hemophilia.

CONCLUSIONS

Prophylactic rFIXFc, administered every 1 to 2 weeks, resulted in low annualized bleeding rates in patients with hemophilia B. (Funded by Biogen Idec; ClinicalTrials.gov number, NCT01027364.).

Micro-ribonucleic Acid 494 regulation of protein S expression

BACKGROUND

Acquired protein S (PS) deficiency is highly associated with elevated circulating estrogen levels resulting from pregnancy, oral contraceptives, and estrogen replacement therapy; however, the mechanism of estrogen-mediated acquired PS deficiency remains poorly understood. Increasing evidence indicates that estrogen receptor signaling can indirectly modulate the expression of target genes at the post-transcriptional level by modulating the expression of microRNAs (miRNAs), and miRNAs have also been demonstrated to be involved in the regulation of hemostasis.

OBJECTIVES

To investigate the mechanism of estrogen-mediated downregulation of PROS1 expression by the microRNA miR-494.

METHODS

Computational analyses of the PROS1 3'-untranslated region (UTR) were performed to identify putative miRNA-binding sites, and direct targeting of the PROS1 3'-UTR by miR-494 was determined with dual luciferase reporter assays in HuH-7 cells. Reporter vectors containing the PROS1 3'-UTR sequence with deleted miR-494-binding sites were also analyzed with luciferase reporter assays. The effects of estrogen on miR-494 and PROS1 mRNA levels in HuH-7 cells were determined by quantitative real-time PCR, and estrogen-mediated changes to secreted PS levels in culture supernatant of HuH-7 cells were measured with an ELISA.

RESULTS

The PROS1 3'-UTR sequence contains three putative miR-494-binding sites. miR-494 directly targets PROS1, and miR-494 levels are upregulated following estrogen treatment in HuH-7 liver cells in association with downregulated PROS1 mRNA and PS levels.

CONCLUSIONS

The results from this study provide the first evidence for miRNA downregulation of PROS1 by miR-494, and suggest that miR-494 is involved in the mechanism of estrogen-mediated downregulation of PS expression.

Soluble glycoprotein VI is raised in the plasma of patients with acute ischemic stroke

BACKGROUND AND PURPOSE

Ischemic stroke induced by thrombosis may be triggered by atherosclerotic plaque rupture and collagen-induced platelet activation. Collagen induces glycoprotein VI shedding.

METHODS

We measured plasma-soluble glycoprotein VI (sGPVI) by enzyme-linked immunosorbent assay in 159 patients with acute (<7-day) ischemic stroke and age/sex-matched community-based control subjects.

RESULTS

sGPVI was elevated in stroke compared with controls (P=0.0168). ORs were higher in Quartile 4 for stroke cases (P=0.0121), and sGPVI was significantly elevated in stroke associated with large artery disease across Quartiles 2 to 4 and small artery disease in Quartile 4. sGPVI decreased 3 to 6 months after antiplatelet treatment, consistent with elevated sGPVI due to platelet activation during the thrombotic event. sGPVI correlated with P-selectin (P=0.0007) and was higher in individuals with the GPVIa haplotype (P=0.024).

CONCLUSIONS

Glycoprotein VI shedding is implicated in the pathology of acute ischemic stroke.

Clinical efficacy and safety of the factor VIII/von Willebrand factor concentrate BIOSTATE in patients with von Willebrand's disease: a prospective multi-centre study

von Willebrand's disease (VWD) is an inherited bleeding disorder characterized by deficient levels of or dysfunctional von Willebrand factor (VWF). This phase II/III open-label, multicentre study evaluated the efficacy and safety of BIOSTATE, a high purity plasma-derived double-virus inactivated FVIII/VWF concentrate, when used in non-surgical bleeds, surgical procedures and prophylactic therapy in VWD patients for whom desmopressin treatment was deemed ineffective, inadequate or contraindicated. Twenty three patients (7 type 1, 9 type 2 and 7 type 3; 12 male, 11 female), who received FVIII/VWF concentrate as part of their VWD management, were recruited prospectively between December 2004 and May 2007 from eight centres in Australia and New Zealand. BIOSTATE dosing was based on pre-treatment FVIII:C and/or VWF:RCo plasma levels and a predetermined dosing guide. Haemostatic efficacy of BIOSTATE was rated as excellent or good for all major and minor surgery events, long-term prophylaxis, and for four of the six assessable non-surgical bleeding events. Blood transfusions were required by two major surgery patients as well as one patient with a non-surgical bleed. The median overall exposure to BIOSTATE across all groups was 8 days, greater in the prophylactic group (range 53-197) compared with major surgery (3-24), minor surgery (1-8) and non-surgical bleeds (1-10). BIOSTATE was shown to be efficacious and well tolerated when treating patients with VWD. This study also provides important insights into dosing regimens with BIOSTATE and the role of monitoring therapy with FVIII:C and VWF:RCo.

A consensus statement on the management of pregnancy and delivery in women who are carriers of or have bleeding disorders

Pregnancy and delivery are critical times for women with bleeding disorders, with mothers, and possibly their affected infants, being exposed to a variety of haemostatic challenges. Management of women with bleeding disorders during pregnancy involves a multidisciplinary team including, but not limited to, an obstetrician, an anaesthetist and a haematologist. This consensus document from the Australian Haemophilia Centre Directors' Organisation (AHCDO) provides practical information for clinicians managing women with bleeding disorders during pregnancy. Included are: the expected physiological response in pregnancy in such women; management of pregnancy, labour and delivery, as well as obstetric anaesthesia issues, postpartum care, and reducing and treating postpartum haemorrhage; and management of infants at risk of a bleeding disorder and of bleeding in neonates. The guidelines were developed after extensive consultation, face-to-face meetings and revisions. The final document represents a consensus opinion of all AHCDO members. Where evidence is lacking, recommendations are based on clinical experience and consensus opinion.

A novel ABCA1 nonsense mutation, R1270X, in Tangier disease associated with an unrecognised bleeding tendency

The ATP binding cassette transporter A1 (ABCA1) is involved in the regulation of lipid trafficking and export of cholesterol from cells to high density lipoprotein (HDL). ABCA1 gene defects cause Tangier disease, an autosomal recessive disorder characterised by the absence of HDL-cholesterol in plasma, abnormal deposition of cholesteryl esters in the reticuloendothelial system, defective platelet dense and lysosomal granule release, and disordered cellular cholesterol efflux. We describe the case of a 62-year-old man with Tangier disease who presented with severe anaemia secondary to a spontaneous splenic haematoma. He underwent elective splenectomy without haemorrhage and his thrombocytopaenia resolved with a platelet count rising from 97 to 560 x 10(9)/L. Macroscopically, the resected spleen was enlarged with evidence of splenic haematoma. Histologic analysis of sections of spleen revealed lipid histiocytosis consistent with the diagnosis of Tangier disease. DNA sequence analysis revealed the subject to be a homozygote for a novel ABCA1 mutation c.4121C>T, which changes arginine 1270 to a stop codon (R1270X). In conclusion, we describe a case of Tangier disease in association with an unrecognised bleeding tendency, in a man homozygous for a novel ABCA1 gene mutation, R1270X.

Compromised ITAM-based platelet receptor function in a patient with immune thrombocytopenic purpura

BACKGROUND

Receptors on platelets that contain immunoreceptor tyrosine-based activation motifs (ITAMs) include collagen receptor glycoprotein (GP) VI, and FcgammaRIIa, a low affinity receptor for immunoglobulin (Ig) G.

OBJECTIVES

We examined the function of GPVI and FcgammaRIIa in a patient diagnosed with immune thrombocytopenic purpura (ITP) who had unexplained pathological bruising despite normalization of the platelet count with treatment.

METHODS AND RESULTS

Patient platelets aggregated normally in response to ADP, arachadonic acid and epinephrine, but not to GPVI agonists, collagen or collagen-related peptide, or to FcgammaRII-activating monoclonal antibody (mAb) 8.26, suggesting ITAM receptor dysfunction. Plasma contained an anti-GPVI antibody by MAIPA and aggregated normal platelets. Aggregating activity was partially (approximately 60%) blocked by FcgammaRIIa-blocking antibody, IV.3, and completely blocked by soluble GPVI ectodomain. Full-length GPVI on the patient platelet surface was reduced to approximately 10% of normal levels, and a approximately 10-kDa GPVI cytoplasmic tail remnant and cleaved FcgammaRIIa were detectable by western blot, indicating platelet receptor proteolysis. Plasma from the patient contained approximately 150 ng mL(-1) soluble GPVI by ELISA (normal plasma, approximately 15 ng mL(-1)) and IgG purified from patient plasma caused FcgammaRIIa-mediated, EDTA-sensitive cleavage of both GPVI and FcgammaRIIa on normal platelets.

CONCLUSIONS

In ITP patients, platelet autoantibodies can curtail platelet receptor function. Platelet ITAM receptor dysfunction may contribute to the increased bleeding phenotype observed in some patients with ITP.

Polymorphisms in the tissue factor pathway inhibitor gene are not associated with ischaemic stroke

The present study aimed to determine whether four previously described polymorphisms found within the tissue factor pathway inhibitor (TFPI) gene are associated with free plasma TFPI levels or with TFPI activity as well as the risk of ischaemic stroke in stroke patients and control individuals. We conducted a case-control study of 162 first-ever ischaemic stroke cases and 170 randomly selected community control individuals. The TFPI genotype was determined for the T-287C, C-399T, Intron 7 C-33T, and Val264Met (G874A) polymorphisms. Free plasma TFPI and TFPI activity were measured during the first 7 days and 3-6 months after the acute stroke event. Free plasma TFPI levels were significantly lowered 3-6 months after stroke compared with levels observed in the patient group during the acute phase of the stroke (mean, 16.3 versus 22.46 ng/ml; P = 0.046) and among the control group (mean, 16.3 versus 22.79 ng/ml; P < 0.0001). Conversely, TFPI activity was significantly up-regulated during the acute phase (mean, 1.30 versus 1.11 U/ml; P = 0.0051) and remained elevated 3-6 months later (mean, 1.28 versus 1.11 U/ml; P = 0.03). The TFPI gene polymorphisms studied were not significantly associated with TFPI levels or activity, nor with the risk of ischaemic stroke. In conclusion, the TFPI activity and concentration in plasma varied significantly after an ischaemic stroke; however, these variations were not found to be due to the presence of any of the genetic mutations analysed in this study. Our results are consistent with the emerging model suggesting the lipoprotein-bound portion of TFPI has a significant influence on coagulation and diseases of haemostasis.

Polymorphisms of the tissue factor pathway inhibitor gene are associated with venous thromboembolism in the antiphospholipid syndrome and carriers of factor V Leiden

Polymorphisms within the tissue factor pathway inhibitor (TFPI) gene may determine TFPI expression and increase the risk of venous thromboembolism (VTE) in predisposed individuals. We tested this hypothesis by comparing TFPI activity and the frequency of common TFPI polymorphisms, -33T->C, -399C->T and -287T->C, in patients with antiphospholipid syndrome (APS) (n = 24) or factor V Leiden (n = 44) who had a history of VTE (n = 26), compared with those without VTE (n = 42) and also with normal control individuals (n = 56). TFPI activity was measured using a modified amidolytic assay and genotypes were determined by polymerase chain reaction and restriction fragment length polymorphism. We found that only APS patients with a history of venous thrombosis had TFPI activity levels significantly different from control individuals (1.77 +/- 0.60 vs 0.77 +/- 0.19 U/ml; P = 0.0001), and this was associated with inheritance of the TFPI -33C allele (1.70 +/- 0.72 U/ml for TC/CC genotypes vs 0.97 +/- 0.56 U/ml for TT; P = 0.01). Multivariate analysis of APS and factor V Leiden patients revealed that the greatest independent contributor to VTE was TFPI activity (adjusted odds ratio = 16.84; 95% confidence interval = 2.47-114.36, P = 0.004), while inheritance of either the TFPI -33C or -399T alleles each increased the odds of VTE by nearly 13 times (95% confidence interval = 2.39-69.91, P = 0.003; and 95% confidence interval = 2.25-71.23, P = 0.004, respectively). These results indicate that the TFPI -33T->C and -399C->T polymorphisms are significantly associated with venous thrombosis in the presence of other risk factors, especially APS, and may be clinically relevant in patients who are prone to hypercoagulability.

Dual ITAM-mediated proteolytic pathways for irreversible inactivation of platelet receptors: de-ITAM-izing FcgammaRIIa

Collagen binding to glycoprotein VI (GPVI) induces signals critical for platelet activation in thrombosis. Both ligand-induced GPVI signaling through its coassociated Fc-receptor gamma-chain (FcRgamma) immunoreceptor tyrosine-activation motif (ITAM) and the calmodulin inhibitor, W7, dissociate calmodulin from GPVI and induce metalloproteinase-mediated GPVI ectodomain shedding. We investigated whether signaling by another ITAM-bearing receptor on platelets, FcgammaRIIa, also down-regulates GPVI expression. Agonists that signal through FcgammaRIIa, the mAbs VM58 or 14A2, potently induced GPVI shedding, inhibitable by the metalloproteinase inhibitor, GM6001. Unexpectedly, FcgammaRIIa also underwent rapid proteolysis in platelets treated with agonists for FcgammaRIIa (VM58/14A2) or GPVI/FcRgamma (the snake toxin, convulxin), generating an approximate 30-kDa fragment. Immunoprecipitation/pull-down experiments showed that FcgammaRIIa also bound calmodulin and W7 induced FcgammaRIIa cleavage. However, unlike GPVI, the approximate 30-kDa FcgammaRIIa fragment remained platelet associated, and proteolysis was unaffected by GM6001 but was inhibited by a membrane-permeable calpain inhibitor, E64d; consistent with this, micro-calpain cleaved an FcgammaRIIa tail-fusion protein at (222)Lys/(223)Ala and (230)Gly/(231)Arg, upstream of the ITAM domain. These findings suggest simultaneous activation of distinct extracellular (metalloproteinase-mediated) and intracellular (calpain-mediated) proteolytic pathways irreversibly inactivating platelet GPVI/FcRgamma and FcgammaRIIa, respectively. Activation of both pathways was observed with immunoglobulin from patients with heparin-induced thrombocytopenia (HIT), suggesting novel mechanisms for platelet dysfunction by FcgammaRIIa after immunologic insult.

Once-Daily Enoxaparin in The Outpatient Setting Versus Unfractionated Heparin in Hospital for the Treatment of Symptomatic Deep-Vein Thrombosis

BACKGROUND

Once- and twice-daily low-molecular-weight heparin administered in hospital have been shown to be effective and safe for treating deep-vein thrombosis. The aim of this study was to compare the efficacy and safety of deep-vein thrombosis treatment using once-daily subcutaneous enoxaparin in the outpatient setting with intravenous unfractionated heparin in hospital.

METHODS

This randomized, parallel-group, open-label study was conducted in 18 centers in 4 countries. In total, 298 patients with symptomatic deep-vein thrombosis who were eligible for home treatment were randomized to treatment with enoxaparin in the outpatient setting (1.5 mg/kg subcutaneously once-daily) or unfractionated heparin in hospital (5000 IU bolus and 1250 IU/hour intravenous infusion) for > or =5 days. Clinical endpoints were assessed during a 6-month follow-up period.

RESULTS

Among all patients treated with enoxaparin, there was a trend towards fewer recurrent deep-vein thromboses (1.3% vs. 5.4%; p = 0.060) and pulmonary emboli (1.3% vs. 4.1%; p = 0.17) compared with patients treated with unfractionated heparin. When considering a post-hoc combined endpoint of deep-vein thrombosis and pulmonary embolism, significantly fewer events occurred in the enoxaparin group than in the unfractionated-heparin group (2.7% vs. 8.8%; p = 0.026). The incidences of bleeding events and adverse events in the enoxaparin and unfractionated-heparin groups were similar.

CONCLUSIONS

Once-daily subcutaneous enoxaparin in the outpatient setting is at least as effective and as well tolerated as in-hospital intravenous unfractionated heparin for treatment of deep-vein thrombosis.

The impact of information technology on haemophilia care

The past decade has seen an explosion in the use of computers, data programs, hand-held electronic devices and the Internet. How these advances impact on haemophilia management both now and in the future are discussed from the perspective of haemophilia registries, Internet-based electronic haemophilia treatment records, and the potential for haemophilia telehealth.

Randomized comparison of low molecular weight heparin and coumarin derivatives on the survival of patients with cancer and venous thromboembolism

PURPOSE

Experimental studies and indirect clinical evidence suggest that low molecular weight heparins may have antineoplastic effects. We investigated the influence of a low molecular weight heparin dalteparin on the survival of patients with active cancer and acute venous thromboembolism.

PATIENTS AND METHODS

Survival data were examined in a posthoc analysis in patients with solid tumors and venous thromboembolism who were randomly assigned to dalteparin or a coumarin derivative for 6 months in a multicenter, open-label, randomized, controlled trial. All-cause mortality at 12 months was compared between treatment groups in patients with and without metastatic malignancy. The effect of dalteparin on survival was compared between the two patient subgroups.

RESULTS

During the 12-month follow-up period, 356 of 602 patients with solid tumors and acute venous thromboembolism died. Among patients without metastatic disease, the probability of death at 12 months was 20% in the dalteparin group, as compared with 36% in the oral anticoagulant group (hazard ratio, 0.50; 95% CI, 0.27 to 0.95; P = .03). In patients with metastatic cancer, no difference in mortality between the treatment groups was observed (72% and 69%, respectively; hazard ratio, 1.1; 95% CI, 0.87 to 1.4; P = .46). The observed effects of dalteparin on survival were statistically significantly different between patients with and without metastatic disease (P = .02).

CONCLUSION

The use of dalteparin relative to coumarin derivatives was associated with improved survival in patients with solid tumors who did not have metastatic disease at the time of an acute venous thromboembolic event. Additional studies are warranted to investigate these findings.

Warfarin reversal: consensus guidelines, on behalf of the Australasian Society of Thrombosis and Haemostasis

For most warfarin indications, the target maintenance international normalised ratio (INR) is 2-3. Risk factors for bleeding complications with warfarin use include age, history of past bleeding and specific comorbid conditions. To reverse the effects of warfarin, vitamin K(1) can be given. Immediate reversal is achieved with a prothrombin complex concentrate (PCC) and fresh frozen plasma (FFP). Vitamin K(1) is essential for sustaining the reversal achieved by PCC and FFP. When oral vitamin K(1) is used for warfarin reversal, the injectable formulation of vitamin K(1) is preferable to tablets because of its flexible dosing; this formulation can be given orally or injected. To temporarily reverse the effect of warfarin when there is a need to continue warfarin therapy, vitamin K(1) should be given in a dose that will quickly lower the INR to a safe, but not subtherapeutic, range and will not cause resistance once warfarin is reinstated. Prothrombinex-HT is the only PCC approved in Australia and New Zealand for warfarin reversal. It contains factors II, IX and X, and low levels of factor VII. FFP should be added to Prothrombinex-HT as a source of factor VII when used for warfarin reversal. Simple dental or dermatological procedures may not require interruption to warfarin therapy. If necessary, warfarin therapy can be withheld 5 days before elective surgery, when the INR usually falls to below 1.5 and surgery can be conducted safely. Bridging anticoagulation therapy for patients at high risk for thromboembolism should be undertaken in consultation with the relevant experts.

Venous thromboembolism in travellers: can we identify those at risk?

To assess the prevalence of clinical and laboratory risk factors in patients who develop venous thromboembolism following travel. The design was a case series of 58 consecutive patients presenting with venous thromboembolism within 30 days of travel. The setting was a major metropolitan teaching hospital and an affiliated private practice. The main outcome measures were prevalence of clinical and laboratory risk factors for venous thromboembolism, time to presentation, mode and duration of travel. Forty-eight [83%; 95% confidence interval (CI), 71-91%] of 58 patients developed venous thromboembolism following air travel. Thirty-four (59%; 95% CI, 45-71%) patients had travelled for more than 8 h and most patients were diagnosed with venous thromboembolism within 1 week of completing their journey. Pulmonary embolism occurred in 24 patients (41%; 95% CI, 29-55%), proximal deep vein thrombosis in 23 patients (40%; 95% CI, 27-53%), calf vein thrombosis in four patients (7%; 95% CI, 2-17%), and superficial thrombophlebitis in seven patients (12%; 95% CI, 5-23%). At least one clinical or laboratory risk factor (other than travel) was found in 49 patients (84%; 95% CI, 73-93%) and two or more risk factors were found in 30 patients (52%; 95% CI, 38-65%). The most common risk factors were oestrogens (24%; 95% CI, 14-37%), a past history of thrombosis (24%: 95% CI, 14-37%), and factor V Leiden (24%: 95% CI, 14-37%). These retrospective uncontrolled data suggest that at least one clinical or laboratory risk factor is present prior to travel in more than 80% of patients who develop venous thromboembolism within 30 days of travel. In most cases these risk factors can be identified by the clinical history alone, without recourse to laboratory testing. Whether patients with known risk factors for venous thromboembolism prior to travel should be targeted with specific thromboprophylaxis requires randomized evaluation.

Endothelial and platelet activation in acute ischemic stroke and its etiological subtypes

BACKGROUND AND PURPOSE

Activation of endothelial cells and platelets is an important mediator of atherothrombosis. Markers of endothelial cell and platelet activation such as soluble adhesion molecules can be measured in plasma. We hypothesized that patients with acute ischemic stroke would have increased blood concentrations of soluble E-selectin and von Willebrand factor (vWF), primarily reflecting activation of endothelial cells, and increased concentrations of soluble P-selectin and platelet-derived microvesicles (PDM), primarily reflecting activation of platelets, compared with healthy controls. We also hypothesized that these markers would be differentially elevated in ischemic stroke caused by large- and small-artery atherothrombosis compared with cardiogenic embolism.

METHODS

We conducted a case-control study of 200 hospital-referred cases of first-ever ischemic stroke and 205 randomly selected community controls stratified by age, sex, and postal code. Using established criteria, we classified cases of stroke by etiological subtype in a blinded fashion. The prevalence of vascular risk factors and blood concentrations of E-selectin, P-selectin, vWF antigen, and PDM were determined in stroke cases within 7 days and at 3 to 6 months after stroke and in controls.

RESULTS

Mean blood concentrations of soluble E-selectin, P-selectin, and PDM within 7 days of stroke onset were all significantly higher in cases compared with controls. At 3 to 6 months after stroke, the mean blood concentrations of E-selectin and P-selectin fell significantly below that of controls, and PDM concentrations remained elevated. There was a strong, graded, and independent (of age, sex, and vascular risk factors) association between increasing blood concentrations of E-selectin during the acute phase and all etiological subtypes of ischemic stroke, particularly ischemic stroke caused by large-artery atherothrombosis. There was also a significant, graded, and independent association between increasing blood concentrations of vWF during the acute phase and ischemic stroke caused by large-artery atherothrombosis.

CONCLUSIONS

We have demonstrated significant associations between acute elevation of blood markers of endothelial cell and platelet activation and ischemic stroke and between acute elevation of blood markers of endothelial cell activation and ischemic stroke caused by large-artery atherothrombosis. Persistent elevated blood concentrations of PDM may be a marker of increased risk of ischemic stroke.

Low-molecular-weight heparin versus a coumarin for the prevention of recurrent venous thromboembolism in patients with cancer

BACKGROUND

Patients with cancer have a substantial risk of recurrent thrombosis despite the use of oral anticoagulant therapy. We compared the efficacy of a low-molecular-weight heparin with that of an oral anticoagulant agent in preventing recurrent thrombosis in patients with cancer.

METHODS

Patients with cancer who had acute, symptomatic proximal deep-vein thrombosis, pulmonary embolism, or both were randomly assigned to receive low-molecular-weight heparin (dalteparin) at a dose of 200 IU per kilogram of body weight subcutaneously once daily for five to seven days and a coumarin derivative for six months (target international normalized ratio, 2.5) or dalteparin alone for six months (200 IU per kilogram once daily for one month, followed by a daily dose of approximately 150 IU per kilogram for five months).

RESULTS

During the six-month study period, 27 of 336 patients in the dalteparin group had recurrent venous thromboembolism, as compared with 53 of 336 patients in the oral-anticoagulant group (hazard ratio, 0.48; P=0.002). The probability of recurrent thromboembolism at six months was 17 percent in the oral-anticoagulant group and 9 percent in the dalteparin group. No significant difference between the dalteparin group and the oral-anticoagulant group was detected in the rate of major bleeding (6 percent and 4 percent, respectively) or any bleeding (14 percent and 19 percent, respectively). The mortality rate at six months was 39 percent in the dalteparin group and 41 percent in the oral-anticoagulant group.

CONCLUSIONS

In patients with cancer and acute venous thromboembolism, dalteparin was more effective than an oral anticoagulant in reducing the risk of recurrent thromboembolism without increasing the risk of bleeding.

Collagen platelet receptor polymorphisms integrin alpha2beta1 C807T and GPVI Q317L and risk of ischemic stroke

Several polymorphisms of integrin alpha2beta1 and glycoprotein (GP) VI that may modify platelet-collagen interactions or subsequent signaling have been described. We conducted a case-control study involving 180 stroke patients and 172 controls to determine whether the alpha2 C807T and GPVI Q317L polymorphisms were associated with an increased risk of ischemic stroke. We found no statistically significant differences in the distribution of alpha2 C807T and GPVI Q317L in patients and controls overall or after stratification by etiological subtype. The GPVI 317QQ genotype was found to be over-represented in a subgroup of patients >/=60 years compared to corresponding controls. However, this association did not remain significant after adjustment for other cardiovascular risk factors. Our results do not support a role for the integrin alpha2 C807T and GPVI Q317L polymorphisms in the development of first-ever ischemic stroke. However, larger studies are required to confirm this.

C-reactive protein in ischemic stroke and its etiologic subtypes

The possible role of C-reactive protein (CRP) in the etiology and prognosis of ischemic stroke remains to be clearly defined. The purpose of this study was to determine whether CRP levels are elevated in patients with stroke, whether they remain persistently elevated, and whether CRP levels are higher in patients with etiologic subtypes of stroke caused by large or small artery disease ("atherogenic hypothesis") or whether they may be higher in patients with more extensive cerebral infarction caused by large artery or cardiogenic embolism ("inflammatory hypothesis"). We conducted a case-control study of 199 hospital cases with a first-ever ischemic stroke and 202 randomly selected community controls. Cases of stroke were classified by etiologic subtype and the prevalence of conventional vascular risk factors and CRP levels were determined in cases and controls. Blood levels of CRP measured within 7 days of acute stroke were significantly higher in cases compared with controls (8.50 vs. 2.18 mg/L, P < .0001) and remained elevated in stroke survivors at 3 to 6 months of follow-up (3.35 vs. 2.18 mg/L, P = .003) although levels were significantly lower compared with the first 7 days (3.35 vs. 8.50 mg/L, P < .001-.003). Compared with the lowest quartile of CRP, the upper 3 quartiles were associated with an adjusted odds ratio (OR) of ischemic stroke of 1.9 (95% CI: 1.0-3.8) for the second quartile, 5.8 (95% CI: 2.9-11.4) for the third quartile, and 16.9 (95% CI: 7.9-36.1) for the fourth quartile (P for trend < .0001). Comparing the upper with the lower quartile, the strongest association was with etiologic stroke subtypes caused by large artery disease (OR 52.5; 95% CI: 13.4-205) and embolism from the heart (OR 56.1; 95% CI: 11.3-278), with a much weaker association with small artery disease (OR 2.4; 95% CI: 0.8-6.0). The mean Oxford Handicap Scale score was lowest in small artery, intermediate in large artery and highest in cardioembolic stroke (2.8 vs. 3.1 vs. 3.6, respectively; P = .001) while the mean Barthel Index was highest in small artery, intermediate in large artery, and lowest in cardioembolic stroke (13.5 vs. 11.5 vs. 8.6, respectively; P = .002). Furthermore, there was a significant correlation between CRP levels during the first 7 days and stroke severity, as measured by the Oxford Handicap Scale score (P = .03) and Barthel index (P = .001). We conclude that there is a strong, independent relationship between elevated blood levels of CRP and ischemic stroke, particularly because of more severe strokes caused by large artery disease and embolism from the heart, which remains evident over the long term. These results are consistent with the inflammatory marker hypothesis of CRP as a marker of the extent of ischemic cerebral injury and its complications.