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Concept: Protein C

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The underlying cause of thrombosis in a large protein C (PC) deficient Vermont kindred appears to be multicausal and not explained by PC deficiency alone. We evaluated the contribution of coagulation factors to thrombin generation in this population utilizing a mathematical model that incorporates a mechanistic description of the PC pathway. Thrombin generation profiles for each individual were generated with and without the contribution of the PC pathway. Parameters that describe thrombin generation: maximum level (MaxL) and rate (MaxR), their respective times (TMaxL, TMaxR), area under the curve (AUC) and clotting time (CT) were examined in individuals ± PC mutation, ± prothrombin G20210A polymorphism and ± thrombosis history (DVT or PE). This family (n = 364) is shifted towards greater thrombin generation relative to the mean physiologic control. When this family was analyzed with the PC pathway, our results showed that: carriers of the PC mutation (n = 81) had higher MaxL and MaxR and greater AUC (all p<0.001) than non-carriers (n = 283); and individuals with a DVT and/or PE history (n = 13) had higher MaxL (p = 0.005) and greater AUC (p<0.001) than individuals without a thrombosis history (n = 351). These differences were further stratified by gender, with women in all categories generating more thrombin than males. These results show that all individuals within this family with or without PC deficiency have an increased baseline procoagulant potential reflective of increased thrombin generation. In addition, variations within the plasma composition of each individual can further segregate out increased procoagulant phenotypes, with gender-associated plasma compositional differences playing a large role.

Concepts: Blood, Coagulation, Platelet, Warfarin, Protein C, Factor V, Thrombin, Thrombophilia

169

Development of inhibitory antibodies to coagulation factor VIII (fVIII) is the primary obstacle to the treatment of hemophilia A in the developed world. This adverse reaction occurs in 20-30% of persons with severe hemophilia A treated with fVIII-replacement products and is characterized by the development of a humoral and neutralizing immune response to fVIII. Patients with inhibitory anti-fVIII antibodies are treated with bypassing agents including recombinant factor VIIa (rfVIIa). However, some patients display poor hemostatic response to bypass therapy and improved treatment options are needed. Recently, we demonstrated that fVIII inhibitors display widely variable kinetics of inhibition that correlate with their respective target epitopes. Thus, it was hypothesized that for antibodies that display slow rates of inhibition, supplementation of rfVIIa with fVIII would result in improved thrombin generation and be predictive of clinical responses to this novel treatment regimen. In order to test this hypothesis, 10 murine monoclonal antibodies (MAbs) with non-overlapping epitopes spanning fVIII, differential inhibition titers, and inhibition kinetics were studied using a thrombin generation assay. Of the 3 MAbs with high inhibitory titers, only the one with fast and complete (classically defined as “type I”) kinetics displayed significant inhibition of thrombin generation with no improvement upon supplementation of rfVIIa with fVIII. The other two MAbs that displayed incomplete (classically defined as “type II”) inhibition did not suppress the potentiation of thrombin generation by fVIII. All antibodies that did not completely inhibit fVIII activity demonstrated potentiation of thrombin generation by the addition of fVIII as compared to rfVIIa alone. In conclusion, fVIII alone or in combination with rfVIIa corrects the thrombin generation defect produced by the majority of anti-fVIII MAbs better than single agent rfVIIa. Therefore, combined fVIII/rfVIIa therapy may provide better hemostatic control than current therapy in some patients with anti-fVIII inhibitors.

Concepts: Immune system, Coagulation, Enzyme inhibitor, Factor VIII, Protein C, Thrombin, Factor X, Coagulation system

168

Hemophilia A is a common X chromosome-linked genetic bleeding disorder caused by abnormalities in the coagulation factor VIII gene (F8). Hemophilia A patients suffer from a bleeding diathesis, such as life-threatening bleeding in the brain and harmful bleeding in joints and muscles. Because it could potentially be cured by gene therapy, subhuman animal models have been sought. Current mouse hemophilia A models generated by gene targeting of the F8 have difficulties to extrapolate human disease due to differences in the coagulation and immune systems between mice and humans. Here, we generated a porcine model of hemophilia A by nuclear transfer cloning from F8-targeted fibroblasts. The hemophilia A pigs showed a severe bleeding tendency upon birth, similar to human severe hemophiliacs, but in contrast to hemophilia A mice which rarely bleed under standard breed conditions. Infusion of human factor VIII was effective in stopping bleeding and reducing the bleeding frequency of a hemophilia A piglet but was blocked by the inhibitor against human factor VIII. These data suggest that the hemophilia A pig is a severe hemophilia A animal model for studying not only hemophilia A gene therapy but also the next generation recombinant coagulation factors, such as recombinant factor VIII variants with a slower clearance rate.

Concepts: Blood, Hemostasis, Factor VIII, Haemophilia A, Haemophilia B, Protein C, Thrombin, Factor X

98

Vitamin K has important functions within the body, some of which are still being discovered. Research has shown that vitamin K is an anticalcification, anticancer, bone-forming and insulin-sensitising molecule. Recent data indicate that subclinical vitamin K deficiency is not uncommon. Additionally, vitamin K antagonists such as warfarin may cause detrimental side effects, which may partly be blunted through vitamin K supplementation.

Concepts: Osteoporosis, Warfarin, Protein C, Vitamin K, Factor X, Protein Z, Coumarin, Vitamin K epoxide reductase

71

Parenterally administered ascorbic acid modulates sepsis-induced inflammation and coagulation in experimental animal models. The objective of this randomized, double-blind, placebo-controlled, phase I trial was to determine the safety of intravenously infused ascorbic acid in patients with severe sepsis.

Concepts: Inflammation, Acid, Pneumonia, Intravenous therapy, Route of administration, Sepsis, Protein C, Ascorbic acid

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Background In patients with severe hemophilia A, standard treatment is regular prophylactic and episodic intravenous infusions of factor VIII. However, these treatments are burdensome, especially for children, and may lead to the formation of anti-factor VIII alloantibodies (factor VIII inhibitors). Emicizumab (ACE910), a humanized bispecific antibody mimicking the cofactor function of factor VIII, was developed to abate these problems. Methods We enrolled 18 Japanese patients with severe hemophilia A (with or without factor VIII inhibitors) in an open-label, nonrandomized, interindividual dose-escalation study of emicizumab. The patients received subcutaneous emicizumab weekly for 12 weeks at a dose of 0.3, 1.0, or 3.0 mg per kilogram of body weight (cohorts 1, 2, and 3, respectively). The end points were safety and pharmacokinetic and pharmacodynamic profiles. An additional, exploratory end point was the annualized bleeding rate, calculated as 365.25 times the number of bleeding episodes, divided by the number of days in the treatment period as compared with the 6 months before enrollment. Results Emicizumab was associated with neither serious adverse events nor clinically relevant coagulation abnormalities. Plasma concentrations of emicizumab increased in a dose-dependent manner. Activated partial-thromboplastin times remained short throughout the study. The median annualized bleeding rates in cohorts 1, 2, and 3 decreased from 32.5 to 4.4, 18.3 to 0.0, and 15.2 to 0.0, respectively. There was no bleeding in 8 of 11 patients with factor VIII inhibitors (73%) and in 5 of 7 patients without factor VIII inhibitors (71%). Episodic use of clotting factors to control bleeding was reduced. Antibodies to emicizumab did not develop. Conclusions Once-weekly subcutaneous administration of emicizumab markedly decreased the bleeding rate in patients who had hemophilia A with or without factor VIII inhibitors. (Funded by Chugai Pharmaceutical; JapicCTI number, 121934.).

Concepts: Blood, Coagulation, Hemostasis, Haemophilia A, Haemophilia B, Protein C, Division, Factor X

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BACKGROUND:: In 1992, the first consensus definition of severe sepsis was published. Subsequent epidemiologic estimates were collected using administrative data, but ongoing discrepancies in the definition of severe sepsis produced large differences in estimates. OBJECTIVES:: We seek to describe the variations in prevalence and mortality of severe sepsis in the United States using four methods of database abstraction. We hypothesized that different methodologies of capturing cases of severe sepsis would result in disparate estimates of prevalence and mortality. DESIGN, SETTING, PARTICIPANTS:: Using a nationally representative sample, four previously published methods (Angus et al, Martin et al, Dombrovskiy et al, and Wang et al) were used to gather cases of severe sepsis over a 6-yr period (2004-2009). In addition, the use of new ICD-9 sepsis codes was compared with previous methods. MEASUREMENTS:: Annual national prevalence and in-hospital mortality of severe sepsis. RESULTS:: The average annual prevalence varied by as much as 3.5-fold depending on method used and ranged from 894,013 (300/100,000 population) to 3,110,630 (1,031/100,000) using the methods of Dombrovskiy et al and Wang et al, respectively. Average annual increase in the prevalence of severe sepsis was similar (13.0% to 13.3%) across all methods. In-hospital mortality ranged from 14.7% to 29.9% using abstraction methods of Wang et al and Dombrovskiy et al. Using all methods, there was a decrease in in-hospital mortality across the 6-yr period (35.2% to 25.6% [Dombrovskiy et al] and 17.8% to 12.1% [Wang et al]). Use of ICD-9 sepsis codes more than doubled over the 6-year period (158,722 - 489,632 [995.92 severe sepsis], 131,719 - 303,615 [785.52 septic shock]). CONCLUSION:: There is substantial variability in prevalence and mortality of severe sepsis depending on the method of database abstraction used. A uniform, consistent method is needed for use in national registries to facilitate accurate assessment of clinical interventions and outcome comparisons between hospitals and regions.

Concepts: Epidemiology, United States, Systemic inflammatory response syndrome, Multiple organ dysfunction syndrome, Septic shock, Sepsis, Protein C, Bacteremia

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Markers for hypercoagulation can be used to explain why some patients may have had thromboembolic disease (TED). This information may then be applied to estimate risk for additional TED that may afflict these patients following subsequent surgeries. This investigation was to determine the frequency of hypercoagulation parameters among patients having had TED, and how frequently these occur in multiples. Consulting hematologists were asked to comment upon potential risk for recurrent TED that may be associated with additional surgeries. The consulting hematologist determined which laboratory tests were to be ordered for each patient. This retrospective study probed the hospital computer logs for patients having had homocysteine, protein C, factor V Leiden or anticardiolipin antibodies measured during a 6-year period. The laboratory records for patients having had any one of these tests were then examined further for any additional hypercoagulation laboratory studies performed. Five hundred and twenty patients were identified in this survey. Abnormal diagnostic results were found for 293 (56.3%) of these patients. Two or more abnormalities (up to 5) were found for 103 (35.6%) of these patients. Laboratory explanations for TED may be found in a large proportion of patients with TED. It is not uncommon to find more than one abnormality among these patients. This information may be used in advising patients and their physicians as to the risks of additional TED following future surgical procedures and can be the basis for recommending life style changes.

Concepts: Medicine, Blood, Hospital, Surgery, Physician, Hematology, Protein C, Factor V Leiden

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After numerous negative randomized trials testing drugs for severe sepsis and/or septic shock, the blood purification approach remains one possibility. Many techniques have been proposed, having in common the goal to eliminate blood and/or plasma factors, supposed to play a negative role in outcomes. Among these, high dose of hemofiltration, high volume hemofiltration, high permeability hemofiltration and specific or non-specific hemoperfusion or hemoadsorption have been proposed. Until now, a poor level of proof has been published, questioning the pertinence of such a strategy. To have a chance to succeed, immune monitoring has to be performed to select suitable patients regarding their immune status, the intensity of inflammation and their cellular function. Because of the potential interaction with mediators and cell capture, Rimmelé and colleagues published the results obtained with an in vitro set up, testing different adsorption cartridges in comparison to hemofiltration. They nicely confirmed the complex impact on mediator levels and cell capture and phenotype. This is certainly a more systematic approach to better understand the action of such adsorbing cartridges, which has to be developed.

Concepts: Inflammation, Pneumonia, Systemic inflammatory response syndrome, Multiple organ dysfunction syndrome, Septic shock, Sepsis, Protein C, Bacteremia

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BACKGROUND: Use of combined oral contraceptives is associated with a three- to six-fold increased risk of venous thrombosis. This increased risk depends on the estrogen dose as well as the progestogen type of combined oral contraceptives. Thrombin generation-based Activated Protein C resistance (APC resistance) and sex hormone-binding globulin (SHBG) levels predict the thrombotic risk of a combined hormonal contarceptive. Recently a four-phasic oral contraceptive containing dienogest (DNG) and estradiol valerate (E2V) has been marketed. The aim of this study was to evaluate the thrombotic risk of the DNG/E2V oral contraceptive by comparing APC resistance by measuring normalized APC sensitivity ratios (nAPCsr) and SHBG levels in users of oral contraceptives containing dienogest and estradiol valerate (DNG/E2V) and oral contraceptives containing levonorgestrel and ethinyl estradiol (LNG/EE). METHODS: We conducted a single centre, randomized, open label, parallel-group study in 74 women using DNG/E2V or LNG/EE, and measured nAPCsr and SHBG levels in every phase of the regimen of DNG/E2V. RESULTS: During the pill cycle SHBG levels did not differ between DNG/E2V users and LNG/EE users. nAPCsr were overall slightly lower in DNG/E2V users than in LNG/EE users, mean difference -0.44 (95% CI -1.04 to 0.17) for day 2, -0.20 (95% CI -0.76 to 0.37) for day 7, -0.27 (95% CI -0.81 to 0.28) for day 24 and -0.34 (95% CI -0.91 to 0.24) for day 26. CONCLUSION: No statistical significant differences in nAPCsr and SHBG levels were found between users of the oral contraceptive containing DNG/E2V and LNG/EE, suggesting a comparable thrombotic risk. © 2013 International Society on Thrombosis and Haemostasis.

Concepts: Hormonal contraception, Combined oral contraceptive pill, Estrogen, Hematology, Estradiol, Menstrual cycle, Protein C, Ethinylestradiol