The Art of Detecting Antibodies against Factor VIII.

Antibodies against factor VIII (FVIII) can be detected based on their ability to neutralize the procoagulant activity of FVIII (neutralizing antibodies, inhibitors), or based on their specific binding capacity to FVIII protein. This article reviews the available assays and their clinical interpretation in patients with congenital and acquired hemophilia.

Emicizumab improves the stability and structure of fibrin clot derived from factor VIII-deficient plasma, similar to the addition of factor VIII.

INTRODUCTION: Emicizumab is an antifactor (F)IXa/FX bispecific antibody, mimicking FVIIIa cofactor function. Emi prophylaxis effectively reduces bleeding events in patients with haemophilia A. The physical properties of emicizumab-induced fibrin clots remain to be investigated, however. AIM: We have investigated the stability and structure of emicizumab-induced fibrin clots. METHODS: Coagulation was initiated by activated partial thromboplastin time (aPTT) trigger and prothrombin time (PT)/aPTT-mixed trigger in FVIII-deficient plasma with various concentrations of emicizumab or recombinant FVIII. The turbidity and stability of fibrin clots were assessed by clot waveform and clot-fibrinolysis waveform analyses, respectively. The resulting fibrin was analysed by scanning electron microscopy (SEM). RESULTS: Using an aPTT trigger, the turbidity was decreased and the fibrinolysis times were prolonged in the presence of emicizumab dose-dependently. Scanning electron microscopy imaging demonstrated that emicizumab improved the structure of fibrin network with thinner fibres than in its absence. Although emicizumab shortened the aPTT dramatically, the nature of emicizumab-induced fibrin clots did not reflect the hypercoagulable state. Similarly, using a PT/aPTT-mixed trigger that could evaluate potential emicizumab activity, emicizumab improved the stability and structure of fibrin clot in a series of experiments. In this circumstance, fibrin clot properties with emicizumab at 50 and 100 µg/mL appeared to be comparable to those with FVIII at ~12 and ~24-32 IU/dL, respectively. CONCLUSION: Emicizumab effectively improved fibrin clot stability and structure in FVIII-deficient plasma, and the physical properties of emicizumab-induced fibrin clots were similar to those with FVIII.

Prothrombotic response to norepinephrine infusion, mimicking norepinephrine stress-reactivity effects, is partly mediated by α-adrenergic mechanisms.

BACKGROUND: Stress-induced prothrombotic changes are mediated by the sympathetic nervous system and critically involved in mental triggering of acute coronary syndromes, but the underlying psychobiology is not fully understood. We tested the hypothesis that a norepinephrine (NE) infusion to mimic effects of stress-induced NE release on blood coagulation elicits prothrombotic changes and examined to what extent these would be mediated by an alpha-adrenergic mechanism. METHODS AND RESULTS: In a single-blind placebo-controlled within-subjects design, 24 middle-aged, non-smoking, non-obese and normotensive men participated in three experimental trials with an interval between one and two weeks. Each trial applied two sequential infusions of 1 and 15 min duration with varying substances [i.e., saline as placebo, the non-specific α-blocker phentolamine (2.5 mg/min), and NE (5 µg/min)]: trial 1=saline + saline; trial 2=saline + NE, and trial 3=phentolamine + NE. Plasma levels of clotting factor VIII activity (FVIII:C), fibrinogen, and D-dimer were assessed from blood samples collected immediately before and 1 min and 20 min after infusion procedures. Compared to saline + saline, saline + NE induced increases over time in FVIII:C, fibrinogen, and D-dimer levels. With phentolamine + NE, fibrinogen levels remained increased compared to saline + saline, but changes in FVIII:C and D-dimer levels were no more different. Coagulation changes did not differ between saline + NE and phentolamine + NE. CONCLUSIONS: NE infusion activates blood coagulation. The resulting prothrombotic state could be one psychobiological mechanism underlying mental triggering of acute coronary syndromes. Blockade of α-adrenergic receptors partly attenuated NE effects on coagulation and could be implied to have preventive potential in susceptible individuals.

Hemlibra's Remarkable Efficacy A Beacon For Hemophilia Patients.

Hemlibra demonstrates how far antibody science has progressed. Genentech's drug, approved late last year, connects two clotting factors to prevent the devastating bleeds in hemophilia patients with inhibitors. The high price may be offset by avoided costs in patients with factor VIII inhibitors.

Desmopressin in moderate hemophilia A patients: a treatment worth considering.

Desmopressin increases endogenous factor VIII levels in hemophilia A. Large inter-individual variation in the response to desmopressin is observed. Patients with a lower baseline factor VIII activity tend to show a reduced response, therefore, desmopressin is less frequently used in moderate hemophilia A patients (baseline factor VIII activity 1-5 international units/deciliter), even though factor VIII levels may rise substantially in some of them. We aim to describe the response to desmopressin in moderate hemophilia A patients and to identify predictors. We selected data on 169 patients with moderate hemophilia from the multicenter Response to DDAVP In non-severe hemophilia A patients: in Search for dEterminants (RISE) cohort study. Adequate response to desmopressin was defined as a peak factor VIII level ≥ 30, and excellent response as ≥ 50 international units/deciliter after desmopressin administration. We used univariate and multiple linear regression techniques to analyze predictors of the peak factor VIII level. Response was considered adequate in 68 patients (40%), of whom 25 showed excellent response (15%). Intravenous administration, age, pre-desmopressin factor VIII activity and von Willebrand factor antigen, peak von Willebrand factor activity and desmopressin-induced rise in von Willebrand factor antigen were significant predictors of peak factor VIII level and explained 65% of the inter-individual variation. In 40% of moderate hemophilia A patients, desmopressin response was adequate, thus it is important not to with-hold this group of patients from desmopressin responsiveness. Among the six predictors that we identified for desmopressin-induced factor VIII rise, factor VIII activity and desmopressin-induced rise in von Willebrand factor antigen had the strongest effect.

Surgery and survival in birth cohorts with severe haemophilia and differences in access to replacement therapy: The Malmö experience.

BACKGROUND: Persons with severe haemophilia require lifelong replacement therapy, prophylaxis, to prevent bleeding. Data describing long-term outcomes of prophylactic treatment are scarce. The aim of this study was to investigate joint surgery and survival among persons with severe haemophilia with special attention to access to prophylaxis in the early years of life. METHODS: Eligible participants had severe haemophilia A or B and were treated at the Malmö centre from the 1960s onward. Time from birth until joint surgery was analysed for participants negative for factor inhibitor and alive in 2000. We compared survival among the entire cohort with severe haemophilia treated at the Malmö centre with the general male population of Sweden and a sample of persons with severe haemophilia from the United Kingdom (UK). RESULTS: Overall, 167 participants were included, 106 (63.5%) of whom had complete data on joint surgery. Among those born before 1970, 1970-1979 and ≥1980 approximately 37%, 21% and 0% had their first joint surgery by age 30, respectively. There were no second joint surgeries reported in cohorts born ≥1970. Persons with severe haemophilia and negative for HIV treated in Malmö have attained approximately similar survival to that of the general male population in Sweden and live slightly longer than persons with severe haemophilia from the UK. DISCUSSION AND CONCLUSION: Prophylaxis in Sweden, although costly, has markedly improved survival and joint outcomes for persons with severe haemophilia. This study highlights the importance of early start of replacement therapy to prevent or postpone serious joint damage.

Perioperative Coagulation Management of a Hemophilia A Patient During Cardiac Surgery.

Perioperative management of cardiovascular surgical procedures requiring cardiopulmonary bypass (CPB) in patients with hemophilia A poses a clinical challenge in coagulation management. Use of CPB requires the administration of an anticoagulant, usually unfractionated heparin, and also causes dilutional coagulopathy, platelet dysfunction or platelet consumption coagulopathy. Hypothermia and activation of the inflammatory cascade also affect coagulation. The effects of CPB on circulating levels of factor VIII have not been clearly defined. In this review, the effects of CPB and hemodilution on FVIII are shown in a case presentation, and perioperative laboratory testing in patients with hemophilia A having cardiac surgery is discussed along with perioperative and postoperative coagulation management.

Impact on hepatic estrogen-sensitive proteins by a 1-year contraceptive vaginal ring delivering Nestorone® and ethinyl estradiol.

OBJECTIVES: Estrogen-sensitive hepatic proteins were assessed in women using a contraceptive vaginal ring (CVR) delivering 150mcg Nestorone® (NES) and 15mcg ethinyl estradiol (EE). STUDY DESIGN: A substudy of the Contraceptive Clinical Trials Network of the National Institute of Child Health and Human Development enrolled 129 participants, with assessments of factor VIII, fibrinogen, protein S (PS) and sex hormone binding globulin (SHBG). Thirty-six participants had used combined hormonal contraceptives (CHCs) in the cycle preceding first CVR use (recent users) and 70 had no history of recent use (nonusers). RESULTS: Mean values at baseline were within the normal range for all four proteins but were higher for factor VIII, fibrinogen and SHBG and significantly lower for PS in recent compared to nonusers. During NES/EE CVR use, factor VIII, fibrinogen and PS were within the normal range; however, SHBG levels were increased by nearly 100% at Cycle 13. The change from baseline to final evaluation was statistically significant for all proteins in nonusers. The change in recent users was significant for factor VIII at Cycle 6 and for SHBG at Cycles 6 and 13, but not for PS or fibrinogen. CONCLUSION: NES/EE CVR for up to 13cycles was associated with changes from baseline in plasma levels of factor VIII, fibrinogen and PS that were within the normal range, with SHBG levels above the normal range by Cycle 6. Nonusers of CHC before CVR showed wider changes in values versus recent users whose baseline values were increased by previous EE exposure. IMPLICATIONS: Recent use of CHCs demonstrated significant changes in all four measured hepatic proteins at baseline compared to nonusers. Use of the NES/EE CVR further changed these hepatic protein markers, but values remained within the normal range. Prebaseline exposure to estrogen can obscure interpretation of hepatic proteins changes associated with a second CHC.

Clotting factor changes during the first cycle of oral contraceptive use.

OBJECTIVES: The risk of venous thromboembolism (VTE) is highest during the initial months of oral contraceptive (OC) use. We sought to evaluate the extent of hemostatic variable changes during the initial OC cycle and if such changes are related to systemic ethinyl estradiol (EE2) exposure. STUDY DESIGN: Participants provided multiple blood samples during a 21-day OC cycle (30mcg EE2; 150mcg levonorgestrel) and after a single dose following a washout period. Analytes included D-dimer, factor VIII activity, protein C total antigen and the hepatic proteins corticosteroid-binding globulin (CBG) and sex-hormone-binding globulin (SHBG). EE2 pharmacokinetic analyses related to the 24h after the first OC tablet (OC1) and at steady state (OC21). RESULTS: Seventeen women completed the study. D-dimer more than doubled by OC6 (p=.013) and remained elevated at OC21 (p=.012). D-dimer levels within women varied widely from day to day. Factor VIII increased 27% by OC2 (p<.001) but declined to a 9% increase by OC21. Protein C increased only 6%. EE2 steady-state area-under-the-curve ranged from 488 to 1103pg∙h/mL; higher levels were not correlated with greater increases in clotting variables. CBG and SHBG increased significantly but were not significantly correlated with levels of EE2 or with the hemostatic variables. CONCLUSIONS: D-dimer increases during the first OC cycle were at least as great as increases seen with longer OC use. These results provide support for the increased VTE risk during initial OC use. The extreme variability in D-dimer levels may be an important component of this risk. IMPLICATIONS: This study showed that increases in D-dimer are clearly evident in the first cycle of OC use and may be larger than are seen after a longer duration of use and thus provide biological support for the increased VTE risk during initial OC use found in epidemiological studies.

Live kidney donation from a person with haemophilia.

There are many documented cases of a person with haemophilia successfully receiving a solid organ transplant, including liver and kidney. However, there is no literature reporting live organ donation by a person with haemophilia. Presumably, this is because the associated risks of excessive bleeding, inhibitor development after a period of intensive treatment with factor replacement and the possibility of variant Creutzfeldt-Jakob disease transmission in those previously treated with blood products, are considered excessive. This case describes a 24-year-old man who was diagnosed with mild haemophilia A during his pretransplant work up as a potential live kidney donor to his sister. He then went on to successfully donate his kidney, without complications. To the best of our knowledge, this is the first description of a person with haemophilia being a living organ donor.

Successful immunoadsorption of life-threatening bleeding in factor VIII inhibitor disease, but no long-term remission with anti-CD20 treatment.

A 62-year-old man and a 64-year-old woman presented to our institution with acquired haemophilia A. They both developed life-threatening bleeding. Immunoadsorption using protein A columns was used to rapidly lower factor VIII inhibitor levels. Immunosuppression with steroids and the anti-CD20 antibody, rituximab, was instituted. Yet their effects were either partial or complicated by an early relapse. Repetitive cyclophosphamide administration led to a sustained immunological response. While immunoadsorption appears effective and safe to lower factor VIII inhibitor levels, it seems that further preferably randomised controlled trials are needed to establish the value of rituximab versus the standard immunosuppressive regime comprising cyclophosphamide.

Modification of interdomain interfaces within the A3C1C2 subunit of factor VIII affects its stability and activity.

Factor (F)VIII consists of a heavy chain [A1(a1)A2(a2)B domains] and a light chain [(a3)A3C1C2 domains]. Several reports have shown significant changes in FVIII stability and/or activity following selected mutations at the A1-A2, A1-A3, A2-A3, and A1-C2 domain interfaces. In this study, the remaining inter-FVIII subunit interfaces (A3-C1 and C1-C2) were examined for their contributions to the stability and activity of FVIII and FVIIIa. We prepared FVIII mutants with nascent disulfide bridges between A3 and C1 domains (Gly1750Cys/Arg2116Cys and Ala1866Cys/Ser2119Cys) or C1 and C2 domains (Ser2029Cys/Pro2292Cys). We also prepared mutants via replacement of Arg2116 with hydrophobic residues (Ala and Val) because this C1 domain residue appears to face a pocket of positive electrostatic potential in the A3 domain. Stability was assessed following the rates of loss of FVIII activity at 55 °C and the spontaneous loss of FVIIIa activity from A2 subunit dissociation. FVIII Gly1750Cys/Arg2116Cys showed a marked increase in thermal stability (∼3.7-fold) compared with that of wild-type (WT) FVIII, while the stability of FVIII Ala1866Cys/Ser2119Cys was reduced (∼4.7-fold). Although the Ser2029Cys/Pro2292Cys variant showed a modest loss of FVIII stability, the specific activity and thrombin generation potential of this variant were increased (up to 1.2-fold) compared with those of WT. Furthermore, this variant demonstrated an ∼2-fold reduced Km for FX. Mutation of Arg2116 to hydrophobic residues resulted in variable decreases in stability and thrombin generation parameters, suggesting a role of this Arg residue contributing to FVIII structure. Taken together, selective modification of the contiguous domain interfaces in the FVIII light chain may improve FVIII stability and/or cofactor function.

Tranexamic acid: less bleeding and less thrombosis?

The early administration of tranexamic acid (TXA) to bleeding trauma patients reduces all-cause mortality without increasing the risk of vascular occlusive events. Indeed, the risk of arterial thrombosis appears to be reduced with TXA. In this commentary we hypothesize that TXA has an antithrombotic effect and explore potential mechanisms. These include inhibition of the inflammatory effects of plasmin, effects on platelets and effects on factors V and VIII. If proven, these antithrombotic effects would have major implications for the systemic use of TXA in surgical patients, where TXA has been clearly shown to reduce bleeding.

Lack of responsiveness to 1-desamino-D arginin vasopressin (desmopressin) in male patients with nephrogenic syndrome of inappropriate antidiuresis: from bench to bedside.

BACKGROUND: Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a recently described entity, linked to gain-of-function mutations (R137C and R137L) in arginine vasopressin (AVP) gene leading to chronic activation of tubular V2 AVP receptor (V2R) and thus free water reabsorption. In addition to collecting duct cells, the V2R is also expressed in endothelial cells, where it mediates the rise in circulating levels of von Willebrand factor (vWF) and coagulation factor VIII (fVIII). Recent in vitro data showed that these mutant receptors are resistant to vasopressin-stimulated cAMP production. We aimed to explore by clinical observations the sensitivity to vasopressin of the R137C-V2R mutant in vivo. MATERIAL AND METHODS: We performed a stimulation test with 1-desamino-D arginin vasopressin (dDAVP) 0·3 µg/kg of bodyweight in three patients (two hemizygous male and one heterozygous female) with NSIAD with R137C mutation and measured on the one hand the levels of vWF and fVIII and the other hand urine osmolality and albumin excretion (UAE). RESULTS: Whereas the female heterozygous patient displayed normal response to simulation by dDAVP (except for UAE), no increase in vWF, fVIII, urinary osmolality and UAE was observed among hemizygous male patients. CONCLUSIONS: Coherent with in vitro observation in transfected cells, our clinical observations demonstrate that the R137C-V2R mutant is resistant to vasopressin stimulation in its physiological sites of expression.

[Evaluation of haemostasis in children treated with valproic acid]. / Untersuchungen zur Hämostase bei Kindern unter Valproatbehandlung.

UNLABELLED: Coagulation parameters were determined in children with valproic acid mono- and valproic acid-lamotrigin combination therapy. PATIENTS, METHODS: Monotherapy group (n = 22; mean age: 10.5 years) was compared to combination therapy (n = 7; 12.9 years) and a control group (n = 22; 8.7 years). The following parameters were measured: aggregation and ATP-release in whole blood (ADP: 20 µmol/l, collagen: 1 µg/ml, thrombin: 0.5 U/ml), PFA-100® closure times (CT), blood cell counts, global tests, VWF:Ag, VWF:CBA, factors VIII and XIII as well as fibrinogen. Bleeding symptoms were evaluated by using a questionnaire. RESULTS: For ADP- and collagen-induced aggregation as well as for ATP release no significant differences between the groups were detected. The combined therapy group showed significantly prolonged CT. Von Willebrand disease was not detected in any of the patients. The platelet count was significantly decreased in the monotherapy group. In six children a mild bleeding tendency was observed, mostly epistaxis. CONCLUSION: A clinically relevant influence of valproic acid on haemostasis was found only in few cases. However, before surgical procedures an extended coagulation diagnostics is recommended in patients with valproic acid therapy.

Molecular and phenotypic determinants of the response to desmopressin in adult patients with mild hemophilia A.

BACKGROUND: The relationship of the biologic response to desmopressin with the F8 mutation and physiological characteristics has been poorly investigated in patients with mild hemophilia A. OBJECTIVES: We prospectively assessed the molecular and phenotypic determinants of the biologic response to desmopressin in a cohort of 50 patients with mild hemophilia A. METHODS: Up to 24 h after desmopressin, blood samples were serially obtained and factor (F)VIII and von Willebrand factor (VWF) measured. The promoter region, all exons and exon-intron boundaries of the F8 gene were screened using denaturing high-performance liquid chromatography (DHPLC). Direct sequencing was done when DHPLC screening was normal. Genomic DNA was also sequenced for exons 18-21, 24 and 27 of VWF. RESULTS: Mean basal FVIII:C was 19 +/- 9 IU dL(-1) (range 6-37) and the median postdesmopressin peak increase was 2.5-fold (range 1.1-7.1). Eleven patients with a cross-reacting material positive (CRM(+)) phenotype had similar basal levels and relative increases of FVIII:C to the remaining patients with low FVIII:Ag. Using multivariate regression, FVIII:C half-life was positively related to basal and peak VWF:Ag levels (P = 0.008) and patient age (P = 0.004). Eleven patients had evidence of reduced FVIII survival. While 27 different gene mutations were identified in 41 patients, nine patients had no detectable mutation. These patients had significantly smaller peaks and smaller relative increase of postdesmopressin FVIII:C (median FVIII:C 26 IU dL(-1) vs. 54 IU dL(-1); P < 0.001; fold 1.8 +/- 0.6 vs. 2.9 +/- 0.8; P = 0.002). CONCLUSIONS: In this cohort of patients with mild hemophilia A, a poor biologic response to desmopressin was frequently associated with the absence of detectable F8 mutations.

Valproate-associated coagulopathies in children during short-term treatment.

Valproic acid is one of the most frequently prescribed antiepileptic drugs for the therapy of generalized and focal epilepsies. Valproate induces a variety of hemostatic disorders such as thrombocytopenia, abnormal platelet function, hypofibrinogenemia, and decreased concentrations of von Willebrand factor, and it rarely causes serious bleeding complications. It may also lead to atherosclerosis and thrombosis. However, there is still lack of knowledge about the incidence and occurrence of these particular side effects. In this prospective systematic study, we assessed the early effects of sodium valproate on both pro- and anticoagulatory factors, homocysteine, and lipoprotein (a) in 24 newly diagnosed epileptic children treated with valproate. Valproate causes decreased factor VII levels, platelet count, factor VIII, Protein C, fibrinogen, and increased lipoprotein (a) levels. To the best of our knowledge, our report is the first in the medical literature, which describes that valproate significantly reduces factor VII levels even during short-term therapy.