Thrombin generation and bleeding in haemophilia inhibitor patients during immune tolerance induction.

BACKGROUND: Inhibitor formation complicates haemophilia treatment and requires immune tolerance induction to rid inhibitors over 5 BU. In the prospective, randomized International Immune Tolerance Study, immune tolerance induction was equally effective with high-dose (HD) (200 IU kg-1 day-1 ) and low-dose (LD) (50 IU kg-1 3× per week) factor VIII, but haemorrhages were twofold higher in the LD arm. This finding was unexpected as inhibitors neutralize FVIII activity. We hypothesized that the thrombin generation assay (TGA), a global measure of clot formation, might predict bleeding better than FVIII levels. METHODS: We evaluated TGA using relipidated tissue factor (TF) on 83 thawed, recalcified corn trypsin inhibitor/citrate plasma samples from 31 subjects (17 HD, 14 LD) who participated on the ITI study, and who had sufficient sample available and appropriate informed consent. RESULTS: There were no significant differences in peak thrombin, estimated thrombin potential, maximum rate or lag time between HD and LD arms; between pre-, during and post-ITI time points, or after FVIII spiking. In 19 subjects (12 HD, 7 LD) with anti-FVIII<1.0 BU, the prevalence of non-neutralizing antibody (NNA) and neutralizing antibody (NA) was 89.5% (17/19), and the latter strongly correlated with anti-VIII titer, r = 0.73 [95% CI: 0.55, 0.88]. CONCLUSION: In haemophilia inhibitor patients, thrombin generation is present, but does not predict bleeding risk. Following tolerance induction, NNA remains detectable in the majority.

Central venous access device (CVAD) complications in Haemophilia with inhibitors undergoing immune tolerance induction: Lessons from the international immune tolerance study.

INTRODUCTION: Central venous access devices (CVADs) are frequently required as stable long-lasting venous access in children with haemophilia, especially those requiring immune tolerance induction (ITI) for inhibitors. CVAD infection is one of the most frequently reported catheter-related complications in this patient population. AIM: Detailed review of CVAD complications from the International ITI (I-ITI) study and analysis of potential risk factors for such complications. METHODS: Retrospective analysis of prospectively obtained data from the I-ITI study primarily focused on CVAD-related complications. RESULTS: A total of 115 children were recruited and 183 CVADs were placed in 99 subjects resulting in 121,206 CVAD-days observed on-study. A total of 124 CVAD infections were reported in 41 of 99 (41%) subjects with an overall infection rate of 0.94 per 1000 CVAD-days (interquartile ranges 0-1.7). A similar number of infections were observed in the two treatment arms (median: 2 and 3 in high dose and low dose respectively). Infections occurred more frequently in the presence of external catheters than with fully implanted catheters (P = 0.026). Infected patients were significantly younger at the time of CVAD insertion (median age: 22 vs. 25 months, P = 0.020). Patients with Gram-positive infections were also significantly younger than those with Gram-negative infections (median age: 17 vs. 25 months, P < 0.0001). CONCLUSION: CVAD infection was the most common complication observed in children with severe haemophilia and inhibitors in the frame of the I-ITI study. Younger age at CVAD insertion and external CVAD were associated with higher risk for infection. ITI outcome was unaffected by CVAD infections.

Use of global assays to understand clinical phenotype in congenital factor VII deficiency.

Congenital factor VII (FVII) deficiency is characterized by genotypic variability and phenotypic heterogeneity. Traditional screening and factor assays are unable to reliably predict clinical bleeding phenotype and guide haemorrhage prevention strategy. Global assays of coagulation and fibrinolysis may better characterize overall haemostatic balance and aid in haemorrhagic risk assessment. We evaluated the ability of novel global assays to better understand clinical bleeding severity in congenital FVII deficiency. Subjects underwent central determination of factor VII activity (FVII:C) as well as clot formation and lysis (CloFAL) and simultaneous thrombin and plasmin generation (STP) global assay analysis. A bleeding score was assigned to each subject through medical chart review. Global assay parameters were analysed with respect to bleeding score and FVII:C. Subgroup analyses were performed on paediatric subjects and subjects with FVII ≥ 1 IU dL(-1). CloFAL fibrinolytic index (FI2 ) inversely correlated with FVII:C while CloFAL maximum amplitude (MA) and STP maximum velocity of thrombin generation (VT max) varied directly with FVII:C. CloFAL FI2 directly correlated with bleeding score among subjects in both the total cohort and paediatric subcohort, but not among subjects with FVII ≥ 1 IU dL(-1) . Among subjects with FVII ≥ 1 IU dL(-1), STP time to maximum velocity of thrombin generation and time to maximum velocity of plasmin generation inversely correlated with bleeding score. These preliminary findings suggest a novel potential link between a hyperfibrinolytic state in bleeding severity and congenital FVII deficiency, an observation that should be further explored.

Clinical trial design in haemophilia.

Progress in the evidence-based care of haemophilia A and B worldwide has been historically challenged by the dearth of evaluable outcome data, including but not limited to the safety and effectiveness of therapeutic interventions. These challenges are partially rooted in the inherent difficulty of conducting prospective clinical trials and observational studies with statistically meaningful endpoints in a rare disease such as haemophilia. Despite the logistical barriers, the need for outcome data has never been more critical than in this time of expansive therapeutic advance tempered by the shrinking economic capacity to fund the rapidly increasing cost of treatment. Given that systematic analyses of published literature have been largely unsuccessful in compensating for the lack of rigorous and purposeful data collection, new approaches to clinical study design and statistical modelling are urgently needed. However, even as these are considered, the lack of broadly accepted and well-defined clinical outcome endpoints poses an additional barrier to progress. The three presentations encompassed by this paper highlight the timely need for quality data from the perspectives of the clinicians, regulatory agencies and health care funders, and describe the ongoing coordinated efforts by the international haemophilia community to further understand and dismantle the barriers to harmonized and standardized data collection on a global scale using well-defined clinical outcome endpoints.

Haemostasis prophylaxis using single dose desmopressin acetate and extended use epsilon aminocaproic acid for adenotonsillectomy in patients with type 1 von Willebrand disease.

In patients with confirmed or suspected type 1 von Willebrand disease (VWD), adenotonsillectomy has been reported to be associated with a rate of peri-operative hemorrhage between 8 and 23%. Desmopressin acetate (DDAVP, 1-deamino 8-D arginine- vasopressin) is the treatment of choice for type 1 patients with baseline von Willebrand factor levels of 10 IU/dL or greater. DDAVP is generally well tolerated; however, severe hyponatremia and seizures have been reported in young children less than 2 years of age, limiting its use in this age group. Antifibrinolytic therapy plays an important adjunctive role in the effective treatment of mucocutaneous bleeding, particularly in the oropharynx where the salivary concentration of fibrinolytic enzymes is high. During the past 10 years, we treated 6 pediatric patients with mild/moderate type 1 VWD undergoing an adenotonsillar procedure at our institution with the same hemostatic regimen consisting of one single dose of DDAVP and an extended use of EACA. In this small case series, the above mentioned prophylactic treatment regimen was both well tolerated and efficacious in controlling hemorrhage. Furthermore, DDAVP-related complications were avoided in a pediatric population with a higher risk of developing them.

Successful hip arthroplasty in an adult male with severe factor XI deficiency using Hemoleven®, a factor XI concentrate.

Severe factor XI (sFXI) deficiency is a rare bleeding disorder (RBD). FXI replacement is most often required for surgical hemostasis. Plasma, the sole US treatment option, is often complicated by life-threatening allergic reactions. In such circumstances, the FDA offers a mechanism for institution-industry collaboration to facilitate limited use of replacement products licensed abroad. A 58 years old man with sFXI deficiency, required hip replacement. In the past, he received prophylactic plasma for thyroidectomy and experienced a severe allergic reaction. A single use institutional IND FDA application was initiated in collaboration with LFB (Les Ulis, France) to access Hemoleven®, a plasma-derived FXI concentrate. The application required an investigator-initiated IRB-approved protocol for treatment and safety/efficacy monitoring that included: preoperative thrombophilia, FXI inhibitor and pharmacokinetic (PK) evaluations; peri- postoperative administration of ≤ 4 doses of 10-15 U/kg Hemoleven® ; DIC monitoring; postoperative thromboprophylaxis; observation for product efficacy and potential complications. PK study demonstrated the expected 1.8% FXI recovery per U/kg with half-life of 62 hours. Mild D-Dimer elevation was noted 6-9 hours post-infusion. The initial dose (15 U/kg) was administered 15 hours before surgery; subsequently, 3 doses (10 U/kg) were infused every 72 hours. Hemostasis was excellent. No complications were observed. Collaboration allowed for successful patient access to Hemoleven® with excellent PK, safety, and efficacy. This case underscores the need for additional efforts to ensure safe and effective licensed replacement therapies for RBD patients.

Power Doppler sonography in the diagnosis of hemophilic synovitis--a promising tool.

BACKGROUND: Recurrent hemarthroses in hemophilia results in synovitis and joint arthropathy. Primary prophylaxis when universally instituted at current doses can prevent joint deterioration but is expensive. Alternatively, the selective implementation of prophylaxis would require a more sensitive tool for detecting synovitis than possible with clinical surveillance or plain radiographs. Magnetic resonance imaging (MRI) is such a tool and is utilized for the evaluation of hemophilic joint disease (HJD). However, it is expensive, and requires sedation in younger children precluding its utility for monitoring of synovitis. Ultrasonography (USG) with power Doppler (USG-PDS) has been utilized to detect and quantitate synovial vascularity in other arthritides and could provide an equally effective but less costly tool for HJD, particularly in children who would not require sedation. OBJECTIVES: To determine whether USG-PDS is comparable to MRI in the evaluation of hemophilic synovitis. PATIENTS: A prospective cohort of 31 subjects including 33 joints (knees, elbows, ankles) underwent dynamic contrast enhanced (DCE)-MRI and USG-PDS. RESULTS: USG-PDS measurements of synovial thickness(r = 0.70, P < 0.0001) and synovial vascularity (r = 0.73, P < 0.0001) correlated strongly with those obtained with DCE-MRI. A cutoff of PDS intensity of 1.3 decibels (dB) per mm(2) was found to yield a sensitivity of 100% and a specificity of 94.1% in 17 joints with/without a history of hemarthroses. Pettersson radiographic scores correlated significantly with synovial thickness in adults but not children. CONCLUSIONS: Our data suggest that USG-PDS may be an inexpensive and easily implemented imaging tool for detecting hemophilic synovitis and could be useful in tailoring effective prophylaxis.

Ethical considerations in clinical investigation: exploring relevance in haemophilia research.

Painful controversy has so far been largely absent from the history of haemophilia-related clinical research. However, the investigative methods now needed to realize evidence-based clinical practice, therapeutic advance, and a progressive standard of care for patients worldwide will be accompanied by the potential for ethical dilemma and transgression. From the current vantage point, three primary ethical issues merit special consideration: (i) the therapeutic misconception inherent to all clinical research and the randomized trial in particular; (ii) high risk and potentially non-beneficial novel technology research in children; and (iii) a collaborative partnership approach to research in the developing world. This study will focus on a discussion of each of these, drawing from the research ethics literature to offer a potential template for future deliberations in clinical trial design.

The use of factor VIII/von Willebrand factor concentrate for immune tolerance induction in haemophilia A patients with high-titre inhibitors: association of clinical outcome with inhibitor epitope profile.

A retrospective chart review of 11 subjects with severe haemophilia A and high-titre inhibitors who received a von Willebrand factor-containing FVIII concentrate (VWF/FVIII) for immune tolerance induction (ITI) was accompanied by B cell inhibitor epitope mapping during 10/11 treatment courses. ITI was successful or partially successful in all seven subjects who received VWF/FVIII for initial ITI, and failed in all four subjects whose ITI with this product was initiated following treatment failure using recombinant factor VIII. Variables including age at inhibitor development and age at ITI initiation, interval between inhibitor detection and ITI initiation, titre at start of ITI, and peak historical titres prior to and during ITI were not statistically significant outcome predictors in this cohort. However, the B cell epitope specificity in all four successful and in one of two partially successful ITI subjects for whom information was available included the C2 and excluded the A2 domains. Conversely, FVIII B cell epitopes in one partially successful ITI and in all three failed ITI subjects for whom data were available mapped to both the C2 and the A2 domains. The FVIII B cell epitope profile was associated with ITI outcome in this VWF/FVIII-treated cohort. Its role in predicting ITI outcome and guiding choice of FVIII product for ITI requires further study.

Rare inherited disorders of fibrinogen.

Fibrinogen, a hexameric glycoprotein encoded by three genes - FGA, FGB, FGG - clustered on chromosome 4q is involved in the final steps of coagulation as a precursor of fibrin monomers required for the formation of the haemostatic plug. Inherited disorders of fibrinogen abnormalities are rare and not as well clinically characterized as some other inherited bleeding disorders. To characterize the clinical manifestations, molecular defects and treatment modalities of these rare disorders, a Medline search from January 1966 to September 2007 for these disorders reported in large studies and registries was undertaken. Inherited fibrinogen disorders can manifest as quantitative defects (afibrinogenemia and hypofibrinogenemia) or qualitative defects (dysfibrinogenemia). Quantitative fibrinogen deficiencies may result from mutations affecting fibrinogen synthesis, or processing while qualitative defects are caused by mutations causing abnormal polymerization, defective cross-linking or defective assembly of the fibrinolytic system. Clinical manifestations vary from being asymptomatic to developing catastrophic life-threatening bleeds or thromboembolic events. Management of bleeds includes use of purified plasma-derived concentrates, cryoprecipitate or fresh frozen plasma. Use of some of these products carries risks of viral transmission, antibody development and thromboembolic events. Establishment of registries in Iran, Italy and North America has fostered a better understanding of these disorders with an attempt to explore molecular defects. Rare Bleeding Disorder Registries developed through the United States and international efforts hopefully will encourage development and licensure of safer, effective products.

International workshop on immune tolerance induction: consensus recommendations.

Although immune tolerance induction (ITI) has been used for 30 years to eliminate inhibitors and restore normal factor pharmacokinetics in patients with hemophilia, there is a paucity of scientific evidence to guide therapeutic decision-making. In an effort to provide direction for physicians and hemophilia treatment center staff members, an international panel of hemophilia opinion leaders met to develop consensus recommendations for ITI in patients with severe and mild hemophilia A and hemophilia B. These recommendations draw on the available published literature and the collective clinical experience of the group and are rated based on the level of supporting evidence.

Inhibitor treatment in haemophilias A and B: inhibitor diagnosis.

The clinical diagnosis and quantitative measurement of polyclonal IgG inhibiting antibodies are the subjects of this review. Inhibitors in congenital haemophilia are usually diagnosed either as part of a routine surveillance schedule or following a bleeding episode that responds poorly to standard specific replacement therapy. Routine surveillance schedules for paediatric haemophilia A patients during high-risk incidence periods are variable and the subject of ongoing discussion. There have never been any published recommendations for following haemophilia B patients at high risk for inhibitor development. The Factor VIII/IX Subcommittee of the International Society on Thrombosis and Haemostasis scientifically endorsed the Nijmegen method for inhibitor measurement in 1996. However, there are many unresolved issues surrounding inhibitor diagnosis using these assays. These issues include: (i) questions of accuracy and inter-assay variability inherent to the one-stage clotting assay; (ii) lack of consensus regarding the assay cut-off for negative determination; (iii) lack of assay standardization and (iv) the clinical importance of capturing non-neutralizing antibodies currently not measured in the functional assays. Ongoing efforts to resolve these issues will be discussed.

Immune tolerance: critical issues of factor dose, purity and treatment complications.

The current practice of immune tolerance induction (ITI) therapy has been largely influenced by the results of small institutional studies and three large registries. However, many questions remain. Successful outcome predictors for ITI in haemophilia A have been suggested by the analyses of two of these registries. Among these predictors, factor VIII (FVIII) dose/dosing regimen remains a controversial outcome parameter, demonstrating a strong direct relationship to ITI success in the international registry and a weaker inverse relationship in the North American registry. There is an international multicentre prospective randomized trial underway to further study the role of FVIII dose in successful ITI induction in a good risk haemophilia A inhibitor patient cohort. FVIII purity also remains an unproved ITI outcome predictor. Institutional experience with von-Willebrand-factor-containing products has suggested its therapeutic advantage in both inhibitor development and eradication. The International ITI Study, although not designed to answer this particular question, may be able to determine an impact on outcome depending on the final distribution of investigator choice of product among the study subjects. Much less is known about the influence of factor IX (FIX) dose and purity on ITI success in haemophilia B. Importantly, nephrotic syndrome has been a major determinant of ITI failure in FIX inhibitor patients, particularly those with the allergic phenotype. Unfortunately, large prospective randomized trials in this group will not be feasible. Rather, we will have to rely on prospectively collected registry data to build our knowledge base of inhibitors and ITI in haemophilia B.

Rare Bleeding Disorder Registry: deficiencies of factors II, V, VII, X, XIII, fibrinogen and dysfibrinogenemias.

A North American registry for rare bleeding disorders [factor (F)II, factor (F)VII, factor (F)X, factor (F)V, factor (F)XIII, fibrinogen deficiencies and dysfibrinogenemias] was established to gather information about disease prevalence, genotyping frequency, diagnostic events, clinical manifestations, treatment and prophylaxis strategies, as well as disease- and treatment-related complications. Questionnaires were sent to 225 hemophilia treatment centers in the USA and Canada. Among 26% of responding centers, 294 individuals [4.4% of the registered children (200/4583) and 2.4% of adults (94/3809)] were diagnosed with one or more of the rare bleeding disorders (RBDs) included in this survey. The ethnic distribution for each disorder paralleled that of the general US population with the exception of the disproportionately large number of Latinos with FII deficiency. Only 5.4% of affected individuals were genotyped. An abnormal preoperative bleeding screen most often led to diagnosis. The most common coagulopathy was FVII deficiency; however, 40% of homozygous patients were asymptomatic. FX and FXIII deficiencies caused the most severe bleeding manifestations. Among all RBDs, the most common sites of bleeding were skin and mucus membranes. Multiple products were used to treat hemorrhage; however, half of the bleeding episodes required no therapy. The majority of patients suffered no long-term complications from hemorrhage. Treatment-related complications included viral seroconversion, anemia, allergic reactions and venous access device-related events. This registry provides the most comprehensive information to date about North American individuals with RBDs and could serve as an important resource for both basic scientist and clinician.

Transjugular liver biopsy is safe and diagnostic for patients with congenital bleeding disorders and hepatitis C infection.

The prevalence of chronic hepatitis C virus (HCV) infection among patients with severe congenital bleeding disorders is as high as 98%. Advances in HCV treatment currently result in sustained virological response rates of > or =50%. Recent recommendations have reaffirmed that liver biopsy, which provides a direct histological assessment of liver inflammation and fibrosis, is still important for accurate diagnosis and therapeutic decision making. Percutaneous liver biopsy is a simple, standardized procedure that can be performed rapidly and relatively inexpensively, and has been safely performed in patients with congenital coagulopathies. However, the safety and efficacy of the transjugular approach (transjugular liver biopsy, TJLB), recommended for patients with acquired coagulopathies, has only been minimally studied in the congenital bleeding diathesis population. We now report our institutional experience with TJLB in 13 such adult patients (mean age 33 years) with severe/mild haemophilia A/B (10); von Willebrand disease (1); factor V deficiency (1) and factor XIII deficiency (1). Data were collected by retrospective chart review and the TJLB was performed according to institutional protocol as described. Haemostasis prophylaxis was given for 1-5 days. Patients were hospitalized for < or =48 h and all tolerated the procedure without bleeding. Three patients experienced self-limited abdominal discomfort; one episode was accompanied by transient transaminaemia. Diagnostic specimens were obtained from all patients and were instrumental in the therapeutic decision-making process. We suggest that with a co-ordinated multidisciplinary approach to care, TJLB is a safe, effective and potentially cost-effective alternative to the percutaneous approach in the congenital bleeding disorders population.

Clinical manifestations of the prothrombin G20210A mutation in children: a pediatric coagulation consortium study.

The prothrombin G20210A mutation is a common risk factor for thrombosis which increases the risk of deep vein thrombosis, stroke, and fetal loss. There are few publications of its clinical manifestations in children. Our objective was to determine the clinical manifestations of the prothrombin mutation in children. Via survey of pediatric hematologists, we collected data on children with thrombosis and the prothrombin mutation. Thirty-eight patients with a thrombotic event were identified as having the prothrombin mutation. Children with arterial thrombosis were younger, less than half had additional risk factors present at the time of the event, and had a high frequency of central nervous system thrombosis. Children with venous thrombosis were older, almost always had additional risk factors present, and had thrombosis occur most often in the extremities, although there were also a significant number of events in the central venous and cerebral circulation. There was a striking predilection for central nervous system events as 30% of all the events and 67% of the arterial events occurred there. In all, 14/38 children (37%) had central nervous system thrombosis. Unlike factor V Leiden and deficiencies of proteins C and S which cause venous thromboembolism, the prothrombin mutation in children is often associated with arterial thrombosis and with central nervous system events. In children with the prothrombin mutation and venous thrombosis, other risk factors are usually present. Therefore, children with arterial or venous thrombosis of any location should be evaluated for the presence of the prothrombin mutation.

Long-term FEIBA prophylaxis does not prevent progression of existing joint disease.

Activated prothrombin complex concentrates have been used to treat bleeding episodes for patients who have developed an inhibitor to factor VIII (FVIII). FEIBA-Vh (FVIII bypassing activity, FEIBA) has been used since 1970 for this purpose and with FVIII for immune tolerance programmes. Studies have not been presented to show the safety and efficacy of FEIBA when given over a long period of time to prevent haemophilic arthropathy with bleeding into the joints of these patients. This study was undertaken to ascertain the outcome of haemophilic arthropathy with FEIBA prophylaxis. Data were collected on seven patients with known long-standing high-titre FVIII inhibitors given FEIBA prophylaxis for 3-6(1/2) years. Patients were given 50-100 units of FEIBA three to four times weekly. A functional joint evaluation revealed some degree of arthropathy already present in all patients at time of prophylaxis initiation. Safety was measured by medical status, evidence of thrombosis, life-threatening bleeding and inhibitor titre. Efficacy was measured for joint outcome by a functional physical therapeutic scale. At the conclusion of the study, efficacy was mixed as all of the joints for which the patients were placed on prophylaxis had progressed and developed synovitis. Two patients had a functional improvement in their arthropathy, and all were functional enough to attend regular school. The product was deemed safe for long-term use, as there were no complications of therapy with no thrombosis, no life-threatening bleeding episodes and no anamnesis caused by FEIBA alone. Inhibitor titres fell in all patients over the course of the study. Total product usage ranged from approximately 9373-15,571 U kg(-1) year(-1). FEIBA is safe for long-term prophylaxis when given in the recommended dosage for an extended period of time. Efficacy to prevent arthropathy could not be seen as all patients had some degree of arthropathy at time of prophylaxis initiation. An additional study needs to be performed using FEIBA before arthropathy has developed.