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.

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.

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.

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.

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.

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.

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.

The North American Immune Tolerance Registry: practices, outcomes, outcome predictors

The North American Immune Tolerance Registry was initiated to study of immune tolerance (ITT) in Canada and the United States with respect to: 1) therapeutic regimens in use for haemophilia A (HA) and B (HB) inhibitor patients; 2) therapeutic outcomes; 3) potential predictors of successful outcome and 4) complications of therapy. Data on 188 ITT courses was collected by questionnaire from 60 haemophilia centers from 1993-99. Among the completed courses, the overall success rate was 70% (115/164) for all HA and 31% (5/16) for all HB. Outcome parameters noted to be predictive of ITT success for all HA were 1) pre-ITT induction (p = 0.003), 2) ITT peak (p = 0.007) and 3) historical pre ITT peak (p = 0.04) inhibitor titres. An inverse correlation between total daily dose (units/kg/day) and success: (80% with under 50; 71% with 50-99; 73% with 100-199; and 41% with > or = 200, p = 0.01) was found. Outcome predictors were not evaluable for HB, although adverse reactions to therapy, including nephrotic syndrome, and access complications were more common among failed courses. Infection most often complicated the use of access catheters. These results are discussed within the context of the international ITT registry and upcoming prospective ITT study.

Continuous infusion of porcine factor VIII: stability, microbiological safety and clinical experience

Porcine factor VIII (pFVIII) is an effective haemostatic treatment for bleeding in selected patients with FVIII inhibitors. Its use is sometimes associated with a transient fall in platelet count and transfusion reactions, the risk of which may be related to the rate of administration. Theoretical considerations suggest that the administration of pFVIII by continuous infusion should be effective, and could have pharmacokinetic advantages that lead to an improvement in the side-effect profile. The results of a retrospective survey of continuous infusion of pFVIII with respect to clinical safety and efficacy are reported. Porcine FVIII stability and microbiological studies are included. It is concluded that pFVIII given by continuous infusion is safe and effective. The risk of transfusion reactions and fall in platelet count appears to be reduced, compared with bolus administration. Stability studies showed that pFVIII activity declined at room temperature, most rapidly in the dilute solution (5-10 U mL(-1)). More concentrated mixtures showed acceptable stability for up to 24 h using a variety of infusion devices. Various concentrations of pFVIII did not support the growth of Escherichia coli or Staphylococcus aureus. These observations suggest that the porcine factor is suitable for continuous infusion (CI).

Heparin and the risk of intraventricular hemorrhage in premature infants

OBJECTIVE

This study was carried out to determine whether the routine use of low-dose heparin in umbilical catheter infusates increases the risk of intraventricular hemorrhage or alters the coagulation profile in premature infants.

METHODS

In a randomized, blinded trial, 113 infants born at less than 31 weeks' gestation were assigned to receive, in their umbilical catheter infusate, either 1 unit of heparin per milliliter (n = 55) or no heparin (n = 58). Prothrombin time, activated partial thromboplastin time, fibrinogen concentration, and antithrombin III activity levels were determined at the start and the completion of the study. Cranial ultrasonography was performed during the first week of life.

RESULTS

There was no difference in the incidence of intraventricular hemorrhage between the heparin and no heparin groups, 35.8% and 31.5%, respectively (p = 0.6). Similarly, no difference was detected in the incidence of severe intraventricular hemorrhage (grades III/IV). Prothrombin time, activated partial thromboplastin time, and fibrinogen levels were not significantly different between the two groups. However, the use of heparin was associated with a lower antithrombin III activity level. Antenatal indomethacin use was associated with a 2.9 increased risk of intraventricular hemorrhage (95% confidence interval, 1.15 to 7.17).

CONCLUSION

A low dose of heparin added to umbilical catheter infusates does not increase the incidence or severity of intraventricular hemorrhage or significantly alter the coagulation profile in premature infants.

Management of an acute hemorrhagic ovarian cyst in a female patient with hemophilia A

PURPOSE

This case report represents a description of a hemorrhagic ovarian cyst in a patient with hemophilia A.

PATIENT

An 18-year-old female patient with severe factor VIII deficiency presented with the acute onset of a hemorrhagic ovarian cyst, meeting the standard indications for surgical intervention. Instead, because of the underlying coagulopathy, factor VIII therapy was instituted.

RESULT

Within 1 day of starting the factor VIII therapy, the hemorrhage had clinically resolved and surgical intervention was avoided.

CONCLUSIONS

Hemorrhagic ovarian cysts in the setting of hemophilia may respond to factor VIII replacement therapy without the need for surgical intervention. Because the incidence of functional ovarian cysts is high in the general population, female patients with hemophilia should be counseled regarding its possibility of occurrence. Moreover, if a female patient with hemophilia displays a propensity toward the development of ovarian cysts, the administration of prophylactic oral contraceptive pills should strongly be considered.

In vitro factor VIII recovery during the delivery of ultrapure factor VIII concentrate by continuous infusion

Factor VIII (FVIII) replacement by continuous infusion has been advocated as a cost-effective method for maintaining stable plasma levels of FVIII in the hemophilia A patients during surgery or life-threatening hemorrhage. Continuous delivery of monoclonal or recombinant FVIII concentrates to our pediatric patients using a traditional delivery system (dilution in normal saline of 2-10 U/ml infused at a rate of 20 ml/hr) has frequently yielded higher than expected factor usage to achieve desired levels and unexpected variability in plasma levels under presumed steady-state conditions. To determine if diminished in vitro FVIII recovery was responsible for these observations, a study of four ultrapure concentrates during 8 hr of in vitro continuous delivery was performed using four delivery systems. When reconstituted concentrate was added to normal saline in polyvinylchloride bags at a concentration of 10 U/ml (method IA), monoclonal products showed a stable recovery of 84-109% of time 0 levels. Recombinant product recovery dropped to 57-76% of time 0 levels before reapproximating the time 0 level at 2 hr. The addition of 10 mg/ml human albumin to the bags (method IB) did not improve recoveries. When reconstituted concentrate was delivered undiluted (method IIA), the early drop in recombinant recovery was eliminated; stable recovery of 78-117% of time 0 level was achieved with all products. In using method IA, a large discrepancy was seen between the actual time 0 recoveries and those expected based on vial assays, most striking for recombinant products (49-57% of expected. Method IIA allowed 75-90% recovery; addition of 20 mg/ml albumin of reconstituted but undiluted concentrate (method IIB) maximized recovery at 85-98% of expected.

Recombinant activated factor VII (rFVIIa) therapy for intracranial hemorrhage in hemophilia A patients with inhibitors

We report the use of recombinant VIIa (rFVIIa) in the treatment of five ICHs in two factor VIII-deficient patients with inhibitors. In four of five ICHs, rFVIIa was the only factor replacement used at doses of 60-135 micrograms/kg every 2-4 hr for 12-14 days. Hemostasis at the primary site of bleeding was achieved in all cases, and all patients survived with no permanent neurologic deficits. However, the patient who received the highest dose of rFVIIa during the first 4 days of therapy developed clinical symptoms consistent with a cerebral vascular accident of the brainstem characterized by acute onset of truncal ataxia and upward-gaze nystagmus on day 8 of rFVIIa therapy. While receiving rFVIIa therapy for treatment of these five ICHs, four treatment courses were complicated by bleeding at sites other than the primary site, including two episodes of localized oozing at central line insertion sites, two episodes of hemarthrosis, and two episodes of epistaxis. Antifibrinolytic therapy with tranexamic acid was effective in two of these episodes. Laboratory evaluation revealed shortening of the PT, variable shortening without normalization of the APTT, peak factor VII activity levels 7-30-fold higher than normal baseline values, and normal antithrombin III (ATIII) and alpha 2-antiplasmin levels. In four of five ICHs, there was a 20-40% decrease in fibrinogen levels from baseline. The decrease in fibrinogen was accompanied by an increase in fibrin degradation products in 3/5 episodes and a 15-35% decrease in plasminogen activity levels in 2/5 episodes. Tissue factor pathway inhibitor (TFPI) levels remained stable and in the normal range. Although rFVIIa is an effective new therapy for the treatment of ICH in hemophilia patients with inhibitors, its optimal use with respect to safety and efficacy requires further clinical study.

Use of DDAVP in inherited and acquired platelet dysfunction

Twenty-one patients with prolonged bleeding times secondary to inherited disorders of platelet function and eight patients with prolonged bleeding times secondary to acquired platelet dysfunction were given 0.3 micrograms per kilogram of DDAVP, 1-deamino-8-D-arginine vasopressin, intravenously. Sixteen of twenty-two DDAVP trials in patients with inherited platelet dysfunction (73%) and seven of the nine DDAVP trials in patients with acquired platelet dysfunction (78%) resulted in normalization or shortening of the prolonged bleeding times by at least 4 min. The bleeding time response did not correlate with changes in the levels of von Willebrand factor (vWf) antigen or ristocetin cofactor activity, nor was it associated with changes in vWf multimeric analysis or in vitro platelet aggregations following the administration of DDAVP. Shortening of the bleeding time with DDAVP was seen in patients with a failure to release/storage pool type defect, thromboxane synthesis type defect, Bernard-Soulier syndrome, Glanzmann's thrombasthenia, the May-Hegglin anomaly, liver disease, nonuremic renal disease, myelofibrosis, and Tangier's disease.

Collagen-binding of von Willebrand's factor antigen in the classification of von Willebrand's disease

Analysis of the multimeric structure of von Willebrand's factor (vWf) was compared with vWf-binding to collagen in subjects' plasma. The percentage binding of vWf to collagen was determined by both an enzyme-linked immunosorbent assay (ELISA) method and quantitative immunoelectrophoresis. Normal subjects, type I von Willebrand's disease (vWd), and type II vWd were studied. The authors have found by correlating collagen-binding results with multimeric analysis that normal controls exhibit 85.4 +/- 5.1% collagen absorption of their vWf, patients with type I vWd 80.8 +/- 5.3%, whereas patients exhibiting a deficiency of high molecular weight vWf have 32.3 +/- 16.6% collagen absorption of vWf. The results suggest that this functional assay of vWf can be used in the classification of vWd and in the detection of new dysfunctional forms of vWf.