Clinical phenotype in heterozygote and biallelic Bernard-Soulier syndrome--a case control study.

Bernard-Soulier syndrome (BSS) is a rare severe autosomal recessive bleeding disorder. To date heterozygous carriers of BSS mutations have not been shown to have bleeding symptoms. We assessed bleeding using a semi-quantitative questionnaire, platelet parameters, PFA-100 closure times, ristocetin response, GP Ib/IX expression and VWF antigen in 14 BSS patients, 30 heterozygote carriers for related mutations and 29 controls. Eight mutations in GP1BA, GP1BB or GP9 were identified including four previously unknown pathogenic mutations. Subjects with BSS reported markedly more mucocutaneous bleeding than controls. Increased bleeding was also observed in heterozygotes. Compared to controls, patients with BSS had lower optical platelet counts (P < 0.001), CD61-platelet counts (P < 0.001) and higher mean platelet volume (17.7 vs. 7.8 fL, P < 0.001) and ristocetin response and closure times were unmeasurable. Heterozygotes had higher MPV (9.7 fL, P < 0.001) and lower platelet counts (P < 0.001) than controls but response to ristocetin and closure times were normal. The VWF was elevated in both BSS and in heterozygotes (P = 0.005). We conclude that heterozygotes for BSS mutations have lower platelet counts than controls and show a bleeding phenotype albeit much milder than in BSS. Both patients with BSS and heterozygote carriers of pathogenic mutations have raised VWF.

Complementary effect of fibrinogen and rFVIIa on clotting ex vivo in Bernard-Soulier syndrome and combined use during three deliveries.

Women with Bernard-Soulier syndrome (BSS) are considered to be at high risk of serious bleeding during childbirth. Due to the frequently occurring platelet transfusion refractoriness, alternative prophylactic therapy is required. Using rotational thromboelastometry, we evaluated the whole blood coagulation profile of a pregnant woman with BSS before and after spiking ex vivo with different concentrations of recombinant activated factor VII (rFVIIa) and fibrinogen. As experiments suggested improved clotting with clinically applicable concentrations of both agents in a complementary manner, the findings were confirmed on blood from a non-pregnant woman and three men suffering from BSS. During delivery, bleeding refractory to platelets occurred and immediately following delivery she received both rFVIIa and fibrinogen intravenously. Immediate cessation of bleeding occurred, and no postpartum hemorrhage was seen. Another woman with BSS later also received the same rFVIIa and fibrinogen treatment prophylactically after delivery without any postpartum bleeding. Eventually, the first woman during her second delivery received the same treatment again prophylactically without any bleeding. No side effects were observed during these three deliveries. Our observations suggest that rFVIIa combined with fibrinogen may provide a beneficial clinical hemostatic effect partly by separate but complementary mechanisms.

Combination of recombinant factor VIIa and fibrinogen corrects clot formation in primary immune thrombocytopenia at very low platelet counts.

Haemostatic treatment modalities alternative to platelet transfusion are desirable to control serious acute bleeds in primary immune thrombocytopenia (ITP). This study challenged the hypothesis that recombinant activated factor VII (rFVIIa) combined with fibrinogen concentrate may correct whole blood (WB) clot formation in ITP. Blood from ITP patients (n = 12) was drawn into tubes containing 3·2% citrate and corn trypsin inhibitor 18·3 µg/ml. WB [mean platelet count 22 × 10(9) /l (range 0-42)] was spiked in vitro with buffer, donor platelets (+40 × 10(9) /l), rFVIIa (1 or 4 µg/ml), fibrinogen (1 or 3 mg/ml), or combinations of rFVIIa and fibrinogen. Coagulation profiles were recorded by tissue factor (0·03 pmol/l) activated thromboelastometry. Coagulation in ITP was characterized by a prolonged clotting time (CT, 1490 s (mean)) and a low maximum velocity (MaxVel, 3·4 mm × 100/s) and maximum clot firmness (MCF, 38·2 mm). Fibrinogen showed no haemostatic effect, whereas rFVIIa reduced the CT and increased the MaxVel. The combination of fibrinogen and rFVIIa revealed a significant synergistic effect, improving all parameters (CT 794 s, MaxVel 7·9 mm × 100/s, MCF 50·7 mm) even at very low platelet counts. These data suggest that rFVIIa combined with fibrinogen corrects the coagulopathy of ITP even at very low platelet counts, and may represent an alternative to platelet transfusion.

Prophylaxis in congenital factor VII deficiency: indications, efficacy and safety. Results from the Seven Treatment Evaluation Registry (STER).

Because of the very short half-life of factor VII, prophylaxis in factor VII deficiency is considered a difficult endeavor. The clinical efficacy and safety of prophylactic regimens, and indications for their use, were evaluated in factor VII-deficient patients in the Seven Treatment Evaluation Registry. Prophylaxis data (38 courses) were analyzed from 34 patients with severe factor VII deficiency (<1-45 years of age, 21 female). Severest phenotypes (central nervous system, gastrointestinal, joint bleeding episodes) were highly prevalent. Twenty-one patients received recombinant activated factor VII (24 courses), four received plasma-derived factor VII, and ten received fresh frozen plasma. Prophylactic schedules clustered into "frequent" courses (three times weekly, n=23) and "infrequent" courses (≤ 2 times weekly, n=15). Excluding courses for menorrhagia, "frequent" and "infrequent" courses produced 18/23 (78%) and 5/12 (41%) "excellent" outcomes, respectively; relative risk, 1.88; 95% confidence interval, 0.93-3.79; P=0.079. Long term prophylaxis lasted from 1 to >10 years. No thrombosis or new inhibitors occurred. In conclusion, a subset of patients with factor VII deficiency needed prophylaxis because of severe bleeding. Recombinant activated factor VII schedules based on "frequent" administrations (three times weekly) and a 90 µg/kg total weekly dose were effective. These data provide a rationale for long-term, safe prophylaxis in factor VII deficiency.

Coagulation and fibrinolytic disturbances are related to carotid intima thickness and arterial blood pressure in Turner syndrome.

OBJECTIVE: Turner syndrome (TS) is characterized by growth retardation, hypogonadism and a high risk of cardiovascular complications and atherosclerosis; case reports suggest that thrombo-embolic complications may be present. DESIGN: Cross-sectional study. PATIENTS: Sixty women with TS. MEASUREMENTS: We characterized the activities of the haemostatic system, elucidated by the assessment of a panel of clotting factors and thrombosis risk factors and related these findings to carotid intima thickness (CIMT) and blood pressure. RESULTS: Most (81%) received hormone replacement therapy. The medians of all measured factors and inflammatory parameters were not different from normative data, but many cases displayed values of C-reactive protein (CRP) (40%), fibrinogen (15%), fibrin D-dimer (15%), factor VIII (25%), von Willebrand factor (vWF) (15%), cholesterol and liver parameters that were greater than normative limits. CRP, fibrinogen, vWF, factor VIII and liver parameters were highly and positively correlated. Haemostatic variables were positively related to both CIMT and blood pressure. The Factor V Leiden G1691A gene polymorphism heterozygosity was detected in 12·5%. CONCLUSION: We describe a significant proportion of individual TS females having high levels of vWF, factor VIII, fibrinogen and CRP (15-40%) and an increased frequency of the Leiden mutation, with important associations with CIMT and blood pressure, suggesting that a subset of TS may have an unfavourable haemostatic balance, which may contribute to the increased risk of premature ischaemic heart disease and possibly increase the risk of deep venous and portal vein thrombosis.

Parallel use of by-passing agents in haemophilia with inhibitors: a critical review.

In the absence of new outbreaks of transfusion-related infections, the occurrence of neutralizing antibodies currently remains the most prominent complication in haemophilia. Coagulation factor products that may circumvent the inadequate activation of factor X in classical haemophilia, often referred to as bypassing agents, have demonstrated a high degree of efficacy. A smaller number of patients have been described in whom either bypassing agent, or both, demonstrate diminished efficacy. In those cases, the use of both bypassing agents in parallel was attempted, either using simultaneous (combined) or alternating (sequential) infusion of the two drugs, reportedly with successful haemostasis. We speculated whether such treatment might cause thromboembolism. A thorough literature search disclosed 17 reports regarding the parallel use of bypassing agents in the same bleeding episode in 49 patients; reporting nine patients with acquired haemophilia and forty patients with congenital haemophilia with inhibitors. Notable incidences of thromboembolic manifestations were observed: in nine patients with acquired haemophilia, five and in 40 patients with congenital haemophilia five suffered from significant thrombotic complications, and overall four cases were fatal. Although efficacy of parallel treatment was reported excellent in most cases, thromboembolism is rare in haemophilia and parallel treatment with activated prothrombin complex concentrate and activated recombinant human factor VII appears to increase the risk of thrombosis in these patients.

Recombinant, activated factor VII for surgery in factor VII deficiency: a prospective evaluation - the surgical STER.

Excessive bleeding represents a major complication of surgical interventions and its control is especially relevant in patients with Congenital Bleeding Disorders (CBD). In factor VII (FVII) deficiency, scanty data on surgery is available to guide treatment strategies. The STER (Seven Treatment Evaluation Registry) is a multi-centre, prospective, observational, web-based study protocol providing the frame for a structured and detailed data collection. Inhibitor occurrence was checked in a centralized fashion. Forty-one surgical operations (24 'major' and 17 'minor') were performed in 34 subjects with a carefully characterized FVII deficiency under the coverage of recombinant activated Factor VII (rFVIIa). Bleeding occurred during three major interventions of orthopaedic surgery, but rFVIIa was given at very low dose in each case. An antibody to FVII was observed in one patient who underwent a multiple dental extraction. No thromboses were reported during the 30-d follow up period. Replacement therapy with rFVIIa proved effective when suitable doses were used, which, during the period of maximum bleeding risk (the day of operation), were calculated (Receiver Operated Characteristic analysis) to be of at least 13 µg/kg/body weight per single dose and no less than three administrations. This indication is important especially in the case of major surgery.

Diagnostic performance and therapeutic consequence of thromboelastometry activated by kaolin versus a panel of specific reagents.

BACKGROUND: Thromboelastography/metry (TEG®; Haemoscope, Niles, IL/ROTEM®; Tem International GmbH, Munich, Germany) is increasingly used to guide transfusion therapy. This study investigated the diagnostic performance and therapeutic consequence of using kaolin-activated whole blood compared with a panel of specific TEM®-reagents to distinguish: dilutional coagulopathy, thrombocytopenia, hyperfibrinolysis, and heparinization. METHODS: Blood was drawn from 11 healthy volunteers. Dilutional coagulopathy was generated by 50% dilution with hydroxyethyl starch 130/0.4 whereas thrombocytopenia (mean platelet count 20 ×109/l) was induced using a validated model. Hyperfibrinolysis and heparin contamination were generated by tissue plasminogen activator 2 nM and unfractionated heparin 0.1U/ml, respectively. Coagulation tests were run on ROTEM® delta. RESULTS: Kaolin-activated whole blood showed no differences between dilutional coagulopathy and thrombocytopenia (mean clotting time 450 s vs. 516 s, α-angle 47.1° vs. 41.5°, maximum clot firmness 35.0 mm vs. 34.2 mm, all P values ≥0.14). Hyperfibrinolysis specifically disclosed an increased maximum lysis (median: 100%, all P values less than 0.001), and heparin induced a distinctly prolonged clotting time (2283 s, all P values less than 0.02). The coagulopathies were readily distinguishable using a panel of TEM-reagents. In particular, dilutional coagulopathy was separated from thrombocytopenia using FIBTEM (maximum clot firmness 1.9 mm vs. 11.2 mm, P < 0.001). The run time of analysis to achieve diagnostic data was shorter applying a panel of TEM-reagents. A transfusion algorithm based on kaolin suggested platelets in case of dilutional coagulopathy, whereas an algorithm applying TEM-reagents suggested fibrinogen. CONCLUSION: Monoanalysis with kaolin was unable to distinguish coagulopathies caused by dilution from that of thrombocytopenia. Algorithms based on the use of kaolin may lead to unnecessary transfusion with platelets, whereas the application of TEM-reagents may result in goal-directed fibrinogen substitution.

The impact of bleeding history, von Willebrand factor and PFA-100(®) on the diagnosis of type 1 von Willebrand disease: results from the European study MCMDM-1VWD.

The relationships between the Platelet Function Analyzer (PFA)-100 and von Willebrand factor (VWF) levels and bleeding score (BS) were evaluated within a multicentre project on Molecular and Clinical Markers for the Diagnosis and Management of type 1 von Willebrand disease (MCMDM-1VWD). PFA-100 closure time, either with epinephrine (EPI) or adenosine diphosphate (ADP)-cartridges, was measured in 107 index cases, 105 affected and 71 unaffected family members, and 79 healthy controls. By regression analysis VWF levels were strongly related to both closure times, with a non-linear progression. In a multiple stepwise regression model, age- and sex-adjusted PFA-100 ADP and VWF ristocetin cofactor activity (VWF:RCo) were independently associated with BS. Most of the variation of BS was predicted by PFA-100 ADP and VWF:RCo alone. In the subgroup of patients with subtle abnormalities of the multimeric pattern, VWF was invariably reduced and closure time prolonged in almost all of them. Neither PFA-100 ADP nor EPI closure times appeared to significantly improve the diagnostic capability of VWF antigen (VWF:Ag) measurement. Thus, in an unselected population a normal PFA-100 would be useful to exclude VWD, but whether it could replace the more specific VWF assay in patients with significant mucocutaneous bleeding symptoms remains to be investigated prospectively.

Identification of type 1 von Willebrand disease patients with reduced von Willebrand factor survival by assay of the VWF propeptide in the European study: molecular and clinical markers for the diagnosis and management of type 1 VWD (MCMDM-1VWD).

The decreased survival of von Willebrand factor (VWF) in plasma has been implicated as a mechanism in a subset of type 1 von Willebrand disease (VWD) patients. We have previously reported that the ratio of plasma levels of VWF and its propeptide (VWFpp) can be used to identify patients with reduced VWF survival. In this study, we report the assay of VWFpp and VWF:Ag in 19 individuals recruited from 6 European centers within the MCMDM-1VWD study. Eight individuals had a VWF:Ag level less than 30 IU/dL. Seven of these patients had a robust desmopressin response and significantly reduced VWF half-life that was predicted by a markedly increased steady-state plasma VWFpp/VWF:Ag ratio. VWF mutations previously associated with reduced VWF survival were identified in each of the 7 individuals. Thus, a substantially increased ratio of steady-state VWFpp/VWF:Ag predicted a reduced VWF half-life in patients with markedly decreased VWF:Ag levels. These data indicate that a reduced VWF survival is found in a subpopulation of patients with type 1 VWD. The systematic assay of both plasma VWF and the VWF propeptide in moderately severe type 1 VWD patients may identify patients with a reduced VWF survival phenotype.

Fibrinogen estimates are influenced by methods of measurement and hemodilution with colloid plasma expanders.

BACKGROUND: Measurement of plasma fibrinogen is often required in critically ill patients or massively bleeding patients being resuscitated with colloid plasma expander. This study aimed at evaluating different assays of plasma fibrinogen after in vitro dilution with commonly used plasma expanders and challenged the hypothesis that levels of fibrinogen are estimated significantly higher in plasma diluted with colloid plasma expander compared with isotonic saline. STUDY DESIGN AND METHODS: Fibrinogen measurements were established in plasma samples each diluted in vitro to 30 or 50% with isotonic saline, hydroxyethyl starch (HES) 130/0.4, and human albumin. Fibrinogen levels were assessed using an antigen determination, three photo-optical Clauss methods, one mechanical Clauss method, a prothrombin-derived method, and viscoelastic measurement through thromboelastometry. RESULTS: Measurement of fibrinogen levels was significantly different when performed on alternate analytical platforms. By 30 and 50% dilution with HES 130/0.4 coagulation analyzers using the photo-optical Clauss methods significantly overestimated levels of fibrinogen. Dilution with human albumin did not affect fibrinogen levels except from one analyzer by 50% dilution level. Viscoelastic measurement of fibrin polymerization was reduced at both dilution levels and appeared to reflect the impairment of fibrin polymerization induced by HES 130/0.4 and to a lesser extent human albumin. CONCLUSION: This study demonstrated that different automated coagulation analyzers revealed significantly different levels of fibrinogen. The presence of colloid plasma expander gave rise to erroneous high levels of fibrinogen returned from some coagulation analyzers employing the method of Clauss.

Evaluation of coagulation kinetics using thromboelastometry-methodologic influence of activator and test medium.

Renewed interest has arisen in the use of thromboelastography/thromboelastometry in evaluating coagulation kinetics. The test medium, type of activator, and its concentration may influence the interpretation of coagulation kinetics. This study aimed to investigate methodologic influences of activator and test medium on thromboelastometric parameters of coagulation kinetics. Dynamic clot formation was evaluated by thromboelastometry using whole blood (WB), platelet-rich plasma, or platelet-poor plasma employing different concentrations of extrinsic (tissue factor) and contact activator (synthasil) and with variable concentrations of phospholipids. Plasma samples displayed prolonged clot initiation and enhanced clot propagation compared with WB. Clot firmness was markedly reduced in platelet-poor plasma as compared with platelet-rich plasma and WB. Increasing concentration of activator shortened the clot initiation and increased the velocity of clot propagation, whereas terminal clot firmness remained unaffected. Platelets accelerated clot propagation and raised clot firmness. Phospholipids shortened the time of clot initiation and increased velocity of propagation, while clot firmness remained unchanged. Our results demonstrate that evaluation of coagulation kinetics using thromboelastometry varies according to the composition of the test medium, type, and concentration of activator, as well as the presence and concentration of phospholipids in the test reagent.

Whole blood coagulation in children with thrombocytopenia and the response to platelet replacement, recombinant factor VIIa, and a potent factor VIIa analogue.

The present study evaluated dynamic coagulation profiles, platelet aggregation, and thrombin generation in whole blood (WB) from eight children with thrombocytopenia during chemotherapy, and the haemostatic potential of platelets (+60 x 10(9)/l), recombinant factor VIIa (rFVIIa - NovoSeven), and a potent rFVIIa analogue (NN1731) both at 1 and 4 microg/ml. Dynamic WB coagulation profiles were recorded by thrombelastometry employing activation with tissue factor (TF - Innovin) at low concentrations. The baseline WB coagulation patterns were characterised by a prolonged clotting time (CT) and a pronounced reduction in clot propagation (MaxVel). WB platelet aggregation signal was five times lower in the study group compared with measurements in modelled thrombocytopenic WB from healthy volunteers. In vitro addition of fresh platelets reversed the coagulopathy. Addition of rFVIIa induced no significant changes in the thrombelastographic profile, whereas spiking with NN1731 shortened the CT significantly. The changes in WB thrombin generation reflected the changes in the MaxVel. In modeled thrombocytopenic WB from healthy individuals, both rFVIIa and NN1731 exhibited a pronounced haemostatic effect with NN1731 showing greater potency than rFVIIa. Compromised platelet function in the study group was assumingly responsible for the weakened haemostatic potential of rFVIIa as well as that of NN1731.

International recommendations on the diagnosis and treatment of patients with acquired hemophilia A.

Acquired hemophilia A (AHA) is a rare bleeding disorder characterized by autoantibodies directed against circulating coagulation factor (F) VIII. Typically, patients with no prior history of a bleeding disorder present with spontaneous bleeding and an isolated prolonged aPTT. AHA may, however, present without any bleeding symptoms, therefore an isolated prolonged aPTT should always be investigated further irrespective of the clinical findings. Control of acute bleeding is the first priority, and we recommend first-line therapy with bypassing agents such as recombinant activated FVII or activated prothrombin complex concentrate. Once the diagnosis has been achieved, immediate autoantibody eradication to reduce subsequent bleeding risk should be performed. We recommend initial treatment with corticosteroids or combination therapy with corticosteroids and cyclophosphamide and suggest second-line therapy with rituximab if first-line therapy fails or is contraindicated. In contrast to congenital hemophilia, no comparative studies exist to support treatment recommendations for patients with AHA, therefore treatment guidance must rely on the expertise and clinical experience of specialists in the field. The aim of this document is to provide a set of international practice guidelines based on our collective clinical experience in treating patients with AHA and contribute to improved care for this patient group.

Citrate artificially masks the haemostatic effect of recombinant factor VIIa in dilutional coagulopathy.

Most often, thrombelastographic analyses are carried out using citrated blood and re-calcification. However, calcium chelation may affect dynamics of tissue-factor-initiated thrombin generation. The present study investigates the effect of sample anticoagulant on the response of a colloid induced dilutional coagulopathy model to recombinant activated factor VII (rFVIIa) as measured by thrombelastography. Thrombelastographic evaluation of whole blood coagulation activated with minute amounts of tissue factor in a model of in vitro haemodilution with hydroxyethyl starch (HES) 130/0.4 in a prospective laboratory study. Whole blood coagulation was evaluated before and after 30% dilution with HES 130/0.4, and following in vitro addition of rFVIIa to whole blood collected into tubes containing citrate, corn trypsin inhibitor (CTI), and no stabilizers. Haemodilution with HES 130/0.4 induces a coagulopathy characterised by a reduced maximum rate of clot formation and a pronounced reduction in the final clot firmness. With all test mediums investigated, rFVIIa significantly shortened clot initiation phase. In cases of native whole blood and CTI-stabilised whole blood, rFVIIa shortens the clotting time but also demonstrated an acceleration of the maximum velocity of clot formation. When citrate is used as anticoagulants in thrombelastographic clotting assays, these may artificially mask the haemostatic effect of rFVIIa in colloid haemodilution. The effect in vitro of rFVIIa in citrated blood samples may underestimate the haemostatic potential of rFVIIa.

Coagulopathy during induced severe intracranial hypertension in a porcine donor model.

BACKGROUND: Development of coagulopathy is a serious complication arising from isolated traumatic brain injury, and it predicts poor outcome. The underlying mechanism has not yet been established, although coagulopathy arising from brain tissue injury and the release of tissue factor may represent the pathophysiology. The authors investigated dynamic whole-blood clot formation (ROTEM) in a recently developed porcine model of induced severe intracranial hypertension. METHODS: In this prospective, randomized experimental study, 17 pigs were designated for severe intracranial hypertension or sham operation. Intracranial hypertension was induced by inflation of an intracranial balloon. Whole-blood clot formation was assessed by clot initiation, and clot propagation and clot strength through thrombelastometry. The authors also assessed thrombin generation and prothrombin time, which were obtained at baseline, immediately after intervention, and 5 h after intervention. RESULTS: A dramatic shortening in time to clot initiation and an increase in clot propagation were observed after induction of intracranial hypertension as compared to the control group. These results were further substantiated by a pronounced increase in thrombin generation and a significantly shortened prothrombin time in the intervention group. No difference in clot strength was detected between the groups. CONCLUSIONS: In a porcine model, induction of increased intracranial pressure causing severe intracranial hypertension was associated with a pronounced activation of the coagulation system. Taken together, the various results indicate that tissue factor probably represents the main trigger of hypercoagulopathy found in these pigs.

Thrombophilia risk factors are associated with intrauterine foetal death and pregnancy-related venous thromboembolism.

Pregnancy in healthy women is accompanied by hypercoagulable changes that may interact with thrombophilia risk factors and threaten pregnancy. However, the literature on this issue is conflicting. In investigating the relationship between pregnancy-associated complications and the presence of thrombophilia risk factors, we studied the records of 414 women who had been examined for inherited and acquired thrombophilia in the period 1996 to 2006 because of pregnancy-associated complications. Of a total of 885 pregnancies among the women, 397 were recorded as foetal loss/intrauterine foetal death during the first (62 %), second (25 %) or third trimester (13 %). One-hundred-and-two (25 %) women had had a thromboembolic event during one of their pregnancies, and 98 (24 %) had had pre-eclampsia on at least one occasion. Intrauterine growth restriction was found in 105 (25 %) of the women, and 29 (7 %) suffered placental abruption. We found that 120 (29 %) women had at least one thrombophilia risk factor. Factor V Leiden heterozygosity was the most common thrombophilia factor (n = 52), mostly linked with the risk of venous thromboembolism during pregnancy or postpartum and to foetal death during the second or third trimester. Fifty-three (13 %) women had antiphospholipid antibodies (lupus anticoagulant and/or anti-beta2-glycoprotein 1 antibodies) mainly associated with the risk of spontaneous abortion during the first trimester. In conclusion, thrombophilia was found to be considerably more common in women with pregnancy-associated complications in comparison with the general population, and most frequently in conjunction with venous thromboembolism during pregnancy and the postpartum period.

Safety and efficacy of sucrose-formulated full-length recombinant factor VIII: experience in the standard clinical setting.

The safety of full-length sucrose-formulated recombinant factor VIII (rFVIII-FS; Kogenate FS) for up to 24 months of use was evaluated in a postmarketing observational study in Europe. Long-term safety and efficacy data were available for 212 patients with severe haemophilia A, including 13 previously untreated patients (PUPs) and 12 patients with 1-19 exposure days (EDs). Patients accumulated a mean (+/- SD) of 187 (121) EDs to rFVIII-FS and received a total of 39,627 infusions, mainly for prophylaxis and for the treatment of 4,283 spontaneous or trauma-related bleeds during an average observation time of 710 (136) days. Of these bleeding episodes, 85.4% were successfully treated with one or two infusions of rFVIII-FS. Haemostasis was also evaluated during 46 minor to major surgical procedures, and the response to infusion was "excellent" or "good" in all cases. FVIII inhibitor formation was observed in six patients (two de novo; four persistent or recurrent). The de novo cases represent 8.0% (2 of 25) of patients who reported 0-19 previous EDs at study entry. Four of the five patients who reported possible drug-related adverse effects developed inhibitors. The results of this observational study demonstrate the efficacy and safety of rFVIII-FS during normal clinical use in the treatment of patients with severe haemophilia A. Furthermore, these findings are consistent with those of previous phase III clinical studies with rFVIII-FS, particularly with regard to its efficacy and low incidence of inhibitor formation.

Evaluation of thromboelastography for monitoring recombinant activated factor VII ex vivo in haemophilia A and B patients with inhibitors: a multicentre trial.

Predicting the clinical effect of bypassing agents such as recombinant activated factor VII in haemophilia patients with inhibitors is hampered by the limited availability of reliable laboratory monitoring tools. This multicentre, open-label trial aimed to explore the dose-response relationship between recombinant activated factor VII concentration and thromboelastography parameters in blood samples from patients with haemophilia A or B with inhibitors in a nonbleeding state. Citrated whole blood samples from 16 patients (>or=16 years) with haemophilia A or B were spiked ex vivo with recombinant activated factor VII (1.2, 1.6, 2.0, 2.6, 3.0, 3.5 microg/ml), corresponding approximately to doses of 90-270 microg/kg. Samples were analysed by Thromboelastograph or Rotation Thromboelastography (three United States and three European centres, respectively) within 30 min (final lipidated recombinant tissue factor 1: 17 000; final CaCl2 15 mM). Thromboelastograph/Rotation Thromboelastography parameters showed large intersubject variation in the baseline profiles. There was a clear effect when recombinant activated factor VII was added; however, a clear concentration-response relationship was only detected for one patient. This is likely due to the fact that the curves were not sufficiently abnormal that led to reduced assay sensitivity. Our preliminary results suggest that thromboelastography may potentially be a clinically useful tool for monitoring changing concentrations of recombinant activated factor VII in haemophilia patients, but only when the baseline curve is significantly abnormal. Thus, test conditions may need to be optimized before Thromboelastograph/Rotation Thromboelastography can be utilized for all inhibitor patients.

Whole blood laboratory model of thrombocytopenia for use in evaluation of hemostatic interventions.

This study describes a laboratory model of whole blood (WB) thrombocytopenia established with blood from healthy volunteers. We obtained a mean platelet count of 16 x 10(9)/l (95% confidence interval, 10-22) in WB by repeatedly replacing the platelet-rich supernatant with autologous platelet-poor plasma from the same individual. Thrombelastographic profiles of WB clot formation and WB clot stability were performed in parallel with measurements of WB platelet aggregation response. Thrombocytopenia reduced the maximum rate of WB clot formation, while ex vivo addition of platelets reversed the coagulopathy of thrombocytopenia. Control experiments revealed minimal changes in coagulation factors, distribution of bloods cells, and platelet activation capabilities. The WB model appears useful in research, development, and evaluation of the effects of hemostatic interventions in thrombocytopenia.