| 1. |
- Budde, U, et al.
(författare)
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Detailed von Willebrand factor multimer analysis in patients with von Willebrand disease in the European study, molecular and clinical markers for the diagnosis and management of type 1 von Willebrand disease (MCMDM-1VWD)
- 2008
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 6:5, s. 762-771
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Tidskriftsartikel (refereegranskat)abstract
- Background: Type 1 von Willebrand disease (VWD) is a congenital bleeding disorder characterized by a partial quantitative deficiency of plasma von Willebrand factor (VWF) in the absence of structural and/or functional VWF defects. Accurate assessment of the quantity and quality of plasma VWF is difficult but is a prerequisite for correct classification. Objective: To evaluate the proportion of misclassification of patients historically diagnosed with type 1 VWD using detailed analysis of the VWF multimer structure. Patients and methods: Previously diagnosed type 1 VWD families and healthy controls were recruited by 12 expert centers in nine European countries. Phenotypic characterization comprised plasma VWF parameters and multimer analysis using low- and intermediate-resolution gels combined with an optimized visualization system. VWF genotyping was performed in all index cases (ICs). Results: Abnormal multimers were present in 57 out of 150 ICs; however, only 29 out of these 57 (51%) had VWF ristocetin cofactor to antigen ratio below 0.7. In most cases multimer abnormalities were subtle, and only two cases had a significant loss of the largest multimers. Conclusions: Of the cases previously diagnosed as type 1 VWD, 38% showed abnormal multimers. Depending on the classification criteria used, 22 out of these 57 cases (15% of the total cohort) may be reclassified as type 2, emphasizing the requirement for multimer analysis compared with a mere ratio of VWF functional parameters and VWF:Ag. This is further supported by the finding that even slightly aberrant multimers are highly predictive for the presence of VWF mutations.
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| 2. |
- Eikenboom, J, et al.
(författare)
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Linkage analysis in families diagnosed with type 1 von Willebrand disease in the European study, molecular and clinical markers for the diagnosis and management of type 1 VWD
- 2006
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 4:4, s. 774-782
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Tidskriftsartikel (refereegranskat)abstract
- Background: von Willebrand disease (VWD) type 1 is a congenital bleeding disorder caused by genetic defects in the von Willebrand factor (VWF) gene and characterized by a reduction of structurally normal VWF. The diagnosis of type 1 VWD is difficult because of clinical and laboratory variability. Furthermore, inconsistency of linkage between type 1 VWD and the VWF locus has been reported. Objectives: To estimate the proportion of type 1 VWD that is linked to the VWF gene. Patients and methods: Type 1 VWD families and healthy control individuals were recruited. An extensive questionnaire on bleeding symptoms was completed and phenotypic tests were performed. Linkage between VWF gene haplotypes and the diagnosis of type 1 VWD, the plasma levels of VWF and the severity of bleeding symptoms was analyzed. Results: Segregation analysis in 143 families diagnosed with type 1 VWD fitted a model of autosomal dominant inheritance. Linkage analysis under heterogeneity resulted in a summed lod score of 23.2 with an estimated proportion of linkage of 0.70. After exclusion of families with abnormal multimer patterns the linkage proportion was 0.46. LOD scores and linkage proportions were higher in families with more severe phenotypes and with phenotypes suggestive of qualitative VWF defects. About 40% of the total variation of VWF antigen could be attributed to the VWF gene. Conclusions: We conclude that the diagnosis of type 1 VWD is linked to the VWF gene in about 70% of families, however after exclusion of qualitative defects this is about 50%.
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| 3. |
- Tosetto, A, et al.
(författare)
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A quantitative analysis of bleeding symptoms in type 1 von Willebrand disease: results from a multicenter European study (MCMDM-1 VWD)
- 2006
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 4:4, s. 766-773
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Tidskriftsartikel (refereegranskat)abstract
- Background: A quantitative description of bleeding symptoms in type 1 von Willebrand disease (VWD) has never been reported. Objectives: The aim was to quantitatively evaluate the severity of bleeding symptoms in type 1 VWD and its correlation with clinical and laboratory features. Patients and methods: Bleeding symptoms were retrospectively recorded in a European cohort of VWD type 1 families, and for each subject a quantitative bleeding score (BS) was obtained together with phenotypic tests. Results: A total of 712 subjects belonging to 144 families and 195 controls were available for analysis. The BS was higher in index cases than in affected family members (BS 9 vs. 5, P < 0.0001) and in unaffected family members than in controls (BS 0 vs. -1, P < 0.0001). There was no effect of ABO blood group. BS showed a strong significant inverse relation with either von Willebrand ristocetin cofactor (VWF:RCo), von Willebrand antigen (VWF:Ag) or factor VIII procoagulant activity (FVIII:C) measured at time of enrollment, even after adjustment for age, sex and blood group (P < 0.001 for all the four upper quintiles of BS vs. the first quintile, for either VWF:RCo, VWF:Ag or FVIII:C). Higher BS was related with increasing likelihood of VWD, and a mucocutaneous BS (computed from spontaneous, mucocutaneous symptoms) was strongly associated with bleeding after surgery or tooth extraction. Conclusions: Quantitative analysis of bleeding symptoms is potentially useful for a more accurate diagnosis of type 1 VWD and to develop guidelines for its optimal treatment.
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| 4. |
- Tosetto, A., et al.
(författare)
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Impact of plasma von Willebrand factor levels in the diagnosis of type 1 von Willebrand disease: results from a multicenter European study (MCMDM-1VWD)
- 2007
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 5:4, s. 715-721
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Tidskriftsartikel (refereegranskat)abstract
- Background: Presence of bleeding symptoms, inheritance and reduced von Willebrand factor (VWF) contribute to the diagnosis of type 1 von Willebrand disease (VWD). However, quantitative analysis of the importance of VWF antigen (VWF:Ag) and ristocetin cofactor activity (VWF:RCo) levels in the diagnosis is lacking. Objectives: To evaluate the relative contribution of VWF measurement to the diagnosis of VWD. Patients and methods: From the MCMDM-1VWD study cohort, 204 subjects (considered as affected by VWD based on the enrolling Center diagnoses and the presence of linkage with the VWF locus) were compared with 1155 normal individuals. Sensitivity, specificity and diagnostic positive likelihood ratios (LR) of VWF:Ag and VWF:RCo were computed. Results: ABO blood group was the variable most influencing VWF levels, but adjustment of the lower reference limit for the ABO group did not improve sensitivity and specificity of VWF:Ag or VWF:RCo. The lower reference limit (2.5th percentile) was 47 IU dL(-1) for both VWF:Ag and VWF:RCo and showed similar diagnostic performance [receiver-operator curve area: 0.962 and 0.961 for VWF:Ag and VWF:RCo, respectively; P = 0.81]. The probability of VWD was markedly increased only for values below 40 IU dL(-1) (positive LR: 95.1 for VWF:Ag), whereas intermediate values (40 to 60 IU dL(-1)) of VWF only marginally indicated the probability of VWD. Conclusions: Although the conventional 2.5 lower percentile has good sensitivity and specificity, only VWF:Ag or VWF:RCo values below 40 IU dL(-1) appear to significantly indicate the likelihood of type 1 VWD. The LR profile of VWF level could be used in a diagnostic algorithm.
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| 5. |
- Teitel, J, et al.
(författare)
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A systematic approach to controlling problem bleeds in patients with severe congenital haemophilia A and high-titre inhibitors
- 2007
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 13:3, s. 256-263
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Tidskriftsartikel (refereegranskat)abstract
- The presence of inhibitory antibodies to clotting factors complicates the treatment of bleeding in haemophilia patients. For patients with high-titre inhibitors, bypassing agents are essential to haemostatic management. To determine optimal treatment practices, an international panel of physicians convened to develop a systematic treatment approach for problem bleeds (i.e. bleeds that are unresponsive to initial therapy with a single agent within a reasonable amount of time) in haemophilia patients with inhibitors. AIM: The goal of this panel was to develop a consensus algorithm that would aid physicians in considering a variety of treatment approaches to optimize patient care by preventing extensive therapy with inadequate treatments that may lead to suboptimal patient outcomes and unnecessary costs. METHODS: Consensus opinions were analyzed for clinical preferences at different time periods, depending on patient response to treatment. Decision-making points were defined based on the type of bleed: every 8-12 h for the first 24 h, then every 24 h thereafter for limb-threatening bleeds; every 2-4 h for 2-7 days for life-threatening bleeds. RESULTS: The resultant consensus guidelines provide a generalized methodology to guide the treatment of problem bleeds in patients with severe haemophilia A and inhibitors, and emphasize changing treatment at the first sign of an inadequate haemostatic response. The treatment algorithms apply to both paediatric and adult patients, although the differences between the two groups were reviewed. CONCLUSION: These guidelines are focused on optimising the timing of treatment decisions, which may lead to faster responses and improved outcomes.
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| 6. |
- Bolton-Maggs, P H B, et al.
(författare)
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von Willebrand disease update: diagnostic and treatment dilemmas
- 2008
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Ingår i: Haemophilia. - : Wiley. - 1351-8216 .- 1365-2516. ; 14:s3, s. 56-61
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Tidskriftsartikel (refereegranskat)abstract
- Although von Willebrand disease (VWD) is now well-described, many facets of diagnosis and management continue to be debated. The diagnosis of type 1 disease can be difficult but recent genetic analyses help to distinguish many factors which can influence von Willebrand factor (VWF) levels and bleeding phenotype. Type 2 disease (functional abnormalities) includes a particularly interesting group of disorders with faulty binding between VWF and FVIIIC (Normandy) where treatment methods need careful consideration. Type 3 VWD is the most severe form of VWD and a new international study is underway to examine the use of prophylaxis.
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| 7. |
- Borel-Derlon, A., et al.
(författare)
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Treatment of severe von Willebrand disease with a high-purity von Willebrand factor concentrate (Wilfactin (R)): a prospective study of 50 patients
- 2007
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 5:6, s. 1115-1124
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Tidskriftsartikel (refereegranskat)abstract
- Background and objectives: A plasma-derived von Willebrand factor (VWF) concentrate with low factor VIII (FVIII) content was specifically developed to treat von Willebrand disease (VWD). Efficacy and safety were investigated by merging the results of two comparable protocols conducted prospectively in 5 European and 12 French centers. Methods and results: Fifty patients with clinically severe VWD (72% had VWF ristocetin cofactor activity less than 10 IU dL(-1) and 46% had FVIII < 20 IU dL(-1)) were treated with the concentrate as the only therapy, except for clinical situations requiring a priming dose of FVIII to rapidly correct an intrinsic coagulation defect. A total of 139 spontaneous bleeding episodes were treated; only 53 (38%) needed a concomitant FVIII dose. Outcome was excellent or good in 89% of the episodes. Forty-four patients underwent 108 surgical or invasive procedures. Outcome was excellent or good in 95 scheduled procedures (only VWF was infused) and 13 emergency procedures (a priming FVIII dose was co-administered with the first VWF infusion). There were no thrombotic complications and none of the 18 patients with type 3 VWD developed anti-VWF or anti-FVIII antibodies. Conclusions. This concentrate safely and effectively provides hemostasis in patients with clinically severe VWD.
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| 8. |
- Goudemand, J, et al.
(författare)
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Pharmacokinetic studies on Wilfactin((R)), a von Willebrand factor concentrate with a low factor VIII content treated with three virus-inactivation/removal methods
- 2005
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 3:10, s. 2219-2227
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Tidskriftsartikel (refereegranskat)abstract
- Objective: In order to correct the primary von Willebrand factor (VWF) defect and avoid supra-physiologic plasma levels of factor VIII, a pure VWF concentrate almost devoid of FVIII was developed and used in France since 1989. Methods: The pharmacokinetic (PK) profile of the most recent version of this concentrate (Wilfactin (R); LFB, Les Ulis, France), treated with three virus-inactivation/removal methods (solvent/detergent, 35 nm filtration, dry heat treatment), was investigated in 25 patients. Seventeen patients with various types of clinically severe von Willebrand disease (VWD) were included in a crossover, randomized trial carried out in five European centers and comparing Wilfactin (R) with concentrates containing both FVIII and VWF (FVIII/VWF). Eight type 3 VWD patients were included in another trial carried out in six French centers comparing Wilfactin (R) with its previous version (Facteur Willebrand-LFB (R); LFB) that adopted one virus-inactivation method only. Results: For both the measurements evaluated in this study (VWF antigen, VWF:Ag; and VWF ristocetin co-factor activity, VWF:RCo), Wilfactin (R) had a PK profile similar to that of the FVIII/VWF concentrates and of Facteur Willebrand-LFB (R). VWF:RCo and VWF:Ag recoveries were 2.1 +/- 0.3 and 1.8 +/- 0.3 per IU kg(-1) respectively, and the half-lives were 12.4 +/- 1.8 and 15.9 +/- 1.5 h. The FVIII synthesis rate was 5.8 +/- 1.0 IU dL(-1) h(-1), with a half-life of 15.8 +/- 2.4 h. Conclusion: The PK of VWF and FVIII have not been altered by the three virus-inactivation/removal steps during the manufacturing of Wilfactin (R).
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