Search

The clinical diagnosis of von Willebrand disease (VWD), particularly type 1, can be complex because several genetic and environmental factors affect von Willebrand factor (VWF) plasma levels. An estimated 60% of the phenotypic variation is attributable to hereditary factors, with the ABO blood group locus being the most influential. However, recent studies provide strong evidence that nonsynonymous single nucleotide variants (SNVs) contribute to VWF and factor VIII phenotypic variability in healthy individuals. This study aims to investigate the role of common VWF SNVs on VWD phenotype by analyzing data from 219 unrelated patients included in the “Molecular and Clinical Profile of von Willebrand Disease in Spain project.” To that end, generalized linear mixed-effects regression models were fitted, and additive and epistatic analyses, and haplotype studies were performed, considering five VWD-related measures (bleeding score, VWF:Ag, VWF:RCo, factor VIII:C, and VWF:CB). According to these analyses, homozygotes: for p.Thr789Ala(C) would be expected to show 39% higher VWF:Ag levels; p.Thr1381Ala(C), 27% lower VWF:Ag levels; and p.Gln852Arg(C), 52% lower VWF:RCo levels. Homozygotes for both p.Thr789Ala(C) and p.Gln852Arg(T) were predicted to show 185% higher VWF:CB activity, and carriers of two copies of the p.Thr1381Ala(T)/p.Gln852Arg(T) haplotype would present a 100% increase in VWF:RCo activity. These results indicate a substantial effect of common VWF variation on VWD phenotype. Although additional studies are needed to determine the true magnitude of the effects of SNVs on VWF, these findings provide new evidence regarding the contribution of common variants to VWD, which should be taken into account to enhance the accuracy of the diagnosis and classification of this condition. ClinicalTrials.gov identifier: NCT02869074.

We hypothesized that inhibitor specificity may predict the outcome of antifactor VIII autoantibodies eradication treatment in acquired hemophilia A. Our objective was to analyze the association between factor VIII domains recognized by inhibitors and outcome of the immunosuppressive therapies (ISTs) in a prospective, observational study. 16 patients were recruited. Inhibitor specificities were assessed at diagnosis and throughout the study. Their association with IST outcome was addressed. First- line IST succeeded in56% of patients. Inhibitors reacted mainly with light chain domains (69%) and/or the A2 domain (44%). 31% inhibitors recognized more than one domain. Significantly, the number of patients whose inhibitors recognized the light chain was significantly higher in the group of those who did not reach complete remission after first line IST when compared with those who did [6/7 (85.7%) vs. 4/9 (44.4%), P< 0.05]. Therefore, inhibitor specificitycould predict the success of IST in acquired hemophilia A. Copyright (C) 2019 Wolters Kluwer Health, Inc. All rights reserved.

SummaryThe diagnosis of von Willebrand disease (VWD) remains difficult in a significant proportion of patients. A Spanish multicentre study investigated a cohort of 556 patients from 330 families who were analysed centrally. VWD was confirmed in 480. Next generation sequencing (NGS) of the whole coding VWF was carried out in all recruited patients, compared with the phenotype, and a final diagnosis established. A total of 238 different VWF mutations were found, 154 were not included in the Leiden Open Variation Database (LOVD). Of the patients, 463 were found to have VWF mutation/s. A good phenotypic/ genotypic association was estimated in 96.5 % of the patients. One hundred seventy-four patients had two or more mutations. Occasionally a predominant phenotype masked the presence of a second abnormality. One hundred sixteen patients presented with mutations that had previously been associated with increased von Willebrand factor (VWF) clearance. RIPA unavailability, central phenotypic results disagreement and difficult distinction between severe type 1 and type 3 VWD prevented a clear diagnosis in 70 patients. The NGS study facilitated an appropriate classification in 63 of them. The remaining seven patients presented with a VWF novel mutation pending further investigation. In five patients with a type 3 and two with a type 2A or 2B phenotype with no mutation, an acquired von Willebrand syndrome (AVWS) was suspected/confirmed. These data seem to support NGS as a first line efficient and faster paradigm in VWD diagnosis.Supplementary Material to this article is available online at www.thrombosis-online.com.

Summary Switching between different therapeutic FVIII concentrate types has been postulated as a possible cause of inhibitor development in patient with haemophilia A. In this single-centre, retrospective study, the incidence, titre and duration of inhibitor development in multitransfused patients, defined as patients with more than 150 exposure days (ED), were analysed from January 1970 to December 2007 in relation to ED and the number of switches between different products. Inhibitor titre was assessed by Bethesda assay (before 1998) or Nijmegen assay (after 1998). Medical records of 167 patients were screened, of which 97 patients met the inclusion criteria. Fourteen products of plasmatic origin (different purities) and five recombinant (three generations) were used. Nine patients (9%) developed inhibitors, all transient, low-titre (1.41 ± 0.54 BU) after 323 ± 287 ED in average. Seventeen patients had no product switches of which four patients (23%) developed inhibitors (97 ED in average), whereas 13 patients (77%) did not (ED: 230). Fifty patients switched between plasmatic products only (median: 10 changes) of which five patients (10%) developed inhibitors (ED: 503), whereas 45 patients did not (ED: 932). Five patients switched between recombinant products only (seven changes) of which no patient developed inhibitors (748 ED). Twenty-five patients switched between plasmatic and recombinant products (13 changes) of which no patient developed inhibitors (ED: 1654). No statistically significant differences between patient groups were observed. Neither the number of different FVIII products administered nor the switching of products influenced the incidence of inhibitor in multitransfused patients.

Background Retrospective publications show a decrease in the bleeding frequency and an improvement in the quality of life (QoL) in severe adult haemophilia A (SAHA) after switching from the on-demand treatment (DT) to secondary prophylaxis (SP). But there are no prospective studies which demonstrate, using a haemophilia-specific questionnaire, an improvement in the QoL after such treatment change. The main objective of this study is to prospectively compare the QoL and the musculoskeletal assessment after switching from DT to SP in SAHA using the A36 Hemofilia-QoL®. As secondary objective, we compare the haemarthrosis frequency and factor VIII consumption in DT and SP during a similar period of time (12 months) after switching. Materials and Methods We have designed a prospective study including SAHA who have been under DT and were changed to a protocol, which combines SP (biweekly administration of factor VIII) with individualized physiotherapy programme. Results Twelve months after switching to SP, the QoL was significantly improved (P = 0·005). Musculoskeletal assessment of pathologic irreversible joints and joints with a reversible alteration was generally improved, although in only a few joints, this improvement was statistically significant. Haemarthrosis was strongly reduced (12·60–1·42, P

Summary. Measuring von Willebrand factor (VWF)activity is essential for the diagnosis of von Willebranddisease (VWD). The VWF activity is usually assessedbased on measurement of the ristocetin cofactor (VWF:RCo). However, that test is technically challenging andhas high intra- and inter-assay variabilities. A newautomated chemiluminescent immunoassay VWFactivity has recently become commercially available(HemosIL AcuStar von Willebrand Factor RistocetinCofactor Activity). The main objective of this study wasto evaluate this new method and to compare it with theVWF:RCo assay as the reference method. We studied91 samples, 18 healthy volunteers samples and 73samples from patients (VWF:RCo level

Head-on comparative studies of factor IX (FIX) concentrates performed under standardized conditions are rarely conducted regardless of being a valuable instrument guiding health care providers towards better informed and cost-effective decisions. This study is an extension of a multicentre study that assessed the efficacy, safety and pharmacokinetics (PK) of AlphaNine(®) in 25 previously treated patients with severe haemophilia B (FIX:C ≤ 2%). After a washout period ≥ 7 days following the last PK performed with AlphaNine(®) after a dose of 65-75 IU kg(-1) , an identical PK study was performed with BeneFIX(®) on 22 of the same patients. Venous blood samples for analysis were taken at baseline and at 0.25, 0.5, 1, 3, 6, 9, 24, 48, 72 and 74 h post infusion. The outcomes of the comparison of the PK parameters were as follows: Mean (± SD) in vivo recovery (IVR) was 1.3 ± 0.4 IU dL(-1) per IU kg(-1) for AlphaNine(®) and 1.0 ± 0.3 IU dL(-1) per IU kg(-1) for BeneFIX(®) (P < 0.01). Mean terminal half-life, mean residence time, area under the curve, clearance and volume of distribution of BeneFIX(®) were 36.0 ± 12.8 h, 39.3 ± 13.9 h, 1631 ± 467 IU h dL(-1) , 0.046 ± 0.01 dL kg(-1) min(-1) and 1.75 ± 0.52 mL kg(-1) respectively. These values were not significantly different to those observed in AlphaNine(®), although BeneFIX(®) displayed higher than expected IVR values and lower than expected clearance values. In conclusion, AlphaNine(®) showed a comparable half-life, but an IVR significantly higher than that of BeneFIX(®). This dissimilarity may have implications on dosing requirements for on-demand treatment regimes affecting optimal resource allocation.

Homozygous patients for null alleles in VWF gene show a severe von Willebrand phenotype, whereas compound heterozygous patients only show the phenotype of the expressed allele. Five members of the same family were studied. The two patients showed borderline VWF levels, a mild factor VIII (FVIII) deficiency and a decrease of the binding of VWF to exogenous FVIII. The genetic analyses of the VWF gene confirmed that the patients were compound heterozygous for c.2561G>A (R854Q) and c.2685G>C (p.Q895H) mutations. The latter, is located in the 3′ extreme of exon 20, and it has not been previously described. Studies of the cDNA from platelet mRNA were performed to investigate the expression of p.H895 allele. The loss of heterozygosity at the cDNA level suggests a lack of expression of the p.H895 allele. The overall studies can explain the type 2N phenotype of the two patients, since the allele carrying the new missense mutation p.Q895H has shown a low expression of VWF gene.

The discrepancy of the levels of factor VIII activity (FVIII:C) by different assays in some mild and moderate haemophilic A patients has been long known. Specific mutations affecting FVIII:C discrepancies have been described. No consensus exit as to which method most accurately represents the FVIII cofactor function in vivo and which has a better correlation with the haemorrhagic clinical expression. We studied 163 mild A haemophiliacs, and detected discrepancies in 20% of the patients, most of whom presented higher levels of FVIII:C with the one-stage assay. In nine families, the FVIII mutation was found, while three showed mutations not previously described (Leu1978Phe and Ser1791Pro associated with higher levels of FVIII:C by one-stage method; Arg1639His in a patient with low level of FVIII:C by the one-stage, but normal, chromogenic assay). Assessing the level of FVIII:C by different methods could help to learn the possible haemorrhagic expressions of patients.