The 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.
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.
Molecular diagnosis of patients with von Willebrand disease is pending in most populations due to the complexity and high cost of conventional molecular analyses. The need for molecular and clinical characterization of von Willebrand disease in Spain prompted the creation of a multicenter project (PCM-EVW-ES) that resulted in the largest prospective cohort study of patients with all types of von Willebrand disease. Molecular analysis of relevant regions of the VWF, including intronic and promoter regions, was achieved in the 556 individuals recruited via the development of a simple, innovative, relatively low-cost protocol based on microfluidic technology and next-generation sequencing. A total of 704 variants (237 different) were identified along VWF, 155 of which had not been previously recorded in the international mutation database. The potential pathogenic effect of these variants was assessed by in silico analysis. Furthermore, four short tandem repeats were analyzed in order to evaluate the ancestral origin of recurrent mutations. The outcome of genetic analysis allowed for the reclassification of 110 patients, identification of 37 asymptomatic carriers (important for genetic counseling) and re-inclusion of 43 patients previously excluded by phenotyping results. In total, 480 patients were definitively diagnosed. Candidate mutations were identified in all patients except 13 type 1 von Willebrand disease, yielding a high genotype-phenotype correlation. Our data reinforce the capital importance and usefulness of genetics in von Willebrand disease diagnostics. The progressive implementation of molecular study as the first-line test for routine diagnosis of this condition will lead to increasingly more personalized and effective care for this patient population.
Measuring von Willebrand factor (VWF) activity is essential for the diagnosis of von Willebrand disease (VWD). The VWF activity is usually assessed based on measurement of the ristocetin cofactor (VWF:RCo). However, that test is technically challenging and has high intra- and inter-assay variabilities. A new automated chemiluminescent immunoassay VWF activity has recently become commercially available (HemosIL AcuStar von Willebrand Factor Ristocetin Cofactor Activity). The main objective of this study was to evaluate this new method and to compare it with the VWF:RCo assay as the reference method. We studied 91 samples, 18 healthy volunteers samples and 73 samples from patients (VWF:RCo level <50 IU dL(-1) ): 29 type 1 VWD, 13 type 2A, 5 type 2B, 5 type 2M, 3 type 2N, 5 type 3, 4 type 3 under treatment, 5 type 3 carriers and 4 samples with other pathologies. The HemosIL AcuStar VWF:RCo assay was 96% sensitive and 100% specific for detecting VWF abnormalities. The good analytical performance, and the sensitivity and specificity of HemosIL AcuStar VWF:RCo to detect VWF deficiency renders it a suitable method for VWD screening.
The incidence of inhibitors in haemophilia A is 21-33%. The development of inhibitors to factor VIII (FVIII) is one of the most serious complications in haemophilia therapy and is an important challenge in haemophilia care. The main short-term objective of the treatment of haemophilic patients with inhibitors is to control bleeding episodes, and the long-term one is to eradicate the inhibitor by means of immune tolerance induction (ITI). The choice of treatment for bleeding in inhibitor patients is dictated by the current inhibitor titre, the severity of the bleed and the previous anamnesic response to FVIII. In low responder inhibitor patients the best treatment is large doses of concentrates of FVIII to attain haemostatic levels of the factor infused. The same approach can also be considered in high responders who have a temporarily low inhibitor level and major haemorrhage. High responders patients with high inhibitors titre or with minor haemorrhage must be treated with bypassing agents, such as FEIBA (factor VIII inhibitor bypassing activity) or recombinant activated FVII (rVIIa); there is no agreement which of both agents should be chosen in the different clinical situations. Only in patients waiting to start ITI treatment the rFVIIa use is clearly recommended, in order to avoide an anamnesic responce. In case of failure with this agents, extracorporeal immunoadsortion may be considered. All haemophiliac children who develop an inhibitor should be considered for ITI. The start of ITI should be deferred until the inhibitor has declined below 10 Bethesda units/mL (BU ml(-1)) where possible. Starting the treatment when inhibitor titre is below 10 BU ml(-1) is the strongest predictor of success. However, there are many other points to clarify: recommended FVIII doses in the ITI; if the results can be affected by concomitant infections during ITI; if there are any differences using plasma derived or recombinant concentrates, even more if the plasma-derived concentrate contains large amounts von willebrand factor or not; age of starting the ITI and the delay in beginning it; if using immunosupresors can help in the treatment of patients with a bad prognosis; and when the treatment must be left in patients without a clear failure.
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