Higher and lower active circulating VWF levels: different facets of von Willebrand disease

Most circulating von Willebrand factor (VWF) is normally inactive and incapable of binding platelets, but numerous disorders may modify the proportion of active VWF. We explored active VWF levels in patients with von Willebrand disease (VWD) whose VWF had a higher affinity for platelet glycoprotein (GP)Ib, but different susceptibilities to ADAMTS13 and multimer patterns (9 patients lacking large multimers, 10 with a normal pattern); 12 patients with VWF C2362F and R1819_C1948delinsS mutations, which make VWF resistant to ADAMTS13 were also studied. Type 2B patients with abnormal or normal multimers had significantly more active VWF (3·33 ± 1·6 and 3·74 ± 0·74, respectively; normal 0·99 ± 0·23). The type of VWF mutation influenced VWF activation: V1316M was associated with the highest levels in patients with abnormal multimers, and R1341W in those with normal multimers. Pregnancy induced gradually rising active VWF levels and declining platelet counts in one type 2B VWD patient without large multimers. Active VWF levels dropped significantly in patients homozygous for the C2362F mutation or heterozygous for R1819_C1948delinsS mutations (0·2 ± 0·03 and 0·23 ± 0·1, respectively), and less in cases heterozygous for the VWF C2362F mutation (0·55 ± 0·17). We demonstrate that VWF may be more or less activated, with or without any direct involvement of the A1 domain, and regardless of ADAMTS13.     

Effect of von Willebrand factor on inhibitor eradication in patients with severe haemophilia A: a systematic review

This systematic review was designed to summarize the reported valid quantitative evidence on the association between use of von Willebrand factor (VWF)‐containing Factor VIII (FVIII) concentrates and successful immune tolerance induction (ITI) in patients with severe haemophilia A. The primary outcome was successful ITI; secondary outcomes were time to success, complications of the inhibitor or ITI and relapse of the inhibitor. A systematic literature search identified 26 randomized controlled trials, registries and cohort studies, evaluating a total of 1284 patients. For a pooled meta‐analysis, 13 studies evaluating 382 patients were included. Due to incomplete data we were not able to assign pre‐ITI risk categories to all patients for risk factor analysis. The meta‐analysis did not demonstrate a difference in the proportion of patients with successful inhibitor eradication between those treated with VWF‐containing products and those treated with FVIII concentrates devoid of VWF (relative risk [RR] 0·70 (95% confidence interval [CI] 0·52–0·89) and 0·84 (95% CI 0·75–0·93) respectively). Bleeding rate during ITI ranged from 0·00 to 0·85 bleeding episodes per year. The proportion of patients with a relapse of the inhibitor (range 0–20%) was mentioned in four studies that were included in the meta‐analysis. The results of this systematic review do not support the idea of a positive effect of VWF‐containing products in ITI.     

Postpartum von Willebrand factor levels in women with and without von Willebrand disease and implications for prophylaxis

The aim of this study was to elucidate the fall in von Willebrand factor (VWF) and factor VIII activity (FVIII) after childbirth in women with and without von Willebrand disease (VWD). VWF:RCo, VWF:Ag, and FVIII were obtained in the third trimester of pregnancy, on admission for childbirth, and 10 times postpartum. Specimens were processed within 4 h and analysed centrally. Means were calculated at each time point. Forty women (40 pregnancies) without VWD and 32 women (35 pregnancies) with VWD were enrolled. 15/32 with VWD were treated (30% of those with type 1 and all of those with type 2) in 17 pregnancies. Treatments prior to delivery consisted of desmopressin (2/17), VWF concentrate (15/17) and after delivery VWF concentrate (16/17). Duration of treatment was 0–21 days (median 6). VWF levels peaked at 250% of baseline – 4 h postpartum in women with VWD and 12 h postpartum in women without VWD. Thereafter, VWF levels fell rapidly, approached baseline at 1 week and reached baseline at 3 weeks. Except immediately postpartum, when the levels among treated cases were higher, levels among women with VWD appeared to parallel, but were lower than those among women without VWD. Levels were lowest among those who received treatment. VWF levels fall rapidly after childbirth. Except immediately postpartum, current treatment strategies do not raise VWF levels to the levels of women without VWD or even to the levels of women with milder, untreated VWD. Consequently, women with VWD may be at risk of postpartum haemorrhage despite treatment.     

Changes in von Willebrand factor level and von Willebrand activity with age in type 1 von Willebrand disease

In a normal population, VWF plasma levels (VWF:Ag) and VWF activity (VWF:RCo) increase by approximately 0.17 and 0.15 IU mL^?1 per decade, but the influence of age is unknown in patients with type 1 von Willebrand disease (VWD). In a retrospective cohort study, the medical records of 31 type 1 VWD patients over the age of 30, who had been followed for ≥5 years, were reviewed for baseline clinical data and previously performed VWF:Ag, VWF:RCo and factor VIII levels (FVIII:C). VWF multimer analysis was normal in 28/31 cases performed. Mean age at diagnosis was 33 (range 16–60 years), and duration of follow‐up ranged from 5 to 26 years (mean 11 years). Patients had 2–10 time points of VWD testing (mean of 5.2). The mean VWF:Ag, VWF:RCo and FVIII:C at time of diagnosis were 0.44 IU mL^?1 0.34 IU mL^?1 and 0.75 IU mL^?1. At last follow‐up, the mean VWF:Ag, VWF:RCo and FVIII:C were significantly increased to 0.71 IU L^?1, 0.56 IU mL^?1 and 0.90 IU mL^?1 (P ≤ 0.001, <0.001, and 0.0081 respectively). Here 18/31 patients had VWF:Ag, VWF:RCo and FVIII: C levels that increased into the normal range. The rate of change in VWF:Ag, VWF:RCo and FVIII was 0.30 IU mL^?1 (0.21–0.39, CI 95%, P < 0.0001), 0.20 IU mL^?1 per decade (0.13–0.27, CI 95%, P = 0.0001) and 0.20 IU mL^?1 (0.11–0.29, CI 95%, P = 0.0011). Patients with type 1 VWD experience age‐related increases to VWF:Ag and VWF:RCo which can result in normalization of VWF levels. Further studies are required to determine if the bleeding phenotype resolves with the increases in VWF:Ag and VWF:RCo levels.     

Correlation between von Willebrand factor antigen,von Willebrand factor ristocetin cofactor activity and factor VIII activity in plasma

Background The laboratory diagnosis of von Willebrand Factor (VWF) deficiencies includes qualitative and quantitative measurements of VWF and clotting factor VIII (FVIII). Since the FVIII activity is frequently normal in patients with mild type 1 or 2 von Willebrand disease (VWD), there is controversy whether FVIII testing should accompany VWF Antigen (VWF:Ag) assay. Methods The aim of this study was to explore the correlation between VWF:Ag, VWF ristocetin cofactor activity (VWF:RCo) and FVIII in 213 consecutive patients undergoing screening for VWD. Results Forty-six patients were identified with VWF:Ag levels lower than the diagnostic threshold (54 IU/dl). A significant correlation was observed between VWF:Ag and VWF:RCo (r = 0.892; p < 0.001), VWF:Ag and FVIII (r = 0.834; p < 0.001), VWF:RCo and FVIII (r = 0.758; p < 0.001). Receiver operating characteristic curve analysis of the VWF:Ag assay revealed an area under the curve of 0.978 and 0.957 for detecting life-threatening values of FVIII (<30 IU/dl) and VWF:RCo (<40 IU/dl), respectively. The negative and positive predictive values at the VWF:Ag threshold value of 54 IU/dl were 100% and 33% for detecting life-threatening FVIII deficiencies, 94% and 80% for identifying abnormal values of VWF:RCo. Conclusions Due to the excellent correlation between VWF:Ag and FVIII and to the diagnostic efficiency of VWF:Ag for identifying abnormal FVIII levels in patients with VWF deficiency, routine measurement of FVIII may not be necessary in the initial screening of patients with suspected VWD. However, the limited negative predictive value of VWF:Ag for identifying type 2 VWD does not allow to eliminate VWF:RCo or VWF:FVIIIB assays from the diagnostic workout.     

Clinical efficacy in bleeding and surgery in von Willebrand patients treated with Fanhdi® a highly purified,doubly inactivated FVIII/VWF concentrate

Summary. Therapy with factor VIII/von Willebrand factor (FVIII/VWF) concentrate is the mainstay therapy in patients with von Willebrand disease (VWD) unresponsive to desmopressin. There are several commercially available FVIII/VWF concentrates that have been tested in VWD patients. We retrospectively analized the clinical efficacy in bleeding episodes and surgery of a highly purified FVIII/VWF complex with two inactivation steps (Fanhdi^®) in VWD patients. Sixty patients were included in the study. Treatment schedule consisted of one or more doses (standard dose 40 IU/kg body weight of FVIII) of Fanhdi^®. One hundred and fifty bleeding episodes were treated. These were: 28 serious bleedings; 92 moderate and 30 mild. An excellent clinical efficacy in almost 95% of cases was observed. Fanhdi^® was administered during 66 surgical procedures (38 major and 28 minor) with an overall efficacy of 98%. Fanhdi^® a highly purified, doubly virus‐inactivated FVIII/VWF concentrate, with a high content of active VWF and an excellent record of clinical safety, is a valid choice in treating VWD.     

The fraction of recombinant factor VIII:Ag unable to bind von Willebrand factor has no FVIII coagulant activity: studies in vitro

A fraction of FVIII:Ag in commercial recombinant FVIII (rFVIII) cannot bind VWF whereas all the FVIII:Ag in plasma‐derived FVIII (pd‐FVIII) concentrates does. To compare the FVIII:C activities of the fractions of rFVIII:Ag that can and cannot bind VWF. The FVIII:Ag contents of the rFVIII Kogenate, and Advate and a pd‐FVIII‐pd‐VWF (Fanhdi) were measured by ELISA. The FX activation was initiated by adding 1.0 IU of FVIII:C of each FVIII‐containing product to a coagulant phospholipids suspension containing 1.0 nm FIXa, 100 nm FX, 1 μm hirudin and 2 mm calcium chloride and measured after 1, 5 and 10 min. The same approach was followed after adding 2.0 IU of pd‐VWF to1.0 IU of FVIII:C of Kogenate or Advate. The FVIII:Ag content/IU of FVIII:C of Kogenate, Advate and Fanhdi were 1.80 ± 0.05, 1.31 ± 0.9 and 0.84 ± 1.5 IU respectively. Only Kogenate and Advate effectively enhanced FX activation 1 min after adding each FVIII:C to the coagulant suspension containing FIXa and FX. Thus, the FXa initially generated by FIXa readily activated FVIII:C in control Kogenate and Advate to thereby effectively enhance FX activation while the VWF in Fanhdi continued to suppress FX activation for up to 10 min. Addition of pd‐VWF to Kogenate or Advate effectively decreased their enhancements of FX activation to the same level as Fanhdi over 10 min. The FVIII:Ag fraction in Kogenate and Advate that cannot bind VWF appears to be inactive as it has no measureable FVIII:C activity in the presence of added VWF in vitro.     

Kinetics of the interaction between anti‐FVIII antibodies and FVIII from therapeutic concentrates,with and without von Willebrand factor,assessed by surface plasmon resonance

The presence of VWF in plasma‐derived FVIII (pdFVIII/VWF) products has been pointed out as a key difference with recombinant FVIII (rFVIII) products with regard to immunogenicity. A Surface Plasmon Resonance (SPR) study was designed to characterize in detail the interaction between anti‐FVIII (IgGs) from a severe haemophilia A patient, and FVIII from concentrates of different sources. Full‐length rFVIII (preincubated or not with purified VWF), B domain‐deleted (BDD)‐rFVIII and pdFVIII/VWF were analysed. To ensure reproducible conditions for accurate determination of kinetic constants, a capture‐based assay format was developed using protein G surfaces for specific and reversible coupling of endogenous anti‐FVIII antibodies. Concentration ranges (nm ) of FVIII products tested were 9–0.03 (rFVIII) and 6–0.024 (pdFVIII/VWF). The association with antibodies was monitored for 3–5 min, whereas dissociation of the complex was followed for 5–20–240 min. A strong interaction of rFVIII and BDD‐rFVIII with patient's IgG was detected with the K _D values in the low picomolar range (5.9 ± 3.0 and 12.7 ± 6.9 pm , respectively) and very slow dissociation rates, while pdFVIII/VWF showed only marginal binding signals. The VWF complexed rFVIII displayed reduced binding signals compared with uncomplexed rFVIII, but the K _D was still in the picomolar range (4.1 ± 1.9 pm ) indicating insufficient complex formation. rFVIII, alone or bound to exogenously added VWF, showed high affinity for anti‐FVIII IgGs from a severe haemophilia A patient whereas pdFVIII/VWF did not. These results are in agreement with those studies that point towards rFVIII concentrates to be more immunogenic than pdFVIII concentrates.     

Analysis of current perioperative management with Haemate® P/Humate P® in von Willebrand disease: Identifying the need for personalized treatment

Introduction

Patients with Von Willebrand disease (VWD) are regularly treated with VWF‐containing concentrates in case of acute bleeding, trauma and dental or surgical procedures.

Aim

In this multicentre retrospective study, current perioperative management with a von Willebrand factor (VWF)/Factor VIII (FVIII) concentrate (Haemate^® P) in patients with VWD was evaluated.

Patients/Methods

Patients with VWD undergoing minor or major surgery between 2000 and 2015, requiring treatment with a VWF/FVIII concentrate (Haemate^® P), were included. Achieved VWF activity (VWF:Act) and FVIII during FVIII‐based treatment regimens were compared to predefined target levels in national guidelines.

Results

In total, 103 patients with VWD (148 surgeries) were included: 54 type 1 (73 surgeries), 43 type 2 (67 surgeries) and 6 type 3 (8 surgeries). Overall, treatment resulted in high VWF:Act and FVIII levels, defined as ≥0.20 IU/mL above predefined levels. In patients with type 1 VWD, respectively, 65% and 91% of trough VWF:Act and FVIII levels were higher than target levels. In patients with type 2 and type 3 VWD, respectively, 53% and 57% of trough VWF:Act and 72% and 73% of trough FVIII levels were higher than target level. Furthermore, FVIII accumulation over time was observed, while VWF:Act showed a declining trend, leading to significantly higher levels of FVIII than VWF:Act.

Conclusion

High VWF:Act and accumulation of FVIII were observed after perioperative FVIII‐based replacement therapy in patients with VWD, both underlining the necessity of personalization of dosing regimens to optimize perioperative treatment.     

A comparative evaluation of a new fully automated assay for von Willebrand factor collagen binding activity to an established method

Introduction

Laboratory diagnosis of von Willebrand disease (VWD) is made by the measurement of von Willebrand factor (VWF) protein level and its activities. Current VWF activity tests include ristocetin cofactor and collagen binding (VWF:CB) assays.

Aim

We have undertaken an evaluation of a new fully automated VWF:CB assay relative to an established enzyme‐linked immunosorbent assay (ELISA) method.

Methods

The two analytical systems operate with different detection principles: a chemiluminescent method performed on ACL AcuStar Analyzer (the former) and a colorimetric ELISA by Asserachrom Stago (the latter) (type III collagen from human placenta). The HemosIL AcuStar VWF:CB assay is a chemiluminescent 2‐step immunoassay that uses magnetic particles coated with a type III collagen triple‐helical peptide. VWF:CB levels were determined in 50 healthy subjects and 100 VWD patients (22 type 1, 73 type 2 and 5 type 3).

Results

Eleven VWD samples reported VWF:CB values below the lower detection limit of one or both methods. The new method showed a good correlation with the ELISA method (r > .9, mean bias 3.85 IU/dL) in both healthy and VWD samples. One of 150 samples gave inconsistent results using the two assays, leading to an uncertain diagnosis of VWD type 1 (ELISA method) or type 2 MCB (fully automated method).

Conclusion

The new assay is rapid and simple to use, with its ready‐to‐use reagent cartridges. This VWF:CB assay, in addition to the measurement of VWF:Ag and VWF:RCo made on the same platform, gives additional information for the diagnosis of VWD in both nonspecialized and reference laboratories.     

Assay of the von Willebrand factor (VWF) propeptide to identify patients with type 1 von Willebrand disease with decreased VWF survival

Type 1 von Willebrand disease (VWD) is characterized by a partial quantitative deficiency of von Willebrand factor (VWF). Few VWF gene mutations have been identified that cause dominant type 1 VWD. The decreased survival of VWF in plasma has recently been identified as a novel mechanism for type 1 VWD. We report 4 families with moderately severe type 1 VWD characterized by low plasma VWF:Ag and FVIII:C levels, proportionately low VWF:RCo, and dominant inheritance. A decreased survival of VWF in affected individuals was identified with VWF half-lives of 1 to 3 hours, whereas the half-life of VWF propeptide (VWFpp) was normal. DNA sequencing revealed a single (heterozygous) VWF mutation in affected individuals, S2179F in 2 families, and W1144G in 2 families, neither of which has been previously reported. We show that the ratio of steady-state plasma VWFpp to VWF:Ag can be used to identify patients with a shortened VWF half-life. An increased ratio distinguished affected from unaffected individuals in all families. A significantly increased VWFpp/VWF:Ag ratio together with reduced VWF:Ag may indicate the presence of a true genetic defect and decreased VWF survival phenotype. This phenotype may require an altered clinical therapeutic approach, and we propose to refer to this phenotype as type-1C VWD.     

Early mortality and complications in hospitalized adult Californians with acute myeloid leukaemia

Few studies have evaluated the impact of complications, sociodemographic and clinical factors on early mortality (death ≤60 days from diagnosis) in acute myeloid leukaemia (AML) patients. Using data from the California Cancer Registry linked to hospital discharge records from 1999 to 2012, we identified patients aged ≥15 years with AML who received inpatient treatment (N = 6359). Multivariate logistic regression analyses were used to assess the association of complications with early mortality, adjusting for sociodemographic factors, comorbidities and hospital type. Early mortality decreased over time (25·3%, 1999–2000; 16·8%, 2011–2012) across all age groups, but was higher in older patients (6·9%, 15–39, 11·4%, 40–54, 18·6% 55–65, and 35·8%, >65 years). Major bleeding [Odds ratio (OR) 1·5, 95% confidence interval (CI) 1·3–1·9], liver failure (OR 1·9, 95% CI 1·1–3·1), renal failure (OR 2·4, 95% CI 2·0–2·9), respiratory failure (OR 7·6, 95% CI 6·2–9·3) and cardiac arrest (OR 15·8, 95% CI 8·7–28·6) were associated with early mortality. Higher early mortality was also associated with single marital status, low neighbourhood socioeconomic status, lack of health insurance and comorbidities. Treatment at National Cancer Institute‐designated cancer centres was associated with lower early mortality (OR 0·5, 95% CI 0·4–0·6). In conclusion, organ dysfunction, hospital type and sociodemographic factors impact early mortality. Further studies should investigate how differences in healthcare delivery affect early mortality.     

Clinical phenotype in genetically confirmed von Willebrand disease type 2N patients reflects a haemophilia A phenotype

Introduction : Von Willebrand disease (VWD) type 2N is characterized by a defective binding of factor VIII (FVIII) to von Willebrand factor (VWF) resulting in diminished plasma FVIII levels and a clinical phenotype mimicking mild haemophilia A. Several mutations in the FVIII binding site of VWF have been reported. Aim: This study aims to examine the effect of genotype on clinical phenotype in a cohort of VWD 2N patients. Methods: Patients with at least one genetically confirmed 2N mutation were selected retrospectively from a cohort of patients with suspected VWD. Clinical and laboratory phenotypes including bleeding scores (BS) were obtained and analysed. Results : Forty‐two VWD 2N patients with a mean age of 44 years were included. Eleven patients were homozygous or compound heterozygous (genetically confirmed group) and 31 patients were heterozygously affected (carriers group). Statistically significant differences between genetically confirmed VWD 2N patients and carriers were found in FVIII activity, VWF antigen levels, VWF‐FVIII binding capacity, FVIII/VWF antigen ratio (all P<0.001), VWF‐ristocetin activity (p=0.001) and VWF collagen binding (P = 0.002). Median BS was 6 in genetically confirmed VWD 2N patients compared with 3 in carriers (P = 0.047). Haemarthrosis, muscle haematomas and postpartum haemorrhage were only reported in genetically confirmed 2N patients. Conclusion : Phenotypic analysis showed that all laboratory parameters are lower in genetically confirmed VWD 2N patients compared with heterozygous 2N carriers. The clinical phenotype in genetically confirmed VWD 2N patients is comparable to mild haemophilia A patients and more severe than heterozygous 2N carriers.     

A comparative evaluation of a new automated assay for von Willebrand factor activity

The ristocetin cofactor assay (VWF:RCo) is the reference method for assessing von Willebrand factor (VWF) activity in the diagnosis of von Willebrand's Disease (VWD). However, the assay suffers from poor reproducibility and sensitivity at low levels of VWF and is labour intensive. We have undertaken an evaluation of a new immunoturbidimetric VWF activity (VWF:Ac) assay (INNOVANCE^® VWF Ac. Siemens Healthcare Diagnostics, Marburg, Germany) relative to an established platelet‐based VWF:RCo method. Samples from 50 healthy normal subjects, 80 patients with VWD and 50 samples that exhibited ‘HIL’ (i.e. Haemolysis, Icterus or Lipaemia) were studied. VWF:Ac, VWF:RCo and VWF:Ag were performed on a CS–analyser (Sysmex UK Ltd, Milton Keynes, UK), all reagents were from Siemens Healthcare Diagnostics. The VWF:Ac assay, gave low intra‐ and inter‐assay imprecision (over a 31‐day period, n = 200 replicate readings) using commercial normal (Mean 96.2 IU dL^?1, CV < 3.0%) and pathological (Mean 36.1 IU dL^?1, CV < 3.5%) control plasmas. The normal and clinical samples exhibited good correlation between VWF:RCo (range 3–753 IU dL^?1) and VWF:Ac (rs = 0.97, P < 0.0001), with a mean bias of 5.6 IU dL^?1. Ratios of VWF:Ac and VWF:RCo to VWF:Ag in the VWD samples were comparable, although VWF:Ac had a superior lower level of detection to that of VWF:RCo (3% and 5% respectively). A subset (n = 97) of VWD and HIL samples were analysed for VWF:Ac at two different dilutions to assess the effect on relative potency, no significant difference was observed (P = 0.111). The INNOVANCE^® VWF Ac assay was shown to be reliable and precise.     

Presentation and diagnosis of patients with type 3 von Willebrand disease in resources-limited laboratory

Von Willebrand disease (VWD) is a bleeding disorder that results from decreased von Willebrand factor (VWF) activity <0.30 iu/mL. Therefore, the diagnosis of type 3 VWD in patients with bleeding requires finding a VWF:Ag and/or VWF:platelet ristocetin cofactor (RiCof) <0.03 iu/mL, no further testing is usually necessary. This is a cohort study that included 64 patients with type 3 VWD who were presented and diagnosed at the National Center of Hematology (NCH) from October 2014 to October 2016. In this study the sensitivity of VWF:Ag is only 78%, the sensitivity of VWF:RiCof is 92% of diagnosed cases. From our results it can be concluded that patients with type 3 VWD are usually presented with moderate/severe mucocutaneous bleeding that is associated with prolonged bleeding time test of >10 min and a family history of similar type of bleeding. This fact was frequently utilized to provisionally diagnose several members of the same family, forming a cohort of patients that is larger than the number of objectively-diagnosed patients included in this study, when they cannot afford to be all tested with VWF:Ag/VWF:RiCof.     

Pregnancy and delivery in women with von Willebrand disease

Given the wide heterogeneity of phenotypes and of the underlying pathophysiological mechanisms associated with the disorder, pregnancy and delivery in von Willebrand disease (VWD) represent a significant clinical challenge. The variable pattern of changes observed during pregnancy of von Willebrand factor (VWF) and factor VIII (FVIII), the protein carried by VWF, prompts a careful evaluation of pregnant women with VWD to plan the most appropriate treatment at the time of parturition. However, there are also instances during pregnancy (amniocentesis, vaginal bleeding associated with placental detachment, sudden abortion) that may require urgent hemostatic treatment to prevent bleeding. Thus, women with VWD should start pregnancy after being well characterised as to their type, subtype and treatments. Women with VWD who have VWF and FVIII basal levels >30 U/dL typically normalise these levels at the end of pregnancy and specific anti‐haemorrhagic prophylaxis is seldom required. On the contrary, those with basal levels <20 U/dL usually show a lesser increase and specific treatment is required. Some women with DNA variants associated with increased clearance can be treated with desmopressin, while those unresponsive or with contra‐indications to this agent need replacement therapy. For these latter women, the risk of vaginal bleeding during pregnancy may be increased and prophylaxis with VWF concentrates required. Similarly, women with type 2 VWD who maintain reduced VWF activity throughout pregnancy require replacement therapy with FVIII/VWF concentrates. Delayed postpartum bleeding may occur when replacement therapy is not continued for some days. Tranexamic acid is useful at discharge to avoid excessive lochia.     

Utility of the von Willebrand factor collagen binding assay in the diagnosis of von Willebrand disease

von Willebrand Disease (VWD) is the most common inherited bleeding disorder and also arises as an acquired defect (AVWS). VWD and AVWS are due to quantitative deficiencies and/or qualitative defects in von Willebrand factor (VWF), an adhesive plasma protein with multiple activities. Diagnosis of VWD is problematic, being subject to overdiagnosis, underdiagnosis, and misdiagnosis. This is largely due to limitations in current test procedures and an over‐reliance on these imperfect test systems for clinical diagnosis. VWF essentially acts to assist in the formation of a platelet thrombus to stop blood loss from sites of injury, achieving this by binding to platelets (primarily through the glycoprotein Ib receptor), binding to subendothelial matrix components (primarily collagen), and binding to factor VIII (FVIII), thus protecting FVIII from degradation and enabling its delivery to sites of vascular injury. VWD is classified into six separate types, which may each be differentially managed therapeutically, and this underscores the importance of a correct diagnosis. The current report concisely reviews the utility of a relatively underutilised assay, the VWF collagen binding assay (VWF:CB), in facilitating the correct diagnosis and typing of VWD. In particular, if laboratories do not utilise the VWF:CB, then (i) type 2M VWD will continue to be missed, and/or misdiagnosed as types 2A or 1 VWD, and (ii) types 2A, 2B and PT‐VWD will continue to be missed, or else be misdiagnosed as type 1 VWD or ITP. Am. J. Hematol. 92:114–118, 2017. © 2016 Wiley Periodicals, Inc.     

Outgrowing the laboratory diagnosis of type 1 von Willebrand disease: A two decade study

Von Willebrand Factor (VWF) levels are known to increase with age in the general population, but that effect is unclear in von Willebrand disease (VWD) patients. Thus, it is important to assess the trends of VWF levels with age, and the extent and rate of their normalization in patients with VWD. In a retrospective cohort study, we reviewed the medical records of 126 patients between 1996 and 2016 who met the NHLBI diagnostic criteria for type 1 VWD or “Low VWF” (LVWF). We followed all their historically documented VWF antigen (VWF:Ag), VWF activity (VWF:RCo), and Factor VIII (FVIII) levels longitudinally over time, correlating data with clinical setting at time of testing. The average duration of follow‐up was 10.5 ± 3.7 years (SD). Out of the total study population, 27.8% achieved the primary outcome of complete normalization (CN) of both VWF:Ag and VWF:RCo levels, including 19.6% and 32.5% of those with VWD and LVWF, respectively. Linear regression demonstrated statistically significant positive trends of VWF:Ag, VWF:RCo, FVIII with time, calculated at 2.4, 1.4, and 1.4 U dL‐1/year, respectively (P < .001 each). In the largest study population of VWD patients to date whose levels were followed longitudinally, there is a statistically significant rise in VWF:Ag, VWF:RCo, and FVIII levels observed with time. CN of both VWF:Ag and VWF:RCo levels was observed in almost a third of patients with VWD or LVWF, over an average of 10 years. Whether the bleeding phenotype also improves is unclear and requires further study.     

von Willebrand factor/factor VIII concentrate (Humate‐P) for management of elective surgery in adults and children with von Willebrand disease

Summary. von Willebrand disease (VWD) is the most common inherited bleeding disorder. Treatment guidelines recommend the use of von Willebrand factor/factor VIII (VWF/FVIII) concentrate for VWD patients with type 2 or 3 VWD undergoing surgery, and type 1 patients undergoing surgery who are unresponsive, or for whom desmopressin acetate is contraindicated. This prospective, open‐label, multinational study evaluated the safety, efficacy and optimal dosing of a VWF/FVIII concentrate (Humate‐P) in subjects with VWD undergoing elective surgery. Dosing was based on VWF ristocetin cofactor (VWF:RCo) and FVIII pharmacokinetic assessments performed before surgery. Pharmacokinetic assessments were completed in 33 adults and 9 children. Haemostatic efficacy was assessed on a 4‐point scale (excellent, good, moderate/poor or none). Overall effective haemostasis was achieved in 32/35 subjects. Median terminal VWF:RCo half‐life was 11.7 h, and median incremental in vivo recovery was 2.4 IU dL^?1 per IU kg^?1 infused. Major haemorrhage occurred after surgery in 3/35 cases despite achieving target VWF and FVIII levels. Median VWF/FVIII concentrate loading doses ranged from 42.6 IU VWF:RCo kg^?1 (oral surgery) to 61.2 IU VWF:RCo kg^?1 (major surgery), with a median of 10 (range, 2–55) doses administered per subject. Adverse events considered possibly treatment‐related (n = 6) were generally mild and of short duration. The results indicate that this VWF/FVIII concentrate is safe and effective in the prevention of excessive bleeding during and after surgery in individuals with VWD.