von Willebrand factor (VWF) is a multimeric glycoprotein critically involved in hemostasis, thrombosis, and inflammation. VWF function is regulated by its antigen levels, multimeric structures, and ...the state of enzymatic cleavage. Population studies in the past have focused almost exclusively on VWF antigen levels in cross-sectional study designs.
To identify subjects in the Atherosclerosis Risk in Community study who had persistently low and high VWF antigen over 10 years and to quantify longitudinal changes in the biological activities and cleavage of VWF in these subjects.
We measured VWF antigen, propeptide, adhesive activities, and cleavage by ADAMTS-13 quantified using a mass spectrometry method that detected the cleaved VWF peptide EQAPNLVY, as well as coagulation factor VIII activity.
We determined the mean subject-specific increase in VWF to be 22.0 International Units (IU)/dL over 10 years, with 95% between -0.3 and 59.7 IU/dL. This aging-related increase was also detected in VWF propeptide levels, ristocetin cofactor activity, and VWF binding to collagen. We identified 4.1% and 25.0% of subjects as having persistently low (<50 IU/dL) and high (>200 IU/dL) VWF antigen, respectively. Subjects with persistently low VWF had enhanced ristocetin cofactor activity, whereas those with persistently high VWF had elevated levels of ADAMTS-13, resulting in a comparable rate of VWF cleavage between the 2 groups.
These results provide new information about the effects of aging on VWF antigens and adhesive activity and identify a functional coordination between VWF and the rate of its cleavage by ADAMTS-13.
Recombinant adeno‐associated virus (rAAV) vectors carry a cassette of interest retaining only the inverted terminal repeats (ITRs) from the wild‐type virus. Conventional rAAV production primarily ...uses a vector plasmid as well as helper genes essential for AAV replication and packaging. Nevertheless, plasmid backbone related contaminants have been a major source of vector heterogeneity. The mechanism driving the contamination phenomenon has yet to be elucidated. Here we identified cryptic resolution sites in the plasmid backbone as a key source for producing snapback genomes, which leads to the increase of vector genome heterogeneity in encapsidated virions. By using a single ITR plasmid as a model molecule and mapping subgenomic particles, we found that there exist a few typical DNA break hotspots in the vector DNA plasmid backbone, for example, on the ampicillin DNA element, called aberrant rescue sites. DNA around these specific breakage sites may assume some typical secondary structures. Similar to normal AAV vectors, plasmid DNA with a single ITR was able to rescue and replicate efficiently. These subgenomic DNA species significantly compete for trans factors required for rAAV rescue, replication, and packaging. The replication of single ITR contaminants during AAV production is independent of size. Packaging of these species is greatly affected by its size. A single ITR and a cryptic resolution site in the plasmid work synergistically, likely causing a source of plasmid backbone contamination.
Target-specific oral anticoagulants are approved for use for the prevention of stroke in atrial fibrillation and for the prevention and treatment of venous thrombosis without the need for laboratory ...monitoring. However, there are clinical settings in which laboratory measurement of anticoagulant effect is needed. These may include patients with life-threatening bleeding or those requiring emergency surgery, in the setting of renal or hepatic failure, or patients with thrombosis on therapy. This chapter reviews the use of laboratory testing to assess the anticoagulant effect of these drugs. In addition, because these drugs can interfere with other laboratory testing, available data on these interactions are presented.
Understanding the genetic basis of human diseases and traits is dependent on the identification and accurate genotyping of genetic variants. Deep whole-genome sequencing (WGS), the gold standard ...technology for SNP and indel identification and genotyping, remains very expensive for most large studies. Here, we quantify the extent to which array genotyping followed by genotype imputation can approximate WGS in studies of individuals of African, Hispanic/Latino, and European ancestry in the US and of Finnish ancestry in Finland (a population isolate). For each study, we performed genotype imputation by using the genetic variants present on the Illumina Core, OmniExpress, MEGA, and Omni 2.5M arrays with the 1000G, HRC, and TOPMed imputation reference panels. Using the Omni 2.5M array and the TOPMed panel, ≥90% of bi-allelic single-nucleotide variants (SNVs) are well imputed (r2 > 0.8) down to minor-allele frequencies (MAFs) of 0.14% in African, 0.11% in Hispanic/Latino, 0.35% in European, and 0.85% in Finnish ancestries. There was little difference in TOPMed-based imputation quality among the arrays with >700k variants. Individual-level imputation quality varied widely between and within the three US studies. Imputation quality also varied across genomic regions, producing regions where even common (MAF > 5%) variants were consistently not well imputed across ancestries. The extent to which array genotyping and imputation can approximate WGS therefore depends on reference panel, genotype array, sample ancestry, and genomic location. Imputation quality by variant or genomic region can be queried with our new tool, RsqBrowser, now deployed on the Michigan Imputation Server.
This manuscript presents—across multiple ancestries, genotype arrays, and imputation reference panels—the minor-allele frequency thresholds above which array genotyping and imputation accurately capture genetic variants genotyped with deep whole-genome sequencing.
Abstract Older patients with hemophilia face many challenges related not only to hemophilia but also to general comorbidity associated with aging. Patients with hemophilia often have known risk ...factors for cardiovascular disease, such as hypertension and hepatitis C virus (HCV) infection, which may counteract any protective effects bestowed by the hypocoagulable state. Arthritis and joint disease are common and contribute to disability and pain. The high prevalence of chronic HCV infection has led to an increased risk for liver failure and hepatocellular carcinoma. Renal function and urological disorders are a concern in these patients, and issues related to sexuality are an important but often-overlooked issue. The use of routine procedures for general health maintenance in the elderly (e.g. colonoscopy) can be more complex in patients with hemophilia due to the inherent risk of bleeding, and serious disorders such as malignancy can be overlooked if signs of abnormal bleeding are attributed to hemophilia, rather than to cancer. Prospective studies are needed to address these challenges so that evidence-based guidance can be given to clinicians who treat older patients with hemophilia.
The use of platelet transfusions to prevent bleeding in patients with thrombocytopenia due to chemotherapy or other causes of marrow suppression is widespread, but the optimal number (dose) of ...platelets is unsettled. In this randomized trial, three doses of platelets were studied: the usual dose, half the usual dose, and twice the usual dose. No major differences in bleeding complications were found among the three groups, but more transfusions were given in the lowest-dose group to prevent bleeding.
In this randomized trial, three doses of platelets were studied: the usual dose, half the usual dose, and twice the usual dose. No major differences in bleeding complications were found among the three groups, but more transfusions were given in the lowest-dose group to prevent bleeding.
The optimal number of platelets in a prophylactic platelet transfusion is controversial.
1
,
2
A standard dose for adults is considered to be approximately 3×10
11
to 6×10
11
platelets.
3
Higher doses than these could potentially result in superior hemostasis,
4
but a lower dose might be equally effective while conserving the platelet supply. Two randomized trials with limited enrollment — one of 111 patients
5
and the other of 119 patients
6
— have compared a low dose of platelets to the standard dose. In both trials, the two doses prevented bleeding to a similar degree. We conducted a randomized trial of prophylactic platelet transfusions . . .
Data are needed on minimal factor activity (FA) levels required to prevent bleeding in hemophilia. We aimed to evaluate associations between hemophilia type and FA level and joint bleeding and ...orthopedic procedures using longitudinal data. Data were collected over an 11-year period on males with nonsevere hemophilia A or B without inhibitors who were receiving on-demand factor replacement therapy. Data on the number of joint bleeds in the previous 6 months and data on procedures from clinical records were analyzed using regression models. Data were collected on 4771 patients (hemophilia A, 3315; hemophilia B, 1456) from 19 979 clinic visits. Ages ranged from 2 to 91 years and baseline FA level ranged from 1% to 49% with a mean of 9.4%. Joint bleeding rates were heterogeneous across the FA range and were highest among men age 25 to 44 years. Adjusted for FA level, the mean number of joint bleeds per 6 months was 1.4 and 0.7 for patients with hemophilia A and B, respectively (P < .001). Regression models predicted 1.4 and 0.6 bleeds per year for hemophilia A and B patients, respectively, at an FA level of 15%. Patients with hemophilia B were 30% less likely than those with hemophilia A to have undergone an orthopedic procedure. We conclude that joint bleed rates for any given FA level were higher among hemophilia A than hemophilia B patients, and target FA levels of 15% are unlikely to prevent all joint bleeding in US males with hemophilia.
•Joint hemorrhages and orthopedic procedures are more frequent in patients with hemophilia A than in those with hemophilia B.•FA levels of 20% may be required to prevent all joint hemorrhages.
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Background
People with hemophilia A or B with inhibitors are at high risk of bleeding complications. Infusion of bypassing agents, such as recombinant activated FVII (rFVIIa) and plasma‐derived ...activated prothrombin complex concentrate, are suggested as alternative therapies to factor VIII (haemophilia A) or IX (haemophilia B) for individuals who no longer respond to these treatments because they develop inhibitory antibodies. The ultimate goal of treatment is to preserve the individual's joints, otherwise destroyed by recurrent bleeds.
Objectives
To assess the effects of bypassing agent prophylaxis to prevent bleeding in people with hemophilia A or B and inhibitors.
Search methods
We searched for relevant studies from the Cystic Fibrosis and Genetic Disorders Group's Coagulopathies Trials Register, comprising of references identified from comprehensive electronic database searches and handsearches of relevant journals and books of conference proceedings. We also searched trial registries (16 February 2017) and bibliographic references of retrieved studies were reviewed for potential articles to be included in the review.
Date of the last search of the Cochrane Cystic Fibrosis and Genetic Disorders Coagulopathies Trials Register: 12 December 2016.
Selection criteria
We included randomized and quasi‐randomized controlled studies (cross‐over or parallel design) evaluating the effect of prophylaxis treatment with bypassing agents compared with on‐demand treatment, or studies evaluating the effects of high‐dose compared with low‐dose prophylaxis in males of any age with hemophilia with inhibitors.
Data collection and analysis
Two authors independently selected studies and extracted data and assessed the risk of bias according to standard Cochrane criteria. They assessed the quality of the evidence using the GRADE criteria.
Main results
We included four randomized studies (duration 7 to 15 months) involving 116 males. Risk of bias was judged to be high in two studies due to the open‐label study design and in one study due to attrition bias.
Two studies compared on‐demand treatment to prophylaxis with bypassing agents. In one study (34 males) prophylaxis significantly reduced mean overall bleeding rates, MD ‐ 7.27 (95% CI ‐9.92 to ‐4.62) (low quality evidence), mean number of overall bleeding events per month, MD ‐1.10 (95% CI ‐1.54 to ‐0.66), mean number of hemarthrosis, MD ‐6.60 (95% CI ‐9.32 to ‐3.88) (low quality evidence) and mean number of joints that had hemarthrosis, MD ‐0.90 (95% CI ‐1.36 to ‐0.44). The meta‐analysis did not conclusively demonstrate significant benefit of prophylaxis on health‐related quality of life as measured by Haem‐A‐QoL score, EQ‐5D total score and utility score, EQ‐5D VAS and SF‐36 physical summary and mental summary score (low quality evidence for all health‐related quality of life analyses).
The remaining two studies compared dose regimens. The results from one study (22 males) did not conclusively demonstrate benefit or harm of high‐dose versus low‐dose recombinant activated factor VIIa (rFVIIa) as a prophylaxis for overall bleeding rate, MD ‐0.82 (95% CI ‐2.27 to 0.63) (moderate quality evidence), target joint bleeding rate, MD ‐3.20 (95% CI ‐7.23 to 0.83) (moderate quality evidence) and serious adverse events, RR 9.00 (95% CI, 0.54 to 149.50) (moderate quality evidence).
The overall quality of evidence was moderate to low due to imprecision from limited information provided by studies with small sample sizes and incomplete outcome data in one study.
Authors' conclusions
The evidence suggests that prophylaxis with bypassing agents may be effective in reducing bleeding in males with hemophilia with inhibitors. However, there is a lack of evidence for the superiority of one agent over the other or for the optimum dosage regimen. Further studies are needed to evaluate the benefits and harms of prophylaxis treatment on health‐related quality of life, as well as the effects of dose of bypassing agents on the outcomes.
The development of antibodies against infused factor VIII (FVIII) in patients with haemophilia A is a serious complication leading to poorly controlled bleeding and increased morbidity. No treatment ...has been proven to reduce high titre antibodies in patients who fail immune tolerance induction or are not candidates for it. The Rituximab for the Treatment of Inhibitors in Congenital Hemophilia A (RICH) study was a phase II trial to assess whether rituximab can reduce anamnestic FVIII antibody (inhibitor) titres. Male subjects with severe congenital haemophilia A and an inhibitor titre ≥5 Bethesda Units/ml (BU) following a FVIII challenge infusion received rituximab 375 mg/m² weekly for weeks 1 through 4. Post-rituximab inhibitor titres were measured monthly from week 6 through week 22 to assess treatment response. Of 16 subjects who received at least one dose of rituximab, three (18.8%) met the criteria for a major response, defined as a fall in inhibitor titre to <5 BU, persisting after FVIII re-challenge. One subject had a minor response, defined as a fall in inhibitor titre to <5 BU, increasing to 5-10 BU after FVIII re-challenge, but <50% of the original peak inhibitor titre. Rituximab is useful in lowering inhibitor levels in patients, but its effect as a solo treatment strategy is modest. Future studies are indicated to determine the role of rituximab as an adjunctive therapy in immune tolerisation strategies.
Introduction
Previous studies reported the efficacy and safety profile of extended half‐life PEGylated recombinant factor VIII (FVIII) rurioctocog alfa pegol (TAK‐660, SHP660, BAX 855) in preventing ...bleeding in haemophilia A patients.
Aim
This study evaluated long‐term safety and efficacy of rurioctocog alfa pegol for prophylaxis and treatment of bleeding in previously treated children and adults.
Methods
In this phase 3b, prospective, open‐label, multicentre study (NCT01945593), eligible patients ≤ 75 years with severe haemophilia A (FVIII < 1%) received prophylactic rurioctocog alfa pegol in a fixed dose (FD, twice‐weekly or less frequent) or pharmacokinetic (PK)‐tailored dose regimen. Co‐primary endpoints were incidence of confirmed FVIII inhibitory antibody development and spontaneous annualized bleed rate (ABR), analysed using a generalised linear model. Secondary endpoints included overall haemostatic efficacy, occurrence of adverse events and health‐related quality of life (HRQoL).
Results
Overall, 216 patients were included; mean (SD) age at enrolment was 22.8 (15.7) years. No patients developed confirmed FVIII inhibitors. The point estimate (95% CI) of mean spontaneous ABR was 1.20 (0.92‐1.56) among 186 patients receiving twice‐weekly FD prophylaxis and 0.96 (0.54‐1.71) among 25 patients receiving PK‐tailored prophylaxis. Overall haemostatic efficacy was rated good or excellent in 88.6% of all bleeds. No new safety signals were observed. Patients reported improvements in HRQoL measures of pain, and physical and mental well‐being.
Conclusion
These results highlight the long‐term safety and efficacy of rurioctocog alfa pegol prophylaxis in previously treated children and adults with severe haemophilia A, with a safety profile similar to previous studies and continuing ABR reduction.
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