The possibility that high factor VIII (FVIII) levels in thrombosis patients is principally explained by a gain of function in the FVIII‐binding domain of von Willebrand factor (VWF), arising from amino acid substitution(s) or polymorphism(s), was investigated. Exons 18–24 of the VWF gene were sequenced in 13 thrombosis patients with high FVIII (> 1·50 IU/ml). No novel mutations were found. Four known polymorphisms were detected: G2615A and C2635T (Ex18), G2805A (Ex20) and G3130A (Ex22). Their frequencies showed no significant differences in a thrombosis vs. control cohort. The data suggest that amino acid substitutions/polymorphisms in the VWF‐FVIII‐binding domain are not the principal explanation for high FVIII in thrombosis patients.
Abstract Introduction Acquired haemophilia A (AHA) is a rare bleeding disorder caused by the development of autoantibodies to endogenous human factor VIII (hFVIII). If treatment of bleeding is required, one option is recombinant porcine FVIII (rpFVIII). Cross‐reactivity between factor VIII inhibitors and rpFVIII has previously been described. Aim The aim of this study was to retrospectively assess the incidence of cross‐reacting anti‐porcine inhibitors in patients diagnosed with AHA in two UK centres. Methods The plasma of fifty‐one patients diagnosed with AHA via reduced FVIII:C and positive FVIII inhibitor titre as detected with a Nijmegen‐Bethesda assay (NBA) was also tested by a porcine Bethesda assay (PBA). The NBA was modified by replacement of human FVIII with rpFVIII in the PBA, with determination of residual FVIII by one‐stage clotting assay. Results The median FVIII inhibitor titre by NBA was 22.8 BU/mL (range: 0.8‐1000 BU/mL). 37% of samples exhibited linear, type 1 kinetics in the NBA. Negative PBA was observed in 26 patients, and 25 were positive (median PBA: 3.5 BU/mL; range: 0.8‐120 BU/mL). Type 1 kinetics were observed in 40% of PBA‐positive patients. At NBA tires of greater than 100 BU/mL, the positive predictive value for the presence of porcine cross‐reactivity was 100%. At NBA below 5 BU/mL, the negative predictive value for the presence of porcine cross‐reactivity was 71%. Conclusion Cross‐reactivity between FVIII inhibitors and rpFVIII was observed in 49% of patients. The presence of inhibitors to rpFVIII may influence the treatment choice for patients with acquired haemophilia A.
Abstract Introduction Recombinant porcine FVIII (rpFVIII) (Obizur, Susoctcog‐alfa, Takeda, Japan) is licensed for the treatment of bleeding in acquired Haemophilia A (AHA). The summary of product characteristics state that monitoring should be by one stage assay (OSA) rather than chromogenic assay (CSA). CSA have been shown to underestimate activity when rpFVIII is added to plasma in vitro. Methods Samples from three AHA patients ( n = 21) (pre‐ and post rpFVIII) were assessed using FVIII:C assays; OSA methods: Actin, Actin FS, Actin FSL and Pathromtin SL performed on CS5100i (Sysmex, Kobe, Japan); APTT‐SP, SynthASil and SynthAFax performed on ACL TOP (Werfen, Barcelona, Spain). CSA methods on CS5100i: Siemens Chromogenic Assay, Biophen FVIII:C, Technochrom FVIII:C; on ACL TOP: Rox Factor VIII, Coamatic Factor VIII and CRYOcheck Factor VIII. Results OSA and CSA varied according to reagent used median OSA 61 IU/dL (range 41.5–81 IU/dL (ANOVA p < 0.0001)) median CSA 46.5 IU/dL (range of method specific medians 36.5–84 IU/dL (ANOVA p < 0.0001)). Amongst OSA, Actin FS was associated with the highest FVIII:C, APTT‐SP was associated with the lowest. Variation in CSA results by different methods was also seen with highest FVIII:C levels obtained using the Technochrom FVIII:C and the lowest levels obtained with Siemens Assay. Conclusion The relationship between OSA and CSA was not consistent between method or patient. Previously there has been reports of underestimation by CSA in in vitro spiked samples. Investigation into concentration of phospholipids in the APTT reagents may explain some of these variations.
Abstract Acquired immune thrombotic thrombocytopenic purpura (iTTP) is a rare disease with a poor prognosis if undiagnosed. It is caused by autoantibody production to the von Willebrand factor (VWF) cleaving protease, A disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). Caplacizumab, an immunoglobulin directed to the platelet glycoprotein Ibα receptor of VWF, has been reported to induce quicker resolution of iTTP compared to placebo. The laboratory measurement of VWF activity was significantly reduced in clinical trials of caplacizumab. Several VWF assays are available in the UK and this study investigated whether differences in VWF parameters were present in 11 patients diagnosed with iTTP and treated with daily caplacizumab. Chromogenic factor VIII activity, VWF antigen, collagen binding activity, VWF multimers and six VWF activity assays were measured prior to caplacizumab therapy and on several occasions during treatment. VWF antigen and collagen binding activity levels were normal or borderline normal in all patients. Ultra‐large molecular weight multimers were present in all patients following treatment. VWF activity assays were normal or reduced during treatment, but this was reagent and patient dependant. In the unusual scenario of a caplacizumab‐treated patient requiring measurement of VWF activity, it is important that laboratories understand how their local reagents perform as results cannot be predicted.
Physicians treating acute pulmonary embolism (PE) are faced with difficult management decisions while specific guidance from recent guidelines may be absent.
Methods
Fourteen clinical dilemmas were identified by physicians and haematologists with specific interests in acute and chronic PE. Current evidence was reviewed and a practical approach suggested.
Results
Management dilemmas discussed include: sub-massive PE, PE following recent stroke or surgery, thrombolysis dosing and use in cardiac arrest, surgical or catheter-based therapy, failure to respond to initial thrombolysis, PE in pregnancy, right atrial thrombus, role of caval filter insertion, incidental and sub-segmental PE, differentiating acute from chronic PE, early discharge and novel oral anticoagulants.
Conclusion
The suggested approaches are based on a review of the available evidence and guidelines and on our clinical experience. Management in an individual patient requires clinical assessment of risks and benefits and also depends on local availability of therapeutic interventions.
Summary Supportive care plays an increasingly important role in the modern management of multiple myeloma. While modern treatments have significantly prolonged overall and progression free survival through improved disease control, the vast majority of patients remain incurable, and live with the burden of the disease itself and the cumulative side effects of treatments. Maintenance of quality of life presents challenges at all stages of the disease from diagnosis through the multiple phases of active treatment to the end of life. Written on behalf of the British Committee for Standards in Haematology (BCSH) and the UK Myeloma Forum (UKMF), these evidence based guidelines summarize the current national consensus for supportive and symptomatic care in multiple myeloma in the following areas; pain management, peripheral neuropathy, skeletal complications, infection, anaemia, haemostasis and thrombosis, sedation, fatigue, nausea, vomiting, anorexia, constipation, diarrhoea, mucositis, bisphosphonate‐induced osteonecrosis of the jaw, complementary therapies, holistic needs assessment and end of life care. Although most aspects of supportive care can be supervised by haematology teams primarily responsible for patients with multiple myeloma, multidisciplinary collaboration involving specialists in palliative medicine, pain management, radiotherapy and surgical specialities is essential, and guidance is provided for appropriate interdisciplinary referral. These guidelines should be read in conjunction with the BCSH/UKMF Guidelines for the Diagnosis and Management of Multiple Myeloma 2011.
Hemophilia A and B are bleeding disorders inherited in an X-linked recessive fashion, caused by deficiencies in factor VIII (FVIII) and factor IX (FIX), respectively. It was initially thought that hemophilia was caused by abnormalities of the vascular system, and it was not until the late 1800s and early 1900s that a deficiency of a component of the blood was thought to be responsible. All racial groups are equally affected by hemophilia with an incidence of 1 in 5000 live male births for hemophilia A, and 1 in 30,000 live male births for hemophilia B. The clinical symptoms and signs of these two disorders are identical in presentation, and specific clotting factor assays are required to distinguish them. With modern management and the ready availability of clotting factors, children with hemophilia today can look forward to a normal life expectancy.
The bispecific antibody, emicizumab, is a prophylactic therapy used for the treatment of haemophilia A (HA). Patients may require additional replacement factor VIII (FVIII) to ensure adequate haemostasis. This study investigated the laboratory measurement of severe HA (SHA) plasma spiked with 36 combinations of emicizumab plus recombinant (r) FVIII concentrates.FVIII assays were performed by one stage assay (OSA) using eight APTT reagents from three manufacturers and chromogenic assays (CSA) using seven kits. CSA kits comprised a range of bovine FX/FIXa, bovine FX/human FIXa or human FX/FIXa. Thrombin generation (TG) was assessed by CAT and ST-Genesia.Emicizumab-calibrated modified OSA and human FX CSA both overestimated rFVIII in the presence of emicizumab; median FVIII:C of up to 89% higher was observed in plasma spiked with both drugs compared to just rFVIII. In bovine FX CSA assays, there was a FVIII:C increase of up to 11% in plasmas spiked with both drugs compared to rFVIII alone. TG parameters were not all normalized by the presence of emicizumab however addition of rFVIII increased TG. ETP and peak thrombin were normalized at 50 μg/ml emicizumab using ST-Genesia but were still reduced at 75 μg/ml with CAT. Addition of rFVIII further normalized results.Modified OSA and human FX CSA could not distinguish between rFVIII or emicizumab. The presence of both emicizumab and rFVIII increased thrombin generation to normal levels compared to each drug alone. Bovine FX CSA can be used to accurately determine FVIII activity of rFVIII in plasma which also contains emicizumab.
Severe FX deficiency is a rare disorder with a variable bleeding tendency but spontaneous life threatening haemorrhage can occur. Treatment for invasive procedures and spontaneous bleeding is with prothrombin complex concentrates (PCC). When used in large or repetitive doses these are associated with a thrombotic tendency. FX:C levels of 0.15 - 0.30 IU/ mL are thought to be haemostatic during surgery . There is only limited information on the outcome and management of pregnancy in severe FX deficiency. Caesarean section is suggested as delivery mode to reduce the risk of intracranial/abdominal neonatal haemorrhage, but successful vaginal deliveries are also described. The calibrated automated thrombin generation assay (CAT) is a global coagulation test that measures the time course of thrombin generation. It has been reported to correlate with prothrombotic states and the severity of bleeding in rare coagulation disorders. The variability in phenotype, the uncertainty of the minimal haemostatic FX:C concentration and the association of PCC's with thrombosis make thrombin generation of interest in the management of FX deficient patients.We describe the use of CAT as a possible means to monitor treatment with PCC (Beriplex) in a patient with severe FX deficiency (FX:C < 0.01 IU/mL) during successful vaginal delivery and epidural anaesthesia.Thrombin generation was normal at FX:C 0.80 IU/mL but only borderline normal at FX:C 0.25 IU/mL. Repetitive doses over 3 days increased thrombin generation to the upper limit of normal at FX:C 0.25 IU/mL consistent with a prothrombotic tendency after multiple doses. The increase in thrombin generation was not related to prothrombin levels.The data suggest that CAT may be used to monitor treatment with PCC in FX deficiency. Higher levels than previously thought may be needed to normalize thrombin generation. Further studies into the correlation with bleeding or thrombosis are needed before the approach can be accepted in clinical practice.
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