A novel approach to laboratory assessment and reporting of platelet von Willebrand factor.

The interaction of platelets with von Willebrand factor is essential for primary hemostasis. Concentration and activity of plasma von Willebrand factor are routine parameters in the assessment of hemostasis disorders. In addition to plasma von Willebrand factor, platelet von Willebrand factor, synthesized in megakaryocytes and stored in α-granules of circulating platelets, is known to contribute to primary hemostasis and the microenvironment of thrombus formation. The laboratory assessment of platelet von Willebrand factor however is cumbersome and not widely established as a routine parameter. We here propose a method for laboratory assessment and reporting of platelet von Willebrand factor potentially useful for laboratory routines in specialized laboratories. Our model allows to describe platelet von Willebrand factor as 1. the concentration of platelet von Willebrand factor in whole blood, 2. the amount of platelet von Willebrand factor in a sample with a defined concentration of 1000 platelets/nl, and 3. the concentration of platelet von Willebrand factor in one platelet. According to our results in healthy individuals, the proportion of platelet von Willebrand factor activity is estimated to be about 10% of total von Willebrand factor in human plasma under physiological circumstances. The concentration of platelet von Willebrand factor is estimated to be 0.4 IU/ml in a sample with a defined concentration of 1000 platelets/nl and to be about 42 IU/ml in one platelet (both expressed as VWF:Ag).

Approximation of emicizumab plasma levels in emergency situations. A practical approach.

INTRODUCTION: A dedicated emicizumab assay based on the modified one-stage factor VIII (FVIII) assay (mOSA) is mainly available in haemophilia treatment centres (HTC). A method to estimate emicizumab plasma levels based on a widely available assay would be desirable, especially for emergency situations. AIM: A method for emicizumab plasma level approximation (ELA) using a routine FVIII activity measurement with standard one-stage assay (sOSA) was developed and evaluated. METHOD: Within this pilot study, 59 samples from patients with severe haemophilia A with (n = 8) and without (n = 8) inhibitors under emicizumab treatment were analysed using sOSA following a manual 1:8 sample pre-test dilution with saline. The sOSA was determined in two different laboratories, using two different analyser platforms each. RESULTS: The results demonstrated an excellent correlation of approximated emicizumab plasma levels (ELA) with the emicizumab plasma concentration determined with mOSA (r > .9; p < .05). The ELA showed a sensitivity of 93.3% and a specificity of 89.6% to predict a pre-defined cut-off-value of ≤30 µg/ml for the discrimination between subtherapeutic and therapeutic emicizumab plasma levels. CONCLUSION: Approximation of emicizumab levels by standard one-stage FVIII assay discriminates between subtherapeutic and therapeutic emicizumab levels and might facilitate clinical decision-making in emergency situations, such as bleeding, trauma or urgent surgery in case that dedicated emicizumab assays are not available.

[Tranexamic acid for bleeding prophylaxis in orthopedic surgery and trauma-standard or customized therapy?] / Tranexamsäure zur Blutungsprophylaxe bei Trauma und orthopädischen Eingriffen ­ Standard oder individualisierte Anwendung?

The use of tranexamic acid (TXA) is established in the treatment of bleeding, especially of bleeding due to hyperfibrinolysis. In recent years the prophylactic use of TXA in trauma and orthopedic surgery has increased leading to open questions regarding potentially associated risks and a possible classification as off label use. The available literature provides a sound basis for the recommendation that TXA can be used in these indications provided that an individual risk assessment is done in patients with increased risks for thromboembolic complications. Although the prophylactic use of TXA in orthopedic surgery and trauma is not explicitly listed in the product characteristics, it should not be regarded as an off label use.

Sensitive and specific assessment of recombinant von Willebrand factor in platelet function analyzer.

BACKGROUND: Recombinant von Willebrand factor (rVWF), which was licensed in the United States in 2015, has the multimeric distribution of freshly secreted VWF with ultralarge (UL) and high molecular weight multimers (HMWM) from endothelial cells and megakaryocytes since it has never been exposed to ADAMTS13 or any other proteolytic enzyme. Measurement of closure time (CT) using the platelet function analyzer-200 (PFA-200) is highly sensitive to the presence of UL VWF multimers in added VWF concentrates. The PFA-200 is fully automated and can be used as a reliable point-of-care method to evaluate primary hemostasis. Although it is sensitive to presence of UL VWF multimers, there could be significant clinical utility when used to monitor rVWF replacement therapy. The ability to monitor and optimize the dosing of rVWF contributes to patient safety, especially in situations where the bleeding and thrombotic risk needs to be carefully balanced (e.g., cardiac assist device). OBJECTIVE: The aim of this in-vitro study was to demonstrate the detectability of rVWF spiked in VWF-deficient blood from patients with severe von Willebrand disease (VWD) with quantitative and functional pathologies using a functional testing device. We hypothesized that (1) whole blood samples from VWD patients spiked with rVWF would show a normalization in PFA-CT and (2) that a dose-response relationship could be demonstrated. METHODS AND RESULTS: We selected 12 patients diagnosed with VWD from our database. A therapeutic dose of rVWF product (1 IU/ml) was spiked in VWD patients´ whole blood samples and PFA-CTs were measured. Furthermore, we investigated PFA-CTs under incremental doses of rVWF (0.1, 0.2, and 0.5 IU/ml). The PFA-CTs were normalized in VWD patients´ whole blood samples spiked with rVWF. Additionally, incremental doses of rVWF resulted in a progressive and dose-dependent PFA-CT correction. CONCLUSION: Our in-vitro data indicate that the PFA-200 is a useful tool to detect rVWF. As the PFA-CT correction is dose dependent, the rVWF might be reliably monitored with a point-of-care analytical method during replacement therapy.

Emicizumab in the Treatment of Acquired Haemophilia: A Case Report.

The prognosis of acquired haemophilia A (AHA) is severe and treatment options are limited. Emicizumab is a novel bispecific humanized monoclonal antibody in the treatment of inherited AHA with inhibitors. An 83-year-old AHA patient with congestive heart failure and a high risk for thromboembolic and cardiac events who had initially been treated successfully with steroids and substitution of recombinant B-domain-deleted porcine FVIII developed severe bleeding complications and a secondary increase in inhibitor titres after 4 weeks of treatment. Conventional therapeutic strategies failed, and the patient was subsequently treated with emicizumab on off-label and named patient use premises. After the application of emicizumab, the clinical conditions stabilized and no further substitution of coagulation factors was needed. The patient could be discharged and survived 36 days in a cardiac rehabilitation centre without indications for spontaneous bleeding or thromboembolic events. We suggest that the effects of emicizumab in acquired haemophilia should be evaluated in clinical trials.

Emicizumab versus immunosuppressive therapy for the management of acquired hemophilia A.

BACKGROUND: Acquired hemophilia A (AHA) is an autoimmune bleeding disorder caused by neutralizing antibodies against coagulation factor VIII (FVIII). Immunosuppressive therapy (IST) is standard of care to eradicate autoantibody production and protect from further bleeding but carries a risk of severe infection and mortality in frail patients with AHA. Recently, emicizumab has been studied for its potential to reduce the need for early and aggressive IST. OBJECTIVE: To compare outcomes of two studies that used either IST (GTH-AH 01/2010; n=101) or prophylaxis with emicizumab (GHT-AHA-EMI; n=47) early after diagnosis of AHA. METHODS: Baseline characteristics were balanced by propensity score matching. Primary endpoint was the rate of clinically relevant new bleeds during the first 12 weeks; secondary endpoints were adverse events and overall survival. RESULTS: The negative binominal model-based bleeding rate was 68% lower with emicizumab as compared with IST (incident rate ratio 0.325, 95% confidence interval (CI) 0.182-0.581). No difference was apparent in the overall frequency of infections (emicizumab 21%, IST 29%) during the first 12 weeks, but infections were less often fatal in emicizumab treated patients (0%) compared with IST treated patients (11%). Thromboembolic events occurred less often with emicizumab (2%) than IST (7%). Overall survival after 24 weeks was better with emicizumab (90% versus 76%, HR 0.44; 95% CI 0.24-0.81). CONCLUSION: Using emicizumab instead of IST in the early phase after initial diagnosis of AHA reduced bleeding and fatal infections, and improved overall survival.

Primary presentation and clinical course of pediatric and adolescent patients with differentiated thyroid carcinoma after radioiodine therapy.

Introduction: Differentiated thyroid carcinoma (DTC) in childhood and during adolescence is extremely rare. Pediatric DTC commonly presents with advanced disease at diagnosis including a high prevalence of cervical lymph node metastases and pulmonary metastases. Studies in children with DTC are limited. Therefore, we aimed to evaluate the initial presentation, effectiveness of radioiodine therapy (RIT), and long-term outcome of prepubertal in comparison to pubertal/postpubertal patients. Methods: Eighty-five pediatric and young patients aged 6.4 to 21.9 years with histopathologically confirmed DTC were retrospectively included. They all underwent total thyroidectomy followed by RIT. Initial presentation and outcome of prepubertal and pubertal/postpubertal patients were compared 1 year after RIT, during follow-up, and at the last visit of follow-up. Results: Prepubertal patients presented with significantly higher T and M stages. One year after RIT, 42/81 (52%) patients still presented with evidence of disease (ED). During follow-up of a median of 7.9 years, prepubertal patients were less often in complete remission (58% vs. 82% in pubertal patients). At the last visit of follow-up, 19/80 (24%) patients still had ED without statistical differences between the two groups (42% prepubertal vs. 18% pubertal/postpubertal, p-value 0.06). None of our patients died disease-related over the observed period. Conclusion: Prepubertal children with DTC presented with a more advanced tumor stage at the initial presentation. During follow-up, they present more often with ED. However, at the end of our study, we did not observe statistically relevant differences in patient outcomes between the prepubertal and pubertal/postpubertal groups.

The Role of Therapeutic Anticoagulation in COVID-19.

Coagulopathy has proven to be a common complication of the novel coronavirus SARS-CoV-2, with evidence of elevated D-dimers and fibrin degradation products associated with an increased incidence of thromboembolism. Despite emerging evidence describing the coagulopathy and its clinical relevance in COVID-19, fewer studies have addressed the potential role of empiric therapeutic anticoagulation in this setting. We report the case of a patient admitted to our intensive care unit (ICU) with severe acute respiratory distress syndrome (ARDS) secondary to COVID-19 whose clinical trajectory improved dramatically after initiation of a therapeutic dose of LMWH. The patient showed progressive elevation of fibrinogen and D-dimers despite a prophylactic dose of LMWH during her ICU stay. This was met with a moderate increase of troponin T-hs, an escalating need for vasopressors, and a progressive decrease in her P/F ratio despite preserved lung static compliance. Her platelet count was normal and had an elevated fibrinogen during the first week of ICU stay. The ECG was normal, and a bedside transthoracic echocardiogram showed no evidence of pulmonary embolism and a preserved EF with no regional wall motion abnormalities (RMWA). The chest X-ray was not dissimilar to previous exams, and the ABG showed hypoxia with normal pCO2 values. The decision was made to commence empiric therapeutic enoxaparin. The patient did not experience bleeding complications, and her clinical trajectory appeared to change dramatically. She was successfully extubated three days later and proceeded to clinical recovery and eventual discharge from the ICU. The available evidence shows that there is undoubtedly coagulopathy associated with COVID-19 with various subsequent forms of clinical manifestation described in the literature. Evidence also shows the benefits of heparin as an anticoagulant. From the discussion of this case report, however, it can be concluded that despite the plausible theoretical rationale, studies pertaining to the role of empiric therapeutic anticoagulation in this setting fall short of providing compelling evidence. Subsequently the role of empiric therapeutic anticoagulation in COVID-19 remains unclear with a pressing call for further research.

Laboratory testing in hemophilia: Impact of factor and non-factor replacement therapy on coagulation assays.

The advent of extended half-life (EHL) recombinant clotting factors and innovative non-factor replacement therapeutics, such as emicizumab, offers several advantages over existing products for the prophylactic treatment of people living with hemophilia (PwH). These include low annual bleeding rates with less frequent dosing, higher trough plasma concentrations, and a more convenient route of administration. However, increasing use of these therapies poses challenges to clinicians and coagulation laboratories due to the lack of standardized assays for monitoring of hemostatic parameters, and the potential for misinterpretation of test results, which may jeopardize patient safety. Definitive diagnosis of hemophilia and treatment monitoring is reliant on demonstrating factor VIII (FVIII; hemophilia A) or factor IX (FIX; hemophilia B) deficiency using a functional coagulation assay. The most frequently used assays are based on activated partial thromboplastin time, using a one-stage or two-stage process. While one-stage and chromogenic assays have performed well with human-derived FVIII and FIX and full-length recombinant products, EHL recombinant factors are heterogeneous in structure and mode of action and therefore show wide variation in activity levels between different one-stage assays, and between one-stage and chromogenic assays. In the context of the recommended stepwise approach for laboratory diagnosis of hemophilia, we examine the diagnostic challenges associated with the use of EHL factors and novel non-factor therapeutics and consider the optimal diagnostic approach in PwH who are receiving these treatments. Ultimately, accurate diagnostic solutions are a prerequisite for personalized therapy to minimize treatment burden and improve quality of life in PwH.

Health Care Transition of Adolescents and Young Adults with Haemophilia: the Situation in Germany and the Munich experience.

Patients suffering from haemophilia encounter various phases in life, in which individual needs, life situations, and self- and disease perception change rapidly. One of these phases spans from the beginning of puberty until early adulthood, in which individuals gain self-responsibility and reach independence and autonomy. In this challenging time that determines future health, adolescents and young adults need sustainable familiar and professional support. A change in health care team and treatment centre may expose adolescent patients to threats but also provides the possible opportunity to be well prepared. While there is emerging evidence that the so-called health care transition programmes are effective in maintaining quality of care in other disease areas, transition programmes for patients with haemophilia are still rare in Germany, and the evidence is limited. We describe the situation in Germany, discuss our experience in Munich and review some of the available guidance; we conclude that transition programmes should become a standard of care in haemophilia.

Laboratory Monitoring in Emicizumab-Treated Persons with Hemophilia A.

Hemophilia A (HA) is an X-linked hereditary bleeding disorder caused by deficiency of coagulation factor (F) VIII activity. One of the greatest complications in the treatment of HA is the development of neutralizing alloantibodies, known as FVIII inhibitors. HA patients who develop FVIII inhibitors have limited treatment options available to them and experience greater disease- and treatment-related burdens than HA patients without FVIII inhibitors. Emicizumab, a recently approved bispecific monoclonal antibody, mimics the function of FVIIIa by bridging FIXa and FX to restore effective hemostasis. Although emicizumab and FVIII show some functional similarities, several key differences influence the results of standard laboratory assays when conducted in the presence of emicizumab, and can result in a misleading interpretation of coagulation assays in emicizumab-treated patients. Here, we discuss current laboratory monitoring methods, including activated partial thromboplastin time, FVIII one-stage clotting assays, FVIII chromogenic assays, and global coagulations assays; address why these conventional methods may be inappropriate for monitoring of HA patients receiving emicizumab; and suggest alternative methods applicable to monitoring HA treatment in an evolving treatment landscape.

Optimizing Platelet GPVI Inhibition versus Haemostatic Impairment by the Btk Inhibitors Ibrutinib, Acalabrutinib, ONO/GS-4059, BGB-3111 and Evobrutinib.

Ibrutinib and acalabrutinib are approved for B cell malignancies and novel Bruton's tyrosine kinase (Btk) inhibitors undergo clinical testing also in B cell-driven autoimmune disorders. Btk in platelets mediates platelet activation via glycoprotein (GP) VI, which is crucial for atherosclerotic plaque-induced platelet thrombus formation. This can be selectively inhibited by Btk inhibitors. Since patients on second-generation Btk inhibitors apparently show less bleeding than patients on ibrutinib, we compared the effects of ibrutinib and four novel irreversible Btk inhibitors on GPVI-dependent platelet aggregation in blood and in vitro bleeding time. Low concentrations of collagen which induced the same low degree of GPVI-mediated platelet aggregation as atherosclerotic plaque material were applied. IC50 values for collagen (0.2-0.5 µg/mL)-induced platelet aggregation after 15-minute pre-incubation were: ibrutinib 0.12 µM, BGB-3111 0.51 µM, acalabrutinib 1.21 µM, ONO/GS-4059 1.20 µM and evobrutinib 5.84 µM. Peak venous plasma concentrations of ibrutinib (0.5 µM), acalabrutinib (2 µM) and ONO/GS-4059 (2 µM) measured after anti-proliferative dosage inhibited collagen-induced platelet aggregation, but did not increase PFA-200 closure time on collagen/epinephrine. Closure times were moderately increased by 2- to 2.5-fold higher concentrations of these inhibitors, but not by BGB-3111 (1 µM) and evobrutinib (10 µM). Prolonging platelet drug exposure to 60 minutes lowered IC50 values of any Btk inhibitor for GPVI-mediated aggregation by several fold, and 5- to 10-fold below anti-proliferative therapeutic drug plasma levels. In conclusion, low blood concentrations of ibrutinib and the novel Btk inhibitors suffice for GPVI selective platelet inhibition relevant for atherothrombosis but do not impair primary haemostasis.

Perioperative Management of a Patient with Severe Factor V Deficiency Presenting with Chronic Subdural Hematoma: A Clinical Report.

BACKGROUND: Severe factor V deficiency is an extremely rare coagulation disorder. Patients with factor V activity <5% usually become symptomatic in early childhood. CASE DESCRIPTION: We report the case of an 82-year-old woman with incidentally diagnosed severe factor V deficiency, who developed a symptomatic chronic subdural hematoma, requiring burr hole craniostomy. Successful management was achieved by a multidisciplinary approach. Preoperatively, factor V activity was increased from 2% to 50% by administration of 25 mL/kg body weight of fresh frozen plasma over 30 minutes under close cardiopulmonary monitoring in the intensive care unit. Straight afterward, the patient was transferred to the operating room where surgery was performed under general anesthesia. Burr hole craniostomy could be performed without perioperative complications. In the postoperative days, there was no relevant recurrence of the subdural hematoma in the follow-up computed tomography scans under frequent control of coagulation parameters. However, despite further transfusion of fresh frozen plasma, factor V activity did not increase >16%. The patient was discharged without any neurologic deficits. In a hemostaseologic follow-up 2 months after surgery, factor V activity <1% was confirmed with evidence of a factor V inhibitor in the modified Bethesda assay. Most likely, the patient suffered from an acquired form of factor V deficiency with preformed antibodies that had been boosted by the initial treatment with fresh frozen plasma. CONCLUSIONS: We conclude that in this rare bleeding disorder, intracranial surgery was successfully managed because of a thoroughly planned perioperative therapeutic strategy. However, if there is time prior to surgery, a full checkup of the bleeding disorder is advisable.