Exploring the effects of Factor Xa inhibitors on thrombin generation in people with haemophilia.

Optimal management of cardiovascular disease (CVD) in people with haemophilia (PWH) is a growing issue, given the continuing improvement in life expectancy among PWH. The evolving treatment paradigms targeting higher trough levels and the advent of non-factor replacement therapies (NFRT) means much of the 'protection' PWH were thought to have against CVD may be lost. There is a paucity of evidence regarding the safety of using anticoagulants in PWH. We designed a study assessing the thrombin generation (TG) of PWH of different severities and treatments, compared to non-haemophilia patients receiving a Factor Xa (FXa) inhibitor (apixaban or rivaroxaban), healthy controls, and assessing TG parameters of adding FXa inhibitor to the plasma of PWH receiving emicizumab prophylaxis. In total, 40 patients were included. TG was initiated with 5pM tissue factor (TF) using the calibrated automated thrombinoscope. Compared to those with mild haemophilia, patients receiving a FXa inhibitor had higher endogenous thrombin potential (ETP) (1278.42 vs 1831.36) and velocity index (40.71 vs 112.56), but both had a similar peak height (154.0 vs 262.63) and time to peak (both 5.83). People with severe haemophilia receiving emicizumab had significantly improved TG parameters compared to those not receiving emicizumab - ETP 1678.11 vs 809.96 and peak height 233.8 vs 92.05; however, when FXa inhibitor was added their TG parameters deteriorated to the severe haemophilia range (ETP 1179.60 and peak height 103.05). TG may provide additional useful information regarding the use of anticoagulants in PWH.

Mutational landscape, inhibitor development, and health-care burden in non-severe haemophilia A: A single-centre Australian experience.

AIM: To characterise non-severe haemophilia A (HA) patients enrolled on the Australian Bleeding Disorders Registry (ABDR) treated through a state-wide Haemophilia Treatment Centre (HTC) with respect to their mutational profile, inhibitor risk and health-care burden. METHOD: We conducted a single-centre observational study of all non-severe HA patients treated at the Alfred Health HTC registered on the ABDR as of the 26th July 2023. Data were extracted from the ABDR and electronic medical record (EMR) regarding demographics, severity, genetic testing, treatment, inhibitors, bleeding events and procedures. Inhibitor risk was calculated as a function of exposure days (EDs) of FVIII replacement. RESULTS: There were 289 non-severe HA patients treated at the Alfred HTC registered on the ABDR as of July 2023, all of whom were adult patients aged > 18 years old. Genotyping had been performed in 228/289 (78.9%). Of the inhibitor analysis population, 14/193 (7.3%) had an inhibitor. The cumulative incidence of inhibitor development at 75 EDs was 31% (95% CI 13%-46%). The median cost of bypassing agents per inhibitor patient was $57,087.50/year. CONCLUSION: These results demonstrate a relatively high inhibitor prevalence and incidence risk in non-severe HA compared to previously published work, although this may partly reflect a smaller population size. High rates of genotyping have allowed representative mutational characterisation. The burden of care imposed by non-severe HA in terms of bleeding events, procedures and bypassing agent cost is larger than expected, particularly within the inhibitor population.

Venous Thromboembolism and Estrogen-Containing Gender-Affirming Hormone Therapy.

Gender-affirming therapy involves the use of hormones to develop the physical characteristics of the identified gender and suppressing endogenous sex hormone production. Venous thromboembolism (VTE) is a known risk of exogenous estrogen therapy, and while evidence of VTE risk among transgender women using modern gender-affirming hormone therapy (GAHT) is still emerging, it is thought to affect up to 5% of transgender women. Historically, GAHT was associated with a high risk of VTE; however, modern preparations are less thrombogenic mainly due to significantly lower doses used as well as different preparations. This review presents the available literature regarding the following four topics: (1) risk of VTE among transgender women receiving estradiol GAHT, (2) how the route of administration of estradiol affects the VTE risk, (3) perioperative management of GAHT, (4) VTE risk among adolescents on GAHT. There is a need for large, longitudinal studies of transgender women using GAHT to further characterize VTE risk and how this is affected by factors such as patient age, duration of GAHT use, tobacco use, body mass index, and comorbidities. Future studies in these areas could inform the development of clinical guidelines to improve the care of transgender people.

The clinicopathological features of thrombosis with thrombocytopenia syndrome following ChAdOx1-S (AZD1222) vaccination and case outcomes in Australia: a population-based study.

Background: Thrombosis with thrombocytopenia syndrome (TTS) associated with viral vector COVID-19 vaccines, including ChAdOx1-S (AstraZeneca AZD1222) vaccine, can result in significant morbidity and mortality. We report the clinicopathological features of TTS following ChAdOx1-S vaccination and summarise the case outcomes in Australia. Methods: In this cohort study, patients diagnosed with TTS in Australia between 23 March and 31 December 2021 were identified according to predefined criteria. Cases were included if they met the Therapeutic Goods Administration (TGA) probable and confirmed case definitions and were reclassified using Centres for Disease Control and Prevention (CDC) definition for analysis. Data were collected on patient baseline characteristics, clinicopathological features, risk factors, treatment and outcomes. Findings: A total of 170 TTS cases were identified, with most occurring after the first dose (87%) of ChAdOx1-S. The median time to symptom onset after vaccination and symptom onset to admission was 11 and 2 days respectively. The median age of cases was 66 years (interquartile range 55-74). All except two patients received therapeutic anticoagulation and 66% received intravenous immunoglobulin. Overall, 85.3% of cases were discharged home after a median hospitalisation of 6 days, 9.4% required ongoing rehabilitation and 5.3% died. Eight deaths were related to TTS, with another dying from an unrelated condition while receiving treatment for TTS. Deaths occurred more commonly in those classified as Tier 1 according to the CDC definition and were associated with more severe thrombocytopenia and disease-related haemorrhage. Interpretation: TTS, while rare, can be severe and have catastrophic outcomes in some individuals. In Australia, the mortality rate was low compared to that reported in other high-income countries. Almost all received therapeutic anticoagulation with no bleeding complications and were successfully discharged. This emphasises the importance of community education and an established pathway for early recognition, diagnosis and treatment of TTS. Funding: Australian Commonwealth Department of Health and Aged Care. H.A Tran, N. Wood, J. Buttery, N.W. Crawford, S.D. Chunilal, V.M. Chen are supported by Medical Research Future Funds (MRFF) grant ID 2015305.

Congenital fibrinogen disorders: Strengthening genotype-phenotype correlations through novel genetic diagnostic tools.

Congenital fibrinogen disorders or CFDs are heterogenous, both in clinical manifestation and array of culprit molecular lesions. Correlations between phenotype and genotype remain poorly defined. This review examines the genetic landscape discovered to date for this rare condition. The question of a possible oligogenic model of inheritance influencing phenotypic heterogeneity is raised, with discussion of the benefits and challenges of sequencing technology used to enhance discovery in this space. Considerable work lies ahead in order to achieve diagnostic and prognostic precision and subsequently provide targeted management to this complex cohort of patients.

Vaccine-induced immune thrombotic thrombocytopenia post dose 2 ChAdOx1 nCoV19 vaccination: Less severe but remains a problem.

BACKGROUND: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but established complication of 1st dose ChAdOx1 nCoV19 vaccination (AZD1222), however this complication after dose 2 remains controversial. OBJECTIVES: To describe the clinicopathological features of confirmed cases of VITT post dose 2 AZD1222 vaccination in Australia, and to compare this cohort to confirmed cases of VITT post 1st dose. METHODS: Sequential cases of clinically suspected VITT (thrombocytopenia, D-Dimer > 5x upper limit normal and thrombosis) within 4-42 days of dose 2 AZD1222 referred to Australia's centralised testing centre underwent platelet activation confirmatory testing in keeping with the national diagnostic algorithm. Final classification was assigned after adjudication by an expert advisory committee. Descriptive statistics were performed on this cohort and comparative analyses carried out on confirmed cases of VITT after 1st and 2nd dose AZD1222. RESULTS: Of 62 patients referred, 15 demonstrated presence of antibody mediated platelet activation consistent with VITT after dose 2 AZD1222. Four were immunoassay positive. Median time to presentation was 13 days (range 1-53) platelet count 116x10^9/L (range 63-139) and D-dimer elevation 14.5xULN (IQR 11, 26). Two fatalities occurred. In each, the dosing interval was less than 30 days. In comparison to 1st dose, dose 2 cases were more likely to be male (OR 4.6, 95% CI 1.3-15.8, p = 0.03), present with higher platelet counts (p = 0.05), lower D-Dimer (p = 01) and less likely to have unusual site thromboses (OR 0.14, 95% CI 0.04-0.28, p = 0.02). CONCLUSIONS: VITT is a complication of dose 2 AZD1222 vaccination. Whilst clinicopathological features are less severe, fatalities occurred in patients with concomitant factors.

Oral Anticoagulant Use in Patients With Atrial Fibrillation and Chronic Kidney Disease: A Review of the Evidence With Recommendations for Australian Clinical Practice.

Chronic kidney disease is common in patients with atrial fibrillation (AF) and is associated with heightened risks of stroke/systemic embolisation and bleeding. In this review we outline the evidence for AF stroke prevention in kidney disease, identify current knowledge gaps, and give recommendations for anticoagulation at various stages of chronic kidney disease. Overall, anticoagulation is underused. Warfarin use becomes increasingly difficult with advancing kidney disease, with difficulty maintaining international normalised ratio (INR) in therapeutic range, increased risk of intracranial and fatal bleeding compared to non-vitamin K oral anticoagulants (NOACs), and high rates of discontinuation. Similarly, the direct thrombin inhibitor dabigatran is not recommended as it is predominantly renally excreted with consequent increased plasma levels and bleeding risk with advanced kidney disease. The Factor Xa inhibitors apixaban and rivaroxaban have less renal excretion (25-35%), modest increases in plasma levels with advancing kidney disease, and are the preferred first line choice for anticoagulation in moderate kidney disease based on strong evidence from randomised clinical trials (RCTs). In severe kidney disease there is a paucity of RCT data, but extrapolation of the pharmacokinetic and RCT data for moderate kidney disease, and observational studies, support the considered use of dose-adjusted Factor Xa inhibitors unless the bleeding risk is prohibitive. In Australia, apixaban is approved for creatinine clearance down to 25 mL/min, and rivaroxaban down to 15 mL/min. For end-stage kidney disease warfarin is the only agent approved, but we recommend against anticoagulation (except in selected cases) due to high bleeding risk, multiple co-morbidities, and questionable benefit.

Osteoporosis management and falls prevention in patients with haemophilia: Review of haemophilia guidelines.

INTRODUCTION: Patients with haemophilia (PWH) have a high prevalence of osteoporosis, falls and fractures at all ages. The role of haemophilia itself may contribute to low bone mineral density (BMD) due to coagulation factor deficiency. Guidelines for the management of osteoporosis, fracture and fall risk may help to reduce fracture and fall risk, and delay osteoporosis onset. AIM: We aim to review current haemophilia guidelines regarding osteoporosis prevention, screening, diagnosis and management, and fall prevention. METHOD: A database search (Ovid MEDLINE) revealed two haemophilia guidelines (World and British) published within the last ten years. Local Australian haemophilia guidelines were identified through a manual search. RESULTS: All haemophilia guidelines were found to contain inadequate recommendations for osteoporosis management and fall prevention due to a lack of evidence in the literature. CONCLUSION: Further studies are required to assess the trajectory of bone health in PWH, the mechanism of bone loss in PWH, and the effectiveness of weight-bearing exercises, interventions for fall prevention, screening programmes, and use of anti-osteoporosis medications in PWH across the lifecourse.

Tranexamic acid modulates the immune response and reduces postsurgical infection rates.

Tranexamic acid (TXA) is an antifibrinolytic agent that blocks plasmin formation. Because plasmin is known to promote inflammatory and immunosuppressive responses, we explored the possibility that plasmin-mediated immunosuppression in patients undergoing cardiac surgery can be directly reversed by TXA and decrease postoperative infection rates. The modulatory effect of TXA on inflammatory cytokine levels and on innate immune cell activation were evaluated with multiplex enzyme-linked immunosorbent assay and flow cytometry, respectively. Postoperative infection rates were determined in patients undergoing cardiac surgery and randomized to TXA (ACTRN12605000557639; http://www.anzca.edu.au). We demonstrate that TXA-mediated plasmin blockade modulates the immune system and reduces surgery-induced immunosuppression in patients following cardiac surgery. TXA enhanced the expression of immune-activating markers while reducing the expression of immunosuppressive markers on multiple myeloid and lymphoid cell populations in peripheral blood. TXA administration significantly reduced postoperative infection rates, despite the fact that patients were being administered prophylactic antibiotics. This effect was independent of the effect of TXA at reducing blood loss. TXA was also shown to exert an immune-modulatory effect in healthy volunteers, further supporting the fibrin-independent effect of TXA on immune function and indicating that baseline plasmin levels contribute to the regulation of the immune system in the absence of any comorbidity or surgical trauma. Finally, the capacity of TXA to reduce infection rates, modulate the innate immune cell profile, and generate an antifibrinolytic effect overall was markedly reduced in patients with diabetes, demonstrating for the first time that the diabetic condition renders patients partially refractory to TXA.

New guidelines from the Thrombosis and Haemostasis Society of Australia and New Zealand for the diagnosis and management of venous thromboembolism.

INTRODUCTION: Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is the third most common cardiovascular disease and, globally, more than an estimated 10 million people have it yearly. It is a chronic and recurrent disease. The symptoms of VTE are non-specific and the diagnosis should actively be sought once considered. The mainstay of VTE treatment is anticoagulation, with few patients requiring additional intervention. A working group of experts in the area recently completed an evidence-based guideline for the diagnosis and management of DVT and PE on behalf of the Thrombosis and Haemostasis Society of Australia and New Zealand (www.thanz.org.au/resources/thanz-guidelines). MAIN RECOMMENDATIONS: The diagnosis of VTE should be established with imaging; it may be excluded by the use of clinical prediction rules combined with D-dimer testing. Proximal DVT or PE caused by a major surgery or trauma that is no longer present should be treated with anticoagulant therapy for 3 months. Proximal DVT or PE that is unprovoked or associated with a transient risk factor (non-surgical) should be treated with anticoagulant therapy for 3-6 months. Proximal DVT or PE that is recurrent (two or more) and provoked by active cancer or antiphospholipid syndrome should receive extended anticoagulation. Distal DVT caused by a major provoking factor that is no longer present should be treated with anticoagulant therapy for 6 weeks. For patients continuing with extended anticoagulant therapy, either therapeutic or low dose direct oral anticoagulants can be prescribed and is preferred over warfarin in the absence of contraindications. Routine thrombophilia testing is not indicated. Thrombolysis or a suitable alternative is indicated for massive (haemodynamically unstable) PE. CHANGES IN MANAGEMENT AS A RESULT OF THE GUIDELINE: Most patients with acute VTE should be treated with a factor Xa inhibitor and be assessed for extended anticoagulation.

Weight-Based Enoxaparin for Venous Thromboembolism in Obesity Gives Similar Anti-Xa Levels to Patients <100 kg, with No Increase in Major Bleeding.

In trials assessing venous thromboembolism (VTE) treatment, obese patients are under-represented or excluded. The main objective of this article is to examine the safety of weight-based enoxaparin dosing in obesity, as assessed by anti-factor Xa (anti-Xa) activity, bleeding, and recurrence. A 5-year retrospective audit of patients with acute VTE, weighing > 100 kg, prescribed enoxaparin 1 mg/kg twice daily, with an anti-Xa level 2 to 6 hours post-dose. The primary outcome was anti-Xa levels, and the secondary outcomes were bleeding and recurrence. Results were compared with patients weighing < 100 kg (n = 64), and obese patients prescribed doses < 1 mg/kg (n = 28). One-hundred sixty-six patients weighing > 100 kg with VTE were identified, with 64 excluded for not fulfilling criteria. The remaining 102 patients had a median weight of 130 kg (range: 105-222 kg). The median peak anti-Xa level was 0.93 U/mL, with 56% of levels being in the proposed therapeutic range (0.5-1.0 U/mL), 40% > 1.0 U/mL, and 4% < 0.5 U/mL. The median anti-Xa levels and distribution were not significantly different between patients > 100 kg and patients < 100 kg, while obese patients prescribed < 1 mg/kg were more frequently subtherapeutic (21%). Regardless of weight, the majority of patients with moderate renal impairment (eGFR 30-59 mL/min) had an anti-Xa level > 1.0 U/mL (61%). In the obese patients, there was no major bleeding or recurrence within 30 days. In comparison, patients weighing < 100 kg, despite similar peak anti-Xa levels, had higher rates of bleeding and recurrence. This was likely due to their older age and comorbidities, particularly renal impairment and cancer. These data support weight-based dosing of enoxaparin in obesity with no maximum dose, ensuring therapeutic drug levels, with anti-Xa levels suggested in obese patients with clinical risk factors for bleeding.

Tooth Fairy Study- The South Texas Oral Health Network Collaboration.

PURPOSE: This study's purpose was to examine the processes and the potential for dental practitioners to address environmental health exposure risks to their patients through dental practice-based research participation. To explore this, the South Texas Oral Health Network (STOHN) initiated a collaboration with The Tooth Fairy National Study investigating toxicants stored in deciduous teeth as a potential neurodevelopmental risk factor. BACKGROUND: Neurodevelopmental disorders (ND), like Autism Spectrum Disorder (ASD), affect 1 in 68 live births. Evidence suggests that environmental chemicals may play a role in ASD risk and/or etiology by acting independently or through interactions with genetic vulnerabilities. Provider awareness of environmental exposure risk during pregnancy and early childhood in South Texas is low. Therefore, it is important to increase provider knowledge and awareness to enable greater communication with patients. STOHN serves as a conduit reaching large numbers of patients. This study also engaged practitioners in an ongoing national study with minimal impact on their practice. METHODS: The goal was to enroll twenty parents with children via ten dental practitioners. STOHN pediatric and general practitioners were recruited for the study. Practitioners were contacted by phone and in person. Upon completion of Human Subject Protection training, each practitioner participated in a study training taught by a public health educator in the department of Family and Community Medicine at University of Texas Health Science Center in San Antonio (UTHSCSA). Training topics included NDs, environmental health exposures, patient engagement, survey administration, and how to collect donated teeth. This collaboration allowed STOHN to gather control teeth as well as demographic and health information for the Tooth Fairy Study repository for future analyses. Participants received a thank you card from the Tooth Fairy and participating providers were highlighted in the monthly STOHN newsletter. EVALUATION RESULTS: Evaluation was threefold: Practitioner enrollment and retention; practitioner confidence in educating their patients about potential environmental risk exposures and completed surveys with donated teeth. CONCLUSION: The interdisciplinary collaboration between dental practitioners and medical researchers through STOHN provided an opportunity to increase practitioner knowledge and awareness of a novel health concern, while also raising their confidence and willingness to educate their patients about potential environmental exposure risks. UTHSCSA IRB Protocol # HSC20170132E.

Approval of the first protease-activated receptor antagonist: Rationale, development, significance, and considerations of a novel anti-platelet agent.

Twenty-three years after the discovery of the first thrombin receptor, now known as protease-activated receptor 1 (PAR1), the first drug targeting this receptor is available for human use. The PAR1 inhibitor, vorapaxar (Zontivity, MSD), was recently approved by the FDA for use in the USA for the prevention of thrombotic cardiovascular events in patients with a history of myocardial infarction or peripheral artery disease. In this review, we detail the rationale, development, as well as the clinical significance and considerations of vorapaxar, the original PAR antagonist and the latest anti-platelet agent in the pharmaco-armoury against arterial thrombosis.

The utility of the Wells clinical prediction model and ventilation-perfusion scanning for pulmonary embolism diagnosis in pregnancy.

Pulmonary embolism is one of the leading causes of mortality in pregnancy in the Western world. No clinical prediction models have been validated in pregnancy. As a result, any pregnant woman presenting with signs possibly consistent with pulmonary embolism is investigated radiologically. This study investigates whether using clinical prediction models for pulmonary embolism in pregnancy should be pursued in future prospective trials. The aim of this study was to retrospectively evaluate the Wells clinical prediction model and ventilation-perfusion scanning for pulmonary embolism in pregnancy. A retrospective study was performed on consecutive pregnant women who presented with suspected pulmonary emboli and underwent ventilation perfusion scanning at two tertiary institutions from 2007 until 2010. The clinical pretest probability was determined as likely or unlikely by two independent clinicians retrospectively using Wells-modified criteria. Scans were determined as normal, nondiagnostic or high probability for pulmonary emboli independently by two experienced radiologists. Disagreements were resolved by a third assessor independently. In 183 pregnant women, the pretest probability was determined as 'pulmonary emboli likely' in 76 (42%) and 'pulmonary emboli unlikely' in 107 (58%) of women. Scans were of high probability in four (2%), nondiagnostic in six (3%) and normal in 173 (95%) of women. This gives the pretest probability using Wells-modified criteria a sensitivity of 100% [95% confidence interval (CI) 0.4-1.0] and a negative predictive value of 100% (95% CI 0.96-1.0). A structured clinical model such as modified Wells criteria may be useful in pregnancy, but further prospective evaluation is required.