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The association of severe COVID-19 with an increased risk of VTE has resulted in specific guidelines for its prevention and management. The VTE risk appears highest in those with critical care admission. The need for post discharge thromboprophylaxis remains controversial and this is reflected in the conflicting recommendations of expert guidelines. Our local protocol provides thromboprophylaxis to COVID-19 patients during admission only. We report post-discharge VTE data from an ongoing quality improvement programme incorporating root cause analysis of hospital-associated VTE (HA-VTE). Following 1,877 hospital discharges associated with COVID-19, there were 9 episodes of HA-VTE diagnosed within 42 days, to give a post-discharge rate of 4.8 per 1000 discharges. Over 2019, following 18,159 discharges associated with a medical admission; there were 56 episodes of HA-VTE within 42 days (3.1 per 1000 discharges). The odds ratio for post-discharge HA-VTE associated with COVID-19 compared to 2019 was 1.6 (95% CI 0.77-3.1). Hospitalisation with COVID-19 does not appear to increase the risk of post-discharge HA-VTE compared to hospitalisation with other acute medical illness. Given the risk-benefit ratio of post discharge thromboprophylaxis remains uncertain, randomised controlled trials to evaluate the role of continuing thromboprophylaxis in patients with COVID-19 following hospital discharge are required.

Background: Coronavirus disease 2019 (COVID-19) is characterised by dyspnoea and abnormal coagulation parameters, including raised D-dimer. Data suggests a high incidence of pulmonary embolism (PE) in ventilated patients with COVID-19. Objectives: To determine the incidence of PE in hospitalised patients with COVID-19 and the diagnostic yield of Computer Tomography Pulmonary Angiography (CTPA) for PE. We also examined the utility of D-dimer and conventional pre-test probability for diagnosis of PE in COVID-19. Patients/methods: Retrospective review of single-centre data of all CTPA studies in patients with suspected or confirmed COVID-19 identified from Electronic Patient Records (EPR). Results: There were 1477 patients admitted with COVID-19 and 214 CTPA scans performed, of which n = 180 (84%) were requested outside of critical care. The diagnostic yield for PE was 37%. The overall proportion of PE in patients with COVID-19 was 5.4%. The proportions with Wells score of ≥4 ('PE likely') was 33/134 (25%) without PE vs 20/80 (25%) with PE (P = 0.951). The median National Early Warning-2 (NEWS2) score (illness severity) was 5 (interquartile range [IQR] 3-9) in PE group vs 4 (IQR 2-7) in those without PE (P = 0.133). Ddimer was higher in PE (median 8000 ng/mL; IQR 4665-8000 ng/mL) than non-PE (2060 ng/mL, IQR 1210-4410 ng/mL, P < 0.001). In the 'low probability' group, D-dimer was higher (P < 0.001) in those with PE but had a limited role in excluding PE. Conclusions: Even outside of the critical care environment, PE in hospitalised patients with COVID-19 is common. Of note, approaching half of PE events were diagnosed on hospital admission. More data are needed to identify an optimal diagnostic pathway in patients with COVID-19. Randomised controlled trials of intensified thromboprophylaxis are urgently needed.

Patients with liver diseases acquire complex alterations in their hemostatic system that may lead to abnormalities in routine diagnostic test of hemostasis. Thrombocytopenia, prolongations in the prothrombin time and activated partial thromboplastin time, and decreased plasma fibrinogen are common in patients with advanced liver disease. Historically, liver diseases therefore have been classified as an acquired bleeding disorder. Laboratory and clinical observations have demonstrated that although routine diagnostic tests of hemostasis suggest a hypocoagulable state, patients with liver disease also tend to develop thrombotic events. Overall, patients have commensurate changes in both pro‐ and antihemostatic pathways. This new hemostatic balance, however, appears much more fragile than the hemostatic balance in individuals with normal liver function, and patients with liver disease can readily experience both hemostasis‐related bleeding and thrombotic events. These insights into the hemostatic balance in patients with liver disease have led to revised recommendations for clinical management of hemostasis. In 2020, an SSC working group within the ISTH has been founded with the aim to disseminate new concepts on prevention and treatment of bleeding and thrombosis in patients with liver disease. The current document will outline the hemostatic changes in patients with liver disease, the limitations of routine diagnostic tests of hemostasis, and the concept of rebalanced hemostasis.

The prevalence of obesity has increased substantially over recent years. Clinicians are increasingly being challenged with making uncertain anticoagulant dosing decisions, as the optimal dosing strategy for most anticoagulants in the obese patient population remains unknown. Research published to date suggests that the clearance of anticoagulants increases with weight. As obesity is associated with an increased risk of venous thromboembolism and arterial disease, there is an urgent need to establish appropriate anticoagulation regimens for this patient group. Research studies applying the method of pharmacokinetic-pharmacodynamic modelling and simulation could establish an appropriate evidence base and provide direction and reassurance to prescribing clinicians.

Essentials The optimal dosing strategy of rivaroxaban for patients at the extremes of body weight is not known.A pharmacokinetic study was conducted based in real‐world patients in a London teaching hospital.In the cohort of patients studied, weight on its own did not impact significantly on rivaroxaban pharmacokinetics.A larger study with patients in the weight categories of interest from the real‐world population is required to further clarify the situation. BackgroundThere is concern amongst clinicians that the fixed dosing strategy of rivaroxaban for the treatment of venous thromboembolism (VTE) might not be optimal in those patients under or overweight.ObjectiveTo develop a pharmacokinetic model for rivaroxaban, based on real‐world patients, specifically focusing on the impact of patients’ body weight on rivaroxaban pharmacokinetics.Patients/methodsOne hundred and one patients prescribed rivaroxaban prophylactic or treatment doses for the prevention or treatment of VTE were recruited at a London teaching hospital. Subjects had up to 3 rivaroxaban concentrations measured during a single dosing period (trough, 1 and 3 hours post dose). Population pharmacokinetic analyses was conducted to develop a rivaroxaban model, which was subsequently evaluated.ResultsA one‐compartment model with between‐subject variability on rivaroxaban clearance and volume of distribution, with a combined (additive and proportional) error model, best fitted the data. Following a full covariate analysis, creatinine clearance on rivaroxaban clearance was found to be the significant covariate impacting on the pharmacokinetic profile of rivaroxaban in the dataset.ConclusionsOur results suggest that the most important covariate impacting on rivaroxaban pharmacokinetics is creatinine clearance and the weight alone has little effect. These findings are in line with previous studies for rivaroxaban. Larger datasets, from real‐world patients who are followed longitudinally, should be conducted to provide front‐line clinicians with further reassurance when prescribing rivaroxaban for the acute management of VTE.

SummaryVenous thromboembolism (VTE) has long been considered a disease that affects predominantly white populations, a misconception resulting from a paucity of epidemiological data from non-Western countries, and the low incidence of hereditary thrombophilia in those of non-Caucasian background. Over the last decade, interest has grown in this area with the emergence of evidence that VTE is as prevalent, if not more so, in the black population and is also common in Asian groups. Much is still to be learned, as our current knowledge of hereditary thrombophilia and acquired risk factors do not fully explain the risk of VTE in non-Caucasian groups. This review summarises the current understanding of ethnic variation in VTE and highlights the need for further research in this area.

Background & Aims Patients with liver disease often show profound abnormalities in their haemostatic system. Studies using thrombin generation demonstrate rebalanced coagulation in patients with chronic liver disease. Our aim was to evaluate the haemostatic profile in patients with acute liver injury/failure (ALI/ALF) compared with healthy controls. Methods Thrombin generation was measured in the presence and absence of thrombomodulin (TM) to activate protein C (PC) with endogenous thrombin potential (ETP; the area under the thrombin generation curve) a key parameter. Routine coagulation assays were also performed. Results Thirty two patients with ALI/ALF and 40 controls were recruited. Patients had grossly abnormal coagulation profiles with decreased pro‐ and anticoagulant factors compared with controls (P < 0.001 for all comparisons), except for median Factor VIII which was increased 247 U/dl [interquartile range: 214–347] in patients compared with 120 U/dl [97–139; P < 0.001] in controls. Mean ETP was significantly lower in patients 886 nM.min (± 436) compared with controls 1596 nM.min (± 259; P < 0.001). However, when the assay was repeated with TM to activate PC, there was no significant difference in mean ETP + TM between patients and controls (632 ± 418 vs 709 ± 301 nM.min respectively; P = 0.666). Furthermore, the ETP ratio (ETP + TM/ETP) was significantly higher in patients 0.89 (0.60–0.97) compared with controls 0.48 (0.3–0.6; P = 0.002) and negatively correlated with PC (R = −0.487, P = 0.003) and Factor V (R = −0.431, P = 0.01). Conclusion ALI/ALF patients have normal ETP in the presence of TM. This supports rebalanced coagulation mediated by acquired PC resistance because of the reduction in PC, Factor V and concomitant increase in Factor VIII.