Association of D-dimer Levels with Clinical Event Rates and the Efficacy of Betrixaban versus Enoxaparin in the APEX Trial

Biomarkers in pediatric venous thromboembolism: a systematic review of the literature

BACKGROUND

Accurate prediction of the individual risk of venous thromboembolism (VTE) remains suboptimal in children, and biomarkers are currently not used to stratify the risk of VTE in children.

OBJECTIVES

This study aimed to assess which biological or radiological biomarkers may predict VTE or VTE complications in children.

PATIENTS/METHODS

A literature search was performed for peer-reviewed publications (1990-2022). We included studies addressing the use of biomarkers for patients aged 29 days to 18 years to predict VTE or its complications, including but not limited to TE-related death, VTE recurrence, or postthrombotic syndrome. Given the heterogeneity of the study designs, populations, and outcomes, no quantitative data synthesis was performed.

RESULTS

Forty studies were included, totaling 10,987 participants (median age: 4.7 years). Reports were often lacking critical methodological data, including blood collection method (68% of studies) and timepoints, laboratory testing technique (41%), or primary outcome definition (20%). Forty-six individual biomarkers were assessed for VTE prediction (32 studies, 9525 participants), including d-dimers, fibrinogen, platelet count, white blood cell count, and factor VIII. Albumin, C-reactive protein, d-dimers, factor VIII, and thrombin-antithrombin levels showed promising results for VTE prediction. In 9 studies (1606 participants), no biomarker was consistently predictive of postthrombotic syndrome, VTE persistence, or VTE recurrence in children.

CONCLUSIONS

Several candidate biomarkers were promising in the prediction of VTE in children. Still, discrepancies between different studies and the high risk of bias from the current literature prevent their widespread use in the clinical setting. Further prospective research in various pediatric subpopulations is required.

Current Opinion on the use of Direct Oral Anticoagulants for the Prophylaxis of Venous Thromboembolism among Medical Inpatients

Venous thromboembolism (VTE) is a known cause of morbidity and mortality, especially among acutely ill medical patients. Although VTE prophylaxis is part of post-discharge clinical care in surgical patients, there is controversy regarding its use in acutely ill medical patients and the current guideline statements suggest against its routine use. Recent clinical trials (APEX, MAGELLAN and MARINER) compared the safety and efficacy of direct oral anticoagulants (including betrixaban and rivaroxaban) with the standard of the care, enoxaparin, to identify the risk–benefit tradeoff. In this review, we summarized the key findings from these trials and substudies and recent updates in society guidelines regarding VTE prevention. In addition, we discussed the potential barriers, cost-effectiveness, and COVID-19 with respect to the implementation of extended-duration or post-discharge usage of direct oral anticoagulants.

Extended Thromboprophylaxis With Betrixaban or Rivaroxaban for Acutely Ill Hospitalized Medical Patients: Meta-Analysis of Prespecified Subgroups

BACKGROUND

Betrixaban and rivaroxaban are the direct anticoagulants approved in the United States for extended venous thromboembolism (VTE) prophylaxis among acutely ill medical patients. The efficacy and safety in specific subgroups remain unclear.

METHODS

A meta-analysis of 3 randomized trials involving extended thromboprophylaxis with betrixaban or rivaroxaban versus enoxaparin for medically ill patients was performed to compare VTE (composite of asymptomatic proximal and symptomatic deep vein thrombosis, pulmonary embolism, or VTE-related death) and major bleeding in subgroups by baseline D-dimer, age, sex, and major medical illness on hospitalization. Risk difference (RD) was computed with the Mantel-Haenszel method by fitting a fixed-effect model. Heterogeneity of treatment effect across subgroups was examined using the nominal thresholds of P < 0.05 and I2 > 75%.

RESULTS

Compared with enoxaparin, extended betrixaban or rivaroxaban reduced VTE (RD = -1.51% [95% CI, -2.32% to -0.69%]; P = 0.0003) without excess major bleeding (RD = 0.12% [-0.05% to 0.29%]; P = 0.16). A significant effect modification was observed in the subgroups by D-dimer (P = 0.004) and age (P = 0.04). Patients with D-dimer >2× upper limit of normal (ULN) experienced a greater VTE reduction (RD = -2.39% [-3.57% to -1.21%]; P < 0.0001) than those with ≤2×ULN (RD = -0.26% [-1.08% to 0.56%]; P = 0.53). Similarly, patients aged ≥75 years had a greater VTE reduction (RD = -2.29% [-3.49% to -1.09%]; P = 0.0002) than those aged <75 years (RD = -0.63% [-1.70% to 0.44%]; P = 0.25). Treatment effect was consistent across the remaining subgroups.

CONCLUSIONS

A more favorable efficacy and comparable safety outcome associated with extended betrixaban or rivaroxaban were observed among medical inpatients with D-dimer >2×ULN or aged ≥75 years. D-dimer and advanced age may assist in decision-making on pharmacological thromboprophylaxis for hospitalized medical patients.

D-dimer: Preanalytical, analytical, postanalytical variables, and clinical applications

D-dimer is a soluble fibrin degradation product deriving from the plasmin-mediated degradation of cross-linked fibrin. D-dimer can hence be considered a biomarker of activation of coagulation and fibrinolysis, and it is routinely used for ruling out venous thromboembolism (VTE). D-dimer is increasingly used to assess the risk of VTE recurrence and to help define the optimal duration of anticoagulation treatment in patients with VTE, for diagnosing disseminated intravascular coagulation, and for screening medical patients at increased risk of VTE. This review is aimed at (1) revising the definition of D-dimer; (2) discussing preanalytical variables affecting the measurement of D-dimer; (3) reviewing and comparing assay performance and some postanalytical variables (e.g. different units and age-adjusted cutoffs); and (4) discussing the use of D-dimer measurement across different clinical settings.

Betrixaban in the prevention of venous thromboembolism in medically ill patients

Despite significant advances in strategies and compliance with venous thromboembolism (VTE) prophylaxis, hospital-acquired VTE remains a leading cause of preventable deaths in acute medically ill patients. A majority of venous thromboembolic events occur posthospital discharge when risk factors persist and pharmacoprophylactic regimens have been completed. Until recently, there has been an unmet need for safe and effective extended-duration VTE prevention. Three major trials evaluated this concept, but excess bleeding outweighed the benefit of reduced thromboembolic events. Betrixaban is an oral direct factor Xa inhibitor recently approved for extended-duration VTE prophylaxis in acute medically ill patients at risk for thromboembolism based on results from the Phase III APEX study. This article reviews the pharmacology and supporting data for betrixaban.