Extracellular vesicles (EVs) are key modulators of hemostasis, influencing coagulation under physiologic and pathologic conditions. Depending on their cellular origin and their releasing conditions, EVs promote coagulation predominantly by the exposure of phosphatidylserine and tissue factor. Elevated EV levels have been reported in various diseases associated with increased thrombotic risk. This review explores how distinct EV subpopulations in the circulation contribute to hemostasis and thrombosis. Furthermore, it highlights their emerging potential as biomarkers for diagnosing and monitoring thrombotic disorders.

Thrombin generation assay (TGA) is a tool to assess bleeding and thrombotic risk in citrated plasma, either in the presence or absence of platelets, and several different commercial assays have been developed and actively marketed. TGA can be used for various research and clinical applications, including the identification of patients at risk of bleeding or thrombosis, as well as monitoring of treatment in at risk patients. Though current implementation is limited to specialized laboratories in university hospitals and research centers, wider implementation will require additional, large clinical trials.

Viscoelastic testing is increasingly recognized as a standard-of-care tool for goal-directed transfusion management, with expanding endorsement from national and international guidelines. Its clinical utility is well established across several high-acuity settings, including cardiothoracic surgery, trauma, liver transplantation, and obstetric hemorrhage. These next-generation systems use alternative detection technologies and generate distinct numerical outputs for comparable TEG 5000 and ROTEM delta parameters, making institution-specific validation of transfusion thresholds essential. This article provides an overview of recent advances in viscoelastic testing and offers practical guidance for laboratorians involved in incorporating these emerging technologies into clinical workflows.

Harmonization of hemostasis testing can be achieved in any laboratory network, including a mix of different instruments and assays. This process requires engagement with key stakeholders. The group should identify ideal streamlined total testing processes for different tests and laboratories. The processing of high volume/simple automated tests can be improved by an expert-rules set that can autoverify certain test results, and well as reflexing to other tests to improve their diagnostic value. Low volume tests can be harmonized to improve testing efficiency and utility. This review provides pointers to achieving workable harmonization across a variety of laboratories and hemostasis tests.

This review explores the role of hypoxia in vascular endothelial dysfunction and its contribution to venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism. It highlights the unique microenvironment of venous valvular sinuses, where stasis and hypoxia promote endothelial activation, inflammation, and coagulation. Key mechanisms, such as hypoxia-inducible factors, reactive oxygen species, and calcium signaling, are discussed in the context of thrombus formation. The review also examines advanced methodologies, including Vein-Chip and vascular organoids, for studying hypoxia-driven processes, and emphasizes the need for patient-specific models to improve understanding and therapeutic strategies for VTE.

Dramatic improvements have been made in antiphospholipid syndrome (APS) diagnosis, but work is still needed around standardization of laboratory practice and lupus anticoagulant (LA) testing with anticoagulated samples. LA testing in anticoagulated patients is common, and can lead to false positivity and possibly false negativity. For patients whose anticoagulation cannot be held, LA testing accuracy can be improved by activated carbon pre-treatment or alternative LA reagents. Solid phase testing for antiphospholipid antibodies remains incompletely harmonized and recent International Society on Thrombosis and Haemostasis (ISTH) and American College of Rheumatology (ACR)/ European League against Rheumatism (EULAR) guidelines do not completely agree.

Thrombophilia testing is a critical aspect of managing venous thromboembolism, a condition affecting approximately 1 in 1000 individuals annually and causing significant morbidity, mortality, and health care costs. This document provides an in-depth overview of current best practices in thrombophilia testing, including clinical guidelines, assay methodologies, and advances in molecular diagnostics, with the aim of optimizing diagnosis, treatment, and prevention strategies.

Direct thrombin inhibitors (DTIs) such as bivalirudin and argatroban have a predictable anticoagulant response, the ability to inhibit thrombin bound to fibrin, and efficacy in thrombotic environments. These properties make them a valuable tool to manage patients at risk of thrombotic events. DTIs require less frequent monitoring and dose adjustments than heparin. Due to poor correlation of activated partial thromboplastin time with DTI concentration, diluted thrombin time is widely used for monitoring bivalirudin anticoagulation. Emerging monitoring methods are promising and reflect the evolution of precision medicine toward more personalized, real-time monitoring techniques that can guide anticoagulation therapy in complex cases.

Inhibitors of the protease factor XIa (FXIa) and its zymogen factor XI (FXI) represent a promising new class of anticoagulants that aim to offer safer alternatives to traditional therapies. With their potential to reduce thrombosis without a dose-dependent increase in bleeding, FXIa inhibitors are currently undergoing rigorous phase 3 testing. This article reviews unmet needs in anticoagulation therapy, explains the role of FXI in distinguishing hemostasis from thrombosis, describes FXI/FXIa inhibitors and their effects on coagulation tests, and provides insights into ongoing clinical trials. Our goal is to equip laboratory hematologists with the knowledge to understand these novel agents.

Platelets play a crucial role in primary hemostasis. Congenital and acquired platelet disorders may be associated with bleeding. High-quality laboratory assessment of platelets is crucial for patient care. Multiple methods have been developed to assess platelet function. While several guidelines have been published related to platelet function testing, surveys demonstrate wide variation in practices. Preanalytical variables such as patient medication use, collection, transport, and storage impact testing results. Test interpretation requires appropriate reference intervals and an understanding of the impact of thrombocytopenia on results. Internal and external quality assessments aid laboratories in monitoring the performance of platelet function assays.

Inherited platelet disorders (IPDs) have a diverse spectrum of clinical features, such as bleeding tendencies of varying intensities, and possible extra-organ involvement (ie, syndromic features). The clinical and laboratory diagnosis of IPDs remains challenging primarily due to the absence of highly specific platelet function assays and the overlapping nature of clinical and laboratory characteristics. Recently, genetic testing, using next-generation sequencing, has gradually become pivotal in the laboratory evaluation of patients with suspected IPDs. A comprehensive clinical and laboratory testing strategy, along with phenotype and genotype correlation investigations involving both affected individuals and their relatives, is essential for accurate IPD diagnosis.

Dysfibrinogenemia is characterized by impaired fibrinogen function and requires specialized laboratory tests for diagnosis. The clinical presentation is highly heterogenous, and dysfibrinogenemia is not a common cause of thrombosis or bleeding. It can be congenital or acquired, and management is highly dependent on dysfibrinogenemia phenotype and clinical context.

Factor XIII (FXIII) is a thrombin-activated coagulation factor that stabilizes the fibrin clot via covalent cross-linking of fibrin. Inherited and acquired FXIII deficiencies are important causes of bleeding, with acquired deficiencies being about 10 fold more prevalent. Acquired FXIII deficiency can arise in the setting of consumptive coagulopathies; massive blood loss; severe infections; hepatic dysfunction; acquired inhibitors of FXIII; and deficiencies of uncertain significance. FXIII deficiency is not detected by routine coagulation assays and requires evaluation by quantitative FXIII activity and antigen assays. Bethesda assay modifications of FXIII activity assays are helpful to diagnose acquired FXIII inhibitors.

The landscape of hemophilia treatment has recently undergone a drastic transformation with the advent of novel therapies, including extended half-life factor concentrates, nonfactor therapies, rebalancing agents, and gene therapies. While these advancements have improved patient outcomes, they have introduced challenges in laboratory monitoring. Traditional assays such as prothrombin time, activated partial thromboplastin time, and 1-stage clotting assays may not accurately reflect the hemostatic status in patients receiving these new treatments. This article reviews the evolution of hemophilia therapies and the corresponding challenges in laboratory testing, emphasizing the need for updated monitoring strategies to ensure optimal patient management.