Theme 2: Epidemiology, Biomarkers, and Imaging of Venous Thromboembolism (and postthrombotic syndrome)

ST Genesia reference values of 117 healthy donors measured with STG-BleedScreen, STG-DrugScreen and STG-ThromboScreen reagents

INTRODUCTION

The ST Genesia is a benchtop, fully automated thrombin generation (TG) device. It is completely standardized and ensures a uniform heat distribution throughout the measurement. We aimed to determine reference values and to compare TG in men and women with and without the use of oral contraceptives (OCs).

MATERIALS AND METHODS

Plasma from 117 healthy donors was measured on the ST Genesia with the available reagent kits: STG-BleedScreen, STG-DrugScreen, and STG-ThromboScreen. All kits include at least two quality controls and a reference plasma to normalize data. STG-ThromboScreen has a second trigger containing thrombomodulin (TM) to include the effect on the protein C pathway. Means were compared with one-way analysis of variance and reference ranges were established with 2.5th to 97.5th percentiles on absolute TG parameters.

RESULTS

Mean age of the donors was 35 years (SD ± 12); 49.6% were men, 37.6% women without OCs, and 12.8% women with OCs. Men and women without OCs had, respectively, a mean peak height of 167 nM and 164 nM with STG-BleedScreen, 335 nM and 351 nM with STG-DrugScreen, and 192 nM and 198 nM with STG-ThromboScreen. Women taking OCs had a mean peak height of 263 nM, 473 nM, and 312nM, respectively (P < .05 compared to men/women without OCs). TM decreased endogenous thrombin potential by 54% in men, 47% in women without OCs, and only 25% in women with OCs (P < .05 compared to men/women without OCs).

CONCLUSIONS

TG in men and women without OCs was similar; however, women taking OCs had significantly higher TG values, and the effect of TM was also less pronounced in these women.

Towards standardization of thrombin generation assays: Inventory of thrombin generation methods based on results of an International Society of Thrombosis and Haemostasis Scientific Standardization Committee survey

BACKGROUND

Thrombin generation (TG) is a better determinant of the overall function of the hemostatic system than the routinely used clotting time-based assays. Nowadays, TG is widely used in hemostasis research teams, for both clinical and basic research. However, there is significant variability between laboratories regarding preanalytics, reagents, TG protocol, analysis interpretation, and normalization.

OBJECTIVES

To document the extent of variation in the methodology of TG, we aim to collect all the methods that are being used to measure TG in a survey.

METHODS

We organized a questionnaire through the Standardization committee for Lupus Anticoagulant/Antiphospholipid Antibodies of the International Society of Thrombosis and Haemostasis Scientific Standardization committee. The questionnaire consisted of 51 questions regarding the different aspects of TG: type of users, methods, sample type, analysis, and interpretation of results, normalization, and quality control.

RESULTS

Of the 240 surveys that were started, 108 were completed (45%). However, not all questions were in scope for all laboratories. One-half of the laboratories were research laboratories and half diagnostic laboratories. The most used TG assay was the calibrated automated thrombinography-based assay (56%). There was a divergence regarding several aspects of the TG assay: type of needle for blood collection, blood tubes, centrifugation, sample storage and thawing, reagents, sample dilution, calibration, reference ranges, data normalization, and so on.

CONCLUSIONS

There is an important variation in the methods used for measuring TG. A standardized protocol and data normalization should lead to a better reproducibility and for comparing data from different laboratories.

Modulating thrombotic diathesis in hereditary thrombophilia and antiphospholipid antibody syndrome: a role for circulating microparticles?

Over the past decades, there have been great advances in the understanding of the pathogenesis of venous thromboembolism (VTE) in patients with inherited and acquired thrombophilia [mainly antiphospholipid antibody syndrome (APS)]. However, a number of questions remain unanswered. Prognostic markers capable of estimating the individual VTE risk would be of great use. Microparticles (MPs) are sub-micron membrane vesicles constitutively released from the surface of cells after cellular activation and apoptosis. The effects of MPs on thrombogenesis include the exposure of phopshatidylserine and the expression of tissue factor and MPs have been described in clinical studies as possible diagnostic and prognostic biomarkers for VTE. This review will provide a novel perspective on the current knowledge and research trends on the possible role of MPs in hereditary thrombophilia and APS. Basically, the published data show that circulating MPs may contribute to the development of VTE in thrombophilic carriers, both in mild and severe states. Moreover, the presence of endothelial-MPs and platelet-MPs has been described in antiphospholipid syndrome and seems to be directly linked to antiphospholipid antibodies and not to other underlying autoimmune disorders or the thrombotic event itself. In conclusion, circulating MPs may constitute an epiphenomenon of thrombophilia itself and could be up-regulated in acute particular conditions, promoting a global prothrombotic state up to the threshold of the clinical relevant thrombotic event.

PDGFB, a new candidate plasma biomarker for venous thromboembolism: results from the VEREMA affinity proteomics study

High-throughput affinity plasma proteomic profiling can identify candidate plasma biomarkers for VTE. Elevated plasma PDGFB levels are identified as associated with VTE in 2 independent case control studies.

Nuclear imaging of thrombosis in small animal

Thromboembolic disorders are a major cause of morbidity and mortality worldwide. The progress in noninvasive imaging techniques has led to the development of radionuclide imaging based on SPECT and PET approaches to observe molecular and cellular processes that may underlie the onset and progression of disease. The advantages of using normal and genetically modified small animal research have spurred the development of dedicated small animal imaging systems. Animal models of venous and arterial thrombosis are largely used and have improved our understanding of the etiology and pathogenesis of thrombosis. Here, we review the literature regarding nuclear imaging of thrombosis in mice and rats.

Measurement of microparticle tissue factor activity in clinical samples: A summary of two tissue factor-dependent FXa generation assays

Thrombosis is a leading cause of morbidity and mortality. Detection of a prothrombotic state using biomarkers would be of great benefit to identify patients at risk of thrombosis that would benefit from thromboprophylaxis. Tissue factor (TF) is a highly procoagulant protein that under normal conditions is not present in the blood. However, increased levels of TF in the blood in the form of microparticles (MPs) (also called extracellular vesicles) are observed under various pathological conditions. In this review, we will discuss studies that have measured MP-TF activity in a variety of diseases using two similar FXa generation assay. One of the most robust signals for MP-TF activity (16-26 fold higher than healthy controls) is observed in pancreatic cancer patients with venous thromboembolism. In this case, the TF+ MPs appear to be derived from the cancer cells. Surprisingly, cirrhosis and acute liver injury are associated with 17-fold and 38-fold increases in MP-TF activity, respectively. Based on mouse models, we speculate that the TF+ MPs are derived from hepatocytes. More modest increases are observed in patients with urinary tract infections (6-fold) and in a human endotoxemia model (9-fold) where monocytes are the likely source of the TF+ MPs. Finally, there is no increase in MP-TF activity in the majority of cardiovascular disease patients. These studies indicate that MP-TF activity may be a useful biomarker to identify patients with particular diseases that have an increased risk of thrombosis.