Activated protein C resistance determined with a thrombin generation-based test predicts for venous thrombosis in men and women

Hemostatic imbalance induced by tamoxifen in estrogen receptor-positive breast cancer patients: An observational study

BACKGROUND

Estrogen receptor (ER)-positive (ER+) breast cancer accounts for approximately 75% of all breast cancers. Tamoxifen, a selective estrogen receptor modulator, is the standard adjuvant treatment. Although better tolerated than aromatase inhibitors, tamoxifen increases the risk of venous thromboembolism (VTE) 1.4-fold.

AIM

To assess the hemostatic imbalance induced by tamoxifen in adjuvant treatment of ER+ breast cancer.

METHOD

Twenty-five patients in remission from ER+ breast cancer under tamoxifen were included. One hundred and thirty one age- and BMI-matched healthy controls were included to establish reference ranges of thrombin generation assay (TGA) parameters. TGA was performed in the absence and presence of exogenous activated protein C (APC) to calculate the normalized APC sensitivity ratio (nAPCsr), a marker of APC resistance.

RESULTS

All TG parameters except the endogenous thrombin potential (ETP) (-APC) were significantly impacted by tamoxifen (p < 0.001). In absence of APC, regardless of TGA parameters, at least 50% of results were outside the reference ranges except for ETP, which was above the upper reference limit in only two individuals. The most impacted parameter was the Peak Height with 52% (-APC) and 80% (+APC) of results above the upper reference range limit, respectively. The nAPCsr was significantly higher in tamoxifen users (mean ± standard deviation = 3.18 ± 0.91) compared to the control group (2.19 ± 0.92, p < 0.0001).

CONCLUSION

This observational study showed that patients in remission from ER+ breast cancer taking tamoxifen had altered thrombin generation, as well as an acquired APC resistance. Moreover, this is the first study using the validated ETP-based APC resistance assay in tamoxifen-treated patients.

Role of tissue factor pathway inhibitor in hormone-induced venous thromboembolism

ABSTRACT

Exposure to higher levels of steroid hormones, like that in pregnancy or during combined hormonal contraception, increases the risk of venous thromboembolism. Development of resistance to activated protein C (APC) thought to be the underlying pathomechanism of this prothrombotic state. This coagulation phenomena is largely to be explained by the hormone-induced impairment of the protein S/ tissue factor pathway inhibitor (TFPI) leading to a less efficient inactivation of factor Va and factor VIIIa by APC. APC resistance and decreased protein S/TFPI function were associated with the risk of first as well as recurrent venous thromboembolism. Preexisting disturbances in these pathways are likely to predispose to thrombosis during hormone exposure and can persist over years after the thrombosis event.Further studies are necessary to investigate the predictive value of forgoing APC resistance and decreased protein S/TFPI function or an excessive alteration in these parameters during hormone intake on the development of hormone-induced venous thromboembolism.

Evaluation of Activated Protein C Resistance Using Thrombin Generation Test

Activated protein C (APC) resistance (APCR) has been identified as a risk factor of venous thromboembolism (VTE). A mutation at the level of factor (F) V has at first permitted the description of this phenotypic pattern and corresponded to a transition (guanine to adenine) at nucleotide 1691 in the gene coding for factor V, resulting in the replacement of arginine at position 506 by a glutamine. This confers to this mutated FV a resistance toward the proteolytic action of the complex formed by activated protein C with protein S. However, many other factors also lead to APCR, such as other F5 mutations (e.g., FV Hong Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy, and postpartum. All these conditions lead to the phenotypic expression of APCR and are associated with an increased risk of VTE. Considering the large population affected, the proper detection of this phenotype is a public health challenge. Currently, two types of tests are available: clotting time-based assays and their multiple variants and a thrombin generation-based assays and the endogenous thrombin potential (ETP)-based APCR assay. As APCR was thought to be uniquely related to the FV Leiden mutation, clotting time-based assays were specifically designed to detect this inherited condition. Nevertheless, other APCR conditions have been reported but were not captured by these clotting methods. Thus, the ETP-based APCR assay has been proposed as a global coagulation test able to these multiple APCR conditions, as it provides much more information, which makes it a potential candidate for screening coagulopathic conditions before therapeutic interventions. This chapter will describe the current method used for the realization of the ETP-based APC resistance assay.

Venous Thromboembolism Issues in Women

The lifetime risk of venous thromboembolism (VTE) is slightly higher in women than in men. There are several issues related to VTE that are unique to women. Combined hormonal contraceptives and pregnancy increase the risk of VTE in women of childbearing age, whereas hormone replacement therapy increases the VTE risk of postmenopausal women. Hereditary thrombophilia and risk factors such as older age, obesity, or smoking contribute to the risk increase. In women diagnosed with acute hormone-related VTE who are treated with oral anticoagulants, adequate contraception is mandatory to avoid unwanted pregnancies. According to current knowledge, hormonal contraception may be continued during anticoagulant therapy but must be switched to an estrogen-free contraception method at least 6 weeks before the termination of anticoagulation. VTE is also a major cause of maternal morbidity and mortality during pregnancy and the postpartum period. Currently, assisted reproduction technologies such as in vitro fertilization are widely used to treat couples affected by infertility. Complications of fertility treatment comprise VTE cases, especially in women with ovarian hyperstimulation syndrome. With this review, we intended to focus on VTE issues in women and summarize current evidence and guideline recommendations.

Laboratory Testing for the Evaluation of Phenotypic Activated Protein C Resistance

Activated protein C (APC) resistance (APCR) is considered a risk factor of venous thromboembolism (VTE). The most common genetic disorder conferring APCR is a factor (F) V Leiden mutation, but many other factors are also implicated, such as other F5 mutations (e.g., FV Hong-Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy and postpartum, depending on how APCR is defined. Considering the large population affected, the detection of this phenotype is crucial. Two types of tests are currently available: clotting time-based assays (with several versions) and thrombin generation-based assays with the endogenous thrombin potential (ETP)-based assay. The purpose of this review is therefore to discuss the performances of these tests and the cases in which it would be appropriate to use one over the other. Initially, as APCR was thought to be solely related to the FV Leiden mutation, the objective was to obtain a 100% specific assay. Clotting-time based assays were thus specifically designed to detect this inherited condition. Later on, an APCR condition without a FV Leiden mutation was identified and highlighted as an independent risk factor of VTE. Therefore, the development of a less specific assay was needed and a global coagulation test was proposed, known as the ETP-based APCR assay. In light of the above, these tests should not be used for the same purpose. Clotting time-based assays should only be recommended as a screening test for the detection of FV mutations prior to confirmation by genetic testing. On the other hand, the ETP-based APC resistance assay, in addition to being able to detect any type of APCR, could be proposed as a global screening test as it assesses the entire coagulation process.

Laboratory Testing for the Evaluation of Phenotypic Activated Protein C Resistance

Activated protein C (APC) resistance (APCR) is considered a risk factor of venous thromboembolism (VTE). The most common genetic disorder conferring APCR is a factor (F) V Leiden mutation, but many other factors are also implicated, such as other F5 mutations (e.g., FV Hong-Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy and postpartum, depending on how APCR is defined. Considering the large population affected, the detection of this phenotype is crucial. Two types of tests are currently available: clotting time-based assays (with several versions) and thrombin generation-based assays with the endogenous thrombin potential (ETP)-based assay. The purpose of this review is therefore to discuss the performances of these tests and the cases in which it would be appropriate to use one over the other. Initially, as APCR was thought to be solely related to the FV Leiden mutation, the objective was to obtain a 100% specific assay. Clotting-time based assays were thus specifically designed to detect this inherited condition. Later on, an APCR condition without a FV Leiden mutation was identified and highlighted as an independent risk factor of VTE. Therefore, the development of a less specific assay was needed and a global coagulation test was proposed, known as the ETP-based APCR assay. In light of the above, these tests should not be used for the same purpose. Clotting time-based assays should only be recommended as a screening test for the detection of FV mutations prior to confirmation by genetic testing. On the other hand, the ETP-based APC resistance assay, in addition to being able to detect any type of APCR, could be proposed as a global screening test as it assesses the entire coagulation process.

Laboratory Testing for the Evaluation of Phenotypic Activated Protein C Resistance

Activated protein C (APC) resistance (APCR) is considered a risk factor of venous thromboembolism (VTE). The most common genetic disorder conferring APCR is a factor (F) V Leiden mutation, but many other factors are also implicated, such as other F5 mutations (e.g., FV Hong-Kong and FV Cambridge), protein S deficiency, elevated factor VIII, exogenous hormone use, pregnancy and postpartum, depending on how APCR is defined. Considering the large population affected, the detection of this phenotype is crucial. Two types of tests are currently available: clotting time-based assays (with several versions) and thrombin generation-based assays with the endogenous thrombin potential (ETP)-based assay. The purpose of this review is therefore to discuss the performances of these tests and the cases in which it would be appropriate to use one over the other. Initially, as APCR was thought to be solely related to the FV Leiden mutation, the objective was to obtain a 100% specific assay. Clotting-time based assays were thus specifically designed to detect this inherited condition. Later on, an APCR condition without a FV Leiden mutation was identified and highlighted as an independent risk factor of VTE. Therefore, the development of a less specific assay was needed and a global coagulation test was proposed, known as the ETP-based APCR assay. In light of the above, these tests should not be used for the same purpose. Clotting time-based assays should only be recommended as a screening test for the detection of FV mutations prior to confirmation by genetic testing. On the other hand, the ETP-based APC resistance assay, in addition to being able to detect any type of APCR, could be proposed as a global screening test as it assesses the entire coagulation process.

Estradiol Valerate vs Ethinylestradiol in Combined Oral Contraceptives: Effects on the Pituitary-Ovarian Axis

CONTEXT

Limited studies have compared the effects of combined oral contraceptives (COCs) containing natural estrogens and synthetic ethinylestradiol (EE) on reproductive hormones.

OBJECTIVE

To compare estradiol valerate (EV) + dienogest (DNG), EE + DNG, and DNG alone (active control) on levels of follicle stimulating hormone (FSH), luteinizing hormone, anti-Müllerian hormone (AMH), ovarian steroids, sex hormone binding globulin (SHBG), and the free androgen index (FAI).

METHODS

This spin-off study from a randomized trial enrolled 59 healthy, 18 to 35-year-old ovulatory women, outpatients at Helsinki and Oulu University Hospitals, Finland, who were randomized to EV 2 mg + DNG 2-3 mg (n = 20); EE 0.03 mg + DNG 2 mg (n = 20); and DNG 2 mg (n = 19) for 9 weeks. Blood samples were drawn at baseline, and at 5 and 9 weeks. Age and BMI were comparable between groups; 3 women discontinued.

RESULTS

EV + DNG suppressed FSH by -27% (-51% to -3%) (median [95% CI]) vs EE + DNG, -64% (-78 to -51), P = 0.04, but AMH levels decreased similarly by -9% (-18 to -0.1) vs -13% (-28 to 0.2), P = 0.38, respectively. EV + DNG increased SHBG levels by 56% (30% to 82%) and EE + DNG by 385% (313% to 423%), P < 0.001. Total testosterone decreased by 16% (-27% to -5%) in the EV + DNG group but it did not decrease in the EE + DNG group, whereas the FAI decreased by -39% (-54% to -25%) vs -72% (-78% to -67%), P < 0.001. DNG alone did not induce changes in any of these parameters.

CONCLUSION

Compared with EE + DNG, treatment with EV + DNG resulted in milder pituitary downregulation and reduced induction of hepatic SHBG synthesis-potentially carrying more beneficial health effects.

Differential impact of tamoxifen and aromatase inhibitors on thrombin generation: the prospective HEMOBREAST cohort

Tamoxifen and aromatase inhibitors (AIs) are potent antitumoral agents against breast cancer. Tamoxifen increases the risk of venous thromboembolism (VTE), but the influence of AIs on the risk of VTE remains unclear. To inform clinical decisions, we evaluated associations of tamoxifen or AIs with changes of surrogate hemostatic biomarkers. This prospective cohort included 107 women with localized breast cancer starting tamoxifen (n = 42) or an AI (n = 65). Thrombin generation (CAT) its sensitivity to thrombomodulin (TM) or activated protein C (APC), and specific coagulation parameters, were measured before and 10-16 weeks after initiation of treatmen Compared with baseline, endogenous thrombin potential and thrombin peak increased in tamoxifen users (+86 nM × min; 95% confidence interval [CI], 30-142; and +33 nM; 95% CI, 21-45) but not in AI users (n = 65; +44 nM × min; 95% CI, -4 to 93; and +7 nM; 95% CI, -3 to 17). Normalized TM sensitivity ratios increased with tamoxifen (+0.26; 95% CI, 0.19-0.33y) but not with AI (+0.02; 95% CI, -0.03 to 0.07). Plasma levels of fibrinogen, antithrombin, protein C, and Tissue Factor Pathway Inhibitor decreased, and free protein S increased with tamoxifen but not with AIs. The observed shift toward increased coagulability associated with tamoxifen is in line with its known increased risk of VTE. In contrast, AIs do not appear to impact hemostasis, suggesting a lack of associated VTE risk. The trial was registered at www.clinicaltrials.gov as #NCT03381963.

Comparison of Acquired Activated Protein C Resistance, Using the CAT and ST-Genesia® Analysers and Three Thrombin Generation Methods, in APS and SLE Patients

Background: Acquired activated protein C resistance (APCr) has been identified in antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Objective: To assess agreement between the ST-Genesia^® and CAT analysers in identifying APCr prevalence in APS/SLE patients, using three thrombin generation (TG) methods. Methods: APCr was assessed with the ST-Genesia using STG-ThromboScreen and with the CAT using recombinant human activated protein C and Protac^® in 105 APS, 53 SLE patients and 36 thrombotic controls. Agreement was expressed in % and by Cohen’s kappa coefficient. Results: APCr values were consistently lower with the ST-Genesia^® compared to the CAT, using either method, in both APS and SLE patients. Agreement between the two analysers in identifying APS and SLE patients with APCr was poor (≤65.9%, ≤0.20) or fair (≤68.5%, ≥0.29), regardless of TG method, respectively; no agreement was observed in thrombotic controls. APCr with both the ST Genesia and the CAT using Protac^®, but not the CAT using rhAPC, was significantly greater in triple antiphospholipid antibody (aPL) APS patients compared to double/single aPL patients (p < 0.04) and in thrombotic SLE patients compared to non-thrombotic SLE patients (p < 0.05). Notably, the ST-Genesia^®, unlike the CAT, with either method, identified significantly greater APCr in pregnancy morbidity (median, confidence intervals; 36.9%, 21.9–49.0%) compared to thrombotic (45.7%, 39.6–55.5%) APS patients (p = 0.03). Conclusion: Despite the broadly similar methodology used by CAT and ST-Genesia^®, agreement in APCr was poor/fair, with results not being interchangeable. This may reflect differences in the TG method, use of different reagents, and analyser data handling.

Assessment of acquired activated protein C resistance with the FibWave and comparison with the ETP-based APC resistance

INTRODUCTION

Activated protein C (APC) resistance is a major risk factor of venous thrombosis which may be acquired by hormonal therapy or other causes. The FibWave, a sensitive global clot-based assay design to analyze the coagulation kinetics in plasma, may be a good candidate to assess this prothrombotic state. This study aims to assess the suitability of the FibWave to differentiate the coagulation kinetics of women on oral contraceptives.

MATERIALS AND METHODS

Fifty-four healthy volunteers were divided into 5 groups: men [n = 13], women not using hormonal contraception [n = 12], women using second [n = 12] or third generation [n = 12] combined oral contraceptives, and women using progestin only contraceptive [n = 5]. Patients with coagulation abnormalities were also assessed [n = 8]. The APC resistance was assessed on the FibWave using exogenous APC or Protac, and on the Calibrated Automated Thrombogram using the ETP-based APC resistance assay.

RESULTS

Either in presence or in absence of APC or Protac, the FibWave was able to detect a hypercoagulable state in plasma samples. All combined oral contraceptives showed a lower FW-Max₁ , FW-Max_2, and FW-Min₂ percentage of inhibition and a lower FW-Ttpeak ratio than the other groups. The sensitivity of the FibWave was similar to the one of the ETP-based APC resistance assay.

CONCLUSION

The FibWave is able to differentiate APC resistance levels observed in women on combined oral contraceptive. The FW-Max₁ , FW-Max_2, and to a lesser degree FW-Min₂ were identified as the most sensitive parameters with a similar performance to the ETP-based APC resistance assay.

Oral Contraceptives and Venous Thromboembolism: Focus on Testing that May Enable Prediction and Assessment of the Risk

Combined oral contraceptives (COCs) induce several changes in the levels of coagulation factors. The levels of procoagulant factors are often increased, while levels of anticoagulant factors are decreased. Fibrinolysis is also affected, even if the effect seems to be more counterbalanced by opposite regulation of profibrinolytic and antifibrinolytic factors. These effects on hemostasis are more pronounced with third- or fourth-generation COC compared with second-generation COC. Venous thromboembolism (VTE) risk increases when multiple risk factors, including genetic and environmental, are present simultaneously. COC use causes changes in coagulation that modify the prothrombotic state induced by preexisting hemostatic alterations in a supra-additive manner. Therefore, testing appears to be of importance not only before implementing COC but also to monitor any potential thrombogenicity induced by COC therapy. Inherited genetic factors, such as factor V Leiden, G20210A prothrombin mutation, antithrombin, protein C or protein S deficiencies, non-O blood group, as well as CYP2C9*2 and the rs4379368 mutations, have all been identified as genetic predictive risk factors of VTE in women. Nevertheless, the screening of these genetic biomarkers is not capable of assessing the phenotypic expression of the risk. This review will focus on the different options for screening the thrombogenic status in this population. Specific attention will be given to the endogenous thrombin potential-based activated protein C resistance, a test aiming at assessing the thrombogenicity induced by hormonal therapies and inherited or acquired thrombophilia.

Thrombin generation in subjects with lupus anticoagulant without prior thrombosis or gestational morbidities

BACKGROUND

Lupus anticoagulant (LA) can be a cause of thrombosis and/or pregnancy morbidities, producing antiphospholipid syndrome (APS). An increase in thrombin generation (TG) is correlated with prothrombotic status. Several changes in TG-derived parameters have been reported in APS patients.

OBJECTIVES

Evaluate whether the TG phenotype of APS can also be described in LA subjects without clinical manifestations of APS, and to investigate the possible influence of both LA potency and antiphospholipid (aPL) profile on it.

RESULTS

TG was analyzed in 153 cases of LA and 41 healthy controls. We have observed prolongation of both lag time (3.7 min vs 2.32 min, p < 0.001) and time to peak (6.48 min vs 5.27 min, p < 0.001), increased peak height (221.7 nM vs 182.7 nM, p < 0.001), slightly higher ETP (221.7 nM·min vs 182.7 nM·min, p = 0.041), and higher velocity index (100.7 nM/min vs 74.53 nM/min, p = 0.001) in LA subjects compared to controls. After adding thrombomodulin (TM), ETP%inh was significantly lower in LA group (37.90% vs 59.90%, p < 0.001) showing resistance to TM/activated protein C (APC). Significant differences were found in lag time, time to peak and ETP%inh according to the potency and aPL profile.

CONCLUSIONS

Previously described differences in TG-derived parameters in APS patients have been confirmed in incidental LA subjects: prolonged lag time and time to peak, slightly higher ETP, higher peak height, and less sensitivity to TM/APC. High LA potency and triple-positive aPL profile enhance differences in lag time, time to peak and, especially, increase APC resistance, but no effect in ETP was observed.

Proof of concept of a new scale for the harmonization and the standardization of the ETP-based APC resistance

BACKGROUND

The evaluation of the activated protein C resistance (APCr) based on the endogenous thrombin potential (ETP) is recommended during the development of steroid contraceptives. Results are usually expressed as "normalized APC sensitivity ratio" (nAPCsr) using a reference plasma that should achieve an ETP ratio of 0.1 in presence of exogenous APC. Because of the interassay variability, achieving exactly an ETP ratio of 0.1 in each run is almost impossible, which significantly affects the theoretical 0-10 scale of nAPCsr.

OBJECTIVES

To compare the nAPCsr to the nAPCsr10 , a newly proposed method to express the degree of APC resistance.

METHODS

Individual plasma samples (n = 854) were analyzed to compare nAPCsr and nAPCsr10 . These values were obtained using the validated ETP-based APCr assay.

RESULTS

The Spearman correlation between nAPCsr and nAPCsr10 had a coefficient of 0.99. Linear regression showed the following equation y = 0.9315*x + 0.03942 (r2  = .97). When differences (nAPCsr10 - nAPCsr) were plotted against nAPCsr10 , the mean difference equaled 0.16% or 4.95%. The correction obtained with the use of the nAPCsr10 showed that the results of the nAPCsr were statistically different (P < .0001).

CONCLUSIONS

This new scale provides a harmonization and normalization of the nAPCsr. Results show a better reproducibility with the nAPCsr10 . It avoids the additional variability and the unharmonized scale introduced by the use of a reference plasma. This adapted method for the calculation of the APC resistance could provide the regulatory and scientific bodies with more reproducible and harmonized evaluations.

Validation and standardization of the ETP-based activated protein C resistance test for the clinical investigation of steroid contraceptives in women: an unmet clinical and regulatory need

Background

Regulatory bodies recommend the use of an assay based on the assessment of the endogenous thrombin potential (ETP) for the investigation of the activated protein C resistance (APCr) in the development of steroid contraceptives in women. However, the assays described in the literature are home-made and not standardized regarding the method, the reagents, the reference plasma and the quality controls. In the absence of any commercially available method, we aimed at validating the ETP-based APCr assay.

Methods

The validation was performed according to regulatory standards. The method targets a 90% inhibition of the ETP in healthy donors in the presence of APC compared to the same condition in the absence of APC. As a large-scale production of a pool of plasma from well-selected healthy donors is impossible, algorithms were applied to a commercial reference plasma to correlate with the selected pool.

Results

Repeatability and intermediate precision passed the acceptance criteria. The assay demonstrated a curvilinear dose response to protein S and APC concentrations (R2 > 0.99). Analysis of plasma samples from 47 healthy individuals (22 women not taking combined hormonal contraceptives [CHC], and 25 men not Factor V Leiden carriers) confirmed the validity of the test, with a mean inhibition percentage of 90%. Investigations in 15 women taking different contraceptives and in two subjects with Factor V Leiden confirmed the good sensitivity and performance of the assay.

Conclusions

This validation provides the pharmaceutical industry, the regulatory bodies and physicians with a reproducible, sensitive and validated gold-standard ETP-based APCr assay.

The effects of oral contraceptive usage on thrombin generation and activated protein C resistance in Saudi women, with a possible impact of the body mass index

BACKGROUND AND OBJECTIVES

The effect of oral contraceptive (OC) usage on coagulation has been studied worldwide. However, no such studies have been conducted in Saudi Arabia on Saudi women using OCs. The aim of this study was to investigate the effects of OC-induced changes of thrombin generation (TG) in the absence and presence of activated protein C (APC) or thrombomodulin (TM) in Saudi women.

METHODS

A total of 115 adult women, 47 on oral contraception (OC users) and 68 controls (not using OCs) were recruited from the obstetrics-gynecology outpatient clinic in Saudi Arabia. OCs that were used in this study include the following: Marvelon, Gynera, Cerrazetem, Yasmine, Microlut, Gracial and Diane. The plasma calibrated automated thrombinography (CAT) was used to determine TG which was expressed as endogenous thrombin potential (ETP; nM/min), lag time (min), peak (nM) and time-to-peak (ttpeak; min). In the presence of TM or APC, TG parameters were expressed relative to the parameters in the absence of TM or APC.

RESULTS AND CONCLUSION

As in other populations, our study demonstrated that OC usage induced prothrombotic changes in plasma of Saudi women, including resistance to the inhibitory actions of TM and APC. More specifically, OC usage in our population predominantly influenced TG and APC/TM sensitivity in overweight and obese individuals, a finding that needs confirmation in large cohort studies. The effects of APC and TM on TG parameters showed a positive association, and the correlation coefficients were higher in OC users for both ETP and peak values.

Thrombin generation test as a marker for high risk venous thrombosis pregnancies

Pregnancy is a well-established risk factor for venous thromboembolism and is associated with a state of hypercoagulability. The use of sensitive and specific biological markers to predict risk factors for thrombosis is essential during pregnancy. Our objective was to investigate the usefulness of thrombin generation test (TGT) as a marker to predict the risk of thrombosis in high risk venous thrombosis (HRVT) pregnancies compared to normal pregnancies. This retrospective study enrolled 134 women with HRVT pregnancies, 78 of whom had monozygotic, spontaneous and untreated pregnancies and formed the study group. The control group comprised 106 women with normal pregnancies. Routine assessment of coagulation activation markers: fibrinogen, D-dimer, prothrombin fragments 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) was performed every 5 weeks in the study group to detect a possible pathological state of hypercoagulability. TGT was performed using platelet-free plasma, 1 and 5 pM tissue factor (TF), supplemented by phospholipids (PL) ± thrombomodulin. Fibrinogen, D-dimer, F1 + 2, and TAT, but not FMC, increased significantly throughout pregnancy in both groups but no difference was shown between the groups. TGT showed an early increase in thrombin generation in both groups, which stabilized during the second month of pregnancy. No correlation was demonstrated between thrombin generation parameters and coagulation activation markers. Based on our results, TGT did not prove conclusive as a marker to predict the risk of thrombosis in HRVT pregnancies. Finding a sensitive and specific biological marker to predict thrombosis risk requires further investigation.

Circulating microparticles in carriers of factor V Leiden with and without a history of venous thrombosis

Although factor V Leiden (FVL) is a major determinant of thrombotic risk, the reason why less than 10% of carriers eventually develop venous thromboembolic (VTE) events is unknown. Recent observations suggest that circulating levels of microparticles (MP) may contribute to the thrombogenic profile of FVL carriers. We measured the plasma level of annexin V-MP (AMP) platelet-MP (PMP), endothelial-MP (EMP), leukocyte-MP (LMP) and tissue factor-bearing MP (TF+MP), and the MP procoagulant activity (PPL) in 142 carriers of FVL (of these 30 homozygous and 49 with prior VTE), and in 142 age and gender-matched healthy individuals. The mean (± SD) level of AMP was 2,802 ± 853 MP/ μl in carriers and 1,682 ± 897 in controls (p<0.0001). A statistically significant difference between homozygous and heterozygous carriers of FVL was seen in the level of PMP, EMP and LMP, but not in that of the remaining parameters. When the analysis was confined to carriers with and without a VTE history, the mean level of AMP was 3,110 ± 791 MP/ μl in the former, and 2,615 ± 839 MP/μl in the latter (p<0.005). The mean level of all subtypes of circulating MP showed a similar pattern. The PPL clotting time was 39 ± 9 seconds (sec) in carriers, and 52 ± 15 sec in controls (p=0.003); and was 35 ± 8 sec in carriers with prior thrombosis, and 41 ± 10 sec in thrombosis-free carriers (p<0.005). Our study results suggest that circulating MP may contribute to the development of thrombosis in carriers of FVL mutation.

Thrombin generation and activated protein C resistance in the absence of factor V Leiden correlates with the risk of recurrent venous thromboembolism in women aged 18–65 years

Identification of patients at high risk of recurrence after a first event of venous thromboembolism (VTE) remains difficult. Resistance to activated protein C (APC) is a known risk factor for VTE, but data on the risk of recurrence is controversial. We wanted to investigate whether APC resistance in the absence of factor V Leiden, determined with global coagulation test such as the thrombin generation assay, could be used as a marker for increased risk of recurrent VTE among women 18–65 years old after a first event of VTE. In a cohort of 243 women with a first event of VTE, plasma was collected after discontinuation of anticoagulant treatment and the patients were followed up for 46 months (median). Thrombin generation was measured via calibrated automated thrombography, at 1 pM and 10 pM of tissue factor (TF). In women without factor V Leiden (n=117), samples were analysed in the absence and in the presence of APC. Increase in ETP (endogenous thrombin potential) and peak height analysed in the presence of APC correlated significantly with higher risk of recurrence. At 1 pM, peak height correlated with increased risk of recurrence. In conclusion, high thrombin generation in the presence of APC, in women after a first event of VTE is indicative for an increased risk of a recurrence. We also found that thrombin generation at low TF (1 pM) is correlated with the risk of recurrence. Our data suggest that APC resistance in the absence of factor V Leiden is a risk factor for recurrent VTE.

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.

Endogenous thrombin potential changes during the first cycle of oral contraceptive use

OBJECTIVES

Venous thromboembolism (VTE) risk increases within months of combination oral contraceptive (COC) initiation. Because elevated endogenous thrombin potential (ETP) has been found in several studies to be a VTE risk factor, we evaluated the extent of ETP changes during the initial cycle of an ethinyl estradiol (EE) and levonorgestrel (LNG) COC. We also assessed the relationship between ETP changes and systemic EE and LNG concentrations.

STUDY DESIGN

Participants provided multiple blood samples during a first 21-day cycle of a 30-mcg EE/150-mcg LNG COC and after a further 7 days without an active COC. Thrombin generation measured with and without addition of activated protein C (APC) yielded ETP+APC and ETP-APC and the normalized APC sensitivity ratio (nAPCsr). EE and LNG pharmacokinetic analyses were conducted over 24 h after the first COC tablet and again at steady state.

RESULTS

Thrombin generation was determined in 16 of the 17 women who completed the study. Mean ETP-APC increased steadily to 21% above baseline at 24 h after the 6th COC tablet (COC624; p<.001) and to 28% above baseline at steady state (COC21; p<.001). The percentage increase in mean ETP+APC was considerably more - 54% at COC624 and 79% at steady state. Mean nAPCsr increased by 28% at COC624 and by 41% at steady state. Higher concentrations of EE or LNG were not correlated with greater increases in ETP.

CONCLUSIONS

ETP increases during the first COC cycle were substantial.

IMPLICATIONS

The early increases in ETP may provide biological support for the rapid increase in VTE risk during initial COC use. The lack of association between this clotting system perturbation and the systemic EE concentration is surprising and deserves further study.

Plasma hypercoagulability in the presence of thrombomodulin but not of activated protein C in patients with cirrhosis

BACKGROUND AND AIMS

Cirrhosis significantly changes all hemostasis steps. Recent studies suggest that cirrhosis is associated with a coagulopathy leading to a hypercoagulable state. The underlying mechanisms are not fully understood, but protein C deficiency is probably a major determinant of this phenotype. The aim of this study was to compare the results of thrombin generation assays performed with addition of thrombomodulin or activated protein C to assess the effect of by-passing the protein C activation step in cirrhotic patients and healthy controls.

METHODS

Fifty-eight patients with cirrhosis and 26 healthy controls were prospectively included in this study. Thrombin generation was determined in platelet-poor plasma using 5 pM of tissue factor and 4 nM of phospholipids, without and with external addition of 1 nM thrombomodulin or 4 nM activated protein C. All results were normalized with the values of a pool of normal plasma samples to limit inter-plate variability.

RESULTS

When thrombin generation assays were performed in the presence of thrombomodulin, endogenous thrombin potential (ETP) and ETP with/ETP without TM ratio were significantly higher in cirrhotic patients than in healthy controls (P < 0.0001). Moreover, these values progressively increased with cirrhosis severity. When thrombin generation assays were performed with activated protein C, all thrombin generation parameters were comparable between healthy controls and cirrhotic patients, despite an acquired protein S deficiency.

CONCLUSION

In the presence of activated protein C, no hypercoagulability was observed, adding to the current evidence that acquired protein C deficiency plays a key role in the coagulation imbalance.

Cross-sectional association of endogenous steroid hormone, sex hormone-binding globulin, and precursor steroid levels with hemostatic factor levels in postmenopausal women

Essentials Endogenous hormone levels' influence on hemostatic factor levels is not fully characterized. We tested for associations of endogenous hormone with hemostatic factor levels in postmenopause. Estrone levels were inversely associated with the natural anticoagulant, protein S antigen. Dehydroepiandrosterone sulfate levels were inversely associated with thrombin generation.

SUMMARY

Background Oral use of exogenous estrogen/progestin alters hemostatic factor levels. The influence of endogenous hormones on these levels is incompletely characterized. Objectives Our study aimed to test whether, among postmenopausal women, high levels of estradiol (E2), estrone (E1), testosterone (T), dehydroepiandrosterone sulfate (DHEAS), dehydroepiandrosterone (DHEA), and androstenedione, and low levels of sex hormone-binding globulin (SHBG), are positively associated with measures of thrombin generation (TG), a normalized activated protein C sensitivity ratio (nAPCsr), and factor VII activity (FVIIc), and negatively associated with antithrombin activity (ATc) and total protein S antigen (PSAg). Methods This Heart and Vascular Health study cross-sectional analysis included 131 postmenopausal women without a prior venous thrombosis who were not currently using hormone therapy. Adjusted mean differences in TG, nAPCsr, FVIIc, ATc and PSAg levels associated with differences in hormone levels were estimated using multiple linear regression. We measured E2, E1, total T, DHEAS, DHEA and androstenedione levels by mass spectrometry, SHBG levels by immunoassay, and calculated the level of free T. Results One picogram per milliliter higher E1 levels were associated with 0.24% lower PSAg levels (95% Confidence Interval [CI]: -0.35, -0.12) and 1 μg mL-1 higher DHEAS levels were associated with 40.8 nm lower TG peak values (95% CI: -59.5, -22.2) and 140.7 nm×min lower TG endogenous thrombin potential (ETP) (95% CI: -212.1, -69.4). After multiple comparisons correction, there was no evidence for other associations. Conclusions As hypothesized, higher E1 levels were associated with lower levels of the natural anticoagulant PSAg. Contrary to hypotheses, higher DHEAS levels were associated with differences in TG peak and ETP that suggest less generation of thrombin.

Tissue Factor Pathway Inhibitor, Activated Protein C Resistance, and Risk of Coronary Heart Disease Due To Combined Estrogen Plus Progestin Therapy

OBJECTIVE

To examine whether tissue factor pathway inhibitor or acquired activated protein C (APC) resistance influences the increased risk of coronary heart disease (CHD) due to estrogen plus progestin therapy.

APPROACH AND RESULTS

Prospective nested case-control study of 205 cases of CHD and 481 matched controls in the Women's Health Initiative randomized trial of estrogen plus progestin therapy. After multivariable covariate adjustment, both baseline tissue factor pathway activity (P=0.01) and APC resistance (P=0.004) were associated positively with CHD risk. Baseline tissue factor pathway activity and APC resistance singly or jointly did not significantly modify the effect of estrogen plus progestin on CHD risk. Compared with placebo, estrogen plus progestin decreased tissue factor pathway inhibitor activity and increased APC resistance but these changes did not seem to modify or mediate the effect of estrogen plus progestin on CHD risk.

CONCLUSIONS

Tissue factor pathway inhibitor activity and APC resistance are related to CHD risk in women, but may not explain the increased CHD risk due to estrogen plus progestin therapy. The data from this study do not support the clinical use of measuring these hemostatic factors to help stratify risk before hormone therapy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000611.

The risk of a first and a recurrent venous thrombosis associated with an elevated D-dimer level and an elevated thrombin potential: results of the THE-VTE study

BACKGROUND

D-dimer and thrombin generation have been associated with the risk of recurrent venous thrombosis. However, for both measurements, different assays are available, and in vitro thrombin generation may be affected by the problem of contact activation during blood sampling.

OBJECTIVES

To determine the association between hypercoagulability and first and recurrent thrombosis by the use of different D-dimer and thrombin generation assays, to assess whether the addition of corn trypsin inhibitor (CTI) prior to blood sampling to inhibit contact activation improved the association between thrombin generation and thrombosis risk, and to calculate the DASH score with two different D-dimer assays.

METHODS

A case-control study (626 patients and 361 controls) with subsequent follow-up of the cases was performed (2987 patient-years after stopping of anticoagulant therapy). Blood was drawn 2-3 months after discontinuation of anticoagulation for the first event in citrate tubes with and without CTI.

RESULTS/CONCLUSIONS

An elevated D-dimer level and elevated thrombin generation were associated with an increased risk of a first event regardless of the assay used (odds ratios: 1.8-3.4). An elevated D-dimer level but not elevated thrombin generation was associated with the risk of recurrence. Patients with elevated D-dimer levels had a more than two-fold increased recurrence rate (Vidas - hazard ratio [HR] 2.3, 95% confidence interval [CI] 1.4-3.8; HemosIL - HR 2.4, 95% CI 1.5-3.9; Thrombinoscope and Technoclone assay - HR 1.3). Elimination of contact factor activation did not improve the predictive value of thrombin generation. In patients with unprovoked first events, the DASH score had a similar predictive value for deep vein thrombosis and pulmonary embolism, both when calculated with Vidas D-dimer and when calculated with HemosIL D-dimer.

Benefits and risks during HRT: main safety issue breast cancer

To assess the benefits and risks during hormone replacement therapy (HRT) in postmenopausal women, the only placebo-controlled study testing clinical endpoints with high statistical power has been the Women's Health Initiative (WHI). Although this trial, conducted mainly in older high-risk women, might not reflect the practical conditions for the normal use of HRT, the WHI for the first time provides the main risks in relative as well as in absolute numbers, which are venous thromboembolism and breast cancer, and in older women also myocardial infarction and stroke. Proven benefits such as treatment of climacteric symptoms, reduction of osteoporotic fractures and decrease of colon cancer risk seem to be only important for younger women, because only with early start of HRT cardiovascular risks can be reduced. Reduction of cardiovascular risks can be achieved using transdermal HRT, which, however, was not tested in a placebo-controlled study design similar to that in the WHI. This review focuses on the results of the WHI, comparing different age groups, and in general especially on the main fear of women, risk of breast cancer, which has been defined as a special project between two universities, a close collaboration of a German and Chinese research group.

Hormone therapy and hemostasis among postmenopausal women: a review

OBJECTIVE

Postmenopausal hormone therapy (HT), which consists of exogenous estrogens with or without combined progestogens, remains the most effective treatment of climacteric symptoms. Depending on its characteristics, it may nevertheless increase the risk of venous thromboembolism, and its effects on hemostasis have been studied for several decades. The aim of this review was to summarize current knowledge on the effects of HT on hemostasis, taking into account the route of estrogen administration, the daily dose and chemical structure of estrogens, and the pharmacologic class of progestogens.

METHODS

Data from randomized controlled trials that included a control group (either placebo or no treatment) were selected, and analysis was conducted on different generations of biomarkers.

RESULTS

Overall, studies showed a hemostasis imbalance among oral estrogen users with a decrease in coagulation inhibitors and an increase in markers of activation coagulation, leading to global enhanced thrombin generation. By contrast, transdermal estrogen use was associated with less change in hemostasis variables and did not activate coagulation and fibrinolysis. No clear difference in HT effects on hemostasis was highlighted between daily doses of estrogens, between estrogen compounds, and between pharmacologic classes of progestogens.

CONCLUSIONS

Changes in hemostasis are in accordance with clinical results showing an increased thrombotic risk with oral--but not transdermal--estrogen use.

Combined oral contraceptives: venous thrombosis

BACKGROUND

Combined oral contraceptive (COC) use has been associated with venous thrombosis (VT) (i.e., deep venous thrombosis and pulmonary embolism). The VT risk has been evaluated for many estrogen doses and progestagen types contained in COC but no comprehensive comparison involving commonly used COC is available.

OBJECTIVES

To provide a comprehensive overview of the risk of venous thrombosis in women using different combined oral contraceptives.

SEARCH METHODS

Electronic databases (Pubmed, Embase, Web of Science, Cochrane, CINAHL, Academic Search Premier and ScienceDirect) were searched in 22 April 2013 for eligible studies, without language restrictions.

SELECTION CRITERIA

We selected studies including healthy women taking COC with VT as outcome.

DATA COLLECTION AND ANALYSIS

The primary outcome of interest was a fatal or non-fatal first event of venous thrombosis with the main focus on deep venous thrombosis or pulmonary embolism. Publications with at least 10 events in total were eligible. The network meta-analysis was performed using an extension of frequentist random effects models for mixed multiple treatment comparisons. Unadjusted relative risks with 95% confidence intervals were reported.Two independent reviewers extracted data from selected studies.

MAIN RESULTS

3110 publications were retrieved through a search strategy; 25 publications reporting on 26 studies were included. Incidence of venous thrombosis in non-users from two included cohorts was 0.19 and 0.37 per 1 000 person years, in line with previously reported incidences of 0,16 per 1 000 person years. Use of combined oral contraceptives increased the risk of venous thrombosis compared with non-use (relative risk 3.5, 95% confidence interval 2.9 to 4.3). The relative risk of venous thrombosis for combined oral contraceptives with 30-35 μg ethinylestradiol and gestodene, desogestrel, cyproterone acetate, or drospirenone were similar and about 50-80% higher than for combined oral contraceptives with levonorgestrel. A dose related effect of ethinylestradiol was observed for gestodene, desogestrel, and levonorgestrel, with higher doses being associated with higher thrombosis risk.

AUTHORS' CONCLUSIONS

All combined oral contraceptives investigated in this analysis were associated with an increased risk of venous thrombosis. The effect size depended both on the progestogen used and the dose of ethinylestradiol. Risk of venous thrombosis for combined oral contraceptives with 30-35 μg ethinylestradiol and gestodene, desogestrel, cyproterone acetate and drospirenone were similar, and about 50-80% higher than with levonorgestrel. The combined oral contraceptive with the lowest possible dose of ethinylestradiol and good compliance should be prescribed-that is, 30 μg ethinylestradiol with levonorgestrel.

Lower risk of cardiovascular events in postmenopausal women taking oral estradiol compared with oral conjugated equine estrogens

IMPORTANCE

Little is known about the comparative cardiovascular safety of oral hormone therapy products, which impedes women from making informed safety decisions about hormone therapy to treat menopausal symptoms.

OBJECTIVE

To compare the relative clinical cardiovascular safety of 2 commonly used oral estrogen drugs-conjugated equine estrogens (CEEs) and estradiol.

DESIGN, SETTING, AND PARTICIPANTS

Population-based, case-control study from January 1, 2003, to December 31, 2009, comparing cardiovascular event risk associated with current CEEs and estradiol use in a large health maintenance organization in which the preferred formulary estrogen changed from CEEs to estradiol during the course of data collection. Participants were 384 postmenopausal women aged 30 to 79 years using oral hormone therapy.

MAIN OUTCOMES AND MEASURES

Incident venous thrombosis was the primary clinical outcome, and incident myocardial infarction and ischemic stroke were secondary outcomes. As validation, an intermediate clotting phenotype, the endogenous thrombin potential-based normalized activated protein C sensitivity ratio, was measured in plasma of controls.

RESULTS

We studied 68 venous thrombosis, 67 myocardial infarction, and 48 ischemic stroke cases, with 201 matched controls; all participants were current users of oral CEEs or estradiol. In adjusted analyses, current oral CEEs use compared with current oral estradiol use was associated with an increased venous thrombosis risk (odds ratio, 2.08; 95% CI, 1.02-4.27; P = .045) and an increased myocardial infarction risk that did not reach statistical significance (odds ratio, 1.87; 95% CI, 0.91-3.84; P = .09) and was not associated with ischemic stroke risk (odds ratio, 1.13; 95% CI, 0.55-2.31; P = .74). Among 140 controls, CEEs users compared with estradiol users had higher endogenous thrombin potential-based normalized activated protein C sensitivity ratios (P < .001), indicating a stronger clotting propensity.

CONCLUSIONS AND RELEVANCE

In an observational study of oral hormone therapy users, CEEs use was associated with a higher risk of incident venous thrombosis and possibly myocardial infarction than estradiol use. This risk differential was supported by biologic data. These findings need replication and suggest that various oral estrogen drugs may be associated with different levels of cardiovascular risk.

Thrombin generation as marker to estimate thrombosis risk in patients with abnormal test results in lupus anticoagulant routine diagnostics

BACKGROUND

Lupus anticoagulant (LA) is known to inhibit thrombin generation although patients have an increased risk to develop thrombosis. We tried to determine whether thrombin generation is altered in plasma samples of patients with abnormal test results in LA routine diagnostics and whether its measurement may improve the risk assessment of thrombosis.

METHODS

Samples from 63 patients (39 with abnormal test results; 24 controls) were included in the study. Measurement of diluted Russel's viper venom time (dRVVT) was part of the initial guideline conform diagnostic procedure for detection of LA. In addition, measurement of anticardiolipin-IgM, -IgG and β2-glycoprotein-I-IgM, -IgG were performed. Thrombin generation was measured using two different phospholipid concentrations in the starting reagent.

RESULTS

Analyzing all samples by logistic regression, thrombin generation after induction with high phospholipid concentrations was the best predictor of thrombosis. After preselection of samples with alterations in dRVVT, specificity of selected thrombin generation derived parameters for the detection of previous thrombosis increased in this subgroup.

CONCLUSIONS

In patients with phospholipid-dependent prolongation of dRVVT, thrombin generation is variably inhibited and the degree of inhibition corresponds to the occurrence of previous thrombosis. Measuring thrombin generation in patients with phospholipid-dependent dRVVT prolongation may improve risk assessment of thrombosis.

Resistance to APC and SHBG levels during use of a four-phasic oral contraceptive containing dienogest and estradiol valerate: a randomized controlled trial

BACKGROUND

The use of combined oral contraceptives is associated with a 3- to 6-fold increased risk of venous thrombosis. This increased risk depends on the estrogen dose as well as the progestogen type of combined oral contraceptives. Thrombin generation-based activated protein C resistance (APC resistance) and sex hormone-binding globulin (SHBG) levels predict the thrombotic risk of a combined hormonal contraceptive. Recently, a four-phasic oral contraceptive containing dienogest (DNG) and estradiol valerate (E2V) has been marketed. The aim of this study was to evaluate the thrombotic risk of the DNG/E2V oral contraceptive by comparing APC resistance by measuring normalized APC sensitivity ratios (nAPCsr) and SHBG levels in users of oral contraceptives containing dienogest and estradiol valerate (DNG/E2V) and oral contraceptives containing levonorgestrel and ethinyl estradiol (LNG/EE).

METHODS

We conducted a single-center, randomized, open label, parallel-group study in 74 women using DNG/E2V or LNG/EE, and measured nAPCsr and SHBG levels in every phase of the regimen of DNG/E2V.

RESULTS

During the pill cycle SHBG levels did not differ between DNG/E2V users and LNG/EE users. nAPCsr levels were overall slightly lower in DNG/E2V users than in LNG/EE users, mean difference -0.44 (95% CI, -1.04 to 0.17) for day 2, -0.20 (95% CI, -0.76 to 0.37) for day 7, -0.27 (95% CI, -0.81 to 0.28) for day 24 and -0.34 (95% CI, -0.91 to 0.24) for day 26.

CONCLUSION

No statistical significant differences in nAPCsr and SHBG levels were found between users of the oral contraceptive containing DNG/E2V and LNG/EE, suggesting a comparable thrombotic risk.

TFPI resistance related to inherited or acquired protein S deficiency

BACKGROUND

Protein S (PS) is an essential component of the protein C pathway and PS deficiency can explain a poor response to activated protein C. It has recently been shown that PS also acts as a cofactor of Tissue Factor Pathway Inhibitor (TFPI).

OBJECTIVES

In the present study, we investigated whether PS deficiency could be responsible for a poor response to TFPI.

PATIENTS/METHODS

Thirty-one patients with inherited PS deficiency, seven pregnant women and 36 controls were enrolled in the study. We measured the plasma response to added TFPI using a two-step diluted prothrombin time (dPT) assay. The response of the different plasmas to the anticoagulant activity of TFPI was expressed as TFPI Normalised Ratio (TFPI NR).

RESULTS

The median TFPI NR was statistically significantly lower in patients with inherited PS deficiency (0.5) than in controls (1.0) (p<0.0001). It was statistically significantly lower in patients with type I inherited PS deficiency (0.47) compared to patients with type III inherited PS deficiency (0.58) (p=0.018). In contrast, it did not differ between patients with and without thrombosis. Median TFPI NR values were statistically significantly lower during pregnancy (0.54) than 3 months after delivery (0.71) (p=0.016). TFPI NR values correlated well with PS activity values (R(2)=0.681) whatever the nature of the PS deficiency.

CONCLUSIONS

Our findings confirm that PS deficiency results in a poor anticoagulant response to TFPI, demonstrating again the cofactor role of PS in TFPI activity.

Venous thrombosis and oral contraceptives: current status

The use of oral contraceptives is associated with an increased risk of venous thrombosis. It is now generally accepted that women who use oral contraceptives that contain so-called third-generation progestins (desogestrel or gestodene) are exposed to a twofold higher risk of venous thrombosis than women who use oral contraceptives that contain the second-generation progestin levonorgestrel. Coagulation studies demonstrated that oral contraceptives increase the plasma level of prothrombin, decrease the level of protein S and induce acquired activated protein C resistance. The changes in hemostatic parameters can explain why women who use oral contraceptives are exposed to an increased risk of venous thrombosis and why the risk is further increased in third-generation oral contraceptive users.

Sex hormone-binding globulin levels are not causally related to venous thrombosis risk in women not using hormonal contraceptives

BACKGROUND

Oral contraceptive use increases the risk of venous thrombosis as well as sex hormone-binding globulin (SHBG) levels. Furthermore, increased SHBG levels are positively associated with activated protein C (APC) resistance and thrombotic risk in oral contraceptive users.

OBJECTIVES

To determine whether increased SHBG levels are causally related to venous thrombosis in women not using hormonal contraceptives.

METHODS

Premenopausal women were selected from a case-control study on venous thrombosis, the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA) study (23 patients; 258 controls). Women using hormonal contraceptives were excluded. First, the risk of venous thrombosis with SHBG levels above the normal reference range (70 nm) was determined. Second, because multiple regulatory factors affect SHBG levels and residual confounding may remain, we determined six single-nucleotide polymorphisms (SNPs) in the SHBG gene and assessed the risk of venous thrombosis in a different case-control study, the Leiden Thrombophilia Study (LETS) (20 patients; 74 controls), and in the MEGA study. Finally, the association between SHBG levels and the normalized activated partial thromboplastin time-based APC resistance (an intermediate endpoint for venous thrombosis) was determined.

RESULTS

Elevated SHBG levels (> 70.0 nm) were associated with venous thrombosis (odds ratio 1.92; 95% confidence interval [CI] 0.74-5.00). However, this finding can be explained by residual confounding. Two SNPs in the SHBG gene affected SHBG levels, but not venous thrombosis risk. Furthermore, SHBG levels in controls were not associated with APC resistance (SHBG level, > 70.0 vs. ≤ 70.0 nm: mean difference in normalized APC sensitivity ratio, 0.03; 95% CI -0.05 to 0.10). Exclusion of women with FV Leiden did not materially change these results.

CONCLUSIONS

Increased SHBG levels are not causally related to the risk of venous thrombosis.

HIV infection is associated with decreased thrombin generation

BACKGROUND

Excess risk of cardiovascular disease occurs in effectively treated individuals with human immunodeficiency virus (HIV) infection. Although elevated plasma D-dimer levels are associated with increased morbidity and mortality, the impact of HIV infection on coagulation in vivo has not been well studied.

METHODS

We measured D-dimers, antithrombin, endogenous thrombin potential (ETP; a functional measure of thrombin generation in vitro), thrombin/antithrombin complexes (TAT; a measure of thrombin generation in vivo), tissue factor, prothrombin fragment 1 + 2 (F1+2), and normalized APC sensitivity ratio (nAPCsr) in 199 HIV-positive men who were receiving antiretroviral therapy and had an undetectable HIV RNA level, in 79 HIV-positive untreated men, and in 39 uninfected controls.

RESULTS

Median antithrombin levels were higher while the ETP was lower among HIV-infected adults (treated and untreated), compared with controls. There were few differences between coagulation markers in the 2 HIV groups. Compared with controls, the nAPCsr was lower in treated men and the TAT level was lower in untreated individuals. We observed little difference among measured levels of D-dimer, tissue factor, or F1+2 between HIV-infected individuals and controls. Antiretroviral therapy exposure was associated with a lower antithrombin level, a lower nAPCsr, and a lower ETP, while history of opportunistic infection was associated with a higher nAPCsr.

CONCLUSIONS

HIV infection is associated with decreased thrombin generation, as measured by the ETP, and an increased antithrombin level. These data suggest that HIV infection may not be associated with increased propensity toward clotting, as has been suggested on the basis of isolated measures of D-dimer levels.

Sex hormone-binding globulin as a marker for the thrombotic risk of hormonal contraceptives

BACKGROUND

It takes many years to obtain reliable values for the risk of venous thrombosis of hormonal contraceptive users from clinical data. Measurement of activated protein C (APC) resistance via thrombin generation is a validated test for determining the thrombogenicity of hormonal contraceptives. Sex hormone-binding globulin (SHBG) might serve as a marker for the risk of venous thrombosis, and can be easily and rapidly measured in routine laboratories.

OBJECTIVE

To determine whether SHBG is a useful marker for the thrombotic risk of hormonal contraceptive users by comparing plasma SHBG levels with normalized APC sensitivity ratio (nAPCsr) values and thrombosis risks reported in the recent literature.

METHODS

We conducted an observational study in 262 users of different contraceptives, and measured nAPCsr and SHBG levels.

RESULTS

Users of contraceptives with a higher risk of causing venous thrombosis, i.e. combined hormonal contraceptives containing desogestrel, cyproterone acetate or drospirenone, and the transdermal patch, had higher SHBG levels than users of combined hormonal contraceptives containing levonorgestrel, which carry a lower thrombosis risk. Users of the patch had the highest SHBG levels, with a mean difference of 246 nmol L(-1) (95% confidence interval 179-349) from that in users of levonorgestrel-containing combined hormonal contraceptives. SHBG levels were positively associated with both the nAPCsr and the risks of venous thrombosis reported in the recent literature.

CONCLUSION

SHBG is a useful marker with which to estimate the thrombotic safety of a preparation.

An overview of the development of combined oral contraceptives containing estradiol: focus on estradiol valerate/dienogest

Natural estrogens such as estradiol (E(2)) or its valerate ester (E(2)V) offer an alternative to ethinyl estradiol (EE). E(2)-containing combined oral contraceptives (COCs) have demonstrated sufficient ovulation inhibition and acceptable contraceptive efficacy. However, earlier formulations were generally associated with unacceptable bleeding profiles. Two E(2)V-containing preparations have been approved to date for contraceptive use: E(2)V/cyproterone acetate (CPA) (Femilar(®); only approved in Finland and only in women >40 years or women aged 35-40 years in whom a COC containing EE is not appropriate) and E(2)V/dienogest (DNG; Qlaira(®)/Natazia(®)). The objective of the current review is to provide an overview of the development of COCs containing natural estrogen, highlighting past issues and challenges faced by earlier formulations, as well as the current status and future directions. The majority of information to date pertains to the development of E(2)V/DNG.