Acquired activated protein C resistance in postmenopausal women is dependent on factor VIII:c levels

An improved algorithm for activated protein C resistance and factor V Leiden screening

OBJECTIVES

To evaluate the performance of a Russell viper venom-based activated protein C resistance (APCR) screening test relative to DNA analysis for the factor V Leiden mutation.

METHODS

We evaluated the concordance between Pefakit APCR screening results and DNA analysis for 435 patients homozygous (n = 11), heterozygous (n = 310), or wild-type (n =114) for the G1691A allele.

RESULTS

Using receiver operating characteristic analysis, we found that a cutoff of 1.89 for the APCR ratio yields a sensitivity and specificity of 99.1%. In patients with discrepant genotype-phenotype correlation, their APCR may provide a more clinically relevant result.

CONCLUSIONS

We compared several strategies for employing reflex testing and found that performing initial APCR screening followed by confirmatory molecular analysis on a subset of cases in the borderline regions between the diagnostic groups can reduce unnecessary testing by approximately 80% without compromising diagnostic accuracy.

Haemostatic changes and acquired activated protein C resistance in normal pregnancy

Influence of changes in levels of coagulation factors and anticoagulants on acquired activated protein C (APC) resistance were studied in 40 healthy women during normal pregnancy. Factor VIII (FVIII), von Willebrand factor antigen (VWF:Ag), free protein S (FPS) and protein C were determined at 5-13, 14-26 and 27-40 weeks gestation and more than 6 weeks postpartum. APC anticoagulant activity was determined by measuring the activated partial thromboplastin time before and after adding human APC, expressed as the APC-sensitivity ratio (APC-SR). During the second and third gestation trimesters a significant increase (P < 0.05) in FVIII and VWF:Ag levels and a decrease in FPS levels were seen compared with the first trimester. Postpartum FVIII and VWF:Ag levels significantly decreased and FPS levels increased compared with the third trimester. Protein C levels remained unchanged during pregnancy and postpartum. Between increased FVIII and lowered APC-SR a trend of inverse correlation (r = -0.329; P = 0.076) occurred in the second trimester. No correlation was found between APC-SR and FPS or VWF:Ag levels. A remarkable finding is the strong inverse relationship between APC-SR and protein C levels (r <or= -0.392; P < 0.05) during pregnancy and postpartum. This may indicate that anticoagulant activity of added human APC measured by activated partial thromboplastin time is diminished in the presence of high endogenous protein C levels. A possible hypothesis is steric hindrance by sample protein C of APC binding sites on target activated factor V and/or cofactor protein S. The clinical significance of this finding should be determined because it complicates the interpretation of lowered APC-SR.

The inflammation and coagulation cross-talk in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory disorder with a high prevalence of cardiovascular disease due to accelerated atherosclerosis, as well as an increased risk of venous thromboembolism. Many of these clinical features have been attributed to the high prevalence of autoantibodies that are directed against phospholipid-bound antigens and that induce prothrombotic effects and disturb endothelial cell function. We conducted a case-control study in a cohort of female patients with SLE and in age-matched and sex-matched normal individuals. Patients had significantly higher levels of plasma inflammatory markers, but their overall coagulation status assessed by prothrombin fragment 1 + 2 and D-dimer plasma levels was not different from controls. Resistance against activated protein C (APC), assessed by a thrombin generation-based as well as an activated partial thromboplastin time-based method, however, was increased in patients. This defect was neither due to factor V Leiden carriership or to the use of oral contraceptives. This acquired form of APC resistance was due to proinflammatory changes associated with lower plasma levels of free protein S. In conclusion, acquired APC resistance may be an important determinant of the risk of thrombosis in patients with SLE, probably due to an active cross-talk between inflammation and coagulation systems.

Short-term effects of estrogen, tamoxifen and raloxifene on hemostasis: a randomized-controlled study and review of the literature

INTRODUCTION

Estrogen therapy (ET), tamoxifen and raloxifene are associated with a two- to three-fold increased risk of venous thrombosis (VT); however, the mechanisms by which each drug increases venous thrombosis propensity are not fully understood. The objectives of this investigation were to compare the effects of these three treatments on hemostasis in a head to head randomized placebo-controlled trial.

PATIENTS/METHODS

Ninety-four postmenopausal women were assigned to receive oral estrogen (conjugated equine estrogen [CEE] 0.625 mg, n=23), tamoxifen 20 mg (n=24), raloxifene 60 mg (n=24) or placebo (n=23) daily for 6 months. Blood samples were analyzed for procoagulant factors (prothrombin, factors VII [fVII], VIII [fVIII], IX [fIX] and XI [fXI], D-dimer and von Willebrand factor [vWf]), anticoagulant factors (antithrombin [AT], total and free protein S, protein C and activated protein C [APC] resistance) and fibrinolytic factors (thrombin activatable fibrinolysis inhibitor [TAFI] and plasminogen activator inhibitor-1 [PAI-1]), at baseline and at 6 months of treatment.

RESULTS

Estrogen increased factor VII and D-dimer, and decreased antithrombin, total and free protein S and PAI-1. Changes with tamoxifen were distinct from estrogen with increases in factors VIII, IX, vWf and free protein S, and decreases in AT, total protein S, protein C and plasminogen activator inhibitor-1. Raloxifene produced similar effects as tamoxifen, but did not increase factor IX or decrease protein C.

CONCLUSIONS

Estrogen, tamoxifen and raloxifene affected hemostasis favoring procoagulation and impairing anticoagulation. The biochemical effects of the selective estrogen receptor modulators (SERMs) were distinct from those of estrogen and differed only subtly from each other.

Hormone replacement therapy and cardiovascular disease: increased risks of venous thromboembolism and stroke, and no protection from coronary heart disease

Hormone replacement therapy (HRT) was increasingly promoted over the last 40 years to improve quality of life, and to reduce the risks of osteoporotic fractures and coronary heart disease (CHD). In recent years, observational studies, randomized trials and systematic reviews of such trials have shown that HRT does not reduce, but actually increases cardiovascular risk. HRT increases the relative risks of venous thromboembolism (twofold), and of fatal or disabling stroke (by 50%); whilst increasing the early risk of myocardial infarction and having no protective effect against CHD on longer term use. Possible mechanisms for these increased cardiovascular risks include down-regulation of several inhibitory pathways of blood coagulation, resulting in increased coagulation activation, which promotes venous and arterial thrombosis. The implications for prescription are discussed, as are lessons for future evaluation of health care interventions.

[High levels of factor VIIIc and risk of venous thrombosis: critical analysis of case-control studies]

INTRODUCTION

Deep venous thrombosis is a frequent and potentially serious disease. Its causes are multifactorial, associating facilitating circumstances and genetic or acquired coagulation abnormalities. Genetic currently well known abnormalities are quantitative deficiencies of some natural anticoagulants (proteins C and S, antithrombin), and mutations of V and II (G20210-A) genes. The Leiden group has recently shown that the elevation of some coagulation factors level could also constitute a risk factor for deep venous thrombosis.

CURRENT KNOWLEDGE AND KEY POINTS

Elevation of factor VIIIc is associated with a higher risk for thrombosis than in the general population but the threshold for normality of this factor is difficult to define. It is a probable constitutional abnormality whose prevalence in the general population vary from 6 to 36%. Risks of deep venous thrombosis associated to this factor elevation is more elevated in patients who have this anomaly (odds ratios vary from 2,2 to 10,3) (95% CI).

FUTURE AND PROJECTS

The frequency of this anomaly and its association with a high risk for thrombosis are reasons to assess the potential usefulness of screening for these anomalies in patients who had thrombosis or in their family. The probable genetic origin of these anomalies has to be confirmed by other studies.

Hormone therapy and venous thromboembolism

Convincing data from randomized trials and observational studies have demonstrated a two- to threefold increased risk of venous thromboembolism (VTE) with the use of hormone replacement therapy (HRT) in post-menopausal women. This risk is highest in the first year of use, but an increased risk persists after the first year if HRT use is ongoing. The risk of VTE is increased for oral oestrogen alone, oral oestrogen combined with progestin and probably for transdermal HRT. There is an increase in both idiopathic and non-idiopathic VTE with HRT. Early evidence suggests an interaction of HRT with thrombophilic states such as the factor V Leiden mutation, resulting in a synergistic increase in the risk of VTE. There is also an increased risk of VTE with raloxifene and tamoxifen, but the effects of low-dose HRT and tibolone on VTE risk are less clear.

A prospective study of venous thromboembolism in relation to factor V Leiden and related factors

The aim of this study was to examine the occurrence of venous thromboembolism (VTE) in relation to factor V-related risk factors. Using a nested case-control design combining 2 population-based prospective studies, we measured factor V Leiden, HR2 haplotype, activated protein C (APC) resistance, and plasma factor V antigen in 335 participants who developed VTE during 8 years of follow-up and 688 controls. The overall odds ratio (OR) of VTE was 3.67 (95% CI, 2.20-6.12) in participants carrying factor V Leiden compared with noncarriers. APC resistance measured after predilution with factor V-deficient plasma conferred an OR of 2.58 (95% CI, 1.62-4.10). All 3 participants homozygous for the HR2 haplotype had a VTE, and the OR of VTE for homozygosity was estimated to be 5.5 (95% CI, 2.45-12.5). Carriers of the HR2 haplotype otherwise were not at increased risk of VTE overall (OR = 1.05; 95% CI, 0.64-1.72), but double heterozygotes for HR2 and factor V Leiden carried an OR of idiopathic VTE of 16.3 (95% CI, 1.7-159) compared with noncarriers. Factor V antigen also was not associated with VTE overall, but for participants with the combination of high factor V antigen plus factor V Leiden the OR of idiopathic VTE was 11.5 (95% CI, 4.2-31.4). In the general population, APC resistance and factor V Leiden were important VTE risk factors; homozygosity for the HR2 haplotype may be a risk factor but was rare; otherwise, HR2 haplotype and factor V antigen were not risk factors except in carriers of factor V Leiden.

Genetic polymorphisms associated with venous and arterial thrombosis: an overview

OBJECTIVE

To provide an overview of genetic polymorphisms associated with thrombotic cardiovascular disease.

DATA SOURCES

A literature search using the National Library of Medicine database.

STUDY SELECTION

The literature on genetic polymorphisms associated with venous and arterial thrombosis was reviewed.

DATA EXTRACTION

Based on the literature review, the clinical significance of polymorphisms in various coagulation proteins was assessed and a summary was developed.

CONCLUSIONS

Thrombosis is a multifactorial disorder, with both congenital and acquired risk factors. It is now clear that there are many genetic abnormalities that impart an increased risk for thrombophilia, and the presence of more than 1 abnormality results in a further increased risk of thrombosis. In hemostasis, there is a balance between procoagulant factors and natural anticoagulant proteins. The first genetic thrombotic disorders described were deficiencies of the natural anticoagulants, such as antithrombin, protein C, and protein S, but these abnormalities are rare and are caused by many different mutations. More recently, single polymorphisms that are relatively common in the general population have been described in procoagulant factors, such as factor V and prothrombin, which impart an increased risk for venous thrombosis. As more scrutiny is placed on the hemostatic system, further polymorphisms have come to light. The current challenge is to elucidate the relationship between these new polymorphisms and either venous or arterial thrombotic cardiovascular disease.

The mechanisms of thrombotic risk induced by hormone replacement therapy

OBJECTIVES

To review the available information on the action of hormones on the mechanisms involved in thrombotic risk.

RESULTS AND CONCLUSIONS

Thrombosis plays a crucial role in the genesis and progression of both coronary heart disease (CHD) and venous thromboembolic disease (VTED), the two main forms of cardiovascular disease. Two main determinants of the thromboembolic phenotype, hypercoagulable state and altered endothelium, accumulate much of the work performed on the influence of hormones on thrombosis. Information has accumulated mainly for oestrogens, but increasing evidences support a role for progestogens. The sensitivity of each of the three components of the hemostatic balance, the coagulation cascade, the anticoagulant system and fibrinolysis, to oestrogens has been widely examined in the literature. Functional tests suggest that HRT is accompanied by a procoagulant state. Much of the work has concentrated on changes induced on reputable indicators of risk for either CHD or VTED. Distinct indicators of increased coagulability, such as resistance to activated C protein, antithrombin or tissue factor pathway inhibitor have been selected for VTED, whereas factor VII, fibrinogen, and defective fibrinolysis, for CHD. Different states of genetic susceptibility have been involved in both forms of the disease. The status of health of endothelium, defines another scenario for attention in CHD. A long-term anti-atherogenic action of oestrogens, which may be associated with short-term risk in cases of atherosclerosis-induced endothelial dysfunction, may most adequately explain much of the clinical observation. In both CHD and VTED, the procoagulant changes initiate soon after HRT administration.

Which antiphospholipid antibody tests are most useful?

Despite an active international effort to improve diagnosis and treatment of the antiphospholipid syndrome (Hughes syndrome), there remain problems of lack of standardization and lack of prospective and multivariate epidemiologic analysis which restrict the diagnostic and predictive ability of commercially available tests. Nevertheless, current published series provide some data from which strategic approaches can be used to maximize the efficiency and usefulness of available tests. For further updates on new research and developments of interest to physicians and patients with this syndrome, the following web sites may prove helpful: www.slrapls.org, www.hematology.org, www.acforum.org, www.americanheart.org, www.rarediseases.org, www.aarda.org, and www.lupus.org.

Oral contraceptive pills and hormonal replacement therapy and thromboembolic disease

The risk of thromboembolic complications with the use of second and third generation oral contraceptives is minimal and probably related to underlying congenital or acquired thrombophilic states. Estrogen dose-dependency leads to increased thrombin generation and increased plasmin generation. There is no convincing evidence that the balance between clotting and fibrinolysis is disturbed. The risk of venous thromboembolism with pregnancy is greater than with oral contraceptives. Hormone replacement therapy is safe for healthy women, and the benefits far outweigh the potential risks.