Inherited Thrombophilia

Laboratory Evaluation of Antithrombin, Protein C, and Protein S

Thrombophilia is a complex disease process, clinically manifesting in various forms of venous thromboembolism. Although both genetic and acquired (or environmental) risks factors have been reported, the presence of a genetic defect (antithrombin [AT], protein C [PC], protein S [PS]) is considered three of the major contributing factors of thrombophilia. The presence of each of these risk factors can be established by clinical laboratory analysis; however, the clinical provider and laboratory personnel must understand the testing limitations and shortcomings associated with the assays for these factors to be able to ensure an accurate diagnosis. This article will describe the major pre-analytical, analytical, and post-analytical issues associated with the various types of assays and discuss evidence-based algorithms for analyzing AT, PC, and PS in plasma.

Laboratory Evaluation of Thrombophilia

Venous thromboembolism (VTE) occurs typically in the veins of the lower extremities and/or as pulmonary embolism. There is a myriad of causes of VTE ranging from provoked causes (e.g., surgery, cancer) to unprovoked causes (e.g., inherited abnormalities) or multiple factors that combine to initiate the cause. Thrombophilia is a complex, multi-factorial disease that may result in VTE. The mechanism(s) and causes of thrombophilia are complex and not completely understood. In healthcare today, only some answers about the pathophysiology, diagnosis, and prevention of thrombophilia have been elucidated. The laboratory analysis for thrombophilia is not consistently applied, and has changed over time, but remains varied by providers and laboratories as well. Both groups must establish harmonized guidelines for patient selection and appropriate conditions for analysis of inherited and acquired risk factors. This chapter discusses the pathophysiology of thrombophilia, and evidence-based medicine guidelines discuss the optimum laboratory testing algorithms and protocols for selection and analyzing VTE patients to ensure a cost-effective use of limited resources.

Lead thrombus under standard-dose edoxaban in a patient with normal to high creatinine clearance and protein S deficiency

BACKGROUND

Non-vitamin K antagonist oral anticoagulants (NOACs) are as effective and safe as warfarin for thromboembolic prevention and treatment. The efficacy of NOACs lacks evidence from large and randomized studies in patients with inherited severe thrombophilia, including protein S deficiency. Further, some concerns still exist regarding the relative efficacy of edoxaban in preventing arterial thromboembolism in patients with normal to high creatinine clearance (CrCl). We present a case of a rare complication of lead thrombus under standard-dose edoxaban in a patient with protein S deficiency and supernormal renal function.

CASE PRESENTATION

A 65-year-old man experienced persistent chest tightness and a high level of D-dimer. Chest computed tomography (CT) showed a lead thrombus at the superior vena cava. He had a medical history including, paroxysmal atrial fibrillation (PAf), sick sinus syndrome after permanent pacemaker implantation, and transient ischemic attack. He received standard-dose edoxaban (60 mg daily) after PAf was diagnosed. His estimated CrCl was 98.6-102.1 mL/min. However, protein S deficiency (22.8%; normal range: 55-130%) was diagnosed. After switching to dabigatran (150 mg twice daily) for 3 months, the chest CT showed lead thrombus resolution and no symptoms were seen during the follow-up period.

CONCLUSIONS

This case was a rare complication of lead thrombus in a protein S deficient patient with normal renal function receiving standard-dose edoxaban. Edoxaban efficacy is uncertain in patients with protein S deficiency, and intracardiac devices also increase the risk of thromboembolic events.

Treatment and secondary prophylaxis of venous thromboembolism with direct oral anticoagulants in patients with severe hereditary thrombophilia

Deficiency of protein C (PC), protein S (PS), antithrombin III (AT III), and homozygosity or combined heterozygosity for Factor V Leiden (FVL) and Factor II (FII) 20210A mutation represent severe hereditary thrombophilia (SHT) and are associated with a higher risk of early-onset venous thromboembolism (VTE). In literature, few papers have described the efficacy and safety of therapy with direct oral anticoagulants (DOACs) in VTE occurring in patients with SHT. In our setting, we identified 8 patients who have suffered from early-onset VTE and underwent therapy with DOACs (6 rivaroxaban, 2 apixaban). Among them, 2 AT III deficiency, 2 PC deficiency, 3 PS deficiency, 1 combined heterozygosity for FVL, and FII 20210A were detected. During the follow-up, neither recurrences of VTE nor hemorrhagic episodes were observed. This report describes the efficacy and safety of therapy with anti-Xa in the treatment and secondary prophylaxis of VTE in patients with SHT.

Patent Foramen Ovale Closure among Patients with Hypercoagulable States Maintained on Antithrombotic Therapy

BACKGROUND

Percutaneous device closure was shown to effectively prevent recurrent strokes in patients with patent foramen ovale (PFO). Whether this protective effect is relevant for patients with hypercoagulable states (HCSs) is unknown as they were not represented in prior studies.

METHODS

Data on 136 consecutive patients with a PFO and clinically significant HCS were retrospectively collected. PFO closure and antithrombotic regimen were decided on an individual basis by the treating physicians, and adherence to therapy was routinely evaluated. The outcome was the occurrence of cerebrovascular accident (CVA) or transient ischemic attack (TIA).

RESULTS

HCS types consisted of antiphospholipid syndrome (31%), factor-5 Leiden mutation (22%), prothrombin mutation (18%), protein S deficiency (15%), protein C deficiency (7%), methyl-tetra-hydro folate reductase mutation (5%), and essential thrombocytosis (2%). 102 patients (75%) were maintained on anticoagulants and the remaining on antiplatelet therapy. PFO closure was undertaken in 85 (63%); antithrombotic therapy was not interrupted prior to or after the procedures. At a mean follow-up of 46 ± 8 months, 23 patients (17%; 95% confidence interval, 9.3-22%) experienced an outcome event, mainly in the form of CVAs (n = 15, 65%). In multivariable analysis, PFO closure was associated with a 5-fold decrease in the risk of CVA/TIA (p = 0.02). This effect was independent of the type of HCS or antithrombotic therapy.

CONCLUSIONS

Among patients with HCSs maintained on anticoagulant or antiplatelet therapies, PFO closure was associated with a significantly lower risk of CVA or TIA.

Direct oral anticoagulants in patients with severe inherited thrombophilia: a single-center cohort study

We investigated the safety and efficacy of direct oral anticoagulants (DOACs) in patients with venous thromboembolism (VTE) associated with severe inherited thrombophilia. In this single-center cohort study, we enrolled 56 consecutive VTE patients with severe inherited thrombophilia, defined as the presence of antithrombin (n = 18), protein C (n = 12) and protein S (n = 12) deficiencies, homozygous Factor V Leiden (n = 3) and prothrombin G20210AA (n = 4) mutations, or combined defects (n = 7). During a median follow-up of 44.5 (IQR 30-52.5) months, rivaroxaban was used in 30 (53.6%), apixabanin 14 (25%), and dabigatran in 12 (21.4%) subjects. Recurrent nonfatal VTE was observed in 5 (8.9%) patients (2.4 per 100 patient-years), treated with rivaroxaban (n = 4) and apixaban (n = 1). Major bleeding and clinically relevant non-major bleeding (CRNMB) occurred in 2 (3.5%) and 4 (7%) subjects, respectively (0.96 per 100 patient-years and 1.92 per 100 patient-years, respectively), including 4 patients on rivaroxaban. The event-free survival analysis showed that the use of rivaroxaban was associated with increased risk of recurrent VTE or bleeding, compared with apixaban or dabigatran (HR 2.76, 95% CI 1.26-3.92, p = 0.039). In conclusion, the results of our cohort study indicate that full-dose dabigatran or apixaban are effective and safe in patients with severe inherited thrombophilia.

Clinical Utilization and Cost of Thrombophilia Testing in Patients with Venous Thromboembolism

Introduction  Testing for inherited and acquired thrombophilias adds to the cost of care of patients with venous thromboembolism (VTE), though results may not influence patient management.

Methods  This is a single-center, retrospective study conducted at Emory University Hospitals from January to December 2015 to (1) determine the pattern of thrombophilia testing in patients with VTE, (2) study the impact of results of thrombophilia testing on clinical decision-making, and (3) determine the direct costs of thrombophilia testing in patients with VTE.

Results  Of the 266 eligible patients, 189 (71%) underwent testing; 51 (26.9%) tested positive and the results impacted management in 32 (16.9%) of tested patients. Patient undergoing testing were more likely to be younger than 40 years (30.9 vs. 18.2%), have had prior pregnancy loss (9.0 vs. 0%), or known family history of hypercoagulability (24.9 vs. 10.4%), and were less likely to have had provoked VTE (37 vs. 79.2%). The most common thrombophilias tested were antiphospholipid syndrome (60.1%), factor V Leiden (59.7%), and prothrombin gene mutation (57.5%). Direct costs of thrombophilia testing were $2,364.32 per patient, $12,331.55 to diagnose 1 positive, and $19,653.41 per patient-management affected.

Conclusion  We noted significant variability in selection of patients and panel of tests, sparse utilization of test results in patient management, but high cost associated with thrombophilia testing in patients with VTE. With guidelines advocating selective use of thrombophilia testing and attention to potential impact of test results in patient management, we propose the need for measures at institutional levels to improve test-ordering practices.

Direct oral anticoagulants in patients with venous thromboembolism and thrombophilia: a systematic review and meta-analysis

Essentials We investigated direct oral anticoagulant (DOAC) use in venous thromboembolism and thrombophilia. A comprehensive search identified 10 studies, 8 of which were included in a meta-analysis. DOACs were overall safe and effective in patients with venous thromboembolism and thrombophilia. Efficacy/safety of DOACs was maintained in low-risk antiphospholipid syndrome patient subgroup. SUMMARY: Background Direct oral anticoagulants (DOACs) are increasingly used in acute and long-term treatment of venous thromboembolism (VTE). However, their role in management of thrombophilia-associated VTE is controversial. Methods Through a comprehensive search on MEDLINE, Cochrane Library, and Clinicaltrials.gov, we identified 10 eligible studies, 8 of which reporting data on 1994 thrombophilia patients were included in a random-effects meta-analysis. Eligible studies were phase 2 to 3 randomized controlled trials comparing DOACs to vitamin K antagonists (VKAs) in patients with VTE, including those with thrombophilia. Results Of eight studies included in meta-analysis, four evaluated rivaroxaban, three dabigatran, and one edoxaban. No results could be obtained on apixaban use. The rates of VTE recurrence (RR, 0.70; 95% CI, 0.34-1.44; I2  = 0%) and major/clinically relevant non-major bleeding events (RR, 0.92; 95% CI, 0.62-1.36; I2  = 23%) were similar between thrombophilia patients treated with DOACs compared to VKAs. Results were comparable to findings in patients without known thrombophilia: RR, 1.02; 95% CI, 0.80-1.30; I2  = 46% for VTE recurrence and RR, 0.72; 95% CI, 0.57-0.90; I2  = 84% for major/clinically relevant non-major bleeding events. Conclusions Rates of VTE recurrence and bleeding events were both low and comparable in patients with various thrombophilias receiving either treatment, suggesting that DOACs are an appropriate treatment option in this population. Due to limited data, it is unclear whether these findings apply to specific subgroups such as high-risk antiphospholipid syndrome, uncommon thrombophilias, or the use of apixaban.

Rare thrombophilic conditions

Thrombophilia, either acquired or inherited, can be defined as a predisposition to developing thromboembolic complications. Since the discovery of antithrombin deficiency in the 1965, many other conditions have been described so far, which have then allowed to currently detect an inherited or acquired predisposition in approximately 60-70% of patients with thromboembolic disorders. These prothrombotic risk factors mainly include qualitative or quantitative defects of endogenous coagulation factor inhibitors, increased concentration or function of clotting proteins, defects in the fibrinolytic system, impaired platelet function, and hyperhomocysteinemia. In this review article, we aim to provide an overview on epidemiologic, clinic and laboratory aspects of both acquired and inherited rare thrombophilic risk factors, especially including dysfibrinogenemia, heparin cofactor II, thrombomodulin, lipoprotein(a), sticky platelet syndrome, plasminogen activator inhibitor-1 apolipoprotein E, tissue factor pathway inhibitor, paroxysmal nocturnal haemoglobinuria and heparin-induced thrombocytopenia.

Classic thrombophilic gene variants

Thrombophilia is defined as a condition predisposing to the development of venous thromboembolism (VTE) on the basis of a hypercoagu-lable state. Over the past decades, great advances in the pathogenesis of VTE have been made and nowadays it is well established that a thrombophilic state may be associated with acquired and/or inherited factors. The rare loss-of-function mutations of the genes encoding natural anticoagulant proteins (i. e. protein C, protein S and antithrombin) and the more common gain-of-function polymorphisms factor V Leiden and prothrombin G20210A are the main genetic determinants of thrombophilia. In addition, non-O blood group has been consistently demonstrated to be the most frequent inherited marker of an increased risk of VTE. The mechanism role of these inherited thrombophilia markers will be discussed in this narrative review.

Uncertain thrombophilia markers

The development of venous thromboembolism (VTE), which includes deep-vein thrombosis and pulmonary embolism, may be associated with inherited or acquired risk factors that can be measured in plasma or DNA testing. The main inherited thrombophilias include the plasma deficiencies of the natural anticoagulants antithrombin, protein C and S; the gain-of-function mutations factor V Leiden and prothrombin G20210A; some dysfibrinogenaemias and high plasma levels of coagulation factor VIII. Besides these established biomarkers, which usually represent the first-level laboratory tests for thrombophilia screening, a number of additional abnormalities have been less consistently associated with an increased VTE risk. These uncertain causes of thrombophilias will be discussed in this narrative review, focusing on their clinical impact and the underlying pathogenetic mechanisms. Currently, there is insufficient ground to recommend their inclusion within the framework of conventional thrombophilia testing.

Impact of Prothrombotic Risk Factors in a Cohort of Egyptian Hemophilia A Patients

INTRODUCTION

Hemophilias are a group of related bleeding disorders that show an X-linked pattern of inheritance. The clinical phenotype of severe hemophilia may vary markedly among patients as a result of many factors, including genetic prothrombotic risk factors.

OBJECTIVES

Our objective was to study the incidence of the most common prothrombotic risk factors for additive effects among Egyptian patients with hemophilia A and their impact on clinical phenotype; annual bleeding frequency and severity of hemophilic arthropathy, as well as the effect of a single variation in these patients.

METHODS

This study was carried out in 100 patients with hemophilia A. Genotyping for factor V Leiden (FVL) G1691A, prothrombin G20210A, MTHFR C677T, and A1298C mutations was conducted using a real time-polymerase chain reaction (RT-PCR) assay.

RESULTS

Our study revealed mutations in hemophilia patients as follows: prothrombin G20210A (3 %), FVL (14 %), MTHFR C677T (42 %), and A1298C (59 %). Despite a lack of statistical significance when each gene was analysed separately, heterozygosity of prothrombin G20210A or FVL was always associated with either a mild or moderate, but never a severe, clinical presentation. The lowest bleeding frequency (less than once per month) was identified among patients with two heterozygous variants irrespective of the involved genes. In addition, the incidence of hemarthrosis was significantly higher among patients with a wild genotype of the prothrombin gene and FVL, and the average number of affected joints was significantly higher among patients with wild-type prothrombin and FVL genes than among heterozygous patients.

CONCLUSION

These prothrombotic mutations have a cumulative effect in amelioration of the severity of bleeding in hemophiliacs. The most prominent effect is that of prothrombin G20210A and FVL, while MTHFR C677A and A1298C gene mutations are less conclusive.

Lipoprotein apheresis for the treatment of elevated circulating levels of lipoprotein(a): a critical literature review

Lipoprotein(a), which consists of a low-density lipoprotein (LDL) particle linked to an apolipoprotein(a) moiety, is currently considered an independent risk factor for cardiovascular disease due to its atherogenic (LDL-like) and prothrombotic (plasminogen-like) properties. The aim of this review is to provide an overview of the current and newer therapies for lowering increased lipoprotein(a) levels, focusing on lipoprotein apheresis. After a systematic literature search, we identified ten studies which, overall, documented that lipoprotein apheresis is effective in reducing increased lipoprotein(a) levels and cardiovascular events.

Alcohol consumption and venous thromboembolism: friend or foe?

A light to moderate consumption of certain types of alcoholic beverages may exert a favorable effect on cardiovascular risk, but no conclusive information is available on the putative relationship between alcohol intake and the risk of venous thromboembolism (VTE). We performed an electronic search on Medline and Scopus, using the keywords "venous thromboembolism", "venous thrombosis" and "alcohol", to identify clinical studies linking alcohol intake and VTE risk. The literature search generated 16 studies, 4 of which are case-control, 1 cross-sectional and 11 prospective. Significant reduction of VTE associated with alcohol intake is observed in only 4/16 studies, and in all these the association is only meaningful for a moderate amount of alcohol (i.e., 2-4 glasses). Unlike these trials, two other studies observe that alcohol intake is associated with an increased risk of VTE, whereas the association is insignificant in the remainder. Binge drinking increases the VTE risk in one study but not in another. The consumption of beer is associated with a decreased VTE risk in one study but not in two others. We hence conclude that the relationship between intake of alcoholic beverages and increased or decreased risk of VTE is largely elusive.

MicroRNAs in hemostasis

Epidemiologic studies have revealed that modification of the levels of individual components of the hemostatic system may have effects on the development of thrombosis or hemorrhage. To maintain the necessary equilibrium, the hemostatic system is finely regulated. It is known that acquired factors and/or alterations in genes (single-nucleotide polymorphisms or mutations) may be the cause of interindividual differences or exacerbated levels of hemostatic proteins in plasma, but there are still many non-characterized factors that provoke such variations. The search for new elements, such as microRNAs (miRNAs), a family of small non-coding RNAs that are novel regulators of protein expression, may reveal an additional layer at which to investigate the causes of hemostatic diseases. In this review, we discuss the latest developments in research into the role of miRNAs in the regulation of several hemostatic factors, and the potential use of miRNAs as prognostic or diagnostic tools in hemostasis and thrombosis.

Upper extremity deep vein thrombosis presenting to a chiropractic clinic: a description of 2 cases

OBJECTIVE

The purpose of this case series is to describe the presentation of 2 patients who presented to a chiropractic teaching clinic with Paget-Schroetter syndrome (PSS) and to discuss the potential role for conservative therapy in the management of symptoms.

CLINICAL FEATURES

Two patients presented with a vascular and muscular findings suggesting activity-related upper extremity deep vein thrombosis. One patient presented with recent onset of symptoms (pain in the neck with a "pinched nerve sensation" in the left upper trapezius); and the other presented with chronic, low-grade neck pain of 1 year's duration.

INTERVENTION AND OUTCOME

The initial treatment approach for the patient with acute symptoms included soft tissue therapy. During the second appointment, he was immediately referred for medical evaluation and management because of worsening symptoms. He was diagnosed with thrombus in the left brachial vein, started immediately on a thrombolytic agent, and referred to a thrombosis clinic. Treatment for the second patient with chronic symptoms included soft tissue therapy, spinal manipulative therapy, and active care. Two months after 3 treatments, she reported improved symptoms. She remains under supportive care and has reported continued relief of her symptoms.

CONCLUSION

Although a rare condition, PSS has the potential to result in significant morbidity and potentially fatal complications; thus, it is critical that practitioners recognize the signs and symptoms to facilitate appropriate and timely referrals. Clinicians should be aware of the presentation and proposed pathogenesis of PSS, and consider this diagnosis in patients with unilateral upper limb and/or neck pain.

C677T methylenetetrahydrofolate reductase gene polymorphism as a risk factor involved in venous thromboembolism: a population-based case-control study

The aim of the current study was to investigate the possible correlation between the C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism and venous thromboembolism (VTE) in a population-based case-control study. Homocysteine (Hcy) was quantified by Abbott IMx immunoassay; screening for C677T MTHFR substitution was performed by polymerase chain reaction (PCR) and restriction analysis. The results from the two groups (440 patients and 440 controls) revealed that the frequency of T alleles and TT carriers was significantly higher in patients compared with that of the healthy controls. The plasma levels of Hcy in the VTE group (13.05±2.37 µmol/l) were significantly higher compared with those in the control group (11.94±2.03 µmol/l, P<0.001). The C677T MTHFR polymorphism is suggested to be associated with the risk for VTE. Plasma levels of Hcy were raised in individuals with the homozygous MTHFR 677TT genotype. In conclusion, the results of the current study suggest that hyperhomocysteinemia and the homozygous 677TT MTHFR genotype are risk factors for VTE.

Sclerotherapy of varicose veins in patients with documented thrombophilia: a prospective controlled randomized study of 105 cases

Objectives

The aim of this study was to assess thrombotic complications following sclerotherapy in thrombophilic patients in combination with thromboprophylaxis, in two randomized arms using low molecular weight heparin (LMWH) or warfarin.

Patients and methods

This study received approval from the Ethics Committee. A total of 105 patients (81 females, 24 males) ranging in age from 20 to 82 years (mean 50) were selected: 75 with Factor V Leiden mutation, 18 with prothrombin 20210A mutation, 7 with high level of Factor VIII, 5 combinations of these. After randomization, 51 and 54 patients received warfarin and LMWH, respectively. A total of 199 sclerotherapy sessions were performed. Foam was used in 160 treatments.

Results

No episodes of symptomatic deep vein thrombosis (DVT) or pulmonary embolism (PE) occurred; no instances of DVT were revealed by ultrasound-monitoring.

Conclusions

This study suggests that in the three most common forms of thrombophilia, sclerotherapy, in combination with thromboprophylaxis, can be performed safely. Prophylaxis with LMWH is easier to use than warfarin.

JAK2V617F and prothrombin G20210A gene mutations in a patient with Budd-Chiari syndrome and essential thrombocythemia

Myeloproliferative disorders and the inherited thrombophilias have been described as the main causes underlying the Budd-Chiari syndrome. Moreover, the presence of the JAK2V617F was associated with a higher frequency of Budd-Chiari syndrome in patients who have overt or even latent myeloproliferative disorder. We herein describe a 28-year-old woman who was diagnosed with Budd-Chiari syndrome and later developed an overt myeloproliferative disorder. The patient was found to carry both the JAK2V617F and the prothrombin G20210A mutation in the heterozygous form. The significance of the chronology of diagnosis is highlighted.

[Thrombophilias and peripheral arterial occlusive disease]

Peripheral arterial occlusive disease is a frequent disease due to the classical vascular risk factors such as smoking, diabetes mellitus, dyslipidemia, and hypertension. Despite these risk factors, many thrombophilias (physiological inhibitors defects, Factor V Leiden and 20210A prothrombin gene variant, antiphospholipid antibodies, mild hyperhomocysteinemia 15-30micromol/l) can be evoked in some clinical forms of peripheral arterial occlusive disease. This paper provides a synthesis of the published data about this topic. Screening for these thrombophilias is justified in patients with venous thromboembolic disease, or signs of antiphospholipid syndrome and possibly in different situations such as premature atheroma of lower limbs, chronic ischaemia, evolutive disease despite adapted treatment and revascularisation failures without evident technical explanation. Except for the antiphospholipid syndrome, there is currently no consensus for systematic screening of thrombophilia and treatment in patients with peripheral arterial occlusive disease.

The hemostatic balance revisited through the lessons of mankind evolution

Under physiologic conditions, a hemostatic balance is achieved through the effects of natural procoagulant and anticoagulant factors which, in equilibrium with each other, provide hemostasis at the sites of vascular injury. Abnormalities of these hemostasis factors can result in a tendency toward hemorrhagic or thrombotic events. In this review the influence of inherited prothrombotic risk factors--especially the more frequent factor V Leiden and prothrombin gene mutations--on normal and abnormal hemostasis is analyzed from an evolutionary point of view. The effect of inherited bleeding disorders on the development of thrombotic or atherosclerotic processes is also discussed.

Clinical evaluation of a functional prothrombin time-based assay for identification of factor V Leiden carriers in a group of Italian patients with venous thrombosis

The efficiency of a new prothrombin-based activated protein C (APC) resistance test to detect factor V Leiden (FVL) was clinically evaluated in 150 Italian patients with deep venous thrombosis. Patient samples are diluted in factor-V-deficient plasma, an APC-containing reagent, and specific factor V activator; after incubation, clotting is initiated by addition of activated-factor-FV-dependent prothrombin activator. Two prothrombin time determinations were performed under identical assay conditions except that no APC was added to one. A ratio over 4.2 for normal individuals and under 2.0 for FVL patients is expected: between 1.3 and 1.9 for FVL heterozygotes, and between 1.0 and 1.1 for FVL homozygotes. Using a predefined cut-off ratio of 2.0, a specificity and a sensitivity of 1.00 for detection of FVL mutation were found. With a cut-off ratio of 1.1, a specificity of 0.98 and a sensitivity of 1.00 were found for discrimination between FVL heterozygous (n = 60) and homozygous (n = 6). No interferences by heparins, oral contraceptives, oral anticoagulant therapy, protein C, protein S, D-dimer, homocysteine, MTHFR mutations and antiphospholipid autoantibodies were detected. In our experience, this new prothrombin time-based APC resistance assay provides improved discrimination between normal individuals and FVL carriers compared with the classical methods. Moreover, this new assay allows good discrimination between homozygous and heterozygous FVL carriers. In the authors' experience this prothrombin time-based method was not influenced by many factors compared with the classical activated partial thromboplastin time-based method.

Hereditary and acquired antithrombin deficiency: epidemiology, pathogenesis and treatment options

Antithrombin is a glycoprotein critical to the regulation of coagulation. Its primary action is the inhibition of the activated coagulation factors IIa (thrombin) and Xa. In addition there is growing evidence to suggest that antithrombin also plays a role in the inhibition of inflammation within the environment of the vascular endothelium. Reduced plasma antithrombin may result from congenital deficiency or arise secondarily from a range of disorders such as liver dysfunction, premature infancy and sepsis, or as a result of interventions such as major surgery or cardiopulmonary bypass. Congenital antithrombin deficiency is the most clinically important of the inherited thrombophilias resulting in thrombosis in the majority of those affected. The challenge in managing these patients is preventing potentially life-threatening thrombosis, while minimising the equally significant risk of haemorrhage associated with long-term anticoagulation. This is achieved in the first instance by identifying high-risk episodes such as surgery, immobility and pregnancy for which prophylactic anticoagulation can be used in the short term. Prophylaxis for such periods is best provided by the use of low molecular weight heparin (LMWH) with substitution by or addition of antithrombin concentrate in particularly high-risk circumstances. In the case of pregnancy, antithrombin concentrate is often used around the time of birth when LMWH may increase the risk of post-partum haemorrhage. As patients with congenital antithrombin deficiency get older so their thrombotic risk gradually increases and for many patients long-term anticoagulation becomes unavoidable because of recurrent episodes of venous thromboembolism. There has been much interest in the role of antithrombin deficiency in the setting of sepsis and the critically ill patient where there is a clear correlation between severity of illness and degree of antithrombin reduction. It is not clear yet, however, to what extent the depletion of antithrombin affects the clinical condition of such patients. A number of trials have investigated the use of antithrombin as a treatment in the intensive care setting with the overall conclusion being that there is some benefit to its use but only if large supra-physiological doses are used. It has also become clear that the concurrent use of any form of heparin removes whatever benefit may be derived from antithrombin treatment in this setting. Until recently, antithrombin replacement was only available as a pooled plasma-derived product, which despite effective viral inactivation still carries an uncertain risk of transfusion transmitted infection. A recombinant antithrombin product now under investigation, and recently licensed in Europe, may provide a useful alternative treatment option.

Lipoprotein[a] and cancer: Anti-neoplastic effect besides its cardiovascular potency

While the death rate from cancer has substantially decreased over the past decade, the search for effective and tolerable therapies is a great challenge as yet. The evidence that malignant cells cannot grow to a clinically detectable tumor mass and spread in the absence of an adequate vascular support, has opened a new area of research towards the selective inhibition or even destruction of tumor vessels. Angiostatin and angiostatin-related proteins are a family of specific angiogenesis inhibitors produced by tumors from a family of naturally occurring proteins, which also includes plasminogen and lipoprotein[a]. The anti-angiogenic activity of these proteins resides in cryptic and highly-repetitive molecular domains hidden within the protein moiety, called kringles. Lipoprotein[a] is an intriguing molecule consisting of a low-density lipoprotein core in addition to the covalently bound apolipoprotein[a]. Apolipoprotein[a] is characterized by an inactive protease domain, a single copy of the plasminogen kringle V and multiple repeats of domains homologous to the plasminogen kringle IV. Reliable studies on animal models indicate that the proteolytic break-down products of apolipoprotein[a] would posses anti-angiogenic and anti-tumoral properties both in vitro and in vivo, a premise to develop novel therapeutic modalities which may efficiently suppress tumor growth and metastasis. This review is focused on the biochemical structure, metabolism and the anti-angiogenic activity of this unique and elusive kringle-containing lipoprotein.

Higher morning serum cortisol level predicts increased fibrinogen but not shortened APTT

BACKGROUND

There is emerging evidence that serum cortisol might be independently associated with prothrombotic activity, suggesting that increased cortisol levels might finally contribute to the pathogenesis of atherosclerotic disorders. Since hypercoagulability is principally sustained by either defective naturally occurring anticoagulant mechanisms or to heightened coagulation factors, most of which are cumulatively explored by the activated partial thromboplastin time (APTT), the present investigation was designed to asses the potential relationship between morning serum cortisol, APTT and fibrinogen in a general population of healthy outpatients.

METHODS

We performed a retrospective analysis on the database of our Laboratory Information System to retrieve results of morning serum cortisol, APTT and fibrinogen, which were performed on consecutive outpatients referred by general practitioners for routine blood testing over the previous 2 years.

RESULTS

Cumulative results for morning serum cortisol, APTT and fibrinogen were retrieved for 302 adults >35 years old (M/F = 61/90; age 49 +/- 13 years; range 35-79). A statistically significant increased concentration of fibrinogen was observed in subject with morning serum cortisol values above the upper limit of the reference range (P < 0.001), whereas the concentration of APTT was not significantly different between the two subgroups of subjects with normal and increased morning serum cortisol (P = 0.432). This difference remained statistically significant even after adjusting for age and sex. In multivariable linear regression analysis, the concentration of fibrinogen, but not the value of the APTT, was significantly associated with morning serum cortisol.

CONCLUSIONS

The results of this retrospective investigation confirm that baseline cortisol levels might predict higher fibrinogen in the general population. This potential biological interrelationship deserves further scrutiny for the potential implications on prediction and prevention of the cardiovascular risk.

Protein Z/Z-dependent protease inhibitor (PZ/ZPI) anticoagulant system and thrombosis

A new anticoagulant system involving a serpin has been recently characterised. The protein Z/Z-dependent protease inhibitor (PZ/ZPI) system inhibits activated factors X, XI and IX by different mechanisms. By homology with other anticoagulant systems (antithrombin or the protein C/protein S), deficiency of the serpin (ZPI) or its cofactor (PZ) might imbalance the haemostatic system with thrombotic consequences. Evidence supports the in vivo anticoagulant role of this complex and the thrombotic consequences of its deficiency. Non-sense variations of the ZPI (W303X and R67X) have been associated with increased risk of venous thrombosis. Moreover, PZ deficient mice carrying the FV Leiden have a thrombotic phenotype. Finally, some reports suggest that PZ deficiency might increase the risk of thrombosis. However, other studies question the thrombotic relevance of both ZPI and PZ deficiencies. This system could play a redundant role in haemostasis that explains the conflicting results on its thrombotic potential, which might be exacerbated in combination with other prothrombotic factors.