Genetic susceptibility to venous thrombosis

Recurrent deep-vein thrombosis based on homozygous factor V Leiden mutation acquired after liver transplantation

Several genetic liver diseases can be treated by liver transplantation (LT). However, some genetic defects also may be acquired by this procedure. We describe a patient who developed recurrent deep-vein thromboses after LT for hepatitis C virus-associated hepatocellular carcinoma on the basis of a homozygous Leiden mutation of the factor V gene in the donor liver. Liver donors with a history of venous thrombosis should be screened for the presence of activated protein C (APC) resistance. In addition, we recommend looking for APC resistance in liver recipients who develop venous thromboembolic disease in the post-LT course. Molecular analysis of donor tissue may be necessary to make a definite diagnosis of factor V Leiden mutation in these patients. As a consequence, intensified postoperative thromboprophylaxis or lifelong anticoagulant therapy may be necessary if this thrombophilic gene defect is detected.

Sirolimus does not increase the risk for postoperative thromboembolic events among renal transplant recipients

BACKGROUND

Deep venous thrombosis (DVT) tends to occur in greater frequency among cyclosporine (CsA)-treated renal-transplant recipients. Because administration of sirolimus may increase the whole-blood concentrations of CsA, we sought to assess the impact of the combination regimen on the incidence, predisposing factors, and consequences of postoperative DVT, transplant renal-vein or artery thrombosis, and pulmonary embolus.

METHODS

We retrospectively evaluated two cohorts of renal transplant recipients: CsA/prednisone (Pred)+/-azathioprine (n=136, group A) or sirolimus+CsA+Pred (n=354, group B) using Fisher's exact t and chi-square tests, as well as Kaplan-Meier analyses, odds ratios, and multiple logistic regression methods.

RESULTS

The 7 of 136 (5.1%) incidence of thrombotic events in group A was similar to the 20 of 354 (5.6%) incidence in group B (P=0.513; NS) and occurred no more frequently ipsilateral to the transplant. Although the occurrence of an acute-rejection episode was not associated with the DVT diagnosis, all affected patients displayed elevated serum creatinine (Scr) values, which remained slightly higher than baseline following recovery (group A 1.63+/-1.22-1.95+/-0.93 mg/dL; group B 1.70+/-1.11-2.01+/-0.88 mg/dL). Renal biopsies failed to show evidence of intrarenal coagulopathy. No patient lost a graft as a complication of DVT, nor did these events produce other lasting adverse effects. Patients in the sirolimus group showed a strong correlation between the occurrence of DVT and the previous existence of an ipsilateral or contralateral lymphocele.

CONCLUSION

Addition of sirolimus to a CsA+Pred regimen does not increase the incidence of postoperative thrombotic events among renal transplant recipients.

Screening for hypercoagulable syndromes following stroke

Patients with ischemic stroke of unclear etiology are often screened for hypercoagulable syndromes or thrombophilias. These have been recognized to cause venous thrombosis, and include hereditary deficiencies of coagulation factors, genetic mutations, or acquired disorders. However, the majority of coagulation disorders are only rarely associated with ischemic stroke. The tests most commonly used to screen for thrombophilias comprise a complex array of assays that may be unreliable in various settings, including acute thrombosis, inflammation, and uses of medications such as anticoagulants. The diagnostic yield of thrombophilia tests in unselected stroke patients is very low, but may improve with careful selection of younger patients who have an otherwise undetermined cause of stroke or a history of venous thrombosis or multiple miscarriages. Various strategies have been developed that can guide the selection of patients (based on specific characteristics) and tests in the evaluation of thrombophilias. Although the diagnosis of thrombophilia aids in the potential explanation of stroke etiology, the best regimen for secondary prevention treatment for the majority of thrombophilias is still unknown.

Review article: inherited thrombophilia in inflammatory bowel disease

Individuals with inflammatory bowel disease frequently experience increased systemic thromboembolic complications, which represent an important cause of morbidity and mortality. Risk factors for thrombosis can be inherited or acquired. The most common inherited risk factors for thromboembolism are factor V Leiden mutation, G20210A mutation in the prothrombin gene, and homozygous C677T mutation in the methylenetetrahydrofolate reductase gene. In the last few years, a great amount of literature has focused on the prevalence of such genetic mutations and their role in determining thrombosis in IBD patients. In this review, we summarize the results of these studies.

Gestational vascular complications

Severe pregnancy complications, primarily severe pre-eclampsia, placental abruption, intrauterine growth restriction (IUGR) and intrauterine fetal death (IUFD) occur in about 1-5% of gestations. This rate is even higher in special medical situations. These pregnancy complications have been shown to increase maternal and fetal morbidity and mortality considerably. Severe pregnancy complications have also been shown to be associated with deficient uteroplacental circulation and are linked with intervillous and spiral vessel thrombosis. Moreover, it has been suggested that these complications could have their basis in a deficient trophoblast invasion in the uterine spiral arteries at a stage much earlier than the clinical manifestations become evident. In the last few years, evidence has accumulated to suggest that severe pregnancy complications could have a common thrombogenic basis associated with inherited and acquired thrombophilia. In this chapter we present a comprehensive update of the aetiology, pathophysiology, clinical manifestations, diagnosis and treatment of these severe pregnancy complications.

Risk factors for thrombosis in pregnancy

Pregnancy is a hypercoagulable state affecting both the coagulation and the fibrinolytic systems. Any exacerbation of the pre-disposing factors for coagulation may well lead to a thrombotic event more often in pregnant women than in the general population. Arterial thrombosis is very rare in pregnancy. Pre-eclampsia may be a risk factor for the development of arterial disease in later life. Venous thromboembolism (VTE) in pregnancy, although still rare, is a major cause of maternal mortality. Risk factors, such as older age, increased weight and emergency Caesarean section, as well as acquired and genetic thrombophilia, often coexist and reinforce each other. Appropriate thromboprophylaxis needs to be considered and applied on an individual basis. Uteroplacental thrombosis provides a common pathophysiological link between various poor pregnancy outcomes, including recurrent miscarriage, stillbirth, placental abruption, fetal growth restriction and pre-eclampsia. Its significance depends on the gestational age. Acquired and genetic thrombophilia may be associated with such conditions, particularly in early-onset disease. More data are required to assess the significance of such thrombophilias in obstetric practice. Any treatment should be in the context of clinical trials.

The inherited thrombophilias: genetics, epidemiology, and laboratory evaluation

It is now possible to identify a predisposing thrombophilic condition for venous thrombosis in well over half of the cases. Certain thrombophilia diagnoses have a major impact on anticoagulant therapy, and hence it is incumbent upon physicians to understand how to diagnose and manage these conditions. This chapter covers the genetics and epidemiology of the inherited thrombophilias and provides a useful, common-sense approach to the laboratory evaluation of a patient with venous thrombosis.

Inherited thrombophilia and gestational venous thromboembolism

Thromboembolic disease is a leading cause of maternal morbidity and mortality during pregnancy and the puerperium. To reduce the incidence of venous thromboembolism in pregnancy and improve outcomes, an individual risk stratification based on probability of thrombosis as a rationale for an individual risk-adapted prophylaxis is required. Within the past 10 years, a significant improvement in risk estimation has been achieved due to the identification of new genetic risk factors of thrombosis. In women without prior thrombosis, the presence of a heterozygous factor V Leiden or heterozygous G20210A mutation in the prothrombin gene is associated with a pregnancy-associated thrombotic risk of approximately 1 in 400. Thus, in pregnant carriers of either one of these mutations the risk of venous thromboembolism is low--indicating that pregnancy-associated thrombosis is multicausal, resulting from the interaction of combined defects. A combination of the two genetic risk factors can increase the risk to a modest level (risk 1 in 25). In women with a single episode of prior thrombosis associated with a transient risk factor, for example, surgery or trauma, and no additional genetic risk factor, the probability of a pregnancy-associated thrombosis appears also to be low. In contrast, in women with a prior idiopathic venous thrombosis who carry an additional hereditary risk factor or who have a positive family history of thrombosis, a high risk (>10%) can be expected, supporting the indication for active antepartum and postpartum heparin prophylaxis. Despite the remarkable progress in risk stratification, the absolute magnitude of risk in many cases is unknown and current recommendations remain empirical.

Activated protein C resistance acquired through liver transplantation and associated with recurrent venous thrombosis

We report a new case of recurrent, extra-hepatic, deep vein thrombosis occurring after orthotopic liver transplantation for hepatocellular carcinoma complicating 'mixed' alcoholic and post-hepatitic C cirrhosis. Coagulation tests showed activated protein C resistance. The patient's genomic DNA was negative for the factor V Leiden mutation. Analysis of the grafted liver DNA showed that the donor was a heterozygous carrier of the factor V Leiden mutation and that the recipient's activated protein C resistance was acquired through the transplantation. Screening of candidate liver donors for a prothrombotic tendency is controversial. However, this case suggests that patients who develop venous thrombosis after liver transplantation should be screened for thrombophilic abnormalities, bearing in mind that genetic abnormalities which do not affect clotting test results, such as the G20210A mutation in the factor II gene, can only be diagnosed by testing the donor or graft.

Prothrombotic conditions in an unselected cohort of children with venous thromboembolic disease

Venous thromboembolic events (VTEs) in children are usually associated with underlying clinical conditions. The added contribution of prothrombotic conditions to the occurrence of VTEs in children is not clear. This study reports the prevalence of prothrombotic conditions in 171 consecutive children with VTE followed in the Hospital for Sick Children Thrombosis Outpatient Clinic. The median age of the children at the time of VTE was 2.3 months (range 1 day to 16.5 years). An underlying medical condition and a central venous line (CVL) were present in 156 (91%) and 132 (77%) of 171 children, respectively. A positive family history was present in 8% of children. The prevalence of factor V Leiden was 4.7%, prothrombin G20210A polymorphism was 2.3%, protein S deficiency was 1.2%, protein C deficiency was 0.6% and increased plasma lipoprotein (a) concentration (>30 mg dL-1) was 7.5% (tested in 107 children). The overall frequency of inherited prothrombotic coagulation proteins was 13% (95% confidence interval 7 to 19%) and the frequency was not significantly different between neonates and older children with VTE. Inherited prothrombotic coagulation proteins were not associated with gender, CVL-related VTE, a positive family history of thrombosis or spontaneous VTE in neonates. Increased frequency of inherited prothrombotic coagulation proteins was, however, found in older children with spontaneous VTE (60%) compared with older children with VTEs secondary to an underlying medical condition (10%) (P = 0.02). In conclusion, this study indicates that inherited prothrombotic coagulation proteins do not contribute significantly to the pathogenesis of VTEs in neonates and children, in whom the most significant etiological factors are the presence of a CVL and/or other medical conditions.

Oral contraception and the risk of thromboembolism: what does it mean to clinicians and their patients?

For four decades the oral contraceptive pill has remained popular with young women because of its convenience and effectiveness. There have, however, been continuing concerns about adverse effects. In the 1960s the risk of venous thromboembolism was linked to the dose of estrogen, which was consequently reduced. Later the risks of arterial disease were linked to progestogen dose, which was also reduced. In 1995, three case-control studies linked the risk of venous thromboembolism, not to dose, but to the type of progestogen. Newer 'third-generation' progestogens appeared to carry a higher risk than older formulations. Although the contraceptive pill was already known to increase the risk of venous thromboembolism 3- to 6-fold, and the risks in the three studies were within this range, the public perception was that a new risk had been discovered. In the UK there were two consequences--a rapid change in prescribing patterns and a sharp increase in the abortion rate. Critics suggested that the studies may have been affected by confounding--e.g. by a 'new user' effect and differential prescribing. Views became very polarised. Between 1995 and 2001 second- and third-generation formulations were compared in 16 studies. Thirteen found that third-generation pills carried a higher risk of venous thromboembolism. Editorials and reviews recommended second-generation pills as the first choice for new users but official advice was that third-generation pills could still be prescribed, provided the risks were explained. Rates of thrombosis, per 100,000 women, are five for nonusers, 15 with second-generation pills and 25 for third-generation pills. The increase in mortality rates is around 1 to 2 per million. Drug-industry sponsored studies tended to find lower risks than independent studies and it was assumed that sponsorship produces bias, conscious or unconscious. It is also possible that some 'independent' researchers, motivated by antipathy to multinational pharmaceutical companies, are biased in the opposite way. Compared with the energy put into this debate, other aspects of pill prescribing remain under-researched. For example, doctors on opposite sides of the Atlantic are given different advice about whether gross obesity (a major risk factor for thromboembolism) is a contraindication to oral contraception. Women in developing countries continue to die of pregnancy-related causes and many deaths could be prevented by effective contraception. Rather than bickering, drug manufacturers and academics should be discussing ways of providing the pill to the women who need it most.

Endovascular management of venous thrombotic and occlusive diseases of the lower extremities

Acute complications of deep vein thrombosis (DVT) of the lower extremities include pulmonary embolism and venous ischemia. Delayed complications include a spectrum of debilitating symptoms referred to as postthrombotic syndrome (PST). Anticoagulation therapy is recognized as the mainstay of therapy in acute DVT. However, there are few data to suggest any major beneficial effect on PTS, which is thought to be mediated by valve damage and/or occlusive chronic thrombus and venous scarring. Endovascular catheter-directed thrombolysis techniques with pharmacologic thrombolytic agents, used alone or in combination with mechanical thrombectomy devices, have been proven highly effective in clearing acute DVT, which may allow the preservation of venous valve function and prevention of subsequent venous occlusive disease. Definitive management of underlying anatomic occlusive abnormalities can also be undertaken.

Factor V Leiden and prothrombin gene mutation may predispose to paradoxical embolism in subjects with patent foramen ovale

The role of paradoxical embolism through patent foramen ovale as a mechanism of cryptogenic stroke is controversial. If a venous source of emboli is relevant, prothrombotic states should be associated with patent foramen ovale and cryptogenic stroke. We assessed the occurrence of several prothrombotic states (factor V Leiden, prothrombin G20210A, deficiencies in protein S, protein C and antithrombin, lupus anticoagulant, anticardiolipin antibodies, elevated factor VIII, resistance to activated protein C) and classical risk factors for venous thrombosis in 57 adult patients with cryptogenic stroke and patent foramen ovale and in 104 matched controls. Prothrombotic states [odds ratio (OR) 2.8; 95% confidence interval (CI), 1.2-6.5; P = 0.021], migraine with aura (OR 4.4; 95% CI 1.8-10.8; P = 0.001) and classical risk factors for venous thrombosis (OR 2.5; 95% CI 1.1-5.7; P = 0.037) were independent risk factors for cryptogenic stroke. In particular factor V Leiden or prothrombin G20210A associated with cryptogenic stroke (P = 0.022) whereas other coagulation abnormalities did not (P = 0.140). Among the patients with prothrombotic states, Valsalva manoeuvre was common at onset of stroke. Our results support the possibility of paradoxical embolism behind strokes in patients with patent foramen ovale.

Thrombophilic disorders and fetal loss: a meta-analysis

BACKGROUND

Our aim was to assess the strength of the controversial association between thrombophilia and fetal loss, and to examine whether it varies according to the timing or definition of fetal loss.

METHODS

We searched Medline and Current Contents for articles published between 1975 and 2002 and their references with terms denoting recurrent fetal and non-recurrent fetal loss combined with various thrombophilic disorders. We included in our meta-analysis case-control, cohort, and cross-sectional studies published in English, the methodological quality of which was rated as moderate or strong. Pooled odds ratios (OR) with 95% CI were generated by random effects models with Cochrane Review Manager software.

FINDINGS

We included 31 studies. Factor V Leiden was associated with early (OR 2.01, 95% CI 1.13-3.58) and late (7.83, 2.83-21.67) recurrent fetal loss, and late non-recurrent fetal loss (3.26, 1.82-5.83). Exclusion of women with other pathologies that could explain fetal loss strengthened the association between Factor V Leiden and recurrent fetal loss. Activated protein C resistance was associated with early recurrent fetal loss (3.48, 1.58-7.69), and prothrombin G20210A mutation with early recurrent (2.56, 1.04-.29) and late non-recurrent (2.30, 1.09-4.87) fetal loss. Protein S deficiency was associated with recurrent fetal loss (14.72, 0.99-218.01) and late non-recurrent fetal loss (7.39, 1.28-42.63). Methylenetetrahydrofolate mutation, protein C, and antithrombin deficiencies were not significantly associated with fetal loss.

INTERPRETATION

The magnitude of the association between thrombophilia and fetal loss varies, according to type of fetal loss and type of thrombophilia.

Neuroimaging fails to identify asymptomatic carriers of familial porencephaly

Familial porencephaly is a rare condition usually transmitted as an autosomal dominant trait with incomplete penetrance. We describe a new family in which six members across four generations had congenital hemiplegia. Cerebral imaging was performed in three patients and showed porencephaly in all cases. In order to provide effective genetic counseling, three asymptomatic carriers were investigated by cerebral computerized tomography (three patients) and cerebral magnetic resonance imaging (one patient). These investigations failed to show any congenital abnormalities. We conclude that cerebral imaging is unreliable to detect obligate carriers of familial porencephaly.

Improving the prediction of complex diseases by testing for multiple disease-susceptibility genes

Studies have argued that genetic testing will provide limited information for predicting the probability of common diseases, because of the incomplete penetrance of genotypes and the low magnitude of associated risks for the general population. Such studies, however, have usually examined the effect of one gene at time. We argue that disease prediction for common multifactorial diseases is greatly improved by considering multiple predisposing genetic and environmental factors concurrently, provided that the model correctly reflects the underlying disease etiology. We show how likelihood ratios can be used to combine information from several genetic tests to compute the probability of developing a multifactorial disease. To show how concurrent use of multiple genetic tests improves the prediction of a multifactorial disease, we compute likelihood ratios by logistic regression with simulated case-control data for a hypothetical disease influenced by multiple genetic and environmental risk factors. As a practical example, we also apply this approach to venous thrombosis, a multifactorial disease influenced by multiple genetic and nongenetic risk factors. Under reasonable conditions, the concurrent use of multiple genetic tests markedly improves prediction of disease. For example, the concurrent use of a panel of three genetic tests (factor V Leiden, prothrombin variant G20210A, and protein C deficiency) increases the positive predictive value of testing for venous thrombosis at least eightfold. Multiplex genetic testing has the potential to improve the clinical validity of predictive testing for common multifactorial diseases.

Hormone replacement therapy: current controversies

Postmenopausal hormonal therapy is used to manage the climacteric symptoms that impair the quality of life of a substantial number of women. The difficulty is achieving the desired effects with minimal side-effects and no adverse health risks. Fundamental to this is understanding the physiology of oestrogen in women and the metabolism of the therapeutic compounds. Although the effects of oral oestrogen therapy have been studied extensively, there is insufficient evidence to assess adequately the independent effects of progestin use, other oestrogen compounds, differing doses and duration of treatment. We have reviewed some basic concepts of oestrogen physiology and how these relate to exogenous oestrogen administration, the risks of greatest concern, and the role of androgens and newer treatment alternatives.

The coagulation system

Congenital and acquired hypercoagulable states arise from an imbalance between procoagulant and anticoagulant activity. Although these imbalances are present throughout the entire vascular tree, thrombotic lesions are usually localized in discrete segments of the veins or arteries and in certain organ systems. Thus, hypercoagulable states are likely to be associated with focal defects in the vascular wall to produce thrombosis. Many recently described factors are associated with hypercoagulability. Because thrombosis is a disease in which genetic and acquired risk factors interact dynamically, a thorough history, family history, and physical examination should be performed before ordering an extensive and costly coagulation panel.

Clinical and laboratory evaluation of thrombophilia

Thrombophilia is the predisposition to venous thromboembolism and is caused by inherited and acquired factors, alone or in combination. With the discovery of APC resistance and the prothrombin gene mutation, more than half of all patients with clinical characteristics of thrombophilia are now diagnosed with an inherited disorder. The hypercoagulable work-up of patients with venous thromboembolism is important, because the causes can influence the duration and management of anticoagulation therapy, as well as affect other decisions regarding life and health issues.

Antenatal causes of cerebral palsy: associations between inherited thrombophilias, viral and bacterial infection, and inherited susceptibility to infection

Cerebral palsy rates of 2 in every 1,000 births have varied little over the last 40 years, despite improvements in obstetric care. In the past, cerebral palsy was thought to be due to poor obstetric care and management; however, epidemiological studies have refuted this, suggesting that there is usually an antenatal timing to the neuropathology of cerebral palsy. There are many known risk factors for cerebral palsy, including multiple gestation, prematurity, and low birth weight. Recently, intrauterine infection, maternal pyrexia, and the presence of thrombophilic disorders (thrombophilia) have been identified as major risk factors for subsequent cerebral palsy. This review examines the links between intrauterine infection, the fetal inflammatory response, and thrombophilia as possible causes of cerebral palsy. The interactions of viral or bacterial infections during pregnancy, normal or abnormal fetal cytokine responses, and hereditary fetal thrombophilias as antenatal causes of the neuropathology of cerebral palsy are now areas of research priority.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe the condition cerebral palsy, list the risk factors for the development of cerebral palsy, outline the ultrasound findings associated with cerebral palsy, and point out other conditions associated with cerebral palsy.

Cerebral venous thrombosis in adults: the role of imaging evaluation and management

Clinical suspicion and excellent neuroimaging are crucial in making a diagnosis of CVT. Intravascular or dural sinus thrombus can be visualized on CT and MRI. Brain edema and intracranial hemorrhage that do not conform to an arterial territory are frequently evident on CT and MRI. Heparin treatment is accepted as the first-line treatment of CVT. Endovascular treatment for management of CVT is usually reserved for selected cases after failure of anticoagulation.

[Pharmacogenomics in gynecology. Replies to the Zurich Discussion Panel]

Leider besteht für diesen Artikel keine Zusammenfassung. Als Einstieg stellen wir den Textanfang zur Verfügung. Mehr als ein Jahrzehnt dauert bereits die wissenschaftliche Auseinandersetzung zwischen deutschen und österreichischen Endokrinologen bzw. Biochemikern, ob eine individuelle Hormonersatztherapie (HRT) sinnvoll ist und wie sie konkret aussehen soll. Dieses Thema wird nicht nur durch rezente Untersuchungen [1] aktualisiert, die klar belegen, dass die behandelten Frauen zu einem hohen Prozentsatz mit ihrer HRT unzufrieden sind und sie – vor allem wegen hyperöstrogenämischen Symptomen – nach relativ kurzer Zeit wieder beenden, sondern auch durch die HERS [2] und die Studie der Nurses’ Health Initiative [3], die sich von ihrem Design durch eine völlig unreflektierte Hormonverordnung auszeichnen. Die dabei vor allem gleich am Beginn auftretenden kardiovaskulären Probleme deuten bereits auf eine genetische Risikodisposition hin, in die stereotyp hineinsubstituiert wurde.

Mid-trimester severe intrauterine growth restriction is associated with a high prevalence of thrombophilia

OBJECTIVE

To investigate the association between severe mid-trimester IUGR, whose causes are unknown in most cases, and maternal thrombophilias.

DESIGN

Case-control study.

SETTING

Lis Maternity Hospital, Tel Aviv Sourasky Medical Center, The Sackler Faculty of Medicine, Tel Aviv University.

POPULATION

Twenty-six women with severe mid-trimester (22-26 weeks of gestation) IUGR (birthweight <3rd centile) and 52 matched multiparous women with normal pregnancies (controls).

METHODS

After excluding pregnancies with vascular maternal disease, chromosomal and structural aberrations and cytomegalovirus infection, 26 women out of 35 with severe mid-trimester IUGR remained and composed the study group. Each was matched for age, ethnicity and smoking status with two healthy women who had normal pregnancies. All the women were tested for genetic and acquired thrombophilias at least eight weeks after delivery.

MAIN OUTCOME MEASURES

Prevalence of maternal thrombophilias.

RESULTS

The frequency of thrombophilias was 69% in the study group compared with 14% in the control group [odds ratio (OR) 4.5; 95% confidence interval (CI) 2.3-9, P < 0.001]. The frequencies of factor V Leiden mutation, prothrombin gene mutation and protein S deficiency were significantly increased in the study group compared with the control group. The frequency of multiple thrombophilias was 33% in the study group versus none among the controls. Of the 26 pregnancies with severe mid-trimester IUGR, 13 ended in intrauterine fetal death before 25 weeks of gestation: 10 of these women had thrombophilia.

CONCLUSION

Women with mid-trimester severe IUGR have an increased prevalence of inherited and acquired thrombophilias.

The management of thrombophilia during pregnancy: a Canadian survey

OBJECTIVE

To determine current Canadian practice patterns in the management of pregnant women with thrombophilia.

METHODS

Physician members of the Society of Obstetricians and Gynaecologists of Canada (SOGC) who provide obstetrical care were invited to complete a closed-ended questionnaire in which they were presented 5 clinical scenarios involving thrombophilic pregnancies and asked to give their management recommendations. The 5 scenarios presented in the survey were of a pregnant woman with (1) asymptomatic factor V Leiden (FVL), (2) asymptomatic FVL and a family history of venous thromboembolism (VTE), (3) FVL and recurrent fetal loss, (4) FVL and a previous VTE, or (5) antiphospholipid antibody syndrome and recurrent fetal loss.

RESULTS

Of the 1448 eligible SOGC members invited, 18 had moved with no forwarding address, and 662 (46.3% of the remainder) responded. The majority (65%) of the respondents were obstetricians and 51% of them had a university-affiliated practice. In scenario 1, 26% of physicians indicated they would recommend some form of antepartum thromboprophylaxis, whereas in the remaining four scenarios, 58% to 84% would definitely recommend antepartum thromboprophylaxis.

CONCLUSION

Most clinicians favour intervening with thromboprophylaxis in pregnant thrombophilic women rather than observing without prophylaxis. This tendency spans a wide range of clinical scenarios, despite a lack of evidence to support such decisions. This survey highlights the need to provide clinicians and women with evidence for the safety and effectiveness of prophylaxis, before these interventions become the default recommendation by clinicians caring for this prevalent group of women.

Diagnostic studies for thrombophilia in women on hormonal therapy and during pregnancy, and in children

OBJECTIVE

To review the role of acquired and inherited prothrombotic risk factors that increase the risk of thrombosis in oral contraceptive users, during pregnancy, and in neonates, infants, and children; and to determine by the consensus opinion of recognized experts in the field which risk factors should be determined in which individuals at which time.

DATA SOURCES

Review of the medical literature and current clinical practice by a panel of experts in the field of thrombophilia.

DATA EXTRACTION AND SYNTHESIS

The experts made an extensive review of the published literature and prepared a draft manuscript, which included preliminary recommendations. The draft manuscript was circulated to participants in the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia prior to the conference. The manuscript and recommendations were then presented at the conference for discussion. Recommendations were accepted if a consensus of the 26 experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.

CONCLUSIONS

This report reviews the options for testing for thrombophilic states in women using oral contraceptives, during pregnancy, and in neonates and children. General guidelines for testing in these clinical situations are provided, along with citation of the appropriate supporting literature.

Venous thromboembolism: implications for gene-based diagnosis and technology development

Venous thromboembolism is an hypercoagulable state that frequently reflects a complex interplay between inherited, acquired and environmental factors. The overall incidence of venous thromboembolism, which increases with age, is approximately 1:1000 in the US and Western Europe. In addition to known risk factors such as pregnancy and cancer, genetic variants can also increase the venous thromboembolism risk. Once such genetic variant, FV Leiden is characterized by single-point mutation and has been found in approximately 20% of idiopathic venous thromboembolism cases. The discovery of FV Leiden unleashed an increased interest in the genetics of venous thromboembolism as well as other cardiovascular diseases. Because FV Leiden was not only defined by only one common single nucleotide polymorphism but was also widely prevalent, impetus for the development of novel mutation detection methodologies and platforms for DNA analysis in both the clinical and research laboratory was greatly accelerated. An overview of this technology and its relationship to the genetics of venous thromboembolism is reviewed.

Clinical utility of factor V leiden (R506Q) testing for the diagnosis and management of thromboembolic disorders

OBJECTIVE

To review the current state of the art regarding the role of the clinical laboratory in diagnostic testing for the factor V Leiden (FVL) thrombophilic mutation (and other protein C resistance disorders), and to generate, through literature reviews and opinions of recognized thought-leaders, expert consensus recommendations on methodology and diagnostic, prognostic, and management issues pertaining to clinical FVL testing.

DATA SOURCES, EXTRACTION, AND SYNTHESIS

An initial thorough review of the medical literature and of current best clinical practices by a panel of 4 experts followed by a consensus conference review, editing, and ultimate approval by the majority of a panel of 28 additional coagulation laboratory experts.

CONCLUSIONS

Consensus recommendations were generated for topics of direct clinical relevance, including (1) defining those patients (and family members) who should (and should not) be tested for FVL; (2) defining the preferred FVL laboratory testing methods; and (3) defining the therapeutic, prophylactic, and management ramifications of FVL testing in affected individuals and their family members. As FVL is currently the most common recognized familial thrombophilia, it is hoped that these recommendations will assist laboratorians and clinicians caring for patients (and families) with this common mutation.

Risk factors and long-term follow-up of patients with the immune type of heparin-induced thrombocytopenia

Dispositional risk factors for developing the immune-type of heparin-induced thrombocytopenia (HIT) are yet unclear. This article presents a long-term follow-up of patients with HIT to define possible risk factors that may increase the risk of HIT. The clinical course of acute HIT was analyzed retrospectively in 52 patients with HIT. Thirteen patients died; 8 due to HIT. A follow-up investigation was performed in 28 of the remaining 39 patients 29 +/- 12 months after the onset of HIT, including genotyping for the factor V G1691A- and the prothrombin G20210A-mutation, measurement of antithrombin, protein C, protein S, factor VIII, and factor XII activity as well as the concentration of antiphospholipid antibodies. The results were compared to an age- and sex-matched control group. New thromboembolic events and re-exposure to heparin were also documented. No difference between patients and controls was observed concerning the factor V Leiden mutation, the prothrombin mutation, factor XII, antithrombin, protein S, or protein C deficiency and antiphospholipid antibodies. Increased factor VIII activity was found in 16 of 21 HIT patients compared to 4 of 21 controls (p=0.0005). New thromboembolic events developed in 5 patients within 9 months after HIT. One patient had been re-exposed to heparin 9 months after acute HIT without any complications. Increased factor VIII activity was frequently observed in patients in whom HIT developed. Thromboembolic complications within the first months after onset of HIT occurred often.

Endovascular management of venous thrombotic diseases of the upper torso and extremities

Central venous thrombosis in the upper torso can be either primary, occurring as a result of longstanding extrinsic compression, or secondary, resulting from an acquired intrinsic occlusive disease or foreign body. As in lower extremity deep vein thrombosis (DVT), anticoagulation therapy is the mainstay of therapy in upper torso and upper extremity DVT. However, in the presence of severely symptomatic acute thrombosis, pharmacologic and/or mechanical thrombolytic therapy represent the main invasive form of therapy for these conditions. After clearance of the acute thrombotic component, definitive management in patients with underlying anatomic abnormalities can be undertaken. Primary subclavian axillary vein thrombosis caused by extrinsic obstruction at the thoracic outlet is treated with thrombolytic therapy and anticoagulation followed by surgical decompression, whereas secondary causes of central venous obstruction and thrombosis are usually amenable to endovascular treatment with balloon angioplasty and stent placement. Postoperative interval anticoagulation is usually recommended. In addition to clinical follow-up, imaging follow-up with duplex sonography or conventional venography is usually recommended to assess the presence of restenosis and/or residual compression.

Prospective reevaluation of the association between thrombotic diathesis and legg-perthes disease

BACKGROUND

Legg-Perthes disease is associated with ischemia of the capital femoral epiphysis in children. Thrombophilia has been implicated as a potential cause of the condition, and screening of patients with Legg-Perthes disease for thrombophilia has been recommended. We analyzed the value of screening for inherited thrombophilia in patients with Legg-Perthes disease by examining the association between Legg-Perthes disease and abnormalities in the thrombotic pathway.

METHODS

A random series of consecutive patients with Legg-Perthes disease were prospectively enrolled in this study. Assays for the detection of factor-V Leiden mutation and the plasma concentrations of protein C, protein S, antithrombin III, and lipoprotein (a) were performed on plasma samples from children with Legg-Perthes disease, and the results were compared with those for pooled plasma from normal controls. Plasma concentrations below the 95% midrange of the control values were classified as protein deficiencies. The estimated population frequency of each coagulation abnormality was compared with the proportion of the study group with the corresponding abnormality.

RESULTS

The proportion of abnormalities observed in the study group did not differ from the estimated population frequency for protein C, protein S, antithrombin III, or factor-V Leiden mutation. A lipoprotein (a) level of >30 mg/dL (>1.07 micro mol/L) was found in 16% of the study group.

CONCLUSIONS

Our data do not suggest that thrombotic diatheses due to deficiency of protein C, protein S, or antithrombin III or due to factor-V Leiden mutation are major causes of Legg-Perthes disease. The elevated levels of lipoprotein (a) in children with Legg-Perthes disease suggest that they may be at risk for atherosclerosis as adults.

Parameters of coagulant and fibrinolytic capacity and activity in postmenopausal women: within-subject variability

We have analyzed the within-subject variability of a battery of parameters of coagulant and fibrinolytic capacity and activity in postmenopausal women. We observed large differences in within-subject variability among the tests and have demonstrated how such data can be used to estimate the number of times a parameter must be measured to produce a statistically adequate sample.

"Black swan in the kidney": renal involvement in the antiphospholipid antibody syndrome

The antiphosphospholipid antibody syndrome (APS) describes a clinical entity with recurrent thrombosis, fetal loss, thrombocytopenia in the presence of lupus anticoagulant and/or antibodies to cardiolipin. These antibodies may be associated with connective tissue diseases such as systemic lupus erythematosus (secondary APS) or be found in isolation (primary APS). Renal syndromes increasingly being reported in association with these antibodies include thrombotic microangiopathy, renal vein thrombosis, renal infarction, renal artery stenosis and/or malignant hypertension, increased allograft vascular thrombosis, and reduced survival of renal allografts. Although much has been understood concerning the biology of these antibodies and the pathogenesis of thrombosis, the optimal therapy remains to be elucidated. This article presents a historical review of the renal involvement in the antiphospholipid syndrome and discusses therapeutic options. Further research is needed.

Determination of the Factor V Leiden Single-Nucleotide Polymorphism in a Commercial Clinical Laboratory by Use of NanoChip Microelectronic Array Technology

Background: Methods for analysis of the single-nucleotide polymorphism (SNP) known as factor V Leiden (FVL) are described. The technique provides rapid, highly accurate detection of the point mutation that encodes for replacement of arginine-506 with glutamine. After formal assay qualification, 758 clinical samples that had previously been analyzed by the InvaderTM Monoplex Assay were tested as research samples in a commercial clinical laboratory.

Methods: Primers specific for factor V (FV) were prepared, and PCR was performed. Samples were analyzed using the NanoChip® Molecular Biology Workstation with fluorescently labeled reporters for wild-type and SNP sequences.

Results: Of the 635 samples classified by the Third WaveTM assay as FV wild type, 10 were identified as heterozygous FVL by the NanoChip technique. Similarly, of the 114 putative heterozygous samples, 4 were wild type, and of the 9 reported homozygous samples, 6 were homozygous, 2 were heterozygous, and 1 was FV wild type by the NanoChip assay. All 17 results that were discordant with the Third Wave analysis were confirmed by DNA sequencing to be correctly classified by the NanoChip technology. The Nanochip system was 100% accurate in characterizing wild-type, heterozygous, and homozygous samples compared with accuracies of 99.2%, 90.2%, and 100% for the comparable Third Wave analysis.

Conclusions: The NanoChip microelectronic chip array technology is an accurate and convenient method for FVL screening of research samples in a clinical laboratory environment.

The epidemiology of peripheral vein infusion thrombophlebitis: a critical review

We critically assessed studies on the clinical importance, diagnosis, incidence, and pathogenesis of peripheral vein infusion thrombophlebitis, including catheter-related and patient-related risk factors. We reviewed the evidence linking thrombosis, particularly prothrombotic states such as the inherited thrombophilic disorders, with peripheral vein infusion thrombophlebitis. Peripheral vein infusion thrombophlebitis occurs in 25% to 35% of hospitalized patients with peripheral intravenous catheters and has both patient-related implications (e.g., sepsis) and economic consequences (e.g., extra nursing time). Although duration of catheterization, catheter-related infection, and catheter material are important risk factors for peripheral vein infusion thrombophlebitis, patient-related risk factors are not well elucidated.

Risk factors for thromboembolism in teens: when should I test?

The discoveries of the factor V Leiden mutation and the prothrombin gene variant 20210 in the last decade have markedly contributed to the understanding of the molecular pathophysiology of inherited risk factors for thrombophilia. Population studies in the adult literature have shown that although the overall prevalence of these defects is low, affected individuals are at increased risk of thrombosis particularly if acquired risk factors for thrombosis are also present. The use of combined hormonal oral contraceptive pills is a well-known acquired risk factor, and recent studies have shown significant increased risk of thrombosis for women who carry the factor V Leiden mutation and use oral contraceptive pills. Despite this significant increased risk, mass screening of asymptomatic women for factor V Leiden prior to prescribing oral contraceptive pills is not a cost-effective use of health care dollars and could result in unnecessarily preventing many women from the contraceptive and noncontraceptive benefits of this medication. Instead, clinicians can use thoughtful screening questions to identify potentially high-risk patients for thrombophilia and consider testing for inherited risk factors on a case-specific basis.

Markers of activated coagulation in patients with factor V Leiden and/or G20210A prothrombin gene mutation

The activated protein C (APC) resistance phenotype associated with an abnormal factor V Leiden (FVL), and the G20210A prothrombin gene mutation are the most common findings in patients with venous thromboembolism (VTE). In a group of 210 patients, we compared the levels of markers of coagulation activation in carriers of FVL (71 heterozygous, 30 homozygous), G20210A prothrombin mutation (88 heterozygous) or both mutations combined (21 heterozygous), in order to assess whether these markers allow identification of a group of patients with a higher risk of thrombosis; they were also compared to normal values. A total of 143 patients had a personal history of VTE and 67 were asymptomatic. None of them had other hereditary causes of thrombophilia or an antiphospholipid syndrome. None were currently treated with either anticoagulant or hormonal treatment. Pregnant women were excluded. No significant difference between the four groups of patients could be found in the levels of F1+2, TAT and DDI. Levels were all significantly higher than the control values (p<0.05). The levels of F1+2 and TAT were similar in patients with or without a history of VTE, regardless of the type of mutation. DDI levels were significantly higher in patients with a history of VTE than in asymptomatic subjects (443+/-248 vs. 333+/-222 ng/ml, p=0.02) but with only 57% sensitivity and specificity. In conclusion, our study confirms the hypercoagulable state found in mutation carriers and points out the inability of F1+2 and TAT assays to identify a group of subjects at higher risk of thrombosis, within carriers of genetic risk factors. Although the sensitivity and specificity of DDI assay are low, high DDI concentrations tend to be associated with the risk of VTE.

Hereditary thrombophilias are not associated with a decreased live birth rate in women with recurrent miscarriage

OBJECTIVE

To assesses the live birth rate without treatment in women with hereditary thrombophilia who have recurrent miscarriage and women without thrombophilia who have recurrent miscarriage.

DESIGN

Prospective observational study.

SETTING

Tertiary referral unit in university hospital.

PATIENT(S)

One hundred twenty women with thrombophilia and 65 women without thrombophilia.

MAIN OUTCOME MEASURE(S)

Number of live births or repeated miscarriages.

RESULTS

Of the 185 patients, 44 with thrombophilia and 26 without thrombophilia have conceived. Nineteen of the 44 pregnancies (43.2%) in thrombophilia patients have terminated in live births, compared with 8 of 26 pregnancies (30.8%) in patients without thrombophilia. This difference is not statistically significant.

CONCLUSIONS

Hereditary thrombophilia did not seem to affect the live birth rate in women with recurrent miscarriage.