D-dimer concentrations during normal pregnancy, as measured by ELISA

Development and Validation of a Clinical Prediction Model for Venous Thromboembolism Following Neurosurgery: A 6-Year, Multicenter, Retrospective and Prospective Diagnostic Cohort Study

BACKGROUND

Based on the literature and data on its clinical trials, the incidence of venous thromboembolism (VTE) in patients undergoing neurosurgery has been 3.0%~26%. We used advanced machine learning techniques and statistical methods to provide a clinical prediction model for VTE after neurosurgery.

METHODS

All patients (n = 5867) who underwent neurosurgery from the development and retrospective internal validation cohorts were obtained from May 2017 to April 2022 at the Department of Neurosurgery at the Sanbo Brain Hospital. The clinical and biomarker variables were divided into pre-, intra-, and postoperative. A univariate logistic regression (LR) was applied to explore the 67 candidate predictors with VTE. We used a multivariable logistic regression (MLR) to select all significant MLR variables of MLR to build the clinical risk prediction model. We used a random forest to calculate the importance of significant variables of MLR. In addition, we conducted prospective internal (n = 490) and external validation (n = 2301) for the model.

RESULTS

Eight variables were selected for inclusion in the final clinical prediction model: D-dimer before surgery, activated partial thromboplastin time before neurosurgery, age, craniopharyngioma, duration of operation, disturbance of consciousness on the second day after surgery and high dose of mannitol, and highest D-dimer within 72 h after surgery. The area under the curve (AUC) values for the development, retrospective internal validation, and prospective internal validation cohorts were 0.78, 0.77, and 0.79, respectively. The external validation set had the highest AUC value of 0.85.

CONCLUSIONS

This validated clinical prediction model, including eight clinical factors and biomarkers, predicted the risk of VTE following neurosurgery. Looking forward to further research exploring the standardization of clinical decision-making for primary VTE prevention based on this model.

Elevated levels of D-dimer tested by immunoturbidimetry are associated with the extent of severity of pre-eclampsia

OBJECTIVE

To establish the association between increased levels of D-dimer and severity of pre-eclampsia.

METHODS

A nested, prospective cohort, analytical case-control study was conducted among women with pre-eclampsia between March 2017 and March 2018. Inclusion criteria were age over 18 years, gestational age of more than 20 weeks, a single pregnancy with a living fetus, and a diagnosis of pre-eclampsia. D-dimer was measured by immunoturbidimetry at the time of diagnosis of pre-eclampsia, applying cut-off points adjusted for gestational age. Statistical analysis involved unconditional logistic regression for the association of elevated D-dimer with severe pre-eclampsia adjusted by confounding variables.

RESULTS

There were 132 patients with pre-eclampsia, of which 44 were classed as controls and 88 were classed as having severe pre-eclampsia (case group). Cohort characteristics included: age between 18 and 45 years (mean 28.0 ± 6.3 years); presence of gestational hypertension (10.6%), chronic arterial hypertension (9.0%); and gestational diabetes (5.3%). In the case group, levels of D-dimer were significantly higher than in controls (19.3% vs 2.3%, odds ratio [OR] 10.30, 95% confidence interval [CI] 1.32-80.14, P=0.004) as well as significant in the unconditional logistic regression model adjusted for maternal age, parity, gestational age, and comorbidities (OR 10.02, 95% CI 1.28-78.68, P=0.028).

CONCLUSION

Elevated levels of D-dimer and severe pre-eclampsia are strongly associated, reinforcing evidence that one of the physiopathologic bases of the condition is the activation of fibrinolysis and the coagulation system.

Obstetric and Gynecologic Disorders and the Nervous System

PURPOSE OF REVIEW

This article highlights the multiple intersections between obstetric/gynecologic issues and neurologic disorders.

RECENT FINDINGS

Neurologic issues can arise related to contraceptive medications, infertility treatments, pregnancy, and menopause. This article explores these areas in chronologic order, beginning with women's neurologic conditions that overlap their reproductive years and those that may occur during pregnancy and continuing through menopause. For each disorder, the epidemiology, pathophysiology, complications, and best sex-based treatment are described. Recent findings and treatments are highlighted.

SUMMARY

Obstetric and gynecologic disorders may present with neurologic symptoms, so it is important for neurologists to understand these intersections to deliver the best care for our female patients.

Racial and Ethnic Differences in Response to Anticoagulation: A Review of the Literature

INTRODUCTION

Anticoagulants are among the most frequently prescribed medications in the United States. Racial and ethnic disparities in incidence and outcomes of thrombotic disorders are well-documented, but differences in response to anticoagulation are incompletely understood.

OBJECTIVE

The objective of this review is to describe the impact of race and ethnicity on surrogate and clinical end points related to anticoagulation and discuss racial or ethnic considerations for prescribing anticoagulants.

METHODS

A PubMed and MEDLINE search of clinical trials published between 1950 and May 2018 was conducted using search terms related to anticoagulation, specific anticoagulant drugs, race, and ethnicity. References of identified studies were also reviewed. English-language human studies on safety or efficacy of anticoagulants reporting data for different races or ethnicities were eligible for inclusion.

RESULTS

Seventeen relevant studies were identified. The majority of major trials reviewed for inclusion either did not include representative populations or did not report on the racial breakdown of participants. Racial differences in pharmacokinetics, dosing requirements, drug response, and/or safety end points were identified for unfractionated heparin, enoxaparin, argatroban, warfarin, rivaroxaban, and edoxaban.

CONCLUSIONS

Race appears to influence drug concentrations, dosing, or safety for some but not all direct oral anticoagulants. This information should be considered when selecting anticoagulant therapy for nonwhite individuals.

Meta-analysis of reference values of haemostatic markers during pregnancy and childbirth

Previously reported haemostatic reference intervals in normal pregnancy displayed considerable contradictions to establish convince gestational age-related haemostatic reference values. 30 clinical reports were recruited to collect and assemble existing clinical reports from the database D-dimer levels increased progressively with gestational ages and exceeded conventional value of 1 mg/L after 29-36 weeks, and reached a peak at 24 h postpartum with mean value of 6.44 mg/L [95% confidence interval (CI): 5.84 to 7.05] and returned to 0.79 mg/L (95% CI: 0.43 to 1.16) at 1-8 weeks postpartum. Analogously, the level of fibrinogen gradually increased throughout the pregnancy, and peaked at 48-72 h after birth, with mean value of 9.05 g/L (95% CI: 2.22 to 15.89) and then returned to 3.62 g/L (95% CI: 3.03 to 4.20) at 1-8 weeks postpartum. However, in the middle trimester, asynchronously prothromb in fragments 1 + 2 (F1+2) level elevated and reached a peak at 28-36 weeks with mean value of 3.05 nmol/L (95% CI: 2.41 to 3.70), and then decreased in the later trimester, and reached 1.92 nmol/L (95% CI: 0.58 to 3.27) at 48-72 h post-partum, close to normal levels. Previously reported gestational age-related haemostatic reference intervals in pregnancy could not be used as a standard.

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

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

The clinical significance of D-dimer concentrations in patients with gestational hypertensive disorders according to the severity

Objective

Pregnancy is a major risk factor of thromboembolism, and the patients with preeclampsia (PE) are known to have higher risk of thromboembolic complications than normal pregnant women. D-dimer is a well-established laboratory marker for the screening of venous thromboembolism (VTE), but the concentrations of d-dimer tend to increase physiologically in pregnant women throughout the gestational age. We performed this study to evaluate the clinical significance of d-dimer concentrations in patients with gestational hypertensive disorders (GHD) according to the severity.

Methods

Retrospective cohort study was performed in one institution. Singleton pregnant women with GHD were enrolled, and their antepartum concentrations of d-dimer were measured as a part of routine evaluation for patients suspected with PE. Patients with multiple gestations, rheumatic diseases, autoimmune diseases, or suspected VTE were excluded. A categorization of severity about PE was based on the general criteria.

Results

In 73.3% of study population, their d-dimer concentrations exceeded the normal range (>0.55 mg/L). A significantly greater proportion of pregnant women had excessive concentrations of d-dimer in the severe GHD than in the non-severe GHD (89.8% vs. 53.7%; P<0.01). Patients with severe GHD had significantly higher median concentrations of d-dimer than those with non-severe GHD (median [range], 2.00 mg/L [0.11 to 7.49] vs. 0.71 mg/L [0.09 to 5.39]; P<0.01) although their earlier gestational ages of sampling.

Conclusion

Maternal concentrations of d-dimer were significantly elevated in patients with severe features than those without severe features among those with GHD. Some pregnant women with GHD can have markedly elevated concentrations of d-dimer without any evidence of current VTE.

Necessity of preoperative activated partial thromboplastin time test as a predictor for surgical hemorrhage in obstetric and gynecological patients in China

BACKGROUND

On an international scale, the necessity of preoperative coagulation screen remains controversial, yet in China, coagulation screen is still a routine test before surgery required by the Ministry of Health of China.

METHODS

A retrospective review of 26,807 patients >18y presenting with problems related to the areas of gynecology and obstetrics from March 2013 to July 2015 was performed, and the rate of major bleeding and the amount of blood lost during surgery were compared among groups of patients grouped according to the values of preoperative APTT, the departments the patients belonged to, or the measures for intervention.

RESULTS

Groups with increased APTT had higher rates of major bleeding (9.80% & 26.14% vs 2.77%, P<0.001) and more blood loss (862.9 and 1455.6ml vs 194.0ml, P<0.001). And the same conclusion could be induced in both the obstetric and gynecological patients when they were taken into account separately. For obstetric patients, once those with high bleeding risks, e.g., placental abruption, placental implantation, or preoperative massive hemorrhage were excluded, groups with increased APTT would no longer demonstrated the higher rate of major bleeding (0.91% & 2.38% vs 0%, P=0.409 & 0.833) and would even have a lower amount of blood loss (202.76 and 228.09ml vs 322.13ml, P=0.003 and 0.027). In increased APTT patients without bleeding or bleeding tendency, FFP intervention would not make a difference in the rate of major bleeding (7.69% vs 8.37%, P=0.203) and the amount of blood loss (271.35ml vs 306.63, P=0.865).

CONCLUSION

For Chinese patients from the Obstetrics and Gynecology Departments, APTT is a good screen test to predict surgical hemorrhage.

Global hemostasis in healthy bitches during pregnancy and at different estrous cycle stages: Evaluation of routine hemostatic tests and thromboelastometry

This study assessed the global hemostasis (including prothrombin time [PT], activated partial thromboplastin time [aPTT], antithrombin activity [ATA], fibrinogen and d-Dimer concentrations, platelet count, plateletcrit and thromboelastometry) in healthy pregnant bitches, comparing the results with those of healthy bitches at different estrous cycle stages, and assessed whether hemostatic changes during pregnancy are associated with serum progesterone concentration or the presence of fetuses in utero. The results show that pregnant bitches have higher fibrinogen concentration, platelet count and platelatecrit, and that fibrin and global clot formations occur faster than in non-pregnant bitches at different estrous cycle stages. Additionally, clot strength was higher in pregnant bitches than in non-pregnant ones. There were no differences in PT, ATA, and D-dimer concentration between all study groups. The aPTT was significantly shorter in bitches at the fourth and last pregnancy weeks, compared to the anestrus group, and shorter in both the fourth and last pregnancy weeks groups, compared to diestrus group. These results all support a hypercoagulable state in healthy pregnant bitches, unassociated with progesterone concentration.

How to use D-dimer in acute cardiovascular care

D-dimer testing is important to aid in the exclusion of venous thromboembolic events (VTEs), including deep venous thrombosis and pulmonary embolism, and it may be used to evaluate suspected aortic dissection. D-dimer is produced upon activation of the coagulation system with the generation and subsequent degradation of cross-linked fibrin by plasmin. Many different assays for D-dimer testing are currently used in routine care. However, these tests are neither standardized nor harmonized. Consequently, only clinically validated assays and assay specific decision limits should be used for routine testing. For the exclusion of pulmonary embolism/deep vein thrombosis, age-adjusted cut-offs are recommend. Clinicians must be aware of the validated use of their hospital's D-dimer assay to avoid inappropriate use of this biomarker in routine care.

Neurology of Pregnancy: A Case-Oriented Review

The anatomic and physiologic changes that occur during pregnancy are unique. A neurologist needs to be aware of normal pregnancy-induced physiologic changes in the cardiovascular, renal, hematologic, and autoimmune systems, and the local anatomic changes, which include alteration of body habitus and pelvic ligaments. These changes are clearly advantageous, but in certain circumstances may predispose to pathology. In addition, pregnancy effects treatment of chronic neurologic conditions as regards medication safety and metabolism. This case-oriented review discusses the important aspects of pregnancy physiology and an approach to treatment of common disorders encountered during pregnancy including stroke, multiple sclerosis, epilepsy, and compression neuropathies.

Hemostatic Abnormalities in Patients With Severe Preeclampsia

Preeclampsia is the most common medical disorder of pregnancy. Early onset preeclampsia is defined as presentation of hypertension and proteinuria before 34 weeks of gestation. Alterations of endothelial cells and fibrin deposition in microvasculature lead to enhanced activation of the coagulation cascade and impaired fibrinolysis associated with multiple organ dysfunctions. Plasma samples were obtained from 50 patients with severe preeclampsia before 34 weeks of gestation and in 61 patients with late preeclampsia. Factor VIIIR:Ag, fibrinogen, D-dimer, and thrombomodulin increased with advanced pregnancy. The platelet count is very important because of the close correlation with the activations parameters of D-dimer and antithrombin. Our results were consistent with activated coagulation and lowering of platelet count in severe cases with early onset preeclampsia. Women who develop early onset preeclampsia characterized a subgroup of patients with more and severe hematologic abnormalities than women with late preeclampsia (after 34 weeks of gestation).

Disseminated intravascular coagulation in the HELLP syndrome: how much do we really know?

The rate of disseminated intravascular coagulation (DIC) during pregnancy varies among nations from 0.03% to 0.35%. The existing reports suggest dissimilarity in the underlying mechanisms leading to DIC during gestation. While in developing countries preeclampsia and the HELLP syndrome are prevalent causes of DIC, the leading causes in the developed countries are placental abruption and postpartum hemorrhage. In different cohort studies, DIC is reported in about 12-14% of women with preeclampsia. Nevertheless, it has been suggested that in most cases these women also had a HELLP syndrome and that the occurrence of DIC in women who had only preeclampsia without manifestations of the HELLP syndrome is rare. The aims of this review are to: (1) highlight the mechanisms leading to DIC; (2) describe the changes in the coagulation system during this complication; and; (3) discuss the diagnostic tool and treatment modalities of DIC, in women who develop a HELLP syndrome.

D-dimer concentration outliers are not rare in at-term pregnant women

OBJECTIVES

To determine the D-dimer levels in pregnant women at term and the differences between pregnant women with different D-dimer levels.

DESIGN AND METHODS

The plasma D-dimer concentrations in pregnant women at term were identified in a cross-sectional study. The clinical indicators that are potentially relevant to D-dimer levels were compared between the pregnant women with different D-dimer levels (i.e., normal, mildly increased, and severely increased).

RESULTS

There were always some D-dimer concentration outliers in the pregnant women at term regardless of the presence or absence of complications, and there were no significant differences in maternal age, gestational age, gravidity, parity, blood count, blood coagulation, or liver function between the pregnant women with different D-dimer levels.

CONCLUSIONS

D-dimer levels may vary significantly during pregnancy for unknown reasons. This variation, particularly in pregnant women at term, might lead to questionable diagnostic information regarding coagulation.

D-dimer: An Overview of Hemostasis and Fibrinolysis, Assays, and Clinical Applications

D-dimer is the smallest fibrinolysis-specific degradation product found in the circulation. The origins, assays, and clinical use of D-dimer will be addressed. Hemostasis (platelet and vascular function, coagulation, fibrinolysis, hemostasis) is briefly reviewed. D-dimer assays are reviewed. The D-dimer is very sensitive to intravascular thrombus and may be markedly elevated in disseminated intravascular coagulation, acute aortic dissection, and pulmonary embolus. Because of its exquisite sensitivity, negative tests are useful in the exclusion venous thromboembolism. Elevations occur in normal pregnancy, rising two- to fourfold by delivery. D-dimer also rises with age, limiting its use in those >80 years old. There is a variable rise in D-dimer in active malignancy and indicates increased thrombosis risk in active disease. Elevated D-dimer following anticoagulation for a thrombotic event indicates increased risk of recurrent thrombosis. These and other issues are addressed.

Changes in thrombin generation and D-dimer concentrations in women injecting enoxaparin during pregnancy and the puerperium

BACKGROUND

It is well accepted that the gravid state is hypercoagulable and a significant cause of both maternal morbidity and mortality in the Western world. Although thrombin generation is reported to be increased in pregnant women, uncertainty exists on the pattern of thrombin generation change during this time. The aim of this study is to describe thrombin generation changes and D-dimer concentrations in women injecting enoxaparin during pregnancy the postnatal period.

METHODS

One hundred and twenty-three women injecting enoxaparin had their thrombin generation, as measured by Calibrated Automated Thombinography (CAT), repeatedly assayed during pregnancy, once in each trimester, at delivery and 8 weeks post-partum. Furthermore, to understand the impact enoxaparin has on D-dimer concentrations during pregnancy, D-dimer concentrations were measured monthly in the recruited women.

RESULTS

Thrombin generation was found to increase in the first trimester (mean endogenous thrombin potential (ETP): 1391 nmol/L.min), further increasing during the second trimester (mean ETP: 1757 nmol/L.min), after which it plateaued through to delivery, where it peaked (mean ETP: 1857 nmol/L.min) and then fell back at 8 weeks post-partum (ETP: 1293 nmol/L.min). In contrast D-dimer concentrations increased exponentially during the antenatal period, despite the enoxaparin prescription.

CONCLUSION

Our results provide further evidence on alterations of thrombin generation during pregnancy and the postnatal period.

Risk-adapted management of acute pulmonary embolism: recent evidence, new guidelines

Venous thromboembolism (VTE), the third most frequent acute cardiovascular syndrome, may cause life-threatening complications and imposes a substantial socio-economic burden. During the past years, several landmark trials paved the way towards novel strategies in acute and long-term management of patients with acute pulmonary embolism (PE). Risk stratification is increasingly recognized as a cornerstone for an adequate diagnostic and therapeutic management of the highly heterogeneous population of patients with acute PE. Recently published European Guidelines emphasize the importance of clinical prediction rules in combination with imaging procedures (assessment of right ventricular function) and laboratory biomarkers (indicative of myocardial stress or injury) for identification of normotensive PE patients at intermediate risk for an adverse short-term outcome. In this patient group, systemic full-dose thrombolysis was associated with a significantly increased risk of intracranial bleeding, a complication which discourages its clinical application unless hemodynamic decompensation occurs. A large-scale clinical trial program evaluating new oral anticoagulants in the initial and long-term treatment of venous thromboembolism showed at least comparable efficacy and presumably increased safety of these drugs compared to the current standard treatment. Research is continuing on catheter-directed, ultrasound-assisted, local, low-dose thrombolysis in the management of intermediate-risk PE.

DIC score in pregnant women--a population based modification of the International Society on Thrombosis and Hemostasis score

Objectives

The objectives of this study were: 1) To determine the component needed to generate a validated DIC score during pregnancy. 2) To validate such scoring system in the identification of patients with clinical diagnosis of DIC.

Material and Methods

This is a population based retrospective study, including all women who gave birth at the ‘Soroka University Medical Center’ during the study period, and have had blood coagulation tests including complete blood cell count, prothrombin time (PT)(seconds), partial thromboplastin time (aPTT), fibrinogen, and D-dimers. Nomograms for pregnancy were established, and DIC score was constructed based on ROC curve analyses.

Results

1) maternal plasma fibrinogen concentrations increased during pregnancy; 2) maternal platelet count decreased gradually during gestation; 3) the PT and PTT values did not change with advancing gestation; 4) PT difference had an area under the curve (AUC) of 0.96 (p<0.001), and a PT difference ≥1.55 had an 87% sensitivity and 90% specificity for the diagnosis of DIC; 5) the platelet count had an AUC of 0.87 (p<0.001), an 86% sensitivity and 71% specificity for the diagnosis of DIC; 6) fibrinogen concentrations had an AUC of 0.95 (p<0.001) and a cutoff point ≤3.9 g/L had a sensitivity of 87% and a specificity of 92% for the development of DIC; and 7) The pregnancy adjusted DIC score had an AUC of 0.975 (p<0.001) and at a cutoff point of ≥26 had a sensitivity of 88%, a specificity of 96%, a LR(+) of 22 and a LR(−) of 0.125 for the diagnosis of DIC.

Conclusion

We could establish a sensitive and specific pregnancy adjusted DIC score. The positive likelihood ratio of this score suggests that a patient with a score of ≥26 has a high probability to have DIC.

Comparison of markers of coagulation activation and thrombin generation test in uncomplicated pregnancies

INTRODUCTION

Pregnancy is a well-established risk factor for venous thromboembolism, and is associated with a state of hypercoagulability or parameters of thrombin generation. Currently, there is a lack of consensual data on thrombin generation during pregnancy. This study aimed to find a sensitive and specific biological marker of coagulation activation and to identify parameters of thrombin generation.

PATIENTS AND METHODS

The population included 101 women with uncomplicated pregnancies. The objective of this study was to correlate thrombin generation test (measured at 5pM tissue factor, 4μM lipids and without thrombomodulin), with fibrinogen and markers of blood coagulation activation: D-dimer, prothrombin fragments 1+2 (F1+2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) in these women. Internal quality control was performed in each set of experiments.

RESULTS

Fibrinogen, D-dimer, F1+2, and TAT concentrations increased significantly throughout pregnancy, and were correlated with term of pregnancy. In our study, thrombin generation seemed to increase early on, and then remained stable throughout normal pregnancy, in contrast with other markers of blood coagulation activation, excepting FMC. The latter are subject to large inter-individual variations, especially during second trimester. No correlation was demonstrated between thrombin generation parameters and other activation markers.

CONCLUSION

While markers of coagulation activation significantly increased during pregnancy, thrombin generation increased only early on and remains stable during pregnancy. Finding a sensitive and specific biological marker for vascular pregnancy complications, such as FMC and thrombin generation levels, requires further investigation.

D-dimer in preeclampsia: systematic review and meta-analysis

Preeclampsia is a multifactorial disease characterized by high blood pressure and proteinuria after the 20th week of pregnancy. Preeclampsia is associated with microvasculature fibrin deposition and maternal organ dysfunction. D-dimer (D-Di) has been used as a marker of production/degradation of fibrin in vivo. D-Di has emerged as a useful diagnostic tool for thrombotic conditions because its plasma concentration has a high negative predictive value for venous thromboembolism. The aim of this study was to evaluate publications that assessed plasma D-Di in preeclampsia and normotensive pregnant subjects to define its diagnostic value. A total of 194 publications were identified. Following the exclusion process, seven studies were in accordance with the pre-defined eligibility criteria. This systematic review was performed with methodologic accuracy, including a careful definition of preeclampsia and a high sensitivity literature search strategy. Quality of the included studies was assessed in accordance with widely accepted literature recommendations. Our meta-analysis indicates that increased plasma D-Di is associated with preeclampsia in the third trimester of gestation vs normotensive pregnant subjects. These preliminary findings in this select group of patients clearly highlight the need for additional comprehensive studies throughout pregnancy, including the establishment of an appropriate cut-off, in order to fully elucidate the diagnostic/prognostic role of D-Di in preeclampsia.

Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Objective testing for DVT is crucial because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. This guideline focuses on the identification of optimal strategies for the diagnosis of DVT in ambulatory adults.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that clinical assessment of pretest probability of DVT, rather than performing the same tests in all patients, should guide the diagnostic process for a first lower extremity DVT (Grade 2B). In patients with a low pretest probability of first lower extremity DVT, we recommend initial testing with D-dimer or ultrasound (US) of the proximal veins over no diagnostic testing (Grade 1B), venography (Grade 1B), or whole-leg US (Grade 2B). In patients with moderate pretest probability, we recommend initial testing with a highly sensitive D-dimer, proximal compression US, or whole-leg US rather than no testing (Grade 1B) or venography (Grade 1B). In patients with a high pretest probability, we recommend proximal compression or whole-leg US over no testing (Grade 1B) or venography (Grade 1B).

CONCLUSIONS

Favored strategies for diagnosis of first DVT combine use of pretest probability assessment, D-dimer, and US. There is lower-quality evidence available to guide diagnosis of recurrent DVT, upper extremity DVT, and DVT during pregnancy.

Deep vein thrombosis: a clinical review

Background:

Deep vein thrombosis (DVT) is the formation of blood clots (thrombi) in the deep veins. It commonly affects the deep leg veins (such as the calf veins, femoral vein, or popliteal vein) or the deep veins of the pelvis. It is a potentially dangerous condition that can lead to preventable morbidity and mortality.

Aim:

To present an update on the causes and management of DVT.

Methods:

A review of publications obtained from Medline search, medical libraries, and Google.

Results:

DVT affects 0.1% of persons per year. It is predominantly a disease of the elderly and has a slight male preponderance. The approach to making a diagnosis currently involves an algorithm combining pretest probability, D-dimer testing, and compression ultrasonography. This will guide further investigations if necessary. Prophylaxis is both mechanical and pharmacological. The goals of treatment are to prevent extension of thrombi, pulmonary embolism, recurrence of thrombi, and the development of complications such as pulmonary hypertension and post-thrombotic syndrome.

Conclusion:

DVT is a potentially dangerous condition with a myriad of risk factors. Prophylaxis is very important and can be mechanical and pharmacological. The mainstay of treatment is anticoagulant therapy. Low-molecular-weight heparin, unfractionated heparin, and vitamin K antagonists have been the treatment of choice. Currently anticoagulants specifically targeting components of the common pathway have been recommended for prophylaxis. These include fondaparinux, a selective indirect factor Xa inhibitor and the new oral selective direct thrombin inhibitors (dabigatran) and selective factor Xa inhibitors (rivaroxaban and apixaban). Others are currently undergoing trials. Thrombolytics and vena caval filters are very rarely indicated in special circumstances.

D-dimer testing in pregnant patients: towards determining the next 'level' in the diagnosis of deep vein thrombosis

SUMMARY BACKGROUND

The role of D-dimer in excluding deep vein thrombosis (DVT) in pregnancy is currently uncertain. We hypothesized that the specificity of sensitive D-dimer assays could be improved without compromising sensitivity by using higher D-dimer cut-off values.

OBJECTIVE

To determine the test characteristics of two rapid enzyme-linked immunosorbent assays and three latex agglutination assays in pregnancy.

METHOD

We recruited consecutive pregnant women who presented to participating centers with suspected DVT for the study. Symptomatic women were investigated with compression ultrasonography, and received 3 months of clinical follow-up to assess for the presence of venous thrombosis. Plasma samples for D-dimer were collected and frozen at the time of presentation. The median and mean D-dimer values for respective trimesters of pregnancy in patients with and without DVT were calculated. Receiver operating curves (ROCs) were plotted for respective assays to establish the best cut-points. The test characteristics corresponding to standard cut-points and these 'pregnancy' cut-points are presented.

RESULTS

The prevalence of DVT in our cohort was 6.6% (95% confidence interval 4.0-10.6%). The mean and median D-dimer values were significantly increased throughout pregnancy. Overall, women with confirmed DVT had higher D-dimer levels than women without DVT (P < 0.0001). Improved specificities (62-79%) were observed with the use of higher cut-points obtained from ROCs for all five assays, and high sensitivities were maintained (80-100%) for DVT diagnosis.

CONCLUSION

Using higher cut-points than those used in non-pregnant patients, the specificity of D-dimer assays for the diagnosis of DVT in pregnancy can be improved without compromising sensitivity. Validation in prospective management studies is needed.

Thromboembolism in pregnancy

Venous thromboembolism in pregnancy is a clinical emergency that has been associated with significant risk for maternal and fetal morbidity and mortality. The adaptation of the maternal hemostatic system to pregnancy predisposes women to an increased risk of thromboembolism. A timely diagnosis of deep venous thrombosis is crucial because up to 24% of patients with untreated deep venous thrombosis develop a pulmonary embolism. Recent clinical guidelines identify compression venous ultrasound as the best way to diagnose deep venous thrombosis in pregnancy and CT pulmonary angiography as the best way to diagnose pulmonary embolism in pregnancy. Therapy involves supportive care and anticoagulation with unfractionated or low molecular weight heparin, depending on the clinical scenario.

Changes in haemostasis during normal pregnancy: does homocysteine play a role in maintaining homeostasis?

Homocysteine, derived from the demethylation of the ammo acid methionine, is either further catabolised by trans-sulfuration to cysteine or remethylated to methionine. Remethylation to methionine requires the cofactors, folate and vitamin B12. Folate is an effective homocysteine-lowering agent and, thus, homocysteine and folate status are inversely related. Hyperhomocysteinaemia is a strong independent risk factor for venous thromboembolism (VTE) and is associated with adverse pregnancy outcomes such as pre-eclampsia, placental abruption, early pregnancy loss and neural-tube defects. Pregnancy is a risk factor for VTE as a result of prothrombotic changes in levels of haemostatic factors. However, despite this hypercoagulable state, the incidence of pregnancy-associated VTE is relatively low. Hyperhomocysteinaemia is associated with abnormalities in markers of coagulation activation, and recent research suggests that folic acid supplementation, as well as lowering homocysteine, lowers markers of coagulation activation and increases levels of coagulation inhibitors. Tissue factor (TF) is the initiator of blood coagulationin vivo, and homocysteine induces TF expressionin vitro. During pregnancy, monocyte TF expression is lower than that in the non-pregnant state, and this lowering of TF may act to counterbalance increases in coagulation activation. Furthermore, despite a high folate requirement, several studies have reported that homocysteine is lower in normal pregnancy than in the non-pregnant state. Although the exact mechanism of homocysteine lowering during pregnancy is unclear, one possible outcome of lower homocysteine may be the protection of women from pregnancy complications and VTE, and thus lower homocysteine may contribute to maintaining homeostasis in haemostasis.

Coagulation-fibrinolysis is more enhanced in twin than in singleton pregnancies

AIMS

To examine whether coagulation-fibrinolysis in late pregnancy in women with twin pregnancies is more pronounced than in women with singleton pregnancies.

PATIENTS AND METHODS

The plasma levels of D-dimer, fibrinogen/fibrin degradation products (FDP), and fibrinogen, the platelet count, and the antithrombin activity were assessed from 3 weeks before delivery until postpartum day 7 in 48 women (24 singleton and 24 twin pregnancies) without preeclampsia who underwent cesarean sections.

RESULTS

Women with singleton or twin pregnancies gave birth at 37.3+/-1.2 weeks or 35.2+/-1.4 weeks, respectively. Compared with singleton mothers, prenatal D-dimer and FDP levels were consistently and significantly higher among women with twin pregnancies. A significantly larger proportion of twin mothers exhibited prenatal levels of D-dimer >5.0 microg/mL, FDP >10.0 microg/mL, fibrinogen <420 mg/mL and antithrombin activity <70%. In addition, prenatal antithrombin activity in plasma was significantly lower.

CONCLUSIONS

Coagulation-fibrinolysis is more enhanced in women with twin gestation than in women with singleton gestation.

Imaging pulmonary embolism in pregnancy: what is the most appropriate imaging protocol?

Pulmonary embolism is the leading cause of death in pregnancy. Despite the difficulties in clinical diagnosis and the concerns regarding radiation of the fetus, the British Thoracic Society guidelines for imaging pulmonary embolism do not specifically address the issue of imaging for pulmonary embolism in this group. This communication discusses the difficulties of diagnosis and imaging pulmonary embolism in pregnancy and proposes a suitable imaging protocol. Clinical exclusion of patients from further imaging is recommended if the patient has a low pre-test probability of pulmonary embolism and a normal d-dimer. It is advised that all remaining patients undergo bilateral leg Doppler assessment. If this test is positive, the patient should be treated for pulmonary embolism; if negative, all patients should be referred for CT pulmonary angiography. Ideally, informed consent should be obtained prior to CT scanning. All neonates exposed to iodinated contrast in utero should have their thyroid function tested in the first week of life due to the theoretical risk of contrast induced hypothyroidism.

The role of d-dimer as first marker of thrombophilia in women affected by sterility: implications in pathophysiology and diagnosis of thrombophilia induced sterility

BACKGROUND: D-dimer is considered a marker of hypercoagulable state and of endogenous fibrinolysis, so increased d-dimer is detectable in patients affected by thrombosis. Yet, several studies showed that also infertility, in particular secondary infertility due to recurrent fetal losses, has been often related to thrombotic events, in particular in women carrying thrombotic risk factors such as inherited thrombophilia (MTHFRC677T, PTHRA20210G, Factor V Leiden polimorphisms and/or inhAfter this screening we selected 39erited protein C, protein S, AT III deficiency) or acquired thrombophilia (primary antiphospholipid syndrome, acquired protein C, protein S, AT III deficiency, drugs induced thrombophilia). However, because its high predictive negative value in case of suspected thrombosis, increased d-dimer has been often associated to subclinical thrombophilia. The aim of this study is to investigate the role of d-dimer as first marker of thrombophilia in women affected by unexplained infertility and subsequently to search the cause of increased d-dimer, such as inherited and/or acquired thrombophilia. PATIENTS AND METHODS: We selected 79 patients with unexplained primary or secondary infertility. We excluded 40 patients affected by hydrosalpinx, uterine fibroids, uterine malformations, endocrinological and immunological diseases, luteal insufficiency, cytogenetical alterations. All remaining 39 patients were tested for d-dimer and divided in two groups: the patients of group A (25 patients) showed increased plasma d-dimer, in group B were included 14 patients with normal plasma level of d-dimer. After this step all 39 patients were screened for MTHFRC677T, PTHRA20210G, Factor V Leiden polimorphisms, protein C, protein S, AT III, anticardiolipin IgM and IgG, lupus anticoagulant. In the control group were included 15 age matched women without sterility problems referred to our outpatient's section of vascular medicine for suspected deep venous thrombosis.Statistical analysis was based on chi2 test, differences were considered to be significant if p < 0.05. RESULTS: D-dimer was increased in 25/39 and 20/25 showed inherited/acquired thrombophilia while patients with normal d-dimer showed inherited/acquired thrombophilia in 7/14 (p: < 0.05, s). DISCUSSION: D-dimer is a well known marker of hypercoagulable state, in particular its high predictive negative value in case of suspected thrombosis has been recognised by several reports. Yet, increased d-dimer has been identified also for subclinical thrombophilia besides for vascular thrombosis. Our data, in fact, for the first time suggest an interesting role of d-dimer to identify women affected by unexplained primary or secondary infertility and thrombophilia. So, probably there is a role for d-dimer in these subjects for its predictive positive value. Of course, further data on large based population are needed to confirm our results, because these findings may speed up a diagnostic screening in these patients also for a good cost/effectiveness of this test.

Thromboembolic disease in pregnancy

Venous thromboembolic disease is a major cause of maternal morbidity and mortality. Virchow's triad of hypercoagulability, venous stasis, and vascular damage all occur during pregnancy. The risk of venous thromboembolism is five to six times higher during pregnancy and the puerperium. Risk factors include age greater than 35, antiphospholipid antibodies, inherited thrombophilias, operative delivery, increased parity, obesity, mechanical heart valves,and family history. Prophylactic and therapeutic anticoagulation is recommended for women at risk. Low molecular weight heparins are safe and effective in most cases.