Philippe de Moerloose

NON-INVASIVE DIAGNOSIS OF VENOUS THROMBOEMBOLISM IN OUTPATIENTS

BACKGROUND We designed a simple and integrated diagnostic algorithm for acute venous thromboembolism based on clinical probability assessment of deep-vein thrombosis (DVT) or pulmonary embolism (PE), plasma D-dimer measurement, lower-limb venous compression ultrasonography, and lung scan to reduce the need for phlebography and pulmonary angiography. METHODS 918 consecutive patients presenting at the emergency ward of the Geneva University Hospital, Geneva, Switzerland, and Hôpital Saint-Luc, Montreal, Canada, with clinically suspected venous thromboembolism were entered into a sequential diagnostic protocol. Patients in whom venous thromboembolism was deemed absent were not given anticoagulants and were followed up for 3 months. FINDINGS A normal D-dimer concentration (<500 microg/L by a rapid ELISA) ruled out venous thromboembolism in 286 (31%) members of the study cohort, whereas DVT by ultrasonography established the diagnosis in 157 (17%). Lung scan was diagnostic in 80 (9%) of the remaining patients. Venous thromboembolism was also deemed absent in patients with low to intermediate clinical probability of DVT and a normal venous ultrasonography (236 [26%] patients), and in patients with a low clinical probability of PE and a non-diagnostic result on lung scan (107 [12%] patients). Pulmonary angiography and phlebography were done in only 50 (5%) and 2 (<1%) of the patients, respectively. Hence, a non-invasive diagnosis was possible in 866 (94%) members of the entire cohort. The 3-month thromboembolic risk in patients not given anticoagulants, based on the results of the diagnostic protocol, was 1.8% (95% CI 0.9-3.1). INTERPRETATION A diagnostic strategy combining clinical assessment, D-dimer, ultrasonography, and lung scan gave a non-invasive diagnosis in the vast majority of outpatients with suspected venous thromboembolism, and appeared to be safe.

Massive transfusion and coagulopathy: pathophysiology and implications for clinical management

PurposeTo review the pathophysiology of coagulopathy in massively transfused, adult and previously hemostatically competent patients in both elective surgical and trauma settings, and to recommend the most appropriate treatment strategies.MethodsMedline was searched for articles on “massive transfusion,” “transfusion,” “trauma,” “surgery,” “coagulopathy” and “hemostatic defects.” Agroup of experts reviewed the findings.Principal findingsCoagulopathy will result from hemodilution, hypothermia, the use of fractionated blood products and disseminated intravascular coagulation. The clinical significance of the effects of hydroxyethyl starch solutions on hemostasis remains unclear. Maintaining a normal body temperature is a first-line, effective strategy to improve hemostasis during massive transfusion. Red cells play an important role in coagulation and hematocrits higher than 30% may be required to sustain hemostasis. In elective surgery patients, a decrease in fibrinogen concentration is observed initially while thrombocytopenia is a late occurrence. In trauma patients, tissue trauma, shock, tissue anoxia and hypothermia contribute to the development of disseminated intravascular coagulation and microvascular bleeding. The use of platelets and/or fresh frozen plasma should depend on clinical judgment as well as the results of coagulation testing and should be used mainly to treat a clinical coagulopathy.ConclusionsCoagulopathy associated with massive transfusion remains an important clinical problem. It is an intricate, multifactorial and multicellular event. Treatment strategies include the maintenance of adequate tissue perfusion, the correction of hypothermia and anemia, and the use of hemostatic blood products to correct microvascular bleeding.RésuméObjectifRevoir la physiopathologie de la coagulopathie chez les adultes transfusés massivement et auparavant compétents sur le plan hémostatique, à la fois dans le contexte d’une intervention chirurgicale réglée ou à la suite d’un traumatisme. Recommander les stratégies thérapeutiques les plus appropriées.MéthodeDans Medline, nous avons cherché les articles traitant de “massive transfusion,” “transfusion,” “trauma,” “surgery,”“coagulopathy” et “hemostatic defects.” Un groupe d’experts a examiné les résultats.Constatations principalesLa coagulopathie résulte de l’hémodilution, l’hypothermie, l’usage de produits sanguins fractionnés et la coagulation intravasculaire disséminée. La portée clinique des effets des solutions d’hydroxyéthyl-amidon sur l’hémostase n’est toujours pas claire. Le maintien d’une température corporelle normale est une stratégie de première intention efficace pour améliorer l’hémostase pendant la transfusion massive. Les globules rouges sont importants dans la coagulation et des hématocrites supérieurs à 30% pourraient être nécessaires à une hémostase adéquate. Chez les patients en chirurgie réglée, une baisse de la concentration de fibrinogène est observée précocement tandis que la thrombocytopénie est plus tardive. Chez les traumatisés, le trauma tissulaire, le choc, l’anoxie et l’hypothermie tissulaires contribuent au développement d’une coagulation intravasculaire disséminée et du saignement microvasculaire. L’utilisation de plaquettes et/ou de plasma frais congelé dépendra du jugement du clinicien ainsi que des résultats des tests de coagulation. La transfusion devra surtout viser le traitement d’une coagulopathie clinique (saignement microvasculaire).ConclusionLa coagulopathie associée à la transfusion massive demeure un important problème clinique. C’est un événement complexe, multifactoriel et multicellulaire. Le traitement comprend le maintien d’une perfusion tissulaire adéquate, la correction de l’hypothermie et de l’anémie et l’usage de produits sanguins hémostatiques pour corriger le saignement microvasculaire.

TAFI antigen and D-dimer levels during normal pregnancy and at delivery

We have investigated whether the levels of thrombin‐activatable fibrinolysis inhibitor (TAFI) were correlated with d‐dimer levels during pregnancy and at delivery. From the 10th week of pregnancy to delivery, 519 samples from 144 women (mean age 29·3 ± 5, range 19–43) were obtained. We confirm the gradual increase of d‐dimer levels, and provide reference intervals for d‐dimer measurements throughout normal pregnancy. TAFI levels increased moderately during pregnancy but no inverse correlation with d‐dimer levels was observed.

Platelet count at term pregnancy: a reappraisal of the threshold ☆

Objective To assess the safety of a new platelet count threshold for the definition of maternal thrombocytopenia late in pregnancy. Methods A platelet count was performed in 6770 pregnant women late in pregnancy and in 6103 of their newborns as well as in a control group of 287 age-matched nonpregnant healthy women. Results The prevalence of maternal thrombocytopenia (platelet count less than 150 × 109/L) was 11.6%. The mean platelet counts (248 compared with 213 × 109/L) and 2.5th percentile (164 compared with 116 × 109/L) were significantly higher in healthy nonpregnant women than in pregnant women. Among thrombocytopenic pregnant women, 621 (79%) had platelet counts between 116 and 149 × 109/L; none (0%; 95% confidence interval 0, 0.6) had complications related to thrombocytopenia, and none of their newborns had severe thrombocytopenia (platelet count less than 20 × 109/L). Conclusion In healthy pregnant women, a platelet count over 115 × 109/L late in pregnancy does not require further investigation during pregnancy and may be considered a safe threshold.

D-Dimer plasma concentration in various clinical conditions: Implication for the use of this test in the diagnostic approach of venous thromboembolism

Plasma measurement of D-Dimer (DD) represents a definite aid in the diagnostic approach of outpatients with suspected venous thromboembolism (VTE). However, the high sensitivity (about 95%) of the test which allows to rule out VTE when concentrations are below a given cutoff (500 micrograms/L as measured by the ELISA technique) is counterbalanced by a poor specificity (about 40%). Because the specificity might even be lower in patients who are hospitalized we determined the DD plasma concentration in 255 patients who were consecutively admitted in general internal medicine wards with various pathological conditions. The proportion of patients who had DD levels below the cutoff of 500 micrograms/L was 6% (1/18) in patients with VTE and 22% (52/237) in hospitalized patients without VTE: the figure was 21% in patients with pulmonary infections, 14% in patients with other infections, 11% in patients with neoplastic diseases, 34% in patients with coronary or cerebrovascular disease, 19% in patients with cardiac failure, 69% in patients with rheumatologic disease and in 16% in subjects with miscellaneous clinical conditions. The high rate of elevated plasma DD in hospitalized patients questions the usefulness of this test in the diagnostic approach of VTE in aged patients who present with concomitant disease like infections, neoplasia, cardiac failure and many other pathological conditions, except rheumatologic affections and coronary or cerebrovascular diseases.

Red blood cell methylfolate and plasma homocysteine as risk factors for venous thromboembolism: a matched case-control study

BACKGROUND Moderate hyperhomocysteinaemia is a risk factor for venous thromboembolism. We do not know whether this risk depends on homocysteine itself or on components of the homocysteine remethylation pathway, such as methylfolate. We did a case-control study to analyse the relation between the major components of the homocysteine remethylation pathway and risk of venous thromboembolism. METHODS We measured concentrations of homocysteine, methionine, and folate in plasma, total folate and methylfolate in red-blood cells, and 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T genotype and other known risk factors for venous thromboembolic disease in 243 patients with deep vein thrombosis or pulmonary embolism and controls matched for sex and age. FINDINGS Concentrations in plasma of homocysteine differed significantly between cases and controls. We noted a strong concentration-dependent association between concentrations of methylfolate in red-blood cells and risk of venous thromboembolism. The adjusted conditional odds ratio ranged from 1.0 for methylfolate 249 microg/L or greater to 7.1 (3.2-15.8) for methylfolate 141 microg/L or less. Methionine concentrations below the median were also independently associated with raised risk of venous thromboembolic disease, as were established risk factors such as high body-mass index, history of cancer, family history of thromboembolism, oral contraceptive use, and factor V Leiden mutation. Furthermore, the association between concentrations of methylfolate in red-blood cells and risk of thromboembolism varied according to MTHFR C677T genotype. INTERPRETATION Measurement of methylfolate concentrations in red-blood cells might help to identify people at risk of venous thromboembolism.

Fibrinogen and the Risk of Thrombosis

Fibrinogen contributes to thrombosis risk in different ways. Indeed, various mutations in the fibrinogen genes predispose to thrombosis. At the same time, high levels of fibrinogen are also associated with thrombotic complications. Although the underlying causative mechanisms are not clear, this most likely involves the associated inflammatory and hypercoagulable states. In the last few years, particular attention has focused on the polymorphisms of fibrinogen genes involved in increased fibrinogen levels or fibrinogen qualitative changes. The association between dysfibrinogenemia and risk of thrombosis is well known, and some mechanisms have been clearly identified. Paradoxically, some patients with either hypofibrinogenemia or afibrinogenemia may also suffer from severe thromboembolic complications. The management of these patients is particularly challenging because they are not only at risk of thrombosis but also of bleeding. This review discusses the various quantitative and qualitative defects of fibrinogen associated with thrombosis, the tests that may predict the thrombotic risk, as well as some preventive or therapeutic approaches.

Toll-like receptor 2 mediates the activation of human monocytes and endothelial cells by antiphospholipid antibodies

The presence of antiphospholipid antibodies (aPLAs) is associated with arterial or venous thrombosis and/or recurrent fetal loss. The proposed pathogenic mechanisms for aPLA effects include the inflammatory activation of monocytes and endothelial cells. Toll-like receptors (TLRs) are candidate signaling intermediates. The aim of this study was to investigate the relative contribution of TLR2 and TLR4 in cell activation by aPLAs. Of 32 patient-derived aPLAs, 19 induced an inflammatory activation of human monocytes and umbilical vein endothelial cells (HUVECs). In HUVECs, inflammatory responses to these aPLAs were increased by TNF pretreatment, which increases the expression of TLR2 but not TLR4. Anti-TLR2 but not anti-TLR4 antibodies reduced the aPLA-induced activation of monocytes and HUVECs. aPLAs activated TLR2-expressing human embryonic kidney 293 (HEK293) cells but not TLR4-expressing cells. Binding studies demonstrated an interaction between aPLAs and TLR2 but not TLR4. A role for CD14, a coreceptor for TLR2 and TLR4, can be inferred by observations that anti-CD14 antibodies reduced responses to aPLAs in monocytes, and that responses in HEK293 cells expressing TLR2 and CD14 were greater than in HEK293 cells expressing TLR2 alone. Our results demonstrate a role for TLR2 and CD14 in human endothelial cell and monocyte activation by aPLAs.

Congenital fibrinogen disorders.

Inherited disorders of fibrinogen affect either the quantity (afibrinogenemia and hypofibrinogenemia) or the quality (dysfibrinogenemia) of the circulating fibrinogen or both (hypodysfibrinogenemia). Most often, patients with congenital fibrinogen disorders suffer from a bleeding diathesis but paradoxically may undergo severe thrombotic episodes. Pregnancy loss is another common clinical complication. Even in specialized laboratories, the precise diagnosis of some fibrinogen disorders may be challenging. Characterization of the molecular defect(s) is important as it provides a more accurate diagnosis, may enable prenatal diagnosis, will help elaborate a diagnostic strategy, and may distinguish in some cases those patients at risk of thrombosis rather than bleeding. However, the phenotype-genotype correlation is not easy to establish, and global hemostasis assays may provide a better evaluation of the patients hemostatic state. Replacement therapy is effective in treating bleeding episodes, but it is important to tailor individual treatments because the pharmacokinetics of fibrinogen after replacement therapy is highly variable among patients. Although the number of cases studied and identified mutations are already quite substantial, the collection and comparison of molecular, biochemical, and clinical data will continue to yield valuable information on the development and course of these diseases, as well as on the choice of the most appropriate treatments.

Congenital fibrinogen disorders: an update

Hereditary fibrinogen abnormalities comprise two classes of plasma fibrinogen defects: Type I, afibrinogenemia or hypofibrinogenemia, which has absent or low plasma fibrinogen antigen levels (quantitative fibrinogen deficiencies), and Type II, dysfibrinogenemia or hypodysfibrinogenemia, which shows normal or reduced antigen levels associated with disproportionately low functional activity (qualitative fibrinogen deficiencies). In afibrinogenemia and hypofibrinogenemia, most mutations of the FGA, FGB, or FGG fibrinogen encoding genes are null mutations. In some cases, missense or late truncating nonsense mutations allow synthesis of the corresponding fibrinogen chain but intracellular fibrinogen assembly and/or secretion are impaired. Afibrinogenemia is associated with mild-to-severe bleeding, whereas hypofibrinogenemia is most often asymptomatic. Thromboembolism may occur either spontaneously or in association with fibrinogen substitution therapy. Women with afibrinogenemia suffer from recurrent pregnancy loss but this can also occur in women with hypofibrinogenemia. Dysfibrinogenemia, caused mainly by missense mutations, is commonly associated with bleeding, thrombophilia, or both; however, most individuals are asymptomatic. Hypodysfibrinogenemia is a subcategory of this disorder. Even in specialized laboratories, the precise diagnosis of some fibrinogen disorders may be difficult. Determination of the molecular defects is important because it gives the possibility to confirm the diagnosis, to elaborate a diagnostic strategy, to distinguish in some cases that the patient is at risk of thrombosis rather than bleeding, and to enable prenatal diagnosis. However, genotype-phenotype correlations are not easy to establish. Replacement therapy is effective in treating bleeding episodes, but because the pharmacokinetics of fibrinogen after replacement therapy is highly variable among patients, it is important to adjust the treatment individually.