Should prophylaxis be used in adolescent and adult patients with severe haemophilia? An European survey of practice and outcome data

A survey of 21 haemophilia doctors, throughout Europe, who care for a total of approximately 5000 patients with bleeding disorders addressing practice and opinions regarding prophylaxis in patients aged 16-24 years and adults aged over 50 years, is presented. The outcome of adolescent patients who reduced or stopped prophylaxis was recorded. Eighteen of 19 respondents would consider modification of established prophylaxis in the adolescent age group, principal considerations being avoidance of risks of further concentrate exposure, predicted poor compliance and treatment costs. The preferred age for modification was 16-20 years, but there was very little consensus on the particular prophylactic regime recommended. Approximately, half of a cohort of 218 patients with severe haemophilia successfully reduced or stopped prophylaxis when they reached adolescence. Only 26 of 92 (28%) of the patient cohort who stopped prophylaxis, required reintroduction of a prophylactic regime and 12 of 59 (20%) of those who reduced the intensity of prophylaxis had to reintroduce a more intensive regime. A majority of respondents would consider starting prophylaxis in those over 50 years. There was no consensus as to indications for this practice or the nature of the prophylaxis protocol. We conclude that there is an absence of consensus on the management of patients with severe haemophilia, as they pass through adolescence and young adulthood, and reach the age of 50. Aggregate outcome data suggest a significant proportion of patients in the 18-22 years age range may be able to reduce or stop prophylaxis. A substantial number of older patients are on prophylaxis.

[Von Willebrand disease: a common and unrecognized bleeding disorder]

The von Willebrand factor plays an important role in primary and secondary hemostasis. Von Willebrand disease is due to a quantitative or qualitative abnormality of von Willebrand factor. It is the most frequent constitutional abnormality of hemostasis. The main manifestation of von Willebrand disease is a mucocutaneous hemorrhagic syndrome; however, von Willebrand disease is characterized by an important clinical and biological heterogeneity. Its transmission is autosomal, usually dominant. A screening can be made by a general practitioner on the basis of a good clinical history. It is then important to confirm the diagnosis in a specialized laboratory because an adequate treatment can be prescribed to avoid hemorrhagic complications, in particular at the time of surgical procedures.

[Inherited thrombophilia and arterial diseases]

Thrombophilia may be defined as an acquired or congenital abnormality of hemostasis predisposing to thrombosis. Some of the inherited abnormalities such as factor V Leiden mutation, factor II G20210A mutation as well as deficiencies in antithrombin, protein C and protein S, are already known to be risk factors for venous thromboembolism. This review focuses on the link between these abnormalities and arterial thrombosis. Routine screening for these disorders is not indicated in most cases of arterial complications, but could be useful in some sub-groups of patients, such as young patients, smokers, patients on oral contraception, or those with premature occlusion after revascularization procedures. Anticoagulation rather than antiplatelet therapy may be preferable for these patients.

Hypofibrinogenaemia caused by a novel FGG missense mutation (W253C) in the gamma chain globular domain impairing fibrinogen secretion

BACKGROUND

Inherited disorders of fibrinogen are rare and affect either the quantity (hypofibrinogenaemia and afibrinogenaemia) or the quality of the circulating fibrinogen (dysfibrinogenaemia). Extensive allelic heterogeneity has been found for all three disorders: in congenital afibrinogenaemia >30 mutations, the majority in FGA, have been identified in homozygosity or in compound heterozygosity. Several mutations have also been identified in patients with hypofibrinogenaemia; many of these are heterozygous carriers of afibrinogenaemia null mutations.

OBJECTIVE

To report the case of a patient from Slovakia diagnosed with hypofibrinogenaemia characterised by fibrinogen concentrations of around 0.7 g/l.

RESULTS

The patient was found to be heterozygous for a novel missense mutation W253C (W227C in the mature protein) in the C-terminal globular domain of the fibrinogen gamma chain. Co-expression of the W253C FGG mutant cDNA (fibrinogen Bratislava) in combination with wild-type FGA and FGB cDNAs showed that fibrinogen molecules containing the mutant gamma chain can assemble intracellularly but are not secreted into the media, confirming the causative nature of the identified mutation.

CONCLUSIONS

Current analysis of fibrinogen Bratislava indicates that the domains important for the processes of hexamer assembly and hexamer secretion should not be considered as strictly restricted to one or other fibrinogen chain.

Biological effects of aspirin and clopidogrel in a randomized cross-over study in 96 healthy volunteers

BACKGROUND

Some data suggest that biological 'resistance' to aspirin or clopidogrel may influence clinical outcome.

OBJECTIVE

The aim of this study was to evaluate the relationship between aspirin and clopidogrel responsiveness in healthy subjects.

METHODS

Ninety-six healthy subjects were randomly assigned to receive a 1-week course of aspirin 100 mg day(-1) followed by a 1-week course of clopidogrel (300 mg on day 1, then 75 mg day(-1)), or the reverse sequence, separated by a 2-week wash-out period. The drug effects were assessed by means of serum TxB2 assay, platelet aggregation tests, and the PFA -100 and Ultegra RPFA -Verify Now methods.

RESULTS

Only one subject had true aspirin resistance, defined as a serum TxB2 level > 80 pg microL(-1) at the end of aspirin administration and confirmed by platelet incubation with aspirin. PFA-100 values were normal in 29% of the subjects after aspirin intake, despite a drastic reduction in TxB2 production; these subjects were considered to have aspirin pseudo-resistance. Clopidogrel responsiveness was not related to aspirin pseudo-resistance. Selected polymorphisms of platelet receptor genes were not associated with either aspirin or clopidogrel responsiveness.

CONCLUSIONS

In healthy subjects, true aspirin resistance is rare and aspirin pseudo-resistance is not related to clopidogrel responsiveness.

The coagulopathy of massive transfusion

Recently, the Groupe d'Intérêt en Hémostase Périopératoire reviewed the pathophysiology of coagulopathy in massively transfused, adult and previously haemostatically competent patients in both elective surgical and trauma settings. In this article, we focus on our main observations. First, in most cases, the onset and severity of coagulopathy associated with massive transfusion differs depending on whether haemorrhage occurs as a result of trauma or elective surgery. In trauma patients, tissue trauma is uncontrolled, the interval between haemorrhage and treatment can vary widely, hypovolemia, shock and hypothermia are frequent, and coagulopathy is often related to the development of disseminated intravascular coagulation. Monitoring of haemostasis occurs late, when coagulopathy is installed, and treatment can be very difficult. In elective surgery patients, the situation remains controlled and, in most cases, a decrease in fibrinogen concentration is observed initially while thrombocytopenia is a late occurrence. Monitoring of haemostasis is ongoing and treatment is usually much simpler. Second, blood products have changed over time and this has affected the management of the bleeding patient. Contrary to the recommendations of studies published at a time when whole blood was readily available, the first line of treatment (at least in elective surgery patients) ought to be with fresh-frozen plasma to correct decreased levels of coagulation factors. The role of recombinant activated factor VII to treat bleeding that cannot be controlled by conventional measures remains to be clarified. Coagulopathy associated with massive transfusion remains an important clinical problem. Treatment strategies must be adapted to the context and to the blood products available. Nevertheless, the level of evidence supporting specific treatment options is low and more studies are required to guide our management of massively transfused patients.

Not all statins interfere with clopidogrel during antiplatelet therapy

BACKGROUND

Clopidogrel and statins are frequently coadministered in patients with ischemic heart diseases. Recent reports suggested that clopidogrel's effectiveness in inhibiting adenosine diphosphate (ADP)-induced platelets aggregation is attenuated by co-administration of certain statins. The objective of the present study was to define which statin might interfere with the antiaggregation property of clopidogrel.

METHODS

We designed a pharmacokinetic study and tested ex vivo platelet function on 21 healthy volunteers who received clopidogrel and all currently commercially available statins: rosuvastatin [10 mg o.d.], simvastatin [20 mg o.d.], fluvastatin [80 mg o.d.], pravastatin [40 mg o.d.], and atorvastatin [20 mg o.d.]. Each statin was administered for 7 days followed by 1 week of wash-out period with clopidogrel treatment alone. Detection of the statins in the plasma was performed on all blood samples, using HPLC analytical method.

RESULTS

All individuals, except one, were responders to clopidogrel with inhibition of ex vivo ADP induced platelet aggregation. All statins, except pravastatin, were detectable in the plasma at the end of each treatment period in all patients, and no statin was detectable after any of the wash-out periods. Clopidogrel was significantly less efficient to prevent platelet aggregation when coadministrated with simvastatin or fluvastatin. No difference was observed in clopidogrel efficacy when coadministered with rosuvastatin, pravastatin or atorvastatin.

CONCLUSIONS

This is the first study investigating clopidogrel-statin interactions on ex vivo platelet function with all commercially available statins and which were administered to the same individuals. It demonstrates in healthy volunteers that at the doses used in this study, simvastatin and fluvastatin, but not atorvastatin, pravastatin or rosuvastatin interfere with the anti-aggregation effect of clopidogrel.

Anti-protein S antibodies following a varicella infection: detection, characterization and influence on thrombin generation

Postinfectious purpura fulminans is a rare disease. Varicella is one of the precipitating conditions and we recently observed such a case. The 4-year-old child was found to have a severe transient protein S deficiency. By enzyme-linked immunosorbent assay and surface plasmon resonance we first demonstrated that anti-protein S antibodies were present and also transient. Next we characterized the epitopes against which these antibodies were directed and found that they predominantly recognized the N-terminal part of protein S. Finally we showed by thrombography a transient dramatic hypercoagulable state as a result of thrombin being unregulated by the dynamic protein C inhibitory system: in vitro thrombin generation, in response to a low concentration of tissue factor, was almost insensitive to activated protein C up to 25 nmol L(-1) on day 4 while it was normally sensitive on day 42. For the first time, we demonstrated a temporal relationship between protein S deficiency, antibodies to protein S and hypercoagulability, thus supporting the pathogenic role of these antibodies.

[Changes in D-dimer levels during pregnancy and the postpartum period: results of two studies]

In outpatients D-dimer (DD) measurement is included in most algorithms to exclude venous thromboembolism (VTE). We have recently performed two studies to evaluate the evolution of DD during pregnancy and the postpartum. During pregnancy, DD increase progressively and are of poor value to exclude VTE after 20 weeks of gestation. During labour, DD are usually very high and decrease quickly during the first 3 days post-delivery. Many weeks are necessary to obtain their normalisation and therefore their utility to rule out VTE is very limited until 4 weeks postpartum. This increase of DD values until 4 to 6 weeks after delivery correlates with the length of antithrombotic prophylaxis recommended for women at high risk of VTE.

[Menorrhagia and hemostatic abnormalities: diagnosis and treatment]

Menorrhagias consisting of heavy menstrual bleeding are a common complaint, encountered in approximately 15% of women between the ages of 30 and 50. Diagnosis is difficult because women present different forms of excessive menses and no simple objective ways of measuring menstrual blood loss exist. A pictorial blood assessment chart was therefore validated for a better management of heavy menstrual bleeding. In half of the cases, no gynaecologic cause is found. Therefore, blood tests should be performed aiming at identifying coagulation disorders. We present here the results of our small series. Identification of coagulation disorders may allow specific treatments. These improve the quality of life and prevent unnecessary radical measures such as notably, hysterectomies.

[Haemostasis. A search for an ideal antithrombotics agent]

Heparins and vitamin K antagonist are the main antithrombotic agents used since several years. These two classes of drugs are very effective but not devoid of side effects and require either injections or regular laboratory controls. Therefore new agents have been developed. Two of these agents (fondaparinux and ximelagatran) are already available. Both are of non animal origin, do not induce thrombocytopenia and do not require laboratory controls. In recent studies fondaparinux has shown a better efficacy than low molecular weight heparin in major orthopedic interventions. Ximelagatran, which can be given orally, is now admitted also for short term use. It was hoped that it could replace vitamin K antagonists but increase of liver enzymes occurring after a few weeks is a major problem. Other new drugs are in advanced stage and will be also described.

Deep venous thrombosis and thrombophilia: indications for testing and clinical implications

In the past 3 decades, numerous biological abnormalities linked with deep venous thrombosis have been described. Among the different possibilities, it is crucial to order tests that can modify the therapeutic attitude towards the patient and/or his family. A combined clinical and laboratory approach taking into account the history of the patient and his family, the prevalence of the defects, and also the accuracy of the tests should allow tailoring a laboratory testing program to each patient. It is essential to keep in mind that the more difficult task is not to perform the tests but to consider who will benefit from testing both for prevention and therapy of venous thromboembolism. This article provides answers to some of these issues. These answers should, however, be considered as tentative and provisional because new findings and study results will certainly modify them in the near future.

Aspirin inhibits endothelial cell activation induced by antiphospholipid antibodies

BACKGROUND

Antiphospholipid antibodies (APLA) have been shown to activate endothelial cells (EC) in vitro, as documented by an increased expression of tissue factor as well as leukocyte adhesion molecules such as intercellular adhesion molecule-1, vascular cell adhesion molecule (VCAM)-1 and E-selectin. Currently, treatment of patients with the antiphospholipid syndrome includes aspirin, particularly for women with recurrent fetal loss.

OBJECTIVE

The present study was undertaken to investigate whether aspirin interferes with EC activation induced by APLA in vitro.

METHODS

IgG from 14 patients with APLA, and suffering from thrombotic complications and/or pregnancy morbidity, and control IgG were tested for their ability to modify the expression of VCAM-1 in human umbilical vein endothelial cells. VCAM-1 antigen was measured by flow cytometry and its mRNA by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Incubation of EC with IgG from most of the patients led to a higher VCAM-1 expression compared with incubation with control IgG. The effect of aspirin was studied for the eight IgG samples that induced a more than 50% increase in VCAM-1. Aspirin (10 mm) treatment of the cells significantly reduced the VCAM-1 response to these APLA.

CONCLUSIONS

Our results indicate that besides its antiplatelet properties, aspirin exerts a protective effect towards APLA at the EC level by decreasing leukocyte adhesion molecule expression at the cell surface.

Analysis of biological phenotypes from 42 patients with inherited factor VII deficiency: can biological tests predict the bleeding risk?

BACKGROUND AND OBJECTIVES

Inherited factor VII (FVII) deficiency is a rare bleeding disorder characterized by a poor relationship between reported FVII clotting activity (FVII:C) and bleeding tendency. Our study was aimed at defining biological parameters that are possibly predictive for bleeding risk in this condition.

DESIGN AND METHODS

Forty-two FVII-deficient patients (FVII:C <30%) were classified into two opposite clinical groups defined as severe and non-or-mild bleeders. For each patient, plasma samples were collected and then investigated for FVII:C (using a sensitive method and human recombinant thromboplastin as the reagent), FVII antigen, activated FVII coagulant activity (FVIIa:C) and the free-form of tissue factor pathway inhibitor.

RESULTS

None of these tests could be used as highly accurate predictors of bleeding. Nevertheless, both FVII:C and FVIIa:C differed significantly between the two clinical groups. Using ROC-curve analysis, two critical values of 8% and 3mIU/mL for FVII:C and FVIIa:C, respectively, could be proposed to discriminate between severe bleeders and non-or-mild bleeders.

INTERPRETATION AND CONCLUSIONS

A highly accurate diagnostic test for predicting bleeding tendency in inherited FVII deficiency still eludes definition, highlighting the fact that factors other than FVII itself interfere with the expression of bleeding phenotypes in this condition. Nevertheless, potential critical values using sensitive FVII:C and FVIIa:C methods may be useful in clinical laboratories for FVII-deficient patients. Those patients with FVII:C levels higher than 8% FVII:C or FVIIa:C higher than 3 mIU/mL, with no other hemostatic defect, seem to have a minimal risk of severe bleeding. Extended clinical studies are needed to support these findings.

Surveillance de l'anticoagulation des circulations extracorporelles par l'héparine non fractionnée : quels sont les problèmes non résolus ?

Cardiac surgery with extracorporeal circulation induces major alterations of haemostasis and requires high level of anticoagulation, usually achieved by unfractionated heparin infusion. Optimization of anticoagulant regimen, through adapted biological monitoring, can probably improve postoperative course, at least for postoperative haemostatic status. Despite increasing knowledge on extracorporeal circulation-induced haemostatic abnormalities and the development of new biological devices for heparin monitoring, the optimal level of anticoagulation remains matter of debate, as well as the monitoring procedures. This critical review presents the current available data on heparin anticoagulation and monitoring in this specific context, and underlines the pending issues about anticoagulation management during extracorporeal bypass.

Effects of statins on adhesion molecule expression in endothelial cells

BACKGROUND

Inhibitors of HMG-CoA reductase are widely used to prevent atherosclerosis progression. The expression of adhesion molecules on activated endothelial cells (EC) is an important step in the initiation and progression of atherosclerosis.

OBJECTIVES

We investigated whether adhesion molecule expression on activated EC is influenced by simvastatin, fluvastatin and pravastatin and, if so, by which mechanisms.

METHODS

Human EC from umbilical veins or saphenous veins were pretreated overnight with statins with or without mevalonate, and also for simvastatin or fluvastatin with the isoprenoid intermediates, farnesyl pyrophosphate (FPP), or geranylgeranyl pyrophosphate (GGPP). After 4-6 h activation with tumor necrosis factor (TNF)-alpha or lipopolysaccharide (LPS), surface adhesion molecule expression was evaluated by ELISA and by flow cytometry. The same experiments were performed with selective inhibitors of geranylgeranyltransferase (GGTI-286) and farnesyltransferase (FTI-277).

RESULTS

Pretreatment with simvastatin, fluvastatin or pravastatin potentiated the TNF-alpha and LPS-induced expression of E-selectin and VCAM-1, and mevalonate reversed the potentiating effect of these statins. GGPP also reversed the potentiating effect of simvastatin or fluvastatin on adhesion molecule expression, while FPP only partially reversed this effect. Furthermore, GGTI-286, but not FTI-277, mimicked the effect of simvastatin by increasing the TNF-alpha-mediated overexpression of E-selectin.

CONCLUSIONS

Statins increase E-selectin- and VCAM-1-induced expression on vascular endothelial cells stimulated with TNF-alpha or LPS. The inhibition of geranylgeranylated proteins could contribute to this effect.

Is measurement of D-dimer useful in the diagnosis of cerebral venous thrombosis?

BACKGROUND

The diagnosis of cerebral venous thrombosis (CVT) is a challenge because its clinical presentation is variable, brain CT may be normal, and MRI is not always available. Furthermore, early treatment may be effective. As D-dimer (DD) measurement is a sensitive test for the exclusion of venous thromboembolism, the authors studied whether this test could be useful in the diagnosis of CVT.

METHODS

A prospective study of 54 consecutive patients with headaches suggestive of CVT was conducted between October 2000 and September 2002. DD levels were tested for all patients in the emergency room before brain CT or MRI was performed.

RESULTS

Twelve (22%) of the 54 patients had CVT, and 10 (83%) of these 12 patients had DD level of >500 ng/mL (sensitivity of 83% and negative predictive value of 95%). Two patients with confirmed CVT and DD of <500 ng/mL had a history of chronic headache of >30 days' duration. In the 42 patients without confirmed CVT, only 4 patients had DD level of >500 ng/mL (specificity of 90% and positive predictive value of 71%).

CONCLUSIONS

DD test is useful in the diagnosis of acute CVT. A value below 500 ng/mL makes acute thrombosis unlikely.

Severe thrombocytopenic purpura due to rubella infection in a patient with systemic lupus erythematosus

We report the case of a woman suffering from systemic lupus erythematosus who developed a severe thrombocytopenic purpura (platelet count < 1 x 10(9)/l) secondary to rubella infection. The search for antiplatelet antibodies revealed transient circulating anti-GPIIb-IIIa and anti-GPIb-IX platelet antibodies. After a few weeks, bound anti-GPIIb-IIIa antiplatelet antibodies were still detectable and they persisted several months after recovery, probably in relation to a mild autoimmune thrombocytopenia related to systemic lupus erythematosus. To our knowledge, this is the first case report of severe thrombocytopenic purpura due to rubella in an adult with systemic lupus erythematosus.

[Diagnosis of deep venous thrombosis of the lower limbs: performance of diagnostic tests]

Deep-vein thrombosis is a frequent affection that needs precise diagnosis. Indeed, the clinical complications (from post-thrombotic syndrome to fatal pulmonary embolism) as well the risk of anticoagulant treatment require a precise diagnosis. Since clinical evaluation cannot assure reliably diagnosis by lack of sensitivity and specificity, complementary exams are needed. However, clinical assessment is an important part to decide further examinations. D-dimers assessment allows to role out the diagnosis of deep-vein thrombosis in a number of cases. Plethysmography and continuous Doppler are progressively given up. Compressive venous ultrasonography is now the exam of first choice. Scintigraphy, scanner and RMI must still be validated. Phlebography remains the gold standard in case of negative compressive venous ultrasonography and a high clinical probability.

Point of care and central laboratory determinations of the aPTT are not interchangeable in surgical intensive care patients

PURPOSE

The objective of the study was to compare a bedside whole blood activated partial thromboplastin time (aPTT) performed by a point of care (POC) apparatus (CoaguCheck(R) Pro) in surgical intensive care (SIC) patients with a conventional aPTT obtained from the central laboratory.

METHODS

The prospective concomitant measurements of the two aPTT were performed in 233 samples from 46 consecutive patients admitted after cardiovascular or major abdominal surgery.

RESULTS

Inter-operator, inter-instrument and inter-cartridge variability of the new device measured in three healthy volunteers and in nine patients in stable condition (controls) was low (F test: P=0.86). The agreement by Bland and Altman between POC and central laboratory aPTT (-20.2 +/- 18.8 sec) was not satisfactory. The agreement between POC and central laboratory aPTT in patients after surgery was worst (-17 +/- 33.1 sec). Heparin treatment or timing of blood sampling after intensive care admission (<48 hr vs >48 hr) did not influence the agreement. The correlation between POC or central laboratory aPTT and anti-factor Xa activity was poor (r(2) 0.077 and 0.181 respectively). The test which correlated the best to heparin doses was anti-factor Xa activity (r(2) 0.714).

CONCLUSION

POC aPTT and central laboratory aPTT showed a poor agreement in SIC patients admitted after surgery, although in healthy volunteers or in control patients, this agreement was better. The best test to monitor heparin treatment in this setting was anti-factor Xa activity.

How and when to monitor a patient treated with low molecular weight heparin

Low molecular weight heparins (LMWHs) are as efficient as unfractionated heparin (UFH) for prevention and treatment of thromboembolism. There is no evidence that monitoring the dose improves the clinical efficacy. In contrast, any overdosage increases the risk of hemorrhage. Because renal function plays a significant role in the elimination of LMWH, curative treatment should be monitored with an anti-factor Xa assay in patients presenting renal insufficiency, in the elderly, and in patients presenting an increased hemorrhagic risk. It is advisable to sample the patient at peak activity (3 to 5 hours after the subcutaneous [sc] administration) and to target the mean anti-factor Xa activity that was found efficient and safe in the clinical trial. This target is different for each LMWH and each dose regimen.

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.

Performance of helical computed tomography in unselected outpatients with suspected pulmonary embolism

BACKGROUND

Helical computed tomography (CT) is commonly used to diagnose pulmonary embolism, although its operating characteristics have been insufficiently evaluated.

OBJECTIVE

To assess the sensitivity and specificity of helical CT in suspected pulmonary embolism.

DESIGN

Observational study.

SETTING

Emergency department of a teaching and community hospital.

PATIENTS

299 patients with clinically suspected pulmonary embolism and a plasma D -dimer level greater than 500 microgram/L.

INTERVENTION

Pulmonary embolism was established by using a validated algorithm that included clinical assessment, lower-limb compression ultrasonography, lung scanning, and pulmonary angiography.

MEASUREMENTS

Sensitivity, specificity, and likelihood ratios of helical CT and interobserver agreement. Helical CT scans were withheld from clinicians and were read 3 months after acquisition by radiologists blinded to all clinical data.

RESULTS

118 patients (39%) had pulmonary embolism. In 12 patients (4%), 2 of whom had pulmonary embolism, results of helical CT were inconclusive. For patients with conclusive results, sensitivity of helical CT was 70% (95% CI, 62% to 78%) and specificity was 91% (CI, 86% to 95%). Interobserver agreement was high (kappa = 0.823 to 0.902). The false-negative rate was lower for helical CT used after initial negative results on ultrasonography than for helical CT alone (21% vs. 30%). Use of helical CT after normal results on initial ultrasonography and nondiagnostic results on lung scanning had a false-negative rate of only 5% and a false-positive rate of only 7%.

CONCLUSION

Helical CT should not be used alone for suspected pulmonary embolism but could replace angiography in combined strategies that include ultrasonography and lung scanning.

Localization of beta2-glycoprotein 1 in late endosomes of human endothelial cells

Antiphospholipid antibodies (APLA) are associated with thrombophilia and recurrent pregnancy loss. Different mechanisms have been proposed to explain their pathogenic effects and among them, we have previously shown that APLA accumulate in late endosomes of human umbilical vein endothelial cells (HUVEC) leading to a redistribution of the cation-independent mannose-6-phosphate receptor (CI-M6PR). Because many APLA are directed towards beta2-glycoprotein 1 (beta2GP1)phospholipid complexes, we investigated the localisation of beta2GP1 in HUVEC. By immunofluorescence analysis, using monoclonal and polyclonal anti-beta2GP1 antibodies, we detected beta2GP1 at the cell surface and in late endosomes. Incubation of HUVEC with anti-beta2GP1 antibodies resulted in antibody accumulation at the cell surface and within late endosomes and in a redistribution of the CI-M6PR from the Golgi apparatus to late endosomes. The anti-beta2GP1 antibodies remained detectable in late endosomes even after several days of incubation in antibody-free medium. The accumulation of anti-beta2GP1 antibodies in late endosomes of endothelial cells and the resulting modification of intracellular protein trafficking may contribute to the pathogenic effects of these antibodies.

D-dimer assays for the exclusion of venous thromboembolism

Many assay systems for D-dimer measurement are available. Their intended use is mainly the exclusion of venous thromboembolism (VTE). Despite standardization attempts, an important variability in assay results is observed, and therefore data obtained by use of one assay cannot be extrapolated to another assay. As a consequence, each assay must be validated in appropriate clinical trials to determine its cut-off value for VTE exclusion. The differences observed can be explained by the heterogeneity of fibrin degradation products present in patient samples, by the reactivity of the various antibodies and their combinations, and by the differences in calibrators and in the format of assays. Among the different assay systems available, the use of automated, observer-independent tests having good analytical sensitivity is highly recommended. The assay should also exhibit a high sensitivity for VTE exclusion to be used as the first step of any diagnostic strategy.

[Thrombopenias induced by heparin: diagnostic and therapeutic innovations]

Heparin-induced thrombocytopenia (HIT) is a difficult immune-mediated phenomenon that physicians have to cope with. It is caused by platelet-activating, heparin-dependent IgG antibody and may be associated with venous and arterial thrombosis, potentially fatal. Simple tests are now available which can detect most antibodies implicated in HIT. The old term "white clot syndrome" suggested that HIT was mostly associated with arterial thromboembolic events, but more recent publications indicate that HIT is also an important risk factor for venous thromboembolism. In case of suspicion of HIT, treatment by heparin should imperatively be stopped and an alternative anticoagulant treatment should be started before any laboratory confirmation.

Performances of a new, automated latex assay for the exclusion of venous thromboembolism

The performance of a new latex-enhanced turbidimetric assay, D-Dimer PLUS, has been evaluated with two analyzers performing various coagulation assays: the BCS Analyzer and the BCT Analyzer. A precision study showed total coefficients of variation ranging from 2.7 to 11.1% with the BCS Analyzer and from 2.5 to 6.6% with the BCT Analyzer. We investigated the ability of D-Dimer PLUS to exclude venous thromboembolism in 312 outpatients suspected of either pulmonary embolism or deep venous thrombosis. Three months follow-up was available for all patients. With the BCS Analyzer, we determined a cut-off value of 190 ng/ml, which gave a sensitivity of 97.9% [95% confidence interval (CI), 92.6-99.7%], a specificity of 37.9% (95% CI, 30.9-43.8%) and a negative predictive value of 97.6% (95% CI, 91.7-99.7%). With the BCT Analyzer, at a cut-off value of 130 ng/ml, sensitivity was 96.8% (95% CI, 91.0-99.3%), specificity was 45.2% (95% CI, 38.5-51.2%) and the negative predictive value was 97% (95% CI, 91.6-99.4). This new assay is fast and fully automated, and its performance is suitable to exclude venous thromboembolism. Management studies should be performed to assess its utility.

Molecular analysis of the fibrinogen gene cluster in 16 patients with congenital afibrinogenemia: novel truncating mutations in the FGA and FGG genes

Congenital afibrinogenemia is an autosomal recessive disorder characterized by the complete absence of detectable fibrinogen. We previously identified the first causative mutations for this disease in a non-consanguineous Swiss family. These were homozygous deletions of approximately 11 kb of the fibrinogen alpha chain gene (FGA). Our subsequent study revealed that the majority of cases were attributable to truncating mutations in FGA, with the most common mutation affecting the donor splice site in FGA intron 4 (IVS4+1 G-->T). Here, we report 13 further unrelated patients with mutations in FGA, confirming the relative importance of this gene compared with FGG and FGB in the molecular aetiology of afibrinogenemia. Three other patients were homozygous for mutations in FGG. Eight novel mutations were identified: five in FGA and three in FGG. Sufficient mutation data is now available to permit an effective strategy for the genetic diagnosis of congenital afibrinogenemia.

Activation of multiple cryptic donor splice sites by the common congenital afibrinogenemia mutation, FGA IVS4 + 1 G-->T

Our recent studies on the molecular basis of the autosomal recessive disorder congenital afibrinogenemia showed that the most common mutation is a donor splice mutation in FGA intron 4, IVS4 + 1 G-->T, accounting for approximately half of disease alleles. The effect of this mutation on messenger RNA (mRNA) splicing, however, remained unproven. COS-7 cells transfected with a normal plasmid construct produced 100% mRNA molecules with correct splicing, whereas cells transfected with a mutant construct produced multiple aberrant mRNAs, due to utilization of cryptic donor splice sites situated in exon 4 and intron 4. One particular site situated 4 base pairs (bp) downstream of the normal site was used in 85% of transcripts causing afibrinogenemia by a 4-bp insertion-frameshift, leading to premature alpha-chain truncation. Our results confirm the utility of transfecting COS-7 cells to study mRNA splice-site mutations and demonstrate that the common FGA IVS4 variant is a null mutation leading to afibrinogenemia.

Fibrin D-Dimer Measurement in Suspected Pulmonary Embolism

Due to increased awareness among physicians, the prevalence of pulmonary embolism (PE) in patients clinically suspected of the disease has steadily decreased during the past 15 years. This has led to the development of simple diagnostic tools in an attempt to reduce the number of invasive or costly exams needed to manage these patients. D-dimer (DD) measurement has proven to be a simple and very useful test to exclude PE and several strategies combining DD with clinical probability and other exams have been validated in large outcome studies. The problem faced by many physicians is the choice of the specific DD test and its more appropriate position in the diagnostic work-up of patients suspected of PE. This article focuses on these questions and also provides some limitations of DD use, such as its poor specificity in hospitalized and elderly patients.

Venous Thromboembolic Disease: Risk Factors and Laboratory Investigation

The etiology of venous thromboembolic disease has been the subject of several recent discoveries, particularly on genetic predisposing factors. The laboratory investigation that may help to evaluate the risk for individual patients includes the measurements of coagulation inhibitors (antithrombin, protein C, and protein S) in plasma assays, the search for the factor V Leiden mutation by the plasma activated protein C resistance test (always to be confirmed by DNA analysis when abnormal), and the search for the prothrombin gene mutation by DNA analysis. Among acquired abnormalities, the most frequently involved are phospholipid-dependent autoantibodies associated or not with a subset of antibodies having an anticoagulant effect in vitro (lupus anticoagulant). Other coagulation abnormalities such as increased FVIII, FIX, or FXI levels or hyperhomocysteinemia have been suggested to be risk factors for thrombosis, although additional studies are required to definitively assess their role.

Severe neonatal alloimmune thrombocytopenia due to anti-HPA-3a

BACKGROUND AND OBJECTIVES

Neonatal alloimmune thrombocytopenia is usually attributable to HPA-la antibodies. We report a case of parental platelet antigen incompatibility associated with a severe neonatal thrombocytopenia secondary to alloimmunization to HPA-3a.

MATERIALS AND METHODS

Platelet antibodies were detected by the monoclonal antibody-specific immobilization of platelet antigens, genotyping of the platelets by PCR, and HLA typing by serologic procedures and PCR.

RESULTS

Genotyping of maternal and paternal platelets confirmed the incompatibility in the HPA-3a system. It is noteworthy that the mother is of the HLA type DRB3*0101, is ABO-incompatible with her husband, and also has HLA class I antibodies.

CONCLUSION

Severe neonatal thrombocytopenia associated with HPA-3a alloimmunization is infrequent and all the factors mentioned above could have played a role in the severity of the disease.

Prophylactic antithrombotic therapy for patients with systemic lupus erythematosus with or without antiphospholipid antibodies: do the benefits outweigh the risks? A decision analysis

BACKGROUND

A high incidence of both arterial and venous thromboembolic events has been reported in patients with systemic lupus erythematosus (SLE), but the risks and benefits of primary prophylactic antithrombotic therapy have not been assessed. We measured the clinical benefit of 3 antithrombotic regimens in patients with SLE without antiphospholipid antibodies, with anticardiolipin antibodies, or with lupus anticoagulant.

METHODS

A Markov decision analysis was used to evaluate prophylactic aspirin therapy, prophylactic oral anticoagulant therapy, and observation. Input data were obtained by literature review. Clinical practice was simulated in a hypothetical cohort of patients with SLE who had not experienced any previous episode of arterial or venous thromboembolic events. For each strategy, we measured numbers of thromboembolic events prevented and major bleeding episodes induced, and quality-adjusted survival years.

RESULTS

Prophylactic aspirin therapy was the preferred strategy in all settings, the number of prevented thrombotic events exceeding that of induced bleeding episodes. In the baseline analysis (40-year-old patients with SLE), the gain in quality-adjusted survival years achieved by prophylactic aspirin compared with observation ranged from 3 months in patients without antiphospholipid antibodies to 11 months in patients with anticardiolipin antibodies or lupus anticoagulant. Prophylactic oral anticoagulant therapy provided better results than prophylactic aspirin only in patients with lupus anticoagulant and an estimated bleeding risk of 1% per year or less.

CONCLUSIONS

Prophylactic aspirin should be given to all patients with SLE to prevent both arterial and venous thrombotic manifestations, especially in patients with antiphospholipid antibodies. In selected patients with lupus anticoagulant and a low bleeding risk, prophylactic oral anticoagulant therapy may provide a higher utility.

Prevalence of factor V Leiden and prothrombin G20210A mutations in unselected patients with venous thromboembolism

We determined the prevalence of factor V Leiden and of prothrombin G20210A mutations in a cohort of unselected outpatients (n = 748) referred for suspected deep vein thrombosis (DVT) and/or pulmonary embolism (PE) and a pooled analysis of similar studies was also performed. Based on the clinical presentation, the prevalence of factor V Leiden was 15.7% in the 83 patients with DVT and 14.1% in the 99 patients with PE compared with 5.3% in patients without DVT and/or PE (control group). The prevalence of the prothrombin G20210A mutation did not differ among the three groups (3.9% for controls, 4. 8% for DVT and 3.9% for PE patients). We then divided the 99 patients with PE by separately analysing those with PE but without DVT (n = 57) and those with PE and DVT (n = 42). Compared with the control group, the prevalence of factor V Leiden was 10.5%, odds ratio (OR) 2.10 [95% confidence interval (95% CI) 0.68-5.45] in patients with primary PE and 19.1%, OR 4.20 (95% CI 1.54-10.30) in patients with DVT and PE. For the prothrombin G20210A mutation, no statistically significant differences were found between the control group and the three other groups. In conclusion, our data and the pooled analysis indicate that patients with primary PE are less often affected by the factor V Leiden mutation. No statistically significant differences were observed between patients and controls for the prothrombin G20210A mutation.