Mutations in the fibrinogen aalpha gene account for the majority of cases of congenital afibrinogenemia

Congenital afibrinogenemia is a rare, autosomal, recessive disorder characterized by the complete absence of detectable fibrinogen. We previously identified the first causative mutations in a nonconsanguineous Swiss family; the 4 affected persons have homozygous deletions of approximately 11 kb of the fibrinogen alpha (FGA) gene. Haplotype data implied that these deletions occurred on distinct ancestral chromosomes, suggesting that this region may be susceptible to deletion by a common mechanism. We subsequently showed that all the deletions were identical to the base pair and probably resulted from a nonhomologous recombination mediated by 7-bp direct repeats. In this study, we have collected data on 13 additional unrelated patients to identify the causative mutations and to determine the prevalence of the 11-kb deletion. A common recurrent mutation, at the donor splice site of FGA intron 4 (IVS4 + 1 G > T), accounted for 14 of the 26 (54%) alleles. One patient was heterozygous for the previously identified deletion. Three more frameshift mutations, 2 nonsense mutations, and a second splice site mutation were also identified. Consequently, 86% of afibrinogenemia alleles analyzed to date have truncating mutations of FGA, though mutations in all 3 fibrinogen genes, FGG, FGA, and FGB, might be predicted to cause congenital afibrinogenemia.

Inability of serial fibrin monomer measurements to predict or exclude deep venous thrombosis in asymptomatic patients undergoing total knee arthroplasty

Fibrin monomer (FM) is a highly sensitive marker of venous thromboembolism and can be used to rule out deep venous thrombosis (DVT) and/or pulmonary embolism in symptomatic outpatients. The aim of the study was to investigate the usefulness of serial fibrin monomer determinations to predict or rule out DVT after total knee arthroplasty in asymptomatic patients. One hundred and thirty consecutive patients underwent total knee replacement. Blood samples were obtained in 104 of them the day before, at days 1, 3, 6 after surgery and at the day of phlebography. Phlebography was performed in all these patients between days 8 and 12 after surgery. There were 44 DVT (44/104, 42%). As compared with the patients without DVT, FM mean levels were 2 and 1.5 times higher in the DVT group at day 3 (P < 0.001) and day 6 (P < 0.01), respectively. However, no useful cut-off values for DVT prediction or exclusion could be determined due to the scattering of the values. Therefore, despite differences between patients with or without DVT, serial FM determinations are of no value for predicting or ruling out DVT in individual patients undergoing total knee arthroplasty.

Risk of major bleeding in unselected patients with venous thromboembolism

PURPOSE

To evaluate the risk of major bleeding in unselected patients given anticoagulant treatment (heparin overlapped and followed by oral anticoagulants) because of deep vein thrombosis (DVT) or pulmonary embolism (PE).

SUBJECTS AND METHODS

We screened the database of 1590 outpatients suspected of DVT and PE in prospective diagnostic studies conducted in Geneva between 1992 and 1998.

RESULTS

Four hundred and eleven of 1590 patients (26%) were anticoagulated for confirmed venous thromboembolism (PE, 300; DVT, 111). One patient was excluded because of concomitant thrombolytic therapy. Five (1.2%; 95% confidence interval, 0.4-2.8) of the remaining 410 patients experienced a major hemorrhagic event during the 3-month follow-up, including two fatal events. All bleedings occurred during the first month of therapy (heparin, two; oral anticoagulants, two; combined treatment, one) and the median age of the patients who bled was 80 years. At least one serious comorbid condition associated with higher bleeding risk was present in four patients and, in one case, the bleeding was clearly related to an excessive intensity of anticoagulation.

CONCLUSION

The rate of bleeding events in this population of unselected outpatients is similar to that reported in controlled therapeutic trials. The hemorrhagic events occurred early in the course of anticoagulant therapy and concerned old patients mostly affected by at least one comorbid condition. Particular care should be used to avoid the risk of overtreatment.

Using clinical evaluation and lung scan to rule out suspected pulmonary embolism: Is it a valid option in patients with normal results of lower-limb venous compression ultrasonography?

BACKGROUND

In patients with a low clinical probability of pulmonary embolism (PE) and a nondiagnostic lung scan, the prevalence of PE is theoretically very low. We assessed the safety and usefulness of this association for ruling out PE.

METHODS

We analyzed data from 2 consecutive cohort management studies performed in 2 university hospitals (Geneva University Hospital, Geneva, Switzerland, and Hospital Saint-Luc, Montreal, Quebec), which enrolled 1034 consecutive patients who came to the emergency department with clinically suspected PE. All patients were submitted to a sequential diagnostic protocol of lung scan, D-dimer testing, lower-limb venous compression ultrasonography (US), and pulmonary angiography in case of inconclusive results of noninvasive workup.

RESULTS

The prevalence of PE was 27.6%. Empirical assessment was accurate for identifying patients with a low likelihood of PE (8.2% prevalence of PE in the low clinical probability category). One hundred eighty patients had a low clinical probability of PE and a nondiagnostic lung scan. Among these patients, US showed deep vein thrombosis in 5. Hence, PE could be ruled out by a low clinical probability, a nondiagnostic lung scan, and a normal US in 175 patients (21.5%). The 3-month thromboembolic risk in these patients was low (1.7%; 95% confidence interval, 0.4%-4.9%).

CONCLUSIONS

Anticoagulant treatment could be safely withheld in patients with a low clinical probability of PE and a nondiagnostic lung scan, provided that the US is normal. This combination of findings avoided pulmonary angiography in 21.5% of patients with suspected PE in this series.

Interaction of anti-phospholipid antibodies with late endosomes of human endothelial cells

Anti-phospholipid antibodies (APLAs) are associated with thrombosis and/or recurrent pregnancy loss. APLAs bind to anionic phospholipids directly or indirectly via a cofactor such as beta(2)-glycoprotein 1 (beta(2)GPI). The lipid target of APLA is not yet established. Recently, we observed that APLAs in vitro can bind lysobisphosphatidic acid (LBPA). The internal membranes of late endosomes are enriched in this phospholipid. The current study was undertaken to determine to what extent binding of APLA to LBPA is correlated with binding to cardiolipin and to beta(2)GPI and to determine whether patient antibodies interact with late endosomes of human umbilical vein endothelial cells (HUVECs) and thus modify the intracellular trafficking of proteins. Binding of patient immunoglobulin G (n=37) to LBPA was correlated significantly with binding to cardiolipin. Although LBPA binding was correlated to a lesser extent with beta(2)GPI binding, we observed that beta(2)GPI binds with high affinity to LBPA. Immunofluorescence studies showed that late endosomes of HUVECs contain LBPA. Patient but not control antibodies recognized late endosomes, but not cardiolipin-rich mitochondria, even when we used antibodies that were immunopurified on cardiolipin. Incubation of HUVECs with patient plasma samples immunoreactive toward LBPA resulted in an accumulation of the antibodies in late endosomes and led to a redistribution of the insulinlike growth factor 2/mannose-6-phosphate receptor from the Golgi apparatus to late endosomes. Our results suggest that LBPA is an important lipid target of APLA in HUVECs. These antibodies are internalized by the cells and accumulate in late endosomes. By modifying the intracellular trafficking of proteins, APLA could contribute to several of the proposed pathogenic mechanisms leading to the antiphospholipid syndrome.

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 x 10(9)/L) was 11.6%. The mean platelet counts (248 compared with 213 x 10(9)/L) and 2.5th percentile (164 compared with 116 x 10(9)/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 x 10(9)/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 x 10(9)/L).

CONCLUSION

In healthy pregnant women, a platelet count over 115 x 10(9)/L late in pregnancy does not require further investigation during pregnancy and may be considered a safe threshold.

[Menorrhagia, hypermenorrhea and disorders of hemostasis]

Menorrhagia is a common clinical problem. About 10% of women aged between 30 and 49 take medical advice for abnormal uterine bleeding. Underlying bleeding disorders are found in about 20% of women, once pelvic abnormalities are excluded. It is important to characterize a bleeding disorder since specific treatments can be provided. Moreover, these women are susceptible to present other haemorrhagic complications, particularly in case of invasive procedures. This review aims at drawing the attention a) on the importance of a careful medical history to assess menorrhagia and a possible bleeding disorder, b) on von Willebrand disease, the main coagulation disorder involved in case of menorrhagia and c) on several therapeutic possibilities.

Contribution of noninvasive evaluation to the diagnosis of pulmonary embolism in hospitalized patients

The effectiveness of new diagnostic tools for suspected pulmonary embolism (PE), such as clinical probability assessment, plasma D-dimer (DD) measurement and lower limb venous compression ultrasonography (US), has not been specifically studied in patients with a suspected PE occurring during hospital stay. This study applied a sequential, decision analysis-based strategy adding these instruments to a ventilation/perfusion lung scan in a cohort of 114 consecutive inpatients clinically suspected of PE in order to establish in how many patients a pulmonary angiogram could thereby be avoided. A definitive diagnosis could be established by the noninvasive protocol in 61% of these patients: normal/near-normal lung scan, 14%; high probability lung scan, 19%; clinical probability combined with lung scan result, 18%; and US, 8%. Specificity of DD was only 7% and contributed to the exclusion of PE in only two patients. Pulmonary angiography was required in 39% of patients. The 3-month thromboembolic risk in patients in whom PE was excluded by the diagnostic process was 0% (95% confidence interval 0-4.9%). In conclusion, a noninvasive work-up for suspected pulmonary embolism is effective in hospitalized patients, allowing to forego angiography in 61% of them, and it appears to be safe, although this should be further investigated. In contrast to outpatients, D-dimer measurement appears to be useless in hospitalized patients.

Performances of the fibrin monomer test for the exclusion of pulmonary embolism in symptomatic outpatients

Many studies have shown that D-dimer determinations can be used for the exclusion of venous thromboembolism in symptomatic outpatients, depending however on the method of D-dimer measurement. Another related assay, the Fibrin Monomer test which measures soluble fibrin levels in plasma by ELISA, is now available. We have evaluated the performances of this assay for the exclusion of pulmonary embolism (PE) in 426 consecutive outpatients presenting at the emergency ward of our institution. Diagnosis of PE was made by D-dimer measurement, compression ultrasonography, lung scintigraphy, venography and pulmonary angiography. With a cut-off of 3 microg/ml. the sensitivity and the negative predictive value were both 100% (95% CI: 97.1-100 and 96.3-100 respectively) and the specificity 33% (95 % CI: 25.7-38.1). With 4 microg/ml, the corresponding figures were 98.4 (95% CI: 94.4-99.8), 98.3 (95% CI: 94.1-99.8) and 39% (95% CI: 33.6-44.7) respectively. The prevalence of PE was 30%, the exclusion rates were 23 and 27% for either cut-off. When compared with a reference D-dimer assay (Asserachrom D-Di), a good correlation was observed. In conclusion, this is the first study suggesting the interest of this Fibrin Monomer test to rule out PE; these results, however, need to be confirmed by other studies.

Maternal antiplatelet antibodies in predicting risk of neonatal thrombocytopenia

OBJECTIVE

To determine the incidence of maternal antiplatelet antibodies in cases of thrombocytopenia during pregnancy, using the monoclonal antibody-specific immobilization of platelet antigens assay; and to assess the usefulness of this assay for predicting risk of neonatal thrombocytopenia.

METHODS

A total of 6770 pregnant women were included in the study, and the monoclonal antibody-specific immobilization of platelet antigens assay was done when platelet counts were less than 150 x 10(9)/L. Platelet counts were determined in 6103 newborns.

RESULTS

The incidence of maternal thrombocytopenia was 11.6% (95% confidence interval [CI] 10.8, 12.4). Among newborns, 1.3% (95% CI 0.5, 2.7) born to thrombocytopenic mothers were thrombocytopenic, compared with 0.4% (95% CI 0.2, 0.6) born to nonthrombocytopenic women. Antiplatelet antibodies were detected in 37 (8.6%) of 430 thrombocytopenic women; autoantibodies were detected in 28 cases (circulating or bound to platelets), alloantibodies in eight cases, and an association of alloantibodies and autoantibodies in one case. The positive and negative likelihood ratios for predicting neonatal thrombocytopenia were 4.6 and 0.7, respectively.

CONCLUSION

The monoclonal antibody-specific immobilization of platelet antigens assay did not predict the risk of neonatal thrombocytopenia in an unselected population of thrombocytopenic pregnant women.

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.

Measurement of plasma D-dimer is not useful in the prediction or diagnosis of postoperative deep vein thrombosis in patients undergoing total knee arthroplasty

Plasma D-dimer, a highly sensitive marker of venous thromboembolism, was measured using an enzyme-linked immunosorbent assay pre-operatively, on the third postoperative day, and at the time of phlebography in 118 patients undergoing elective total knee arthroplasty. Deep venous thrombosis (DVT) was detected using systematic bilateral phlebography between the eighth and 12th postoperative day in 47 (39.8%) patients. D-dimer plasma concentrations did not differ between patients who had DVT and those who had no DVT, either pre-operatively (n = 118, P = 0.63) or at the time of phlebography (n = 111, P = 0.70). On the third postoperative day, D-dimer concentration was significantly higher (P < 0.01) in the patients who had DVT (median 3270 microg/l, range 1156-9996, n = 47) than in those who did not (2287 microg/l, 685-7062, n = 64). However, receiver operating characteristics curve analysis did not provide any useful cutoff values that would allow individual diagnoses to be made. In conclusion, the results of the present study suggest that plasma measurement of D-dimer concentration is of no value for predicting, diagnosing or ruling out DVT in patients undergoing total knee arthroplasty.

The place of D-dimer testing in an integrated approach of patients suspected of pulmonary embolism

When a patient is suspected of having pulmonary embolism (PE), the first procedure performed in most institutions is lung scintigraphy. Here we propose an alternative diagnostic strategy based on the following sequential combination of procedures: clinical assessment, D-dimer measurement, ultrasonography of lower limbs, and lung scan. This integrated approach may rule out PE in the majority of outpatients suspected of PE and permits district hospitals without lung-scan facilities to manage approximately 50% of outpatients without referral. D-dimer alone will exclude PE in about 30% of patients at low cost. This stepwise strategy is especially useful because only 20-35% of patients suspected of PE really have the disease. Thus, in the majority of patients, ruling out the disease has replaced ruling in the disease.

Screening test for thrombophilic patients: which tests, for which patient, by whom, when, and why?

In the past two decades, several mechanisms leading to thrombophilia have been elucidated, and corresponding laboratory tests developed. At a time of financial constraints, it is crucial to distinguish between the tests of proven value (which can modify the therapeutic attitude toward the patient and/or his family) from those of unproven value. We have listed in the first category determination or measurement of factor V Leiden, factor II G20210A, antithrombin, protein C, protein S, as well as antiphospholipid antibodies and hyperhomocysteinemia. 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 individual 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. The present review provides answers to some of these issues. These answers should, however, be considered as provisional because new findings and study results will certainly modify them in the future.

Evaluation of a new antigen capture ELISA for detection and characterization of platelet alloantibodies

The monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay is considered as a possible reference method for the detection of maternal alloantibodies when a foetomaternal alloimmunization is suspected. However, this method is tedious. In this study, we have compared the MAIPA results of 54 samples of mothers with (n=34) or without (n=20) alloantibodies with those obtained with a new antigen capture ELISA. Using the cutoff of 2.0 given by the manufacturer, the new kit had a sensitivity of 88.2% (95% CI 72.6-96.7) and a specificity of 100% (95% CI 98.0-100). From a receiver-operating characteristic curve analysis, the more appropriate cutoff for a screening assay would be 1.6, which gives a sensitivity of 100% (95% CI 89.7-100) with a specificity of 94.0% (95% CI 89.4-96.9). In conclusion, this new simple assay appears promising and could be used, with the modified cutoff, as a screening assay for the detection of platelet alloantibodies.

[Preoperative evaluation of hemorrhagic risk]

Should we consider that haemostasis tests may help guide the anaesthesiologist's therapeutic choices when the patients is on the operating table and bleeds without evident explanation? The response is yes, provided that the results will be available rapidly. Haemostasis tests that are performed in laboratory wards distant from the surgery room often prove to be unuseful in emergency situations as haemostasis abnormalities usually occur in a shorter time than is required to get biological test results. Devices located in the vicinity of the surgery room should therefore be available to the anaesthesiologist. Furthermore, these devices should be able to perform not only platelet counts and haematocrit determination, but other blood tests that may be useful to get further insights in the patient's haemostasis function. Such devices are already available, allowing rapid haemostasis tests in the surgery room and prompt decision with regard to appropriate transfusion policy. However, the haemostasis laboratory is still useful, as it permits to refine coagulation profile and also offers quality controls for those tests that were done in the surgery room.

Superficial vein thrombosis of lower limbs: influence of factor V Leiden, factor II G20210A and overweight

Superficial vein thrombosis (SVT) has been reported in patients with thrombophilia. In the present unmatched case-control study, the two most common thrombophilic abnormalities (factor V Leiden and factor II G20210A) were searched for in 112 consecutive patients with SVT of lower limbs and in 180 healthy donors. FV Leiden was present in 16/112 (14.3%) SVT patients and 11/180 (6.1%) controls (odds ratio 2.51, 95% CI 1.04-6.24) and FII G20210A in 4/112 (3.6%) patients and 2/180 (1.1%) controls (OR 3.28, 95% CI 0.46-36.84). In addition, body mass index (BMI) > or =28 kg/m2 was also associated with SVT (OR 2.81, 95% CI 1.60-5.00). After adjustment for BMI > or =28 kg/m2, the association between FV Leiden and SVT remained strong though no longer statistically significant. Among patients with SVT, the presence of FV Leiden was independently associated with the absence of varicose veins (OR 4.62, 95% CI 1.25-18.0) and with a BMI > or =28 kg/m2 (OR 3.74, 95% CI 1.05-15.1). In conclusion, both FV Leiden and overweight seem to predispose to SVT, a finding that should be confirmed in larger studies.

[Polytrauma and hemostatic anomalies]

OBJECTIVE

Polytraumatized patients present with defects of haemostasis that manifest clinically either by haemorrhage and/or thrombosis. During the initial, as well as during the later phases of treatment, clinicians should take into account the most recent developments in the understanding, in the evaluation of the risk, and in the prevention of haemorrhagic and thrombotic complications.

SOURCE

A group of experts, convened by the "Groupe d'intérêt en hémostase périopératoire" (Perioperative Haemostasis Interest Group) during the Annual Meeting of the Association of Anaesthetists of Quebec, held a symposium to review and integrate recent developments on haemostatic complications associated with trauma.

MAIN FINDINGS

The normal haemostatic balance is strongly compromised by trauma and shock. The percentage of patients with a coagulopathy and surgically uncontrollable haemorrhage varies between 18 and 40%. Abnormal coagulation after trauma is of multifactorial origin. Coagulopathy secondary to haemodilution is no longer considered the main cause of haemorrhage. Disseminated intravascular coagulation (DIC) is often manifest in the traumatic context. One out of every three polytraumatized patient will develop a deep vein thrombosis despite the preventive measures available at present. Clinical or laboratory detection of venous thrombosis either lacks sensitivity (physical examination or ultrasonography), or cannot be performed serially (phlebography).

CONCLUSIONS

Prevention and treatment of disorders of haemostasis relies upon the rapid and effective treatment of shock associated with trauma. Prevention of thromboembolic complications is paramount, taking into account the evolving balance between the risk of haemorrhage and the risk of thrombosis.

Simultaneous administration of antithrombin III and protein C concentrates for the treatment of a devastating coagulopathy in a child

Severe disseminated intravascular coagulation (DIC) is a rare event in childhood. We report here a young body with a devastating DIC unresponsive to heparin, fresh frozen plasma and platelet support. This prompted the use of antithrombin III and protein C concentrates and the effects of this combination were temporarily spectacular. We suggest that the simultaneous administration of two inhibitors of blood coagulation could be of interest and should be evaluated in appropriate trials for the treatment of a devastating coagulopathy.

A lipid associated with the antiphospholipid syndrome regulates endosome structure and function

Little is known about the structure and function of membrane domains in the vacuolar apparatus of animal cells. A unique feature of late endosomes, which are part of the pathway that leads to lysosomes, is that they contain a complex system of poorly characterized internal membranes in their lumen. These endosomes are therefore known as multivesicular or multilamellar organelles. Some proteins distribute preferentially within these internal membranes, whereas others are exclusively localized to the organelle's limiting membrane. The composition and function of this membrane system are poorly understood. Here we show that these internal membranes contain large amounts of a unique lipid, and thus form specialized domains within endosomes. These specialized domains are involved in sorting the multifunctional receptor for insulin-like growth factor 2 and ligands bearing mannose-6-phosphate, in particular lysosomal enzymes. We also show that this unique lipid is a specific antigen for human antibodies associated with the antiphospholipid syndrome. These antibodies may act intracellularly by altering the protein-sorting functions of endosomes.

Neonatal thrombocytopenia: incidence and characterization of maternal antiplatelet antibodies by MAIPA assay

Neonatal thrombocytopenia (NNT) which is frequent in distressed newborns was uncommon in a non-selected population of neonates. The aim of this prospective study was to determine the frequency of NNT and, in confirmed NNT, to search for maternal antiplatelet antibodies with a monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay. Among the 8388 newborns studied, 40 (0.5%, 95% CI 0.3-0.6) had confirmed NNT, which was severe (platelet count < 50 x 10[9]/l) in 10 cases (0.12%, 95% CI 0.05-0.20). Antiplatelet antibodies were detected in 10/31 studied mothers of thrombocytopenic newborns (32.3%): they were alloantibodies in five cases and autoantibodies in five other cases. Among these 10 newborns, seven had severe thrombocytopenia and four had bleeding complications. As controls, antiplatelet antibodies were also searched for in mothers of non-thrombocytopenic newborns: antiplatelet antibodies were present in 8.5% (95% CI 5.9-11.7) of thrombocytopenic mothers (n = 400) and 3.2% (95% CI 0.7-9.0) of non-thrombocytopenic mothers (n = 95). The difference was significant between the control groups and the group of mothers of thrombocytopenic newborns. In conclusion, our data indicate that an immune origin is frequent in NNT and should be looked for, particularly when the platelet count is < 50 x 10(9)/l.

Thrombomodulin levels during normal pregnancy, at delivery and in the postpartum: comparison with tissue-type plasminogen activator and plasminogen activator inhibitor-1

Some studies suggest that soluble thrombomodulin (TM) could be used as a marker of preeclampsia or eclampsia. However little is known about the sequential changes of TM during the course of normal pregnancy. Levels of TM were determined in 100 women with uneventful pregnancies. Samples (n = 394) were divided into five study intervals, three during pregnancy, one at delivery and one three days postpartum. As compared with TM levels (median 34.3 ng/ml, range 17.6-61) of a control group of 60 healthy non-pregnant women, TM levels were shown to increase throughout pregnancy, median (and range) values being respectively 38.5 (17.6-72.7) from 11 to 20 weeks, 45.2 (22.6-75.2) from 21 to 30 weeks and 54.3 (25.1-114.5) ng/ml from 31st week to delivery. One hour after delivery TM levels were still elevated and dropped three days postpartum to 40.5 (20.9-79.4) ng/ml. The increase of TM levels was correlated with those of tissue-type plasminogen activator and plasminogen activator inhibitor-1 antigens. The large overlap in TM levels between the study periods seems to preclude a clinical use of TM based on reference values from a control group. Our data suggest that it would be more appropriate to take into account TM baseline values in a given woman to examine her TM increase during pregnancy.

Longitudinal study on activated factors XII and VII levels during normal pregnancy

Levels of activated factor XII (FXIIa) and VII (FVIIa) were determined in 100 women with uneventful pregnancies. Samples were divided into five study intervals: three during pregnancy, one at delivery and one 3 d postpartum. The median (range) for FXIIa levels were 3.4 ng/ml (1.2-9.1) from 11 to 20 weeks, 4.6 ng/ml (1.4-15.2) from 21 to 30 weeks, 5.4 ng/ml (1.9-14.3) from 31st week to delivery, 5.2 (1.3-11.4) at delivery and 4.3 (1.8-8.5) ng/ml in the postpartum sample. For FVIIa the median and range levels for the five periods were 4.9 (1.7-77.3), 7.2 (2.5-80.4), 11.1 (2.9-90.6), 12.0 (3.1-64.1) and 8.2 (4.0-23.5) ng/ml. Although the increase of FVIIa was higher than that of FXIIa during pregnancy, the overall changes of FXIIa and FVIIa were highly correlated (P<0.0001). At each time period the changes of FVIIa correlated with FVII:C which was not the case with FVII:Ag. These data indicate that during pregnancy both the contact phase and extrinsic pathway are activated.

Cost-effectiveness of noninvasive diagnostic aids in suspected pulmonary embolism

BACKGROUND

Noninvasive instruments such as plasma D-dimer measurement (DD) and lower-limb compression ultrasonography (US) are being increasingly advocated to reduce the number of necessary angiograms in patients having suspected pulmonary embolism (PE) and a nondiagnostic lung scan. We therefore designed a decision analysis model (1) to evaluate the cost-effectiveness of combining these noninvasive diagnostic aids with lung scan and angiography in the diagnosis of PE and (2) to determine the optimal sequence and combination of tests taking into account the clinical probability of PE.

METHODS

We performed a cost-effectiveness analysis based on literature data, including data from a management study in our institution. Six diagnostic strategies were compared with the reference, ie, lung scan followed when nondiagnostic (low or intermediate probability) by angiography. In all strategies, PE was ruled out by a normal or near-normal scan, a negative DD (plasma level below 500 micrograms/L), or a negative angiogram. Pulmonary embolism was diagnosed and anticoagulant treatment was undertaken in the presence of a high-probability lung scan, deep vein thrombosis showed by US, or a positive angiogram. In case of a nondiagnostic scan (low or intermediate probability), patients could be either treated or not treated, or undergo other tests, according to the selected strategy.

RESULTS

Under baseline conditions (prevalence of PE, 35%), strategies combining DD and US with lung scan, angiography being done only in case of an inconclusive noninvasive workup (DD level > 500 micrograms/L, normal US, and nondiagnostic lung scan), were most cost-effective. This approach yielded a 9% incremental cost reduction and a 37% to 47% decrease in the number of necessary angiograms compared with the reference strategy (scan +/- angiography). For patients with a low clinical probability of PE (< or = 20%), withholding treatment from those with a low-probability lung scan without performing an angiogram proved safe and highly cost-effective (30% cost reduction), provided US showed no deep vein thrombosis.

CONCLUSION

The DD test and US are cost-effective in the diagnostic workup of PE, whether performed after or before lung scan, thus allowing centers devoid of lung scanning and/or angiography facilities to screen patients with suspected PE and avoid costly referrals. In patients with a low clinical probability, a low-probability lung scan, and a normal US, treatment may be withheld without resorting to angiography.

D-dimer testing for suspected pulmonary embolism in outpatients

The plasma level of D-dimer, a fibrin degradation product (FDP), is nearly always increased in the presence of acute pulmonary embolism (PE). Hence, a normal D-dimer level (below a cutoff value of 500 micrograms/L by enzyme-linked immunosorbent assay [ELISA]) may allow the exclusion of PE. To assess the negative predictive value of a D-dimer concentration below 500 micrograms/L in outpatients with suspected PE, and the safety of withholding anticoagulant treatment from such patients, we performed D-dimer assays, lower limb venous compression ultrasonography, and lung scans in 671 consecutive outpatients presenting in the Emergency Center of the Geneva University Hospital with suspected PE. Pulmonary angiography was reserved for patients with an inconclusive noninvasive workup. Patients with a normal D-dimer concentration were discharged without anticoagulant treatment and followed for 3 mo. The prevalence of PE was 29%, and D-dimer (using a cutoff of 500 micrograms/L) had a diagnostic sensitivity for PE of 99.5%. Overall diagnostic specificity of D-dimer was 41%, but it was lower among older patients. Of the 198 patients with a D-dimer concentration below the cutoff value, 196 were free of PE, one had a PE, and one had incomplete information because of loss to follow-up. Thus, the negative predictive value of D-dimer concentration fell between 197 of 198 and 196 of 198 cases of PE (99% [95% CI: 96.4 to 99.9]). Using a cutoff value of 4,000 micrograms/L, the overall specificity of D-dimer concentration for PE was 93.1%. In conclusion, a plasma D-dimer concentration below 500 micrograms/L allows the exclusion of PE in 29% of outpatients suspected of having PE. Withholding anticoagulation from such patients is associated with a conservative 1% risk of thromboembolic events during follow-up.

Effects of intermittent pneumatic compression on venous haemodynamics and fibrinolytic activity

Pneumatic intermittent compression is an effective method to prevent postoperative venous thromboembolism. Its efficacy has been ascribed to both a haemodynamic action (increase of blood flow velocity) and a stimulation of endogenous fibrinolytic activity [via the production of tissue-type plasminogen activator (t-PA) by the vascular endothelium]. The relative contribution of these two effects is still debated. In a randomized, cross-over study in ten healthy volunteers, we compared the haemodynamic and fibrinolytic effects of two different pneumatic intermittent compression devices: a classical, low-pressure, whole-leg boots system, and a novel, high-pressure, plantar compression system. The study was performed at rest, to compare haemodynamics and fibrinolytic activity modifications, and under induced venous leg stasis, in order to compare the two compression systems in experimental conditions mimicking laparoscopic surgery. Our data show that (1) a pneumatic compression device that exerts its compression on the plantar venous plexus only induced an increase of venous blood peak velocity and flow in the common femoral vein that is very similar to that induced by the classical whole-leg boots compression system; (2) the venous stasis induced by an external pressure mimicking the conditions of laparoscopic surgery further increased the absolute velocity and flow increase, with the two intermittent compression systems tested; (3) no changes of t-PA or plasminogen activator-inhibitor 1 antigens were observed with either pneumatic compression device. In conclusion, the present study indicates that the antithrombotic effect of mechanical prophylaxis is probably mainly due to its ability to increase venous peak velocity and flow, especially under venous stasis conditions.

Clinical features in 36 patients homozygous for the ARG 506-->GLN factor V mutation

We analyzed the clinical features of 36 patients homozygous for the Arg 506 to Gln factor V mutation and found a circumstantial event at risk for thrombosis in 29 of the 31 patients with thrombosis. The most frequent predisposing factors were the post-partum period and the use of oral contraceptives in women, and surgery in both sexes. Venous thrombosis recurred in 48% of the patients. One patient had a myocardial infarction at age 33 years, and also had an antiphospholipid syndrome. Homozygous Gln 506 mutation leads to far less severe thrombotic complications than homozygous protein C and protein S deficiencies and does not seem to predispose patients to arterial thrombosis.

Haemostatic properties of human pulmonary and cerebral microvascular endothelial cells

Little is known on the haemostatic profiles of human microvascular endothelial cells (MVEC) from different tissues. In addition it is not known whether MVEC from patients display the same haemostatic pattern as MVEC coming from healthy controls. To address these questions MVEC from human lung and brain were isolated and stimulated with tumour necrosis factor alpha (TNF) and E. coli lipopolysaccharide (LPS) for 24 h. The level and the kinetics of procoagulant activity (PCA) and thrombomodulin (TM) expression were found to be different depending on the tissue of origin and on the agonist used. In particular, the inducible PCA was higher in lung than in brain MVEC, an observation that may be related to the frequency of lung involvement in septic shock. Differences were also observed for tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) with MVEC supernatants or cell lysates. These variables were then measured in lung MVEC purified from patients with acute respiratory distress syndrome (ARDS) and compared to controls. Cells from ARDS patients constitutively expressed more PCA and PAI-1 than controls. The fibrinolytic potential, expressed as t-PA/PAI-1 ratio, was lower in ARDS than in lung MVEC. It is concluded that MVEC display different haemostatic features depending on the tissue they come from and that lung MVEC from ARDS patients present a procoagulant profile when compared with those from controls.

Laboratory evaluation of hemostasis before cardiac operations

BACKGROUND

Several opinions prevail on the necessity and on the choice of laboratory coagulation tests to perform before cardiac operations. This review aims at providing simple and clinically relevant recommendations.

METHODS

The literature on preoperative coagulation testing was reexamined, taking into account the low prevalence of unknown and unsuspected hemorrhagic disease, and the risk of false positive results.

RESULTS

Carefully controlled, randomized trials are lacking but it seems appropriate to perform a few inexpensive tests (platelet count, activated partial thromboplastin time, and prothrombin time), mainly to obtain baseline values for patients who are about to undergo a major hemostatic challenge. A more complete coagulation profile (eg. bleeding time, fibrinogen concentration, thrombin time) should be considered in patients who present with a history of bleeding.

CONCLUSIONS

A careful medical history is the key element to detect a bleeding disorder. Only a very limited coagulation profile should be obtained in asymptomatic patients before cardiac operations.

[Oral contraception and menopausal hormone replacement: effects on hemostasis and risk of venous thromboembolism]

The estrogen component of oral contraceptives enhances both coagulation and fibrinolysis. These contradictory effects result in activation of coagulation and an increased risk of venous thromboembolism. The relative risk is about 4-fold as compared with a nonuser of the same age. However, the risk of deep vein thrombosis or pulmonary embolism attributable to the pill is small (2 cases per 10,000 users per year). Pills containing a progestagen of the so-called 3rd generation seem to increase the risk by an additional factor of 2. Though small, the risk of venous thromboembolism makes it necessary before any oral contraceptive prescription to take a thorough personal and family history (including risk factors) and to study the risk-benefit ratio on an individual basis. Moreover, patients should receive detailed information on the evaluation. Postmenopausal hormone replacement therapy does not induce significant hemostatic changes (especially with transdermal application) and is not associated with a proven risk of venous thromboembolism. Venous risk factors thus do not contraindicate the use of hormone replacement therapy, except perhaps in the immediate (one-year?) period after an acute event.

Optimal duration of oral anticoagulant therapy following deep vein thrombosis of lower limbs

Deep vein thrombosis of the lower limbs is usually treated with an initial course of heparin or low-molecular-weight heparin associated with oral anticoagulants which are started simultaneously, thereby allowing heparin to be stopped after 4-7 days. Although consensus conferences have proposed a uniform duration of oral anticoagulant therapy of 3 months, great uncertainties remain as to the optimal treatment duration in an individual patient. Two large-scale studies have recently demonstrated that short treatment durations (4 weeks or 6 weeks, respectively) are associated with about two-fold higher rates of thromboembolic recurrences over follow-up periods of 1-2 years compared with longer treatment durations (3 months or 6 months, respectively). However, because treatment duration is also a major determinant of the hemorrhagic risk on oral anticoagulants, it is essential to balance the protective effect of these agents against their bleeding risk. This paper reviews the literature on the antithrombotic effects and hemorrhagic risks of different durations of oral anticoagulant therapy following lower limb deep vein thrombosis and suggests tentative recommendations which range from a short anticoagulant course of 4 weeks in a patient with a low risk of thromboembolic recurrence and a high hemorrhagic risk (e.g. postoperative distal vein thrombosis) to 6 months or more in a patient with a low hemorrhagic risk and a high risk of thromboembolic recurrence (e.g. idiopathic proximal vein thrombosis in a patient with inherited thrombophilia or malignancy).

Resistance to activated protein C in an unselected population of patients with pulmonary embolism

BACKGROUND

Resistance to activated protein C (APC) is the most frequent cause of inherited thrombophilia. This phenomenon has been reported in 10-50% of selected patients with venous thromboembolism, a variation that might result from different degrees of selection in different reports.

METHODS

We measured the APC sensitivity ratio in 494 frozen blood samples from unselected consecutive outpatients suspected of pulmonary embolism and referred over a 30-month period to the emergency ward of the University Hospital of Geneva, the only public primary-tertiary care hospital in the region of Geneva (400,000 inhabitants).

FINDINGS

Prevalence of resistance to APC was 5.5% (95% Cl 2.4-10.5%) (8/146) in patients with confirmed pulmonary embolism and 4.0% (2.2-6.7%) (14/348) in patients in whom the diagnosis could be ruled out (p = 0.66), giving an odds ratio of 1.36 (0.56-3.32).

INTERPRETATION

The very different risks of venous thromboembolism in the presence of resistance to APC that have been reported in trials published so far are probably due to variable recruitment conditions. The lower prevalence observed in our totally unselected population of patients with pulmonary embolism may be more representative of the real risk with which clinicians will be confronted. Therefore, more data are needed from various populations of patients with venous thromboembolism to help decide which patients will benefit from screening for resistance to APC.

[Ambulatory follow-up in oral anticoagulation: recommendations for clinical practice]

The aim of this investigation performed in 75 outpatients taking oral anticoagulant after an episode of pulmonary embolism was to specify the modalities of ambulatory monitoring during oral anticoagulation. All patients were followed up by their family doctor after hospital discharge. The principal results of this investigation were (1) the general difficulty of obtaining and maintaining anticoagulation stability in a recommended therapeutic range (INR 2-3) for venous thromboembolic disease, (2) that in only 15% of personal anticoagulation notebooks were the laboratory results expressed in INR, (3) the lack of information given to the patients taking oral anticoagulant. Based on these results we started an education programme for nurses and physicians designed to promote the use of INR and to improve the quality of information given to anticoagulated patients. A new anticoagulation monitoring notebook should help medical staff and patients to increase the safety of anticoagulation.

Diagnosis of pulmonary embolism by a decision analysis-based strategy including clinical probability, D-dimer levels, and ultrasonography: a management study

BACKGROUND

Assessment of the clinical probability of pulmonary emboli sm, plasma D-dimer measurement, and lower-limb venous compression ultrasonography have all been advocated in the workup of suspected pulmonary embolism, to minimize the requirement for pulmonary angiography in patients with nondiagnostic lung scans. However, their contribution has not been assessed prospectively.

METHODS

Three hundred eight consecutive patients who came to the emergency department with suspected pulmonary embolism were managed according to a diagnostic protocol that included clinical probability assessment, lung scan, and sequential noninvasive tests: plasma D-dimer measurement by enzyme-linked immunosorbent assay (a concentration <500 microgram/L ruled out pulmonary embolism) and lower-limb B-mode venous compression ultrasonography (a positive finding was diagnostic of venous thromboembolism). Patients without pulmonary embolism according to the diagnostic workup did not receive anticoagulant treatment. The safety of this approach was assessed by a 6-month follow-up.

RESULTS

of the 308 patients, 106 (34%) had a diagnostic lung scan (normal in 43 and high probability in 63). For the remaining 202 patients, noninvasive workup was diagnostic in 125 (62%). Pulmonary embolism was ruled out by a low clinical probability and a nondiagnostic scan in 48 patients and a D-dimer level less than 500 microgram/L in 53; pulmonary embolism was established by a high clinical probability and a nondiagnostic scan in seven patients and by a finding of a deep vein thrombosis on ultrasonography in 17. Therefore, only 77 of these 202 patients underwent pulmonary angiography (negative in 55; positive in 22). At 6-month follow-up (completed for 99.4% of the study population), only two of the 199 patients in whom the diagnostic protocol had ruled out pulmonary embolism (1.0% [95% confidence interval, 0.1 to 3.6]) had a thromboembolic event (pulmonary embolism, one; deep vein thrombosis, one).

CONCLUSIONS

This decision analysis strategy yielded a definitive noninvasive diagnosis in 62% of patients with a nondiagnostic scan and appears to be safe.