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Biomedical subjects

G Reber

Publications and source records attributed to G Reber.

At least 37 records · Page 2Linked to original sources
PubMed2001

Quantification of lupus anticoagulants in clinical samples using anti-beta2GP1 and anti-prothrombin monoclonal antibodies.

Quantification of lupus anticoagulant (LA) in clinical samples is hampered by the lack of a suitable standard of activity. We evaluated the use of mAbs displaying LA activity for this purpose. As most patient samples contain both beta2Glycoprotein I (beta2GP1) and prothrombin dependent LA, a combination of two mAbs, one of each specificity, was added to normal plasma in a concentration from 0 to 60 microg/ml. Eight assay systems using different reagents and instruments were used. The calibration curves were linear for all but one, with marked differences between the responsiveness to each mAb. A panel of plasmas from 69 patients with persistent LA diagnosed using the SSC-ISTH criteria was tested. An antiphospholipid syndrome (APS) was present in 40, whereas 29 were asymptomatic. LA activities of individual plasmas varied between assays (p < 10(-4)), but homogeneous subgroups were identified. In a majority of samples, LA activity displayed a prothrombin-dependent profile, with a variable contribution of beta2GP1-dependent activity. The latter was associated to beta2GP1 antibodies detected by solid-phase immunoassay. By using 3 dilute Russell viper venom time assays, higher LA titers were found in APS, compared to asymptomatic patients (p <0.05).

Adult↗
PubMed2000

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.

Adult↗
PubMed2000

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.

Antifibrinolytic Agents↗
PubMed2000

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.

Antibodies, Antiphospholipid↗
PubMed2000

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.

Arthroplasty, Replacement, Knee↗
PubMed1999

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.

Emergencies↗
PubMed1999

Differential inhibition of thrombin activity and thrombin generation by a synthetic direct thrombin inhibitor (napsagatran, Ro 46-6240) and unfractionated heparin in patients with deep vein thrombosis. ADVENT Investigators.

BACKGROUND: Direct thrombin inhibitors belong to a new class of antithrombotic drugs whose effects on blood coagulation in vivo in patients suffering from acute thrombotic conditions have not yet been fully explored. METHODS AND RESULTS: One hundred and five patients with acute proximal deep-vein thrombosis were randomized to receive a continuous intravenous infusion of napsagatran, a novel synthetic thrombin inhibitor, at a fixed dose of 5 mg/h (n = 36) or 9 mg/h (n = 25) for five days, or APTT-adjusted unfractionated heparin (UFH, n = 44) for the same time. In these patients, thrombin activity and thrombin generation could be assessed by measuring thrombin-antithrombin III complexes (TAT) and prothrombin fragment 1+2 (F1+2), respectively, on three occasions. At baseline, TAT and F1+2 did not differ among the three groups. On Day 2 (steady state), TAT significantly decreased in all groups, and the decrease was significantly more pronounced in the patients given higher-dose napsagatran. F1+2 decreased significantly only in UFH-treated patients. Two hours after cessation of the infusion, the TAT levels increased in the two napsagatran groups but not in the UFH group, whilst F1+2 went back to the baseline levels in the napsagatran-treated patients but remained low in the UFH-treated patients. There was no rebound effect. CONCLUSIONS: The data presented suggest that direct thrombin inhibition with napsagatran at 9 mg/h is more potent than UFH in attenuating thrombin activity, but is less potent than UFH in inhibiting thrombin generation. The real significance of these findings will have to be substantiated in further trials with clinically relevant endpoints.

Antithrombins↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Adult↗
PubMed1998

Control of oral anticoagulation in patients with the antiphospholipid syndrome--influence of the lupus anticoagulant on International Normalized Ratio. Groupe Méthodologie en Hémostase du Groupe d'Etudes sur l'Hémostases et la Thrombose.

The recommended therapeutic range of International Normalized Ratio (INR) for oral anticoagulant treatment in patients with the antiphospholipid syndrome remains controversial. As a part of this controversy, it has been suggested that lupus anticoagulants (LA) could interfere with the determination of prothrombin time, thus questioning the validity of monitoring the treatment of these patients using INR. To clarify this point, we compared the values of INR obtained in the plasmas of two groups of patients, one without LA (n = 47), and the other with LA (n = 43). INR were determined using 8 different thromboplastin reagents on the same automated coagulation instrument. Chromogenic factor X, which is supposed to be insensitive to the presence of LA, was also measured. The results are the following: provided INR was calculated using calibrated reference plasmas, there was no significant difference between INR values obtained with the 8 reagents, both in the non-LA and in the LA groups (CV: 5.9 and 6.7%. respectively). Closer examination revealed that INR results obtained with one reagent (the recombinant thromboplastin Innovin) diverged from those of the 7 others, leading to an overestimation of INR, to a very large extent in some instances. However this effect was restricted to a subset of the patient population with LA (6 out of 43). Finally, the relationship between INR (average value obtained using the 8 reagents) and factor X was identical in non-LA and in LA patient groups. We conclude that, provided the reagents which display the LA interference are identified and excluded for this purpose, the INR system is valid for monitoring oral anticoagulant treatment in patients with LA.

Administration, Oral↗
PubMed1998

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.

Adult↗