Artefactual elevation of the automated white cell count in the context of a bone marrow aspirate analysis.
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Adipose Tissue↗
Biomedical subjects
T Lecompte
Publications and source records attributed to T Lecompte.
Further evidence for the presence of anti-protein S autoantibodies in patients with systemic lupus erythematosus.
Acquired protein S (PS) deficiency in systemic lupus erythematosus (SLE) has been previously reported, but its mechanism and its possible thrombotic role have not been established. The aim of our study was to provide further evidence for auto-immune PS deficiency in 27 Tunisian SLE patients, using PS-specific enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance technology (SPR). PS deficiencies for PS activity, free PS or total PS, respectively, were found in 19, 18 and 12 patients. A significant correlation (r= -0.475, P< 0.016) was found between free/total PS ratio and C4bBP levels, suggesting a role of inflammation in free PS deficiency. Immunoglobulin IgG antibodies to PS were detected in four patients by both ELISA and SPR, in six patients only by ELISA, and in two patients only by SPR. Signals for anti-PS IgG by ELISA and SPR were, however, significantly correlated (r = 0.549, P = 0.003). These results suggest that an auto-immune mechanism could account for low PS activity in patients with SLE. Auto-antibodies to PS may form immune complexes, inducing increased clearance of PS or interfering with the protein C-protein S system.
Autoantibodies↗
[Determination of polymorphonuclear neutrophil adhesion receptors. Effect of pre-analytic factors].
UNLABELLED: Polymorphonuclear neutrophil (PMN) adherence receptors expression varies with leukocyte activation state. Their quantification need accurate and inter-laboratories reproducible methods, without artefactual activation. OBJECTIVE: The aim of this study was to study the influence of cell preparation on PMN adherence receptors expression. MATERIALS AND METHODS: It was proposed to quantify, using immunolabeling standard (QIFIKIT(R), Dako), surface expression of the main adherence receptors (L-selectin and B(2) integrins), from different preparations of PMN: total blood collected with EDTA, isolated PMN by density gradient Polymorphprep(TM) 1,113 (Nycomed Pharma) and formaldehyde fixed PMN. RESULTS: A decrease of all receptors was noted after isolation and fixation of PMN, in comparison with whole blood PMN analysis. These results differed from data previously reported since, in these studies, activated phenotypes (increased of B(2) integrins) were observed after isolation and fixation methods. CONCLUSION: The present study provides strong evidence that pre-analytical conditions are sources of biological variations and thus extreme care must be taken in the interpretation of results. It underlines the interest of consensual practices for these pre-analytic and analytic parameters in order to compare results in multicenter and longitudinal studies.
CD18 Antigens↗
[Antiplatelet agents and their therapeutic use].
Antiplatelet agents have a well established effect against thrombosis complicating atherosclerosis. Drugs currently in use in France are: aspirin and flurbiprofen, inhibiting thromboxane synthesis; ticlopidine and clopidogrel, inhibiting platelet activation by adenosine diphosphate; dipyridamole, inhibiting platelet activation through adenosine; abciximab, acting on the mechanism of aggregation. Their molecular and cellular pharmacology is in agreement with the clinical effects and the guidelines for practical use. These drugs have in common that they carry a risk of hemorrhage, albeit low but difficult to cope with in case of invasive procedures. There is no antidote. They also have specific contraindications. No laboratory tests aimed at assessing their effect on primary haemostasis are proved of any clinical value.
Arteriosclerosis↗
[Improvement in prevention of venous thromboembolism in medical environment. Mission impossible?].
PURPOSE: In France, low molecular weight heparins are widely used for prophylaxis of venous thromboembolism. This practice is not based on strong evidence supporting the use of this technique, thus leading to important difficulties in defining accurate guidelines. Improvement in the prophylaxis must focus on the process leading to prescription or non-prescription. Our primary objective was to identify and describe this process. We also analyzed the causes for dysfunction and implemented corrective actions. METHODS: Basic tools and methods specific to improvement of quality were used including: flow charting for process description, causes-effect diagram for updating and analysis of dysfunction, weighted vote for decisions regarding corrective actions, and agenda and designation of leaders for the implementation of corrective actions. RESULTS: The theoretical process beginning with the recognition of a risk and ending with the adequate treatment or prevention of this risk was demonstrated. The most important dysfunction was the lack of epidemiological and clinical trials. Key corrective actions were the following: standardization of practices where evidence was available; if not, collaborative efforts to collect valid epidemiological data through multicenter surveys and clinical trials; systematic appraisal of the quality of published data; assessment of the risk for venous thromboembolism during hospitalization. To achieve real improvement in practice, priority was given to repeated measures of the risk for thromboembolism. The use of low molecular weight heparins has been so wide however, that it has led to some difficulties. We must draw lessons from this experience. CONCLUSION: Improvement of quality in terms of healthcare is not only based on auditing the practices or modifying the defective processes, but also on our ability not to use new drugs before fully assessing their validity.
Anticoagulants↗
Both kinetic data and epitope mapping provide clues for understanding the anti-coagulant effect of five murine monoclonal antibodies to human beta2-glycoprotein I.
The interaction between five murine monoclonal antibodies (mAb) and beta2-glycoprotein I (beta2GPI) in the absence of phospholipids was studied using surface plasmon resonance-based biosensor technology. Two separate epitope regions were confirmed for the five mAb but epitopes of two mAb were shown to be overlapping but not identical. The characteristics of binding on both immobilized beta2GPI, using different chemistries of coupling to a dextran matrix and antibody surfaces prepared by two strategies of immobilization, were compared. Binding was strongly influenced by the orientation of the immobilized partner, and the five mAb showed heterogeneity in their binding to immobilized and soluble beta2GPI. The observed stoichiometries of mAb-beta2GPI complexes and the detailed analysis of the kinetics of the association and dissociation phases of the interactions with soluble and immobilized beta2GPI revealed differences in the dissociation rate constants, resulting in a 10-fold higher affinity for immobilized beta2GPI compared to soluble beta2GPI for four out of five mAb. This suggests bivalent binding of these mAb to immobilized beta2GPI. In addition, the kinetic data helped explain the differing anti-coagulant properties of these mAb.
Animals↗
[Vascular disease and cellular activation: exploration of cell adhesion phenotype by quantitative flow cytometry].
The pathogenesis of atheromatous and/or thrombotic vascular diseases involves rheological parameters, soluble mediators and cellular agents. The many studies that have tried to establish correlations between plasma factors, shear stress and the risk of ischemia have left some questions unanswered. Current exploration methods are now focusing on the determining role of cells. Activated cells express adhesion molecules on their membranes, which allow to communicate in a homo- or heterotypical manner. Quantifying adherence molecules on the surface of platelets, leukocytes and endothelial cells provides an assessment of the "adhesive phenotypical profile". Quantitative cytometry, using beads coated with a known amount of immunoglobulins as calibrators, is perfectly suited, through its multiple parameter analyses and the specificity provided by monoclonal antibodies, for the quantification of membrane antigens. Measuring the adhesive profile on the surface of cells that are implicated in vascular disease makes it possible to correlate that phenotype to the ischemic risk in such diversified pathologies or circumstances as intermittent angor, myocardial infarction, angioplasty, insulin-dependent diabetes or pre-eclampsia. In addition, that quantification permits monitoring the action of new therapeutical agents targeting adherence molecules.
Angioplasty, Balloon, Coronary↗
[New thrombolytic agents in myocardial infarction].
Myocardial infarction is the result of thrombotic coronary artery occlusion. Although present-day thrombolytics have major value by increasing the frequency of reopening of arteries responsible for myocardial infarction, by preserving myocardial function and, thereby, significantly reduce mortality. Nevertheless, they are subject to the following limitations: 1) excellent arterial partency is only obtained in 50% of cases: 2) reocclusion occurs in 5 to 10% of cases; 3) severe complications such as cerebral haemorrhage are observed in about 0.5% of cases. Therefore, the search to improve thrombolytic agents is intense. This article reports the recent advances in concept and production of new thrombolytic agents. The most recent results concern the production of mutants of T-PA (tissue plasmogen activator). Of these mutants, the reteplase (r-PA) has already received authorization for its commercialisation. Other t-PA mutants under development (phase 3) include TNK-t-PA and lanoteplase. Over the last few years, there has been renewed interest in staphylokinase. The results of the initial clinical trials with this agent have also been reported. Paradoxically, the mode of action of thrombolytic agents has an inherent pro-thrombotic effect. This explains some of the interest for anti-thrombotic agents as an adjuvant treatment of thrombolysis. The initial results of the association of thrombolytics with new glycoprotein IIb/IIIa platelet inhibitors and anti-thrombin agents are reported.
Coronary Disease↗
Heparin-induced thrombocytopenia in France, 1980-1998.
Due to the extensive use of unfractionated heparins in France, there is considerable experience with heparin-induced thrombocytopenia (HIT). It is recommended that platelet counts be performed twice a week for three weeks when patients are treated with any form of heparin. A drop in platelet counts can, however, occur not only in HIT patients but also for other unrelated reasons. For diagnosing HIT, all laboratories in France use platelet aggregometry inspite of poor sensitivity. Both false positive and false negative results are obtained. The serotonin release test is not used in France. The ELISA test for HIT does not always correlate with the platelet aggregation test and many patients with a positive ELISA test do not necessarily have other evidence for HIT. This is especially true in patients following cardiopulmonary bypass surgery. None of the available laboratory tests reliably identify patients with HIT. Patients with HIT should not be managed with low-molecular-weight heparins, but danaparoid, argatroban and ancrod are viable options. Also, recombinant hirudin has been employed. All have advantages and disadvantages. At present, the diagnosis and management of patients with HIT remains difficult and properly designed clinical studies are needed to obtain answers to several open questions.
Anticoagulants↗
[Heparin-induced thrombopenia].
Heparin-induced thrombocytopenia remains a topical subject for at least two reasons. The first reason is the increasing prescription of low molecular weight heparins (LMWH) rather than unfractionated heparins, with limited laboratory surveillance, raising the question concerning the need for twice-weekly platelet counts, according to the recommendations of the Vidal drug directory. The second reason is the recent release onto the market of two products, danaparoid (Orgaran) and lepirudin (Refludin) for this precise indication of heparin-induced thrombocytopenia. These products greatly facilitate the management of this complication. Many basic research teams are trying to optimize the detection of heparin-dependent antibodies and to more clearly elucidate the mechanism of this particular thrombocytopenia, which carries a risk of very severe thrombotic complications when the diagnosis is delayed.
Antibodies↗
Immunopurification of human beta2-glycorprotein I with a monoclonal antibody selected for its binding kinetics using a surface plasmon resonance biosensor.
The beta2-glycoprotein I (beta2GPI)-binding properties of five murine monoclonal antibodies immobilized as capture antibodies were studied using surface plasmon resonance detection. The monoclonal antibody with the fastest dissociation kinetics (6F3) was selected for the development of an immunoaffinity chromatography procedure, assuming that its behaviour would be similar in both systems since the covalent coupling chemistries involved amino groups in both cases. Under our experimental conditions of a fast one-step procedure, beta2GPI was purified to homogeneity from human plasma with a yield of about 50%. Beta2GPI was eluted under fairly mild conditions, either at low pH or at high pH. The immunoadsorbent was used five times without any apparent loss of binding capacity. The immunopurified protein showed similar binding to cardiolipin-coated polystyrene wells as beta2GPI purified by conventional methods. However, differences in the pattern of immunoreactivity in relation to the purification procedure were observed by surface plasmon resonance using the monoclonal antibody with the highest association kinetics (9G1) immobilized on the sensor surface.
Animals↗
[Prevention of venous thromboembolism. Survey of in-hospital medical practice].
OBJECTIVES: In an effort to improve the prevention of venous thromboembolism, the Nancy University Hospitals conducted a survey of medical practice concerning indications for preventive therapy and surveillance of platelet counts and anti Xa activity. METHODS: The survey involved 163 medical files. Questionnaires were filled out in 6 units (3 medical wards and 3 intensive care units). RESULTS: Indications for preventive therapy were found to be quite variable with the exception of very low risk of thromboembolism where the treat/do not treat ratio was 0.1/1, indicating a clear tendency for abstention. This ratio was 0.77/1 and 0.38/1 respectively for low and moderate risk and 2/1 for high risk. There was undoubtedly a ward effect. The attitudes in practice tended toward non-prevention in patients without limited mobility. For platelet counts, an initial count was performed in 95% of the cases and during treatment in 38% although the specific rates were not the same for different types of units. Anti-Xa activity, which according to prevention recommendations need not to be determined, was not monitored in 88% of the cases. In accordance with prevention recommendations, anti-Xa activity was not determined in 88% of the cases. CONCLUSION: Further progress is needed in the prevention of venous thromboembolism and should be based on wider use of existing methods.
France↗
[Heparin-induced thrombopenias: new treatments].
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Anticoagulants↗
Antibodies against phospholipids and beta 2-glycoprotein I increase the risk of recurrent venous thromboembolism in patients without systemic lupus erythematosus.
We studied the prognostic significance of antiphospholipid antibodies for recurrence of venous thromboembolism (VTE), in 71 patients admitted for acute VTE (deep-vein thrombosis or pulmonary embolism) in a single internal medicine unit. Lupus anticoagulant (LA), antibodies directed against beta 2-glycoprotein I (beta 2GPI) and antibodies against both beta 2GPI and a mixture of phospholipids (cardiolipin, phosphatidylserine and phosphatidic acid) (APAs) were measured. The patients were followed-up (mean 4.9 years) to determine the time to the next VTE. We found LA in nine patients, anti-beta 2GPI antibodies in seven patients and APAs in six patients. The cumulative risk of recurring VTE was higher in patients with beta 2GPI-binding antibodies (hazard ratio 12.6, 95% CI 1.5-104.9; p = 0.0029). The risk associated with APAs was 11.5 (95% CI 1.3-98.9; p = 0.0049) and that for LA was 3.7 (95% CI 0.9-15.6; p = 0.055). The risk of VTE recurring was higher both in patients with antibodies directed against beta 2GPI, and in patients with antibodies directed against beta 2GPI and a mixture of phospholipids, than in patients without these antibodies.
Adolescent↗
Meta-analysis of the risk of venous thrombosis in individuals with antiphospholipid antibodies without underlying autoimmune disease or previous thrombosis.
Patients with systemic lupus erythematosus (SLE) and antiphospholipid antibodies (aPL) are at a greater risk for venous thromboembolism (VTE) than SLE patients without these antibodies. For patients without SLE there is a controversy about the risk associated with these antibodies and about their prognostic significance. We reviewed the degree of evidence and describe the odds ratio for VTE associated with aPL, namely the lupus anticoagulant (LA) and anticardiolipin antibodies (aCL), in patients without SLE. The study was a meta-analysis of seven observational studies of risk for antiphospholipid associated venous thromboembolism (VTE), excluding SLE patients. The strategies to identify published research included a computerized literature search and the review of citations in primarily relevant articles for the period 1983 to 1997. A summary of study characteristics and a critical appraisal of study quality were done. Summary odds ratios were obtained conducted using a random and a fixed effects-model. The overall odds ratio for aCL associated VTE obtained by fixed-effects model was 1.56 (95% CI, 1.10-2.24) and 1.64 (95% CI, 0.93-2.89) by random-effects model. The heterogeneity of these results appeared to be due in part to the detection limit of the aCL assay: the odds ratio was 3.21 (95% CI, 1.11-9.28) with both models when high titres only were considered. The overall odds ratio for LA associated VTE was 11.1 (95% CI, 3.81-32.3). In conclusion meta-analysis of the risk for antiphospholipid associated thrombosis demonstrated a higher risk in patients with the LA than in other patients. This risk was also higher than in patients with aCL even when high titres only were considered.
Antibodies, Antiphospholipid↗
A chromogenic assay allows reliable measurement of factor VIII levels in the presence of strong lupus anticoagulants.
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Blood Coagulation Tests↗
[Hirudin for heparin-induced thrombopenia: a new step forward].
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Anticoagulants↗
Use of different molecular typing techniques for bacteriological follow-up in a clinical trial with AIDS patients with Mycobacterium avium bacteremia.
One hundred ninety-six Mycobacterium avium isolates from blood samples recovered from 93 AIDS patients for several months were typed by serotyping, by IS1245 restriction fragment length polymorphism (RFLP) analysis and in some cases RFLP analysis with plasmids pVT2 and pLR7 as probes, and by pulsed-field gel electrophoresis (PFGE). PCR typing of single colonies was also used to detect polyclonal infections. Strains belonged mainly to serotypes 1, 4, and 8. pVT2- and pLR7-related plasmids were detected in strains from 49% of the patients. The IS1245 RFLP and PFGE analyses showed a 96.8% diversity of the M. avium strains from the 93 patients. The vast majority (95.2%) of infections were monoclonal, indicating that recent infection is unlikely, even at an advanced stage of AIDS. For one patient, sequential isolates gave divergent patterns of sensitivity and resistance to clarithromycin, but all were identified as the initial clone. RFLP analysis and PCR typing of single colonies allowed for the detection of three polyclonal infections during the bacteriological follow-up. Among strains from patients whose samples were positive by culture after treatment for 2 to 15 months, 97.4% were the same as the initial strain. In conclusion, relapses and failures were mostly due to the initial strain. These relapses and failures resulted either from the selection of resistant mutants or the reappearance of sensitive strains, suggesting the persistence of nonsterilized tissue reservoirs.
Acquired Immunodeficiency Syndrome↗