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Biomedical subjects

G Reber

Publications and source records attributed to G Reber.

At least 55 records · Page 3Linked to original sources
PubMed1997

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.

Adult↗
PubMed1996

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.

Adult↗
PubMed1996

Time course of procoagulant activity and D dimer in bronchoalveolar fluid of patients at risk for or with acute respiratory distress syndrome.

Intraalveolar fibrin deposition is a typical finding in acute lung injury and is not necessarily harmful. However, persistence of intraalveolar fibrin deposit may lead to hyaline membrane formation and subsequent alveolar fibrosis, a histologic hallmark of late stages of acute respiratory distress syndrome (ARDS). Thus, timing of the intraalveolar clotting disorder seems to be critical. To explore the time course of factors contributing to fibrin deposition and resolution, we sequentially analyzed procoagulant activity and fibrin degradation (by D dimer) in bronchoalveolar lavage (BAL) fluid of patients developing ARDS and those at risk for, but finally not developing, the syndrome. A total of 36 bronchoalveolar lavages were performed in 11 patients developing ARDS and 15 lavages in 10 patients at risk for but not developing this syndrome. All patients were admitted to the intensive care unit for the treatment of sepsis, trauma, or shock. In early phases of ARDS, the procoagulant activity (PCA) in BAL was significantly higher than in the patients at risk, 320 +/- 83 U (mean +/- SEM) versus 50 +/- 25 U, p < 0.05. A similar difference was noted in subacute stages (280 +/- 91 versus 46 +/- 16 U, p < 0.05). In early ARDS we observed higher levels of D dimer in BAL than in patients at risk: 1,841 +/- 827 versus 293 +/- 134 ng/ml, p < 0.05. Similarly, values of D dimer in the subacute phase were 2,776 +/- 836 versus 237 +/- 125 ng/ml, p < 0.05. In ARDS as well as in the at-risk group, D dimer in BAL fluid showed good correlation with the polymorphonuclear leukocyte count and with protein content of BAL. There was no correlation between plasma and BAL levels of D dimer. We conclude that in ARDS both the procoagulant pathway and the fibrin degradation are markedly activated compared with these in patients at risk but finally not developing this syndrome. These findings expand our understanding of intraalveolar coagulation abnormalities by providing evidence of increased fibrin breakdown in this syndrome.

Acute Disease↗
PubMed1996

VIDAS D-dimer: fast quantitative ELISA for measuring D-dimer in plasma.

VIDAS D-dimer (bioMérieux) is a new quantitative ELISA for D-dimer determination designed for the VIDAS automated system. The test contains single-dose, ready-to-use reagents and is completed within 35 min. Quantitative results are obtained from a calibration curve stored in the software of the system and expressed as fibrinogen equivalent units. The two-step capture/tag test relies on two complementary monoclonal anti-D-dimer antibodies, the second one being labeled with alkaline phosphatase. The upper limit of the measuring range is 1000 micrograms/L and the lower detection limit is <50 micrograms/L, which is below the lower limit of the reference interval (68-494 micrograms/L). Reproducibility (CV) within and between runs ranges from 5% to 7%. There is no interference from heparin, bilirubin, hemoglobin, fibrinogen degradation products, or plasma turbidity. Comparison with a conventional ELISA (y) gave good correlation (r= 0.91, n= 579) and comparable results (y= 1.35x - 148, S(y/x)= 750), especially for D-dimer concentrations ranging from 0 to 1000 micrograms/L (y= 1.09x - 10.6, r= 0.88, S(y/x)= 170).

Alkaline Phosphatase↗
PubMed1996

Contribution of a new, rapid, individual and quantitative automated D-dimer ELISA to exclude pulmonary embolism.

The performance of a new automated ELISA for a rapid, individual and quantitative measurement of plasma D-dimer (VIDAS D-dimer) has been evaluated. First, a study of 100 patients was performed in order to choose the best couple of antibodies in comparison with an already clinically validated ELISA. Then the results were certified in a prospective study including 195 consecutive patients suspected of pulmonary embolism (PE). For a cut-off level of 500 ng/ml VIDAS D-dimer showed a sensitivity of 100% (95% confidence interval 92-100), a specificity of 37.6%, a negative predictive value of 100% (95% CI 93.3-100) and a positive predictive value of 33.1%. During a 6 months' follow-up no patient (95% CI 0-6.4) with D-dimer < 500 ng/ml presented a new suspicion of venous thromboembolic disease. These results suggest that this rapid and single-dose ELISA provides a very useful tool for the clinician to exclude on a day-to-day basis the diagnosis of PE.

Autoanalysis↗
PubMed1995

A new, semi-quantitative and individual ELISA for rapid measurement of plasma D-dimer in patients suspected of pulmonary embolism.

The performance of a new membrane ELISA for semi-quantitative determination of plasma D-dimer has been evaluated. Its cut-off is about 500 ng/ml FEU and this single test is completed within 10 min. D-dimer was measured in 301 patients suspected of pulmonary embolism by conventional microplate and membrane ELISA. For the latter, readings were made by eye and some differences were noticed between the readers for reactions in the grey zone. Sensitivity and negative predictive values were similar for the two ELISA (higher than 90%). The 95% confidence intervals of sensitivity and negative predictive values obtained with this membrane ELISA suggest that this new test may be used as a diagnostic tool to exclude the presence of pulmonary embolism.

Adolescent↗
PubMed1995

Multicenter evaluation of nine commercial kits for the quantitation of anticardiolipin antibodies. The Working Group on Methodologies in Haemostasis from the GEHT (Groupe d'Etudes sur l'Hémostase et la Thrombose).

The performances of nine commercial kits and an in-house method (HM) for the quantitation of anticardiolipin antibodies (ACA) have been evaluated in a multicenter study. Ninety control and patient samples and six standards from Louisville University were run with kits and with the HM. Marked differences in positivity rate between kits were observed, ranging from 31 to 60% for IgG and 6 to 50% for IgM. Concordance between kits occurred in 59 and 51% of samples for IgG and IgM respectively. Concordance coefficients (kappa) ranged from 0.13 to 0.92. Slopes of regression lines between the declared units of Louisville standards and the units measured from the calibrators of the kits showed great diversity and ranged from 0.159 to 0.931 for IgG and from 0.236 to 0.836 for IgM. The beta 2-glycoprotein I (beta 2-GPI) content of the dilution buffers and the wells supplied with the kits revealed noticeable differences. However samples containing anti-beta 2-GPI antibodies were classified similarly by all but one kit. In contrast the ability to measure samples devoid of anti-beta 2-GPI antibodies differed markedly between the kits. This study shows that differences in positivity rates between the commercial kits may contribute to the differences in ACA prevalence rate found in the literature. The choice of cut-off levels may partly explain the moderate concordance between the kits. In addition some samples behave very differently depending on the kits. In spite of the expression of results in PL units, standardization of ACA assays has not been achieved.

Antibodies, Anticardiolipin↗
PubMed1995

Development of an ELISA for autoantibodies to prothrombin showing their prevalence in patients with lupus anticoagulants.

Some lupus anticoagulants (LA) have been shown to be directed against phospholipid-bound prothrombin. While developing an ELISA to detect anti-prothrombin autoantibodies in patient serum or plasma, no or very low signal was observed using human prothrombin immobilized on plain polystyrene plates. In contrast, the same LA-positive samples bound specifically to prothrombin coated on gamma-irradiated plates, depending on the radiation dose, in the absence of added calcium and phospholipid. Optimization of the assay required the addition of 0.1% Tween 20 to the buffers. Antibody specificity for immobilized prothrombin was ascertained by competition using liposome-bound prothrombin, since fluid-phase prothrombin competed poorly. Seventy-seven of 139 patients (55.4%) with LA related to a variety of underlying diseases possessed anti-prothrombin antibodies (27 IgG, 35 IgM and 15 both isotypes), either isolated or more often associated with anti-beta 2 glycoprotein I (beta 2GPI) antibodies. These included 67-71% of the patients with systemic lupus erythematosus and related disorders, primary antiphospholipid antibody syndrome or drug-induced LA (autoimmune groups), but only 19-20% of those with infection or malignancy (p < 0.001). As previously shown for anti-beta 2GPI antibodies, IgG2 was the predominant IgG subclass reactive with prothrombin. Thus, autoimmune patients with LA have a high incidence of antibodies to beta 2GPI and prothrombin, the binding of which could similarly require high antigen density and/or exposure of cryptic epitopes resulting from protein interaction with an irradiated (i.e. more anionic) polystyrene surface.

Autoantibodies↗
PubMed1994

Preferential use of dilutions of single sera than mixture of sera to standardize the quantitation of anticardiolipin antibodies.

The aim of this study was to compare four house standards coming from two University Hospital laboratories with the standards provided by the Antiphospholipid Standardization Laboratory (ASL) in order to quantify anticardiolipin antibodies. Using two different plates and two different buffered protein solutions, slopes from the serial dilutions of each of the four house standards were found comparable. In contrast different slopes were obtained when using the ASL standards which consist of a mixture of sera. Our results indicate that dilutions of single sera are more suitable than mixture of sera when quantification of anticardiolipin antibodies is required.

Antibodies, Anticardiolipin↗
PubMed1994

D-dimer plasma measurement in patients undergoing major hip surgery: use in the prediction and diagnosis of postoperative proximal vein thrombosis.

Plasma D-Dimer (DD), a highly sensitive marker of venous thromboembolism, was measured with an ELISA assay preoperatively and on the 12th postoperative day in 173 patients undergoing major hip surgery (78 elective arthroplasties and 95 operations for fractures). Proximal deep venous thrombosis (DVT) was detected by systematic compression venous ultrasonography on the 12th postoperative day in 12 (7%) patients. In one additional case, proximal DVT was diagnosed by venography. Preoperative DD level was significantly higher in patients with fracture than in patients undergoing elective arthroplasty. At a cutoff of 500 micrograms/L as determined by ROC curve analysis, the sensitivity, specificity, positive and negative predictive values of the pre-operative DD concentration for the development of subsequent proximal DVT were 93%, 23%, 36% and 96%, respectively. The diagnostic exclusion value of the DD measurement on the 12th postoperative day was similar but for a cutoff of 2000 micrograms/L. These data suggest that plasma DD measurement might be useful to predict and diagnose proximal DVT following major hip surgery.

Adult↗
PubMed1994

D-dimer determination to exclude pulmonary embolism: a two-step approach using latex assay as a screening tool.

D-dimer (DD), when measured by a quantitative enzyme-linked immunosorbent assay (ELISA), is a valuable test to exclude venous thromboembolism (VTE). However, DD ELISA technique is not appropriate for emergency use and the available agglutination latex assays are not sensitive enough to be used as an alternative to rule out the diagnosis of VTE. Latex assays could still be used as screening tests. We tested this hypothesis by comparing DD levels measured by ELISA and latex assays in 334 patients suspected of pulmonary embolism. All but one patient with a positive (DD > or = 500 ng/ml) latex assay had DD levels higher than 500 ng/ml with the ELISA assay. Accordingly, ELISA technique could be restricted to patients with a negative result in latex assay. This two-step approach would have spared about 50% of ELISA in our cohort. In conclusion, our data indicate that a latex test can be used as a first diagnostic step to rule out pulmonary embolism provided a negative result is confirmed by ELISA and the performance of the latex assay used has been assessed properly.

Enzyme-Linked Immunosorbent Assay↗
PubMed1994

Plasma measurement of D-dimer as diagnostic aid in suspected venous thromboembolism: an overview.

This paper reviews the published experience with plasma measurement of D-dimer (DD), a specific degradation product of crosslinked fibrin, in the diagnostic approach of venous thromboembolism (VTE). Pooling 11 studies (with weighting of the figures according to sample size) with a total of 1337 patients clinically suspected of deep venous thrombosis (DVT) (prevalence of DVT 35%) disclosed an average weighted sensitivity of 96.8% (95% CI: 95.2-98.4) and specificity of 35.2% (95% CI: 32.0-38.4) for the presence of DVT when the ELISA technique was used. In 908 patients suspected of pulmonary embolism (PE) from 9 trials (prevalence of PE 38%), the ELISA technique was associated with a weighted sensitivity of 96.8% (95% CI: 95.0-98.6) and specificity of 45.1% (95% CI: 40.8-49.4) for the disease. Figures obtained with latex assays were definitely lower, precluding their use in the diagnostic approach of VTE. These results show that a low concentration of plasma DD measured by the ELISA technique (usually less than 500 micrograms/l) might be used to rule out VTE in clinically suspected patients. Increased plasma concentrations are of no utility because of the low specificity of this test result. The clinical usefulness of the DD ELISA test should now be assessed in management trials under routine conditions, in the frame of clinical decision-making diagnostic processes. Lastly, the promising data obtained in a small number of asymptomatic, postoperative patients at risk of VTE deserve confirmation before the test can be recommended for initial screening in thrombo-prophylactic trials.

Biomarkers↗
PubMed1993

Lack of association between antiphospholipid antibodies and migraine.

We prospectively studied the prevalence of lupus anticoagulant, anticardiolipin antibodies (aCL) and various haemostatic parameters in 71 patients with migraine and compared the results with a control group of 32 subjects with back pain never having experienced migraine. The patients with migraine were divided into two groups: group I with migraine without (n = 18) and with aura lasting less than 60 min (n = 24) and group II with migraine with prolonged aura or migrainous infarction (complicated migraine, n = 29). The following results were obtained: a) no difference in aCL positivity was noted between migrainous patients and controls and between common migraine and complicated migraine patients and b) no statistically significant difference in haemostatic parameters (except for thrombin-antithrombin III complexes) was found between the two groups of migraine and between aCL positive and negative migrainous patients. These data suggest that anticardiolipin antibodies are not involved in the pathogenesis of migraine complications.

Adult↗
PubMed1993

D-dimer plasma concentration in various clinical conditions: implication for the use of this test in the diagnostic approach of venous thromboembolism.

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

Aged↗