1,721,059 research outputs found
ANTIPHOSPHOLIPID ANTIBODIES ARE NOT PRESENT IN THE MEMBRANE OF GEL-FILTERED PLATELETS OF PATIENTS WITH IGG ANTICARDIOLIPIN ANTIBODIES, LUPUS ANTICOAGULANT AND THROMBOSIS
No full textTo explore the possibility of an interaction between platelets and antiphospholipid antibodies and its relationship with thromboembolic events, platelets from six patients with IgG anticardiolipin antibodies, lupus anticoagulant and thrombosis were isolated by gel filtration. Five patients had primary antiphospholipid syndrome and one had a form secondary to systemic lupus erythematosus. Two patients had mild thrombocytopenia. The six platelet membrane eluates contained less than 1.09 GPL units of anticardiolipin antibodies and displayed no lupus anticoagulant activity. Similarly, lysates of disrupted platelets did not show anticardiolipin or lupus anticoagulant activity. These results suggest that antiphospholipid antibodies do not interact with circulating platelets, at least in patients on oral anticoagulant treatment with no evidence of acute thrombosis
Purification of anticardiolipin and lupus anticoagulant activities by using cardiolipin immobilized on agarose beads.
No full textWe describe a novel method for the purification of aPL, in which pure CL is immobilized on octyl-sepharose beads by hydrophobic interaction. No lipid contamination was present in eluates, and the system could be reutilized three times without loosing extracting capacity. Four patients with antiphospholipid syndrome were studied. A marked decrease in aCL and LA activities was found in all patient plasmas after the passage through a CL-octyl-sepharose column. Both activities were recovered in eluates which contained beta 2-GP-I and IgGs. beta 2-GP-I was also present in normal plasma eluates, which showed no aCL and slight LA activity. This method represents an improvement in the purification of aPL, and could be useful in explaining the mechanism of action of antibodies that are obtained using pure phospholipid as extracting matrix
Autoimmune antiphospholipid antibodies are directed against a cryptic epitope expressed when β2-glycoprotein I is bound to a suitable surface
No full textThe antiphospholipid antibodies (aPL) present in autoimmune disorders are associated with thromboembolic episodes, and their binding to phospholipids (PL) is mediated by a plasma cofactor, beta 2-glycoprotein I (beta 2GPI). Both PL and beta 2GPI seem necessary for binding, thus indicating that the two components comprise the epitope against which aPL are directed. Using an anti-beta 2GPI antibody ELISA with the antigen adsorbed onto polyvinylchloride (PVC) plates, we detected high antibody titres in 12 out of 12 plasma from patients with the antiphospholipid syndrome. No or very low positivity was obtained when the same ELISA was carried out in polystyrene (PST) plates, while an increasing positivity was found when processed (i.e. more hydrophilic) or COOH-surface PST plates were used. When beta 2GPI dependent IgG-aPL were purified using agarose-immobilized cardiolipin, 4 out of 4 preparations were highly positive in anti-beta 2GPI antibody ELISA using PVC plates, while beta 2GPI was not fully recognized by aPL-IgG when adsorbed onto PST plates. These findings demonstrate that aPL are, in fact, anti-beta 2GPI antibodies directed against a cryptic epitope which is expressed when beta 2GPI is bound to anionic phospholipid, or another suitable surface.The antiphospholipid antibodies (aPL) present in autoimmune disorders are associated with thromboembolic episodes, and their binding to phospholipids (PL) is mediated by a plasma cofactor. β2-glycoprotein I (β2GPI). Both PL and β2GPI seem necessary for binding, thus indicating that the two components comprise the epitope against which aPL are directed. Using an anti-β2GPI antibody ELISA with the antigen adsorbed onto polyvinylchloride (PVC) plates, we detected high antibody titres in 12 out of 12 plasmas from patients with the antiphospholipid syndrome. No or very low positivity was obtained when the same ELISA was carried out in polystyrene (PST) plates, while an increasing positivity was found when processed (i.e. more hydrophilic) or COOH-surface PST plates were used. When β2GPI dependent IgG-aPL were purified using agarose-immobilized cardiolipin, 4 out of 4 preparations were highly positive in anti-β2GPI antibody ELISA using PVC plates, while β2GPI was not fully recognized by aPL-IgG when adsorbed onto PST plates. These findings demonstrate that aPL are, in fact. anti-β2GPI antibodies directed against a cryptic epitope which is expressed when β2GPI is bound to anionic phospholipid, or another suitable surface
REVERSAL OF EXCESSIVE EFFECT OF REGULAR ANTICOAGULATION - LOW ORAL DOSE OF PHYTONADIONE (VITAMIN-K1) COMPARED WITH WARFARIN DISCONTINUATION
No full textTo determine the best way to reverse the excessive effect of regular anticoagulation in patients with INR > 5 and no bleeding complications, 23 patients with INR > 5 were randomly subdivided into two groups: group A (n = 12) discontinued warfarin for one day and group B (n = 11) received 2 mg of vitamin K1 orally in addition to the usual warfarin dose. INR was determined after 24 h (day 1), after which both groups continued with their usual dose of warfarin. After 48 h (day 2), warfarin dosage was changed according to the INR value. On day 9, INR values were determined again. Five out of twelve patients in group A had INR values > 5 on day 1. One patient in group A had an INR value < 5 both on days 1 and 2. All eleven patients in group B had INR values < 5 on day 1, and all but one on day 2. On day 9, INR values were acceptable (INR 2.0-4.5) in ten group A patients and eight group B patients. These findings suggest that a low oral dose of vitamin K1 is a convenient treatment for excessive anticoagulation in patients with no bleeding complications
Mechanical prosthetic heart valve thrombosis despite optimal anticoagulation in a patient with congenital thrombophilia (factor V Leiden)
No full textFailure of anticoagulant therapy in a patient with a St. Jude heart valve in the mitral position is reported. After 8 years of optimal anticoagulation at an International Normalized Ratio between 2.5 and 3.5, a floating thrombus was discovered by chance during transthoracic echocardiography and then surgically removed. A study for congenital or acquired thrombophilia disclosed a positivity for activated protein C resistance, due to the presence of factor V Leiden. The intensity of warfarin anticoagulation was increased to provide more protection for the patient
Anti phospholipid antibody ELISAs: Survey on the performance of clinical laboratories assessed by using lyophilized affinity-purifled IgG with anticardiolipin and anti-beta 2-glycoprotein I activity
No full textLupus anticoagulant (LA) and anticardiolipin (aCL) antibodies are the classical tests used to diagnose the antiphospholipid syndrome (APS). Unfortunately, since these are nonspecific and standardization is lacking, the results of laboratory work-ups upon which diagnosis are made are often misleading. The performance of clinical laboratories in detecting LA using lyophilised affinity purified immunoglobulin has been previously reported. The same material was used to investigate the inter-laboratory variability of aCL and anti-beta(2)-Glycoprotein I (beta(2)-GPI) antibody measurements. Laboratories were asked to test normal plasma spiked with purified IgG or distilled water in order to obtain 3 samples positive for aCL and anti-beta(2)-GPI at different antibody concentration (A, B and C) and 3 samples of normal plasma. Thirty-five laboratories participated and interpreted their test results. All performed an ELISA for IgG aCL antibodies, while 17 also tested samples using IgG anti-beta(2)-GPI antibody ELISA. Sensitivity and specificity were calculated on the basis of the responses provided by each laboratory. Overall, 99/105 samples were correctly interpreted as positive and 97/101 as negative for the presence of IgG aCL, corresponding to a sensitivity and specificity of 94% and 96%, respectively. Likewise, 46/51 samples were correctly defined as positive and 50/51 as negative for the presence of IgG anti-beta(2)-GPI corresponding to a sensitivity and specificity of 90% and 98%, respectively. A wide variability in results pertaining to the positive samples was found for aCL-ELISA (coefficient of variation of 79%, 59%, and 53% for samples A, B, and C, respectively) as well as for abeta(2)-GPI-ELISA (coefficient of variation of 85%, 95%, and 50% for samples A, B, and C, respectively). This was confirmed when the analysis was restricted to those centres using the same commercial kit. Median antibody concentrations reported by centres for positive samples were consistent with the prolongation of coagulation tests assessing lupus anticoagulant (LA). Among these, dRVVT showed a good sensitivity and linear correlation with aCL antibody concentration. In conclusion, on the whole this survey found correct interpretation of positive and negative samples by both ELISAs. Nonetheless the high variability of reported data remains a major problem that only a consensus on the part of laboratories and manufacturers to utilize standard, uniform materials and procedures can hope to overcome
A two-step coagulation test to identify antibeta-glycoprotein I lupus anticoagulants
No full textLupus anticoagulants (LA) are immunoglobulins which inhibit phospholipid (PL)-dependent coagulation tests. LA are not specific, as they may reflect the presence of antibodies to human prothrombin, human beta(2)-Glycoprotein I (beta(2)GPI), an association of previous antibodies or other antibodies. Antibodies to human beta(2)GPI act as in vitro anticoagulants by enhancing the binding of beta(2)GPI to PL, and this binding may be influenced by calcium ion concentration. A reduction in final calcium concentration, from 10 mm to 5 mm, increased coagulation times in both dilute Russell Viper Venom Time (dRVVT) and dilute Prothrombin Time (dPT) when plasmas of patients with antibeta(2)GPI antibodies were used. Ten LA patients showed increased dRVVT and dPT ratios from means of 1.5 to 1.7 (P < 0.001) and 2.4 to 4.3 (P = 0.002), respectively. Instead, all LA-positive antibeta(2)GPI antibody-negative patients showed decreased coagulation times from mean ratios of 1.5 to 1.3 (P = 0.004) in dRVVT and from 2.0 to 1.5 (P = 0.01) in dPT. These results are confirmed by running dRVVT of normal plasma spiked with affinity purified IgG antibeta(2)GPI antibodies. Therefore, when a PL-dependent coagulation test is run twice, at different final calcium concentrations, antibeta(2)GPI LA can be identified
Low intensity warfarin therapy.
No full textBACKGROUND AND OBJECTIVE: Several studies comparing different intensities of oral anticoagulant treatment have clearly shown a relationship between bleeding complications and prolongation of prothrombin time. In the early '50s, de Takats suggested that low-dose oral anticoagulants might be as effective as higher doses in preventing thrombosis, at a lower risk of bleeding. This review article examines the potential of low dose warfarin therapy.
INFORMATION SOURCES: The authors have been working in this field, contributing original papers. In addition, the material examined in this article includes articles published in the journals covered by the Science Citation Index and MedLine.
STATE OF ART AND PERSPECTIVES: The hypothesis that low-dose oral anticoagulants can be effective in preventing thrombosis was first proven by experiments in animal models, and showed that a prothrombin time ratio as low as 1.14 using rabbit brain thromboplastin was still able to confer some inhibition of experimental thrombosis. Low-dose or very low-dose warfarin were subsequently demonstrated to be effective in patients with morbid obesity and decreased antithrombin III functional and antigenic levels, in patients with indwelling catheters, in patients undergoing gynecological surgery, as well as in patients with stage IV breast cancer. Low-dose warfarin is also effective in the prevention of embolic strokes in patients with non-rheumatic atrial fibrillation. However, older patients (> 75 years), who have a very high risk of bleeding, might be safer taking a very low dose of warfarin (i.e., a daily dose of 1-1.25 mg). Moreover, after a period of run-in, a fixed, very low-dose warfarin schedule does not need further laboratory control, which is a factor that could contribute to the full acceptance of treatment by patients and could stimulate a broader prescription of warfarin for the primary prevention of stroke in older patients with nonrheumatic atrial fibrillation. Therefore, we have organized a multicenter clinical trial in which 1000 patients with non-rheumatic atrial fibrillation will be randomized to receive either a fixed mini-dose of warfarin or a standard dose. Positive results might permit the treatment of most older patients with non-rheumatic atrial fibrillation, creating a benefit for the community as a consequence of its effective prevention of disabling strokes.Background and Objective. Several studies comparing different intensities of oral anticoagulant treatment have clearly shown a relationship between bleeding complications and prolongation of prothrombin time. In the early 50s, de Takats suggested that low-dose oral anticoagulants might be as effective as higher doses in preventing thrombosis, at a lower risk of bleeding. This review article examines the potential of low dose warfatin therapy. Information sources. The authors have been working in this field, contributing original papers. In addition, the material examined in this article includes articles published in the journals covered by the Science Citation Index® and MedLine®. State of art and Perspectives. The hypothesis that low-dose oral anticoagulants can be effective in preventing thrombosis was first proven by experiments in animal models, and showed that a prothrombin time ratio as low as 1.14 using rabbit brain thromboplastin was still able to confer some inhibition of experimental thrombosis. Low-dose or very low-dose warfarin were subsequently demonstrated to be effective in patients with morbid obesity and decreased antithrombin III functional and antigenic levels, in patients with indwelling catheters, in patients undergoing gynecological surgery, as well as in patients with stage IV breast cancer. Low-dose warfarin is also effective in the prevention of embolic strokes in patients with non-rheumatic atrial fibrillation. However, older patients (>75 years), who have a very high risk of bleeding, might be safer taking a very low dose of warfarin (i.e., a daily dose of 1-1.25 mg). Moreover, after a period of run-in, a fixed, very low-dose warfarin schedule does not need further laboratory control, which is a factor that could contribute to the full acceptance of treatment by patients and could stimulate a broader prescription of warfarin for the primary prevention of stroke in older patients with non-rheumatic atrial fibrillation. Therefore, we have organized a multicenter clinical trial in which 1000 patients with non-rheumatic atrial fibrillation will be randomized to receive either a fixed mini-dose of warfarin or a standard dose. Positive results might permit the treatment of most older patients with non-rheumatic atrial fibrillation, creating a benefit for the community as consequence of its effective prevention of disabling strokes
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