Molecular studies on phospholipid-binding sites and cryptic epitopes appearing on beta 2-glycoprotein I structure recognized by anticardiolipin antibodies.
Explore the source record for details and available documents.
Antibodies, Anticardiolipin↗
Biomedical subjects
D A Triplett
Publications and source records attributed to D A Triplett.
Anticardiolipin antibodies recognize beta 2-glycoprotein I structure altered by interacting with an oxygen modified solid phase surface.
Anticardiolipin antibodies (aCL) derived from the sera of individuals exhibiting the antiphospholipid syndrome (APS) directly bind to beta 2-glycoprotein I (beta 2-GPI), which is adsorbed to an oxidized polystyrene surface. Oxygen atoms were introduced on a polystyrene surface by irradiation with electron or gamma-ray radiation. X-ray photoelectron spectroscopy revealed the irradiated surfaces were oxidized to generate C-O and C = O moieties. aCL derived from either APS patients or (NZW x BXSB)F1 mice bound to beta 2-GPI coated on the irradiated plates, depending on the radiation dose. Antibody binding to beta 2-GPI on the irradiated plates was competitively inhibited by simultaneous addition of cardiolipin (CL)-coated latex beads mixed together with beta 2-GPI but were unaffected by addition of excess beta 2-GPI, CL micelles, or CL-coated latex beads alone. There was a high correlation between binding values of aCL in sera from 40 APS patients obtained by the anti-beta 2-GPI enzyme-linked immunosorbent assay (ELISA) using the irradiated plates and those by the beta 2-GPI-dependent aCL ELISA. Therefore, aCL have specificity for an epitope on beta 2-GPI. This epitope is expressed by a conformational change occurring when beta 2-GPI interacts with an oxygen-substituted solid phase surface.
Animals↗
Obstetrical implications of antiphospholipid antibodies.
Explore the source record for details and available documents.
Abortion, Spontaneous↗
Factors affecting the performance of factor VIII coagulant activity assays. Results of proficiency surveys of the College of American Pathologists.
To evaluate sources of interlaboratory variation in factor VIII coagulant assays and the effects of uniform calibration on it, data were analyzed from Survey Set H2-C, 1987, of the College of American Pathologists, Northfield, Ill, into which the College of American Pathologists Reference Preparation for Factor VIII was incorporated. Peer group performance and its improvement by uniform calibration were evaluated by comparing means, precisions, and numbers of acceptable survey scores. Results showed a poorer performance by less experience laboratories and by those that used undesirable calibrators. Substantial improvement was seen with uniform calibration, especially among laboratories that had employed poorer calibrators. Although variance component analysis showed that the type of calibrator was the most important contributor to interlaboratory variation, it accounted for only 10% of total variability. Participant summaries and questionnaires that spanned several years revealed steady improvement in methodology but no striking changes in interlaboratory variation.
Analysis of Variance↗
Coagulation assays for the lupus anticoagulant: review and critique of current methodology.
Several coagulation assays identify lupus anticoagulants, but there is no uniform opinion regarding minimum criteria for the diagnosis or the most sensitive procedure to be used to screen for lupus anticoagulants. Based on test availability and the cumulative literature, a sensitive activated partial thromboplastin time appears to be the most appropriate screening test. The dilute Russell's viper venom time may be used as both a screening and a confirmatory procedure. The platelet neutralization procedure is the most sensitive and specific of the confirmatory procedures that use an increased amount of phospholipid to either "bypass" or "neutralize" the lupus anticoagulant.
Anticoagulants↗
Guidelines for testing and revised criteria for lupus anticoagulants. SSC Subcommittee for the Standardization of Lupus Anticoagulants.
Explore the source record for details and available documents.
Autoantibodies↗
Superwarfarin ingestion and detection.
Because of the emergence of warfarin resistance, new potent long-acting anticoagulants are now readily available in several over-the-counter rodenticide products. The availability of these "superwarfarin" compounds has led to accidental and purposeful human ingestions, one of which has resulted in a death. We summarize the prior case reports and report a second death. In addition, we report the availability of an assay to detect the presence of brodifacoum (a superwarfarin compound) in human plasma and tissues.
4-Hydroxycoumarins↗
Laboratory diagnosis of von Willebrand's disease.
The laboratory diagnosis of von Willebrand's disease (vWD) has become much more difficult because of the identification of numerous variant forms of vWD. The biologic and pathologic variability in individual patients necessitates a comprehensive assessment. Patients with classic type I vWD may be easily identified by using the bleeding time, activated partial thromboplastin time, platelet count, von Willebrand antigen, and ristocetin cofactor tests. In patients with variant forms of vWD, however, multimeric analysis of both platelet and plasma von Willebrand factor may be necessary. Furthermore, more than one assessment may be needed to detect an abnormal result in many of the aforementioned tests.
Bleeding Time↗
Evaluation of different mixing study reagents and dilution effect in lupus anticoagulant testing.
Until recently, the laboratory identification of lupus anticoagulants (LA) was not considered important. Often LA were regarded as a nuisance, resulting in factor assays and other coagulation tests with inconclusive results. However, the recognition of important clinical complications associated with the presence of LA has resulted in an emphasis on the detection of this phospholipid-dependent inhibitor. Most studies have evaluated the sensitivity of various screening or confirmatory procedures used in establishing the diagnosis of LA. The authors have focused on the variables involved in the mixing studies used to identify the presence of a circulating inhibitor. To detect the latter, attention to the ratio of patient plasma to normal plasma is important, particularly in the case of a minimally prolonged APTT. Also the source of "normal" plasma must be platelet poor to maximize sensitivity in the case of a weak LA.
Blood Coagulation Factors↗
Serologic characterization of Rocky Mountain spotted fever. Appearance of antibodies reactive with endothelial cells and phospholipids, and factors that alter protein C activation and prostacyclin secretion.
Rocky Mountain spotted fever (RMSF) takes its name from the characteristic rash that occurs as a consequence of vasculitis associated with rickettsial invasion of the endothelium. The authors examined sera from 14 patients with serologically confirmed RMSF for the presence of antibodies (IgG and IgM) reactive with human umbilical vein-derived endothelial cells and with the phospholipids cardiolipin (CL) and phosphatidyl serine (PS). Sera from 7 patients (50%) exhibited antiendothelial antibodies, and 10 (71%) patient sera reacted with CL and/or PS. Because such antibodies may interfere with or augment endothelial thrombosis-related activities, acute and convalescent sera were tested for their effects on endothelial PGI2 secretion and protein C activation. Acute sera from two patients and convalescent sera from four patients stimulated protein C activation. Additionally, sera from five acute and nine convalescent cases inhibited basal endothelial PGI2 secretion, but sera from two acute and three convalescent cases stimulated thrombin-dependent PGI2 secretion. These results demonstrated that, in a significant proportion of patients, RMSF was accompanied by the appearance of antibodies that bound to endothelial cells and to phospholipids; some of these antibodies may have altered anticoagulant endothelial functions.
Adolescent↗
Effect of lupus anticoagulants on the activated partial thromboplastin time. Results of the College of American Pathologists survey program.
Lupus anticoagulants are antibodies that interfere with in vitro phospholipid-dependent coagulation reactions. In vivo, they have been associated with a variety of thromboembolic problems. Samples from patients with lupus anticoagulants were included in the 1986 and 1987 College of American Pathologists proficiency survey program. Participant performance on these samples demonstrated significant variation in the responsiveness of different activated partial thromboplastin reagents to lupus anticoagulants. The level of factor VIII in these samples reported by the participants also varied with the reagent used. Follow-up studies demonstrated striking reagent-dependent differences in the dilutional effect on apparent factor VIII, IX, XI, and XII activity. These results point out the importance of selecting sensitive and responsive reagents for appropriate identification of lupus inhibitors. In addition, the results indicate that the choice of reagent used for factor assays can affect the apparent factor activity as well as whether a dilutional effect is noted when a lupus anticoagulant is present in the test sample, an important consideration when trying to distinguish a lupus anticoagulant from a specific factor inhibitor.
Autoantibodies↗
Corticosteroid-associated blue toe syndrome: role of antiphospholipid antibodies.
Explore the source record for details and available documents.
Aged↗
Comparison of test methods for the lupus anticoagulant: international survey on lupus anticoagulants-I (ISLA-1).
Six lyophilized plasma samples were sent to 20 "expert" laboratories for assessment of lupus anticoagulant (LA). Four samples contained pooled LA of graded potency mixed with aged normal plasma. One contained LA plus cephalin phospholipid and one contained a nonspecific venom anticoagulant. Sixteen methods were used overall with some participants using up to 8 methods. Results were scored in regard to the known potencies of LA in the samples and other known induced defects. Activated partial thromboplastin time (APTT) tests used by most participants for preliminary screening were relatively sensitive, but non-specific. Platelet or phospholipid neutralization procedures (PNP) appeared to be sensitive and specific but showed a non-linear response to increased LA content. Kaolin clotting time (KCT) tests showed the most sensitive response to increased LA content but the weaker LA were not scored as abnormal by most laboratories as the samples may have contained platelet fragments. Other commonly used tests such as the tissue thromboplastin inhibition (TTI) test and the dilute Russell's viper venom test (DRVVT) were carried out somewhat inconsistently. The variability in performance of tests in different laboratories indicates that standardization of methodology is urgently required. Generally it seemed that most clotting tests were "bypassed" by the addition of phospholipid to a known LA-positive sample in apparently direct proportion to their sensitivity. Sample preparation, especially prevention of contamination with activated platelets is a vital preliminary part in the assay of LA.
Autoantibodies↗
Laboratory diagnosis of lupus anticoagulants.
Explore the source record for details and available documents.
Autoantibodies↗
Heat treatment of serum and plasma induces false positive results in the antiphospholipid antibody ELISA.
We found that levels of antiphospholipid antibodies (aPLA), measured with an ELISA increase if serum or plasma samples are heated. The phenomenon is dependent on duration and degree of heating, optimum levels being reached at 3 h at 56 degrees C. Negative samples become positive after heating. The heating effect is more pronounced for IgG-aPLA than for IgM-aPLA and is not observed for adsDNA, atetanus or lymphocytotoxic antibodies. The presence of serum/plasma components in addition to IgG is essential for the phenomenon to occur. Ultracentrifugation and mixing experiments with isolated IgG did not enable us to explain our observations. Nevertheless, knowledge of this phenomenon is of practical importance.
Abortion, Habitual↗
Evaluation of APTT reagent sensitivity to factor IX and factor IX assay performance. Results from the College of American Pathologists Survey Program.
Hereditary factor IX deficiency (hemophilia B) is among the more common hereditary bleeding disorders and factor IX assays are among the more common specific factor assays performed by coagulation laboratories. To assess the sensitivity of various reagents used for performance of activated partial thromboplastin times and factor IX assays, a series of samples with varying levels of factor IX were included in the 1988 College of American Pathologists Survey Program. We found significant differences in the sensitivity of reagents to factor IX deficiency. Surprisingly, the least sensitive reagents were among the most commonly used reagents. Significant differences in the classification of activated partial thromboplastin times as abnormal were noted between H1 and H2 survey participants. As with factor VIII assays, significant differences in the dose-response curves for factor IX deficiency were noted between reagents, with more responsive reagents giving more precise results for factor IX assays. Comparison of factor IX assay performance in 1988 with 1980 performance indicates a substantial improvement in assay precision. However, a further improvement in assay performance could be expected if current recommendations were followed.
Blood Coagulation Tests↗
Laboratory identification of the lupus anticoagulant.
Explore the source record for details and available documents.
Autoantibodies↗
Antiphospholipid antibodies and recurrent pregnancy loss.
Antiphospholipid antibodies (APA) have recently been linked to a variety of clinical findings including arterial and venous thrombosis, recurrent spontaneous abortions and fetal loss, as well as thrombocytopenia. These observations have stimulated multidisciplinary interest in the laboratory identification of APA and the clinical management of patients with positive tests for APA.
Abortion, Habitual↗