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Biomedical subjects

D A Triplett

Publications and source records attributed to D A Triplett.

120 records · Page 7Linked to original sources
PubMed1977

The prediction of prothrombin time system performance using secondary standards.

A method for the comparison of prothrombin time systems using single large lots of lyophilized plasma in the College of American Pathologists Surveys is presented. Systematic biases for prothrombin time methods as well as for thromboplastins have been measured, and their use allows a very accurate (within 2.25%) prediction of the prothrombin time for the great number of prothrombin time systems presently being used in the United States.

Blood↗
PubMed1976

Clinical and laboratory aspects of Yersinia pseudotuberculosis infections, with a report of two cases.

Yersinia pseudotuberculosis infections in two bacteriologically confirmed cases are described. A child was found to have mesenteric adenitis and an adult had septicemia. Invariably simulating acute appendicitis, mesenteric adenitis most often occurs in male children and adolescents. Septicemia with this organism usually affects elderly, debilitated patients, who frequently have chronic hepatic disease. The infrequent diagnosis of infection with Yersinia pseudotuberculosis in the United States is probably due to failure to consider it a human pathogen. Currently classified with the Enterobacteriaceae, Yersinia pseudotuberculosis in a non-lactose-fermenting, Gram-negative coccobacillus. It is sensitive to a wide range of antibiotics, including tetracycline and streptomycin, but usually is resistant to ampicillin. Yersinia pseudotuberculosis has a worldwide distribution in wild and domestic mammals and birds. Infections in man may result from direct contact with infected animals or their excreta.

Aged↗
PubMedDate not supplied

Use of the activated partial thromboplastin time for the diagnosis of congenital coagulation disorders: problems and possible solutions.

The activated partial thromboplastin time (APTT) is a commonly performed laboratory procedure which is used for multiple purposes including monitoring of heparin therapy, detection of coagulation factor deficiency, and detection of lupus anticoagulants. Among the hereditary coagulation deficiencies, factor VIII and factor IX are the most common. APTT reagents differ widely in both their sensitivity to factor VIII and factor IX deficiencies as well as their responsiveness. Sensitivity may be defined as the ability to identify a deficiency state while responsiveness is indicated by the degree of prolongation of the APTT result as compared to the upper limit of normal. Reagents may be both sensitive and responsive or alternatively sensitive and relatively nonresponsive. Consequently, it is extremely important for each laboratory to carefully identify the upper limit of the normal range. A variety of preanalytical variables will also effect the sensitivity of the APTT to factor deficiency states. These variables include specimen handling and the preparation of platelet poor plasma. The instrument effect is also of importance. Selection of the reagent tends to have the most impact on sensitivity and responsiveness while instrumentation affects the precision of a given APTT. The composition and concentration of phospholipid in APTT reagents does have an effect on reagent responsiveness and sensitivity. Sensitivity to factor deficiencies does not necessarily parallel sensitivity to lupus anticoagulants.

Blood Coagulation Disorders↗
PubMedDate not supplied

Screening for the lupus anticoagulant.

The lupus anticoagulant may be defined as an immunoglobulin (IgG, IgM or both) which interferes with one or more of the in vitro phospholipid-dependent tests of coagulation. For many years, lupus anticoagulants were regarded as a laboratory nuisance; consequently, reagents were often selected on the basis of insensitivity to lupus anticoagulants. Recently, lupus anticoagulants have been associated with a variety of clinical conditions including recurrent thromboembolic events (both arterial and venous), obstetrical complications including fetal death and spontaneous abortion, and a variety of hematologic and neurologic complications. As a result, many laboratories are now being asked to identify the presence of lupus anticoagulants in selected patient populations. In addition to assays for lupus anticoagulants, there are immunologic assays designed to detect phospholipid antibodies using solid phase systems (RIA or ELISA). A variety of screening tests have been designed to enhance sensitivity to lupus anticoagulants. Test systems with decreased amounts of phospholipid (phosphatidylserine) appear to be most sensitive to lupus anticoagulants. Of the various tests used, the activated partial thromboplastin time (APTT) appears to be most sensitive. The sensitivity of any screening test system is inversely proportional to the residual platelets in the patient sample. APTT reagents differ widely in their sensitivity to lupus anticoagulants. The dilute Russell viper venom time is also highly dependent on the choice and concentration of phospholipid with respect to its sensitivity. Once an abnormality of a screening test has been identified, it is necessary to prove the abnormal result is due to the presence of an inhibitor. This step in the diagnosis may utilize either mixing studies or plasma agarose gels. The final step in the diagnosis of lupus anticoagulants is the demonstration of phospholipid specificity of the inhibitor. Two approaches have been utilized: 1. test systems designed to enhance anticoagulant effect (phospholipid-depleted), and 2. test systems with increased or altered phospholipids which will bypass or neutralize the anticoagulant.

Blood Coagulation Factors↗
PubMedDate not supplied

Antiphospholipid antibodies and reproduction.

Antiphospholipid antibodies (APAs) may be identified in the laboratory by using either coagulation studies or solid-phase immunologic assays (ELISA; RIA). These methodologies do not necessarily evaluate the same antibody; consequently, it is appropriate to screen a patient's plasma by utilizing both assays. APAs have been associated with a variety of obstetrical complications including recurrent spontaneous abortion, intrauterine fetal death, early onset preeclampsia, deep vein thrombosis, and postpartum serositis syndrome. The Kaolin Clotting Time appears to be the most sensitive coagulation test for identifying the lupus anticoagulant. However, preliminary studies would suggest the presence of anticardiolipin antibodies as detected by solid-phase assays are more sensitive and predictive of the clinical course. Although there are no prospective trials to analyze treatment of patients with APA, preliminary data suggest the use of prednisone in combination with aspirin significantly improves the probability of delivery of a viable infant. In addition, heparin, intravenous gammaglobulin, and exchange plasmaphoresis have all been tried with varying degrees of success in individual patients in small series.

Abortion, Habitual↗
PubMedDate not supplied

Antiphospholipid antibodies: proposed mechanisms of action.

Antiphospholipid antibodies (APA) are a family of immunoglobulins that react with anionic phospholipids, or anionic phospholipids-protein complexes. Recent evidence would support the latter definition. Lupus anticoagulants (LA) inhibit in vitro phospholipid dependent coagulation tests [e.g., activated partial thromboplastin time (APTT), prothrombin time (PT), and dilute Russell viper venom time (dRVVT)]. This inhibition appears to be specific for reagent phospholipids. The addition of freeze-thawed platelets or activated platelets will result in correction of the LA-induced abnormality. Anticardiolipin antibodies (ACA) are related to LA but appear to be distinct. ACA are detected by solid phase assays (ELISA, RIA) and require a plasma cofactor: beta 2 Glycoprotein-I (beta 2 GPI). ACA and LA activities can be separated in individual patient plasmas by affinity chromatography. In some instances they are of differing isotypes. Preliminary evaluation of beta 2 GPI in coagulation assays suggests it may function as a cofactor for LA activity. Recent work also suggests human prothrombin may represent a necessary cofactor for in vitro LA activity. Paradoxically, patients with LA/ACA may sustain thromboembolic events involving both venous and arterial sites. The prothrombotic properties of LA/ACA have not been satisfactorily characterized. A number of proposals have been reported, including inhibition of prostacyclin (PGI2) generation by endothelial cells, decreased activity of the protein C system, impaired fibrinolysis, and inhibition of beta 2GPI. Among these various hypotheses, down regulation of the protein C system appears most plausible. Also, LA/ACA may interfere with the phospholipase A2-phospholipid substrate complex involved in the generation of arachidonic acid from membrane phospholipids.

Animals↗
PubMedDate not supplied

Lupus anticoagulants: diagnostic dilemma and clinical challenge.

Lupus anticoagulants (LAs) are immunoglobulins which prolong 1 or more of the in vitro phospholipid-dependent tests of coagulation (e.g., activated partial thromboplastin time [APTT], dilute Russell viper venom time [dRVVT], kaolin clotting time [KCT], and textarin time [TT]). Paradoxically, patients with LAs rarely experience hemorrhagic problems. Approximately 1/3 of individuals with LAs experience thromboembolic complications such as stroke, deep vein thrombosis, and pulmonary emboli. LAs are members of the antiphospholipid antibody (APA) family. The APA family includes: LAs, anticardiolipin antibodies (ACAs), and reagin (the antibody responsible for the positive serologic test for syphilis). In approximately 60% of the patients, a LA and an ACA will both be present. The diagnosis of LAs requires an organized approach. Careful preparation of platelet poor plasma (PPP) is essential to assure maximum detection of LA. In order to rule out LAs, it is necessary to perform at least 2 screening tests (e.g., APTT, dRVVT). Additional steps in the diagnosis of LAs include mixing studies to identify the presence of an inhibitor and confirmatory procedures to demonstrate phospholipid-dependence of the inhibitor. It is also important to rule out any other potential coagulopathies which may account for the prolonged screening studies.

Adult↗
PubMedDate not supplied

A report on the First International Workshop for Lupus Anticoagulant Identification.

Recognition that the lupus anticoagulant (LA) is associated with an increased risk for arterial and venous thrombosis, recurrent spontaneous abortions and fetal loss has led to increased laboratory requests for identification of LA. It is of interest not only to laboratory medicine and obstetrics but also to rheumatology, neurology and cardiology. Due to the antibody's heterogeneous expression, no single test confirms its presence. Recent criteria for LA identification include the performance of one or more screening tests to demonstrate LA interference with phospholipid-dependent tests, differential studies to determine the presence of an inhibitor, and confirmatory procedures to prove that the inhibitor is phospholipid dependent. An international workshop was conducted to study a panel of tests for LA identification and to select those most helpful for diagnosis.

Blood Platelets↗
PubMedDate not supplied

The relationship between lupus anticoagulants and antibodies to phospholipid.

The relationship between lupus anticoagulants and antibodies directed against negatively charged phospholipids, as measured by an enzyme-linked immunosorbent assay, was explored in a series of plasma samples from 100 patients with well-characterized lupus anticoagulants. Only 73% of the patients had detectable IgG, IgM antibodies, or both, to one or more of four phospholipids. Of these patients, 29% had IgG-type antibodies only, 56% had both IgG and IgM antibodies, and 15% had IgM antibodies only. Of the 100 patients, 19% had a history of thrombosis, 8% had a history of spontaneous abortion, and 6% had a history of seizure disorder. These complications occurred in the presence (80%) and absence (20%) of detectable antiphospholipid antibodies. Drug-related antibodies were observed in 34 patients; of these, 71% had detectable anti-phospholipid antibodies and 24% had a history of thrombosis. There were ten patients with lupus anticoagulants associated with infections; none of these patients had a history of thrombosis. The results indicate that antiphospholipid antibodies are not present in all patients with lupus anticoagulants, that the presence of antiphospholipid antibodies in patients with lupus anticoagulants does not increase the risk of thrombosis in these patients, and that drug-related antibodies are associated with an increased risk of thrombosis. Lupus anticoagulants and antiphospholipid antibodies seem to define two distinct but related patient populations, each associated with an increased risk of thrombosis.

Adolescent↗
PubMedDate not supplied

Burkitt's lymphoma: tumor lysis following malignant hyperthermia.

An adult patient with massive abdominal Burkitt's lymphoma developed malignant hyperthermia during exploratory laparotomy. Simultaneously, evidence of tumor lysis appeared. The lethal effect of heat on cancer cells has been amply demonstrated experimentally, and clinical trials of regional and whole-body hyperthermia in various human malignancies have appeared. Lymphomas have not been reported among those tumors studied. Burkitt's lymphoma, a rapidly growing tumor, is likely to respond to hyperthermia, and the evidence reported here should be pursued with controlled clinical trials involving induced hyperthermia in refractory malignant lymphomas.

Adult↗