Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “THROMBOPLASTIN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources
PubMed1996

Prothrombin time sensitivity and specificity to mild clotting factor deficiencies of the extrinsic pathway: evaluation of eight commercial thromboplastins.

Prothrombin-time (PT) sensitivity and specificity to mild clotting factor II, V, VII and X deficiencies have rarely been studied. We therefore carried out a prospective study, in 350 patients, of eight commercial thromboplastins (CTs) in their ability to detect mild clotting factor deficiencies, notably in factor VII. In each patient the factor II, V, VII and X clotting activities and PT performed with each CT were determined. For each CT, PT sensitivity and specificity in detecting factor deficiencies below 0.5 U/ml or below 0.4 U/ml were determined at various PTs, and then Receiver Operator Characteristic curves constructed. At optimum PT threshold level (sensitivity = specificity), exactitude varied from 0.64 to 0.74 (p < 0.01) and from 0.67 to 0.81 (p < 0.0001) in detecting deficiencies below 0.5 and 0.4 U/ml respectively. In conclusion, this study shows the limits of the PT test as performed with 8 CTs in patients with mild clotting factor deficiencies. The impact of such differences in sensitivity and specificity on monitoring certain patients subjects to decrease in coagulation factor, and, in particular, of those under low dose oral anticoagulant, remains to be determined.

Blood Coagulation Disorders↗
PubMed1996

Effect of a sliding scale protocol for heparin on the ability to maintain whole blood activated partial thromboplastin times within a desired range in hemodialysis patients.

A prospective, randomized and open study was conducted to evaluate the ability of an individualized heparin dosing protocol to achieve and maintain whole blood activated partial thromboplastin times (WBAPPT) within a predetermined range in hemodialysis patients. Thirty-one hemodialysis outpatients who received a total of 99 dialyses were studied. Systemic heparinization was achieved with a loading dose and a continuous infusion. WBAPPT, used as a monitoring parameter for heparin therapy, was measured at 5 minutes and 1, 2, 3 and 3 1/2 hours after the start of heparinization. An initial heparin loading dose of 50 u/kg dry weight was used, with a continuous infusion of 15 u/kg/h and a sliding scale to adjust infusion rates to target WBAPPT in the goal range of 150-190 seconds. Individual heparin loading doses for subsequent treatment sessions were titrated to achieve the lowest dose which would still result in clear dialyzers at the end of hemodialysis. There was a high degree of interindividual variability in heparin requirements. A loading dose of 20-25 u/kg placed the majority (72.4%) of the patients within the 150-190 seconds range at the 5 min WBAPPT measurement. The sliding scale method was effective in keeping about 60% of the WBAPPT within the desired range throughout the rest of the hemodialysis session. As the loading or total doses were increased, the incidence of clear dialyzers increased. In conclusion, this heparin protocol is effective for individualizing heparin doses to achieve therapeutic WBAPPT in hemodialysis patients.

Anticoagulants↗
PubMed1996

European Concerted Action on Anticoagulation (ECAA)-the multicentre calibration of rabbit and human ECAA reference thromboplastins. Steering Committee.

Two candidate ECAA reference preparations have been calibrated in a multicentre exercise at 14 representative national laboratories to provide reference thromboplastin for a large field study in 16 European countries. Two preparations were required because of the established differences in ISI arising from the two main routes of calibration via rabbit and human IRP. To be comparable with working reagents in everyday use a human plain recombinant reagent of low ISI and a rabbit plain preparation of moderately high ISI were selected. A precise calibration of the two candidate preparations has been achieved with the manual PT technique and an ISI of 0.95 (SE 0.0078) for the human reagent and 1.67 (SE 0.0322) for the rabbit reagent.

Animals↗
PubMed1997

Reliability of a modified tissue factor-dependent factor V assay for activated protein C resistant factor Va using a calcium-containing thromboplastin.

The original tissue factor-dependent factor V assay for activated protein C resistant factor Va (Blood 1995; 85: 1704-1711) has been modified to use a calcium containing thromboplastin and to express results as an observed to expected ratio (Obs/Exp.). The latter permits establishing a normal range independent of variations due to differences in reagents. Comparing Obs/Exp ratios with DNA analysis in 72 persons revealed that an Obs/Exp ratio of 0.6 distinguished without overlap normals from heterozygotes for FV R506Q. Three homozygotes had a ratio of < 0.1. Application of this Obs/Exp cut-off ratio of 0.6 to a total of 226 plasma samples tested to date discriminated without overlap between normals and heterozygotes. We conclude that this assay-readily adaptable to any dedicated coagulation laboratory and capable of yielding reliable results in all clinical circumstances in which testing is indicated-can distinguish between normals and heterozygotes for the FV R506Q mutation without the need for confirmatory DNA analysis.

Bleeding Time↗
PubMed1997

[Interference of factor VIII excess on the detection of lupus anticoagulants by the activated partial thromboplastin time].

Antiphospholipids antibodies (AAP) were investigated in plasma of 62 patients with systemic lupus erythematosus, and studied for the possible interference of the excess in factor VIIIc-Von Willebrand factor (VWF-VIIIc) complex in the detection of lupus anticoagulants (LA) by the activated partial thromboplastin time (APTT). We used four commercial reagents and noted that each one exhibited a different level of sensitivity of LA; the most sensitive one allowed the detection of 16 LA positive plasmas while the less sensitive reagent detected only 6 positives. The Elisa test for IgG and IgM AAP detection was positive in 25 out of 62 plasmas (40%). Comparison of the Von Willebrand factor antigen level and the APTT values showed a significant negative corrélation with 2 reagents (r = 0.369, p < 0.01 and r = 0.272, p < 0.05 respectively) that were also the less sensitive to LA. The interference of an excess in VWF-VIIIc complex was further studied by the addition of purified factor VIII in 3 LA positive plasmas. Our results suggests that an excess of factor VIIIc could lead to false negative LA, using certain APTT reagents. We conclude that a more accurate LA detection require: sensitive reagents, a pool of normal plasmas selected with normal factor VIII level, as well as repeated testing of blood sampling withdrawn away of an inflammatory process to avoid false negative LA detection.

Adolescent↗
PubMedDate not supplied

[Serum thermostable and thermolabile inhibitors of tissue thromboplastin].

Besides a thermolabile inhibitor of tissue thromboplastin a thermostable inhibitor was found in human blood serum; molecular weight of the inhibitor (estimated by gel filtration) is 210000-235000 daltons, while molecular weight of a thermolabile inhibitor--480000 daltons. Inhibition of the thrombin formation system by the termostable inhibitor was reversible and was characterized kinetically as a mixed type of inhibition. Both inhibitors were found in blood of rats. Their content varied irrespectively of the state of hemocoagulation. Content of the thermostable inhibitor was distinctly decreased in blood serum after the blockade of reticuloendothelial system by administration of tripane blue.

Hot Temperature↗
PubMed1997

Comparison of an activated partial thromboplastin time with a Russell viper venom time test in screening for factor V(Leiden) (FVR506Q).

Factor V(Leiden) is the most common abnormality detected in patients examined because of hereditary thrombophilia. The most widely used clot-based screening test is based on the activated partial thromboplastin (aPTT) time. This test has a low sensitivity. A comparison of the aPTT-based test with a Russell viper venom time test (RVVT) was performed in matched samples. All samples were analyzed by polymerase chain reaction (PCR) for the factor V(Leiden) defect. We studied 139 samples, of which 109 were PCR-negative; 30 were PCR-positive. Using the manufacturer's suggested threshold ratio of 2, the aPTT test showed a sensitivity of 0.43, a specificity of 0.86, and a positive predictive value (PPV) of 0.97. The RVVT test had a sensitivity of 1.0, a specificity of 0.95, and a PPV of 0.91. Segregation of a subpopulation of this study population into ABO group O vs non-group O showed an effect of ABO group on the aPTT test but not on the RVVT test, consistent with an influence of factor VIII clotting (factor VIII:C) on the aPTT test. The RVVT test seems superior to the unmodified aPTT test as a screening test for factor V(Leiden).

Factor V↗
PubMed1997

Preparation of lyophilized partial thromboplastin time reagent composed of synthetic phospholipids: usefulness for monitoring heparin therapy.

To contribute to the development of a reference reagent for monitoring heparin therapy, a lyophilized partial thromboplastin time (PTT) reagent was prepared from synthetic dioleoylphosphatidylcholine, dioleoylphosphatidylserine, and dioleoylphosphatidylethanolamine, with colloidal silica as activator. The reagent, coded 91/558, was contained in sealed glass ampoules; it deteriorated in a heat degradation experiment, but its activity remained constant for at least 4 years when stored at -70 degrees C. Within- and between-run precision with this reagent complied with the requirements proposed by the International Committee for Standardization in Haematology (ICSH) Panel on PTT. The response of this reagent and of two other reagents to heparin added to pooled normal plasma was nonlinear. Citrated samples from 58 patients receiving intravenous heparin and from 24 apparently healthy volunteers were tested with reagent 91/558, with Automated APTT (Organon Teknika), with Manchester APTT reagent, with an antifactor Xa assay, and with an anti-factor IIa assay. The correlation of APTT with anti-Xa and anti-IIa activity was poor. The best correlation was observed between reagent 91/558 and the Organon Teknika reagent. Correlations were improved when individual patients' samples were replaced by pooled plasmas from heparinized patients, in whom the effect of oral anticoagulation was minimal. These results suggest that preparation of a lyophilized synthetic phospholipid reagent is feasible for use in monitoring heparin therapy.

Anticoagulants↗
PubMed1997

Inability of the activated partial thromboplastin time to predict heparin levels. Time to reassess guidelines for heparin assays.

BACKGROUND: In treating venous thromboembolic disorders, patient outcomes appear to correlate with heparin levels. Due to pharmacokinetic and pharmacodynamic variations, a relationship between heparin dose and level cannot be reliably predicted in individual patients. Some patients have low heparin levels despite therapeutic activated partial thromboplastin times (aPTTs), which may increase their risk for recurrent thromboembolism. Patients with high heparin requirements appear to have fewer bleeding episodes with heparin level-guided therapy. The aPTT does not reliably correlate with heparin blood concentrations or antithrombotic effects. Consequently, heparin therapy monitored with heparin levels may be more effective and safer. OBJECTIVES: To prospectively determine whether (1) the aPTT therapeutic range adequately predicts heparin levels in 38 patients used to establish the therapeutic aPTT range as is currently recommended and (2) whether 3 paired sets of aPTT-antifactor Xa levels provide the basis for using aPTTs to predict subsequent heparin levels in individual patients (n = 27) receiving intravenous heparin for coronary artery disease or venous thromboembolic disease. RESULTS: In the therapeutic aPTT range established, the R2 value for the relationship was 0.4. Prediction intervals were wide. For an aPTT of 60 seconds, the 95% prediction interval estimates were heparin levels of 0.05 to 1.0 U/mL. In individual patients, the aPTT-antifactor Xa relationship had an average R2 value of 0.75. There was no consistent relationship between the aPTT and anti-factor Xa level in a significant number of patients. CONCLUSIONS: The aPTT does not appear to be a useful surrogate for heparin levels. These findings suggest that the current recommendations on the use of heparin levels should be expanded.

Adult↗
PubMed1998

International collaborative study for the calibration of a proposed reference preparation for thromboplastin, human recombinant, plain. On behalf of the Subcommittee on Control of Anticoagulation.

Stocks of the International Reference Preparation (IRP) for thromboplastin, human, plain, coded BCT/253 and held by the World Health Organization (WHO) are nearly exhausted and must be replaced. For practical reasons the choice of the replacement candidate was restricted to two available human recombinant preparations which were coded as X/95 and Y/95 and calibrated in an international collaborative study involving 19 laboratories from Europe, Australia, Canada and Argentina. To minimize the differences between routes of calibration, the two candidates were calibrated against the existing WHO-IRP from human, rabbit and bovine origin and the final ISI was the resultant average value. On the basis of predefined criteria (i.e., within- and between-laboratory precision of the calibration and the conformity to the calibration model), X/95 was the preferred candidate. The assigned ISI (SE of the mean) value is 0.940 (0.0060) and the interlaboratory coefficient of variation 4.7%.

Animals↗
PubMed1998

[Changes in platelet function, activated partial thromboplastin time and plasminogen activator inhibitor in patients with bronchial asthma after prednisone treatment].

Twenty patients with recently recognised bronchial asthma and 22 age and sex-matched healthy control subjects were studied. In both groups the activated partial thromboplastin time (APTT), prothrombin ratio (INR), fibrinogen, euglobulin lysis time (ELT), platelet number and platelet adhesion and aggregation, tissue plasminogen activator antigen (t-PA Ag) and activity of plasminogen activator inhibitor (PAI-1) were tested and compared. Statistically significant differences between asthmatic and control groups concerning adhesion, aggregation, APTT and ELT were found. In asthmatic group after 14 days of prednisone administration in a dose of 20 mg/d statistically significant (p < 0.05) shortening of APTT, and a significant increase of adhesion, aggregation and PAI-1 activity were found. These results suggest that in asthmatic patients after prednisone treatment platelet activity appeared in a form of intensification of adhesion and of aggregation degree, also the activity of PAI-1 probably of the platelet origin increased.

Adult↗
PubMed1976

[The anticoagulant system following intravenous administration of factor XIII and thromboplastin].

The inactivated factor XIII does not change the functional state of the anticoagulating system. The i.v. administration of thromboplastin activates the anticoagulating system in rats which cannot be prevented by an artificial rise of the titre of the inactivated factor XIII in blood. The i.v. injections of the secondary adreanlin-heparin--fibrinogen complex with higher level of the factor XIII is followed by a sharp increase in the functional activity of the anticoagulating system.

Animals↗
PubMed1989

Factor XI (plasma thromboplastin antecedent) deficiency in Ashkenazi Jews is a bleeding disorder that can result from three types of point mutations.

Factor XI (plasma thromboplastin antecedent) deficiency is a blood coagulation abnormality occurring in high frequency in Ashkenazi Jews. Three independent point mutations that result in a blood coagulation abnormality have been identified in the factor XI gene of six unrelated Ashkenazi patients. These mutations either disrupt normal mRNA splicing (type I), cause premature polypeptide termination (type II), or result in a specific amino acid substitution (type III). The three different genotypes were present in the six patients as type I/II, type II/III, and type III/III. Thus far no correlation was found between the three genotypes and the bleeding tendency in these patients.

Adult↗
PubMedDate not supplied

Alpha 1 antitrypsin deficiency and plasma thromboplastin antecedent deficiency--a new association?

We report a 74-year-old woman presenting with vaginal bleeding and hepatomegaly and was found to have plasma thromboplastin antecedent deficiency and alpha 1 antitrypsin deficiency. She also had liver and lung disease of the type associated with the antiprotease deficiency. The relative rarity of the two deficient states led to family and genetic studies. The possibility of a new genetic syndrome is entertained.

Aged↗
PubMed1971

Separation of plasma thromboplastin antecedent from kallikrein by the plasma 2 -macroglobulin, kallikrein inhibitor.

Plasma thromboplastin antecedent (PTA, factor XI) is an important intermediate in the intrinsic coagulation system, and plasma kallikrein has been implicated as a mediator of the inflammatory process. Whereas their biologic activities are functionally distinct, their identity as separate entities in plasma has not been fully established, and the nature of their plasma inhibitors has not been completely characterized. A partially purified preparation containing the clotting, tosyl arginine methyl ester (TAMe) esterase and kinin-producing activities of these substances has been prepared by DEAE-cellulose chromatography of a Celite eluate obtained from acid-treated human plasma. These activities were not separable by acrylamide gel electrophoresis nor by isoelectric focusing, their pI being approximately 8.7. Human plasma alpha(2)-macroglobulin has been shown to inhibit the proteolytic activity of kallikrein and to inhibit partially its TAMe esterase activity. An alpha(2)-macroglobulin, PTA, kallikrein incubation mixture was separated by gel filtration chromatography. The alpha(2)-macroglobulin formed a high molecular weight complex with kallikrein and appeared in early chromatographic fractions. The PTA-clotting activity was not inhibited by the alpha(2)-macroglobulin; 64% of the initial PTA activity was isolated in later fractions free of kallikrein-induced kinin-like activity. In contrast, clotting, TAMe esterase, and kinin-forming activities were inhibited after gel filtration chromatography of an incubation mixture of these activities and partially purified C1 inactivator (C1 esterase inhibitor). Electrofocusing of an incubation mixture of an activated PTA, kallikrein preparation, and alpha(2)-macroglobulin resulted in the isolation of a PTA fraction free of kallikrein proteolytic activity, and with 4% of the original TAMe esterase activity. In this manner, activated PTA and plasma kallikrein have been shown to be distinct substances, and methods have been introduced for the further purification of active coagulation factor XI.

Animals↗
PubMed1976

Coexistence of factor XI (plasma thromboplastin antecedent) deficiency and Gaucher's disease.

The findings of Factor XI (plasma thromboplastin antecedent) deficiency in a patient with Gaucher's disease was investigated. A family study, which included measurements of leukocyte glucocerebrosidase activity and Factor XI levels, revealed that the two genetic disorders segregated independently. One of 12 additional unrelated patients with Gaucher's disease showed a diminished Factor XI level and two of seven unrelated Factor XI-deficient patients showed decreased glucocerebrosidase activity. It is possible that the common occurrence of both genetic disorders results from a high gene frequency of both defects in Ashkenazic Jews.

Adult↗
PubMed1975

[Coagulation tests from capillary blood. Determination of thromboplastin time, thrombin time, fibrinogen, factor II (prothrombin), factor V (accelerin) and factor X (Stuart-Prower factor) from capillary blood].

Methods are described for the determination of the thromboplastin time, the thrombin time, for fibrinogen and factor II, V and X from capillary blood. These methods are easy to perform and comparison of the results from venous and capillary blood showed a very good correlation. The described methods seem suitable for routine coagulation tests in pediatrics.

Automation↗