[Current biological surveillance of oral anticoagulant treatment].
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The prothrombin time is the coagulation time of citrated plasma in the presence of calcium and a tissue extract, thromboplastin, added in excess. The prothrombin time was historically the first method of evaluation and control of oral anticoagulation. Over the years, the different thromboplastins have changed, diversified, so affecting the result of the prothrombin ration established from the prothrombin time and a reference curve. In 1985, the International Committee on Thrombosis and Haemostasis requested that all the losts of thromboplastin have their international sensitivity index (ISI) indicated. This allowed uniformity of the results by the introduction of the INR (International Normalized Ratio) calculated by the formula: INR = (PTR)ISI, the PTR or prothrombin time ratio corresponding to the patients' prothrombin time divided by that of reference control plasma. It is, in fact, impossible to interpret the results of a prothrombin ration without knowing their expression in INR. The consequences of the absence of uniformity in the control of anticoagulant therapy are important and serious. The uncertainty concerning the degree of anticoagulation inherent in the use of a single prothrombin ratio may be the source of bleeding or thromboembolic complications. Curiously, the system based on the INR is neither generalised, nearly 10 years after its recommendation, nor adopted by the majority of practitioners. However, the stakes are high because the principal complication of oral anticoagulants remains bleeding, including the dramatic strokes. Moreover, the global mortality due to haemorrhagic complications is about 0.1 to 0.5% for treatments of short duration and much higher in prolonged therapy.(ABSTRACT TRUNCATED AT 250 WORDS)Keywords:
Prothrombin time
Thromboplastin
Oral anticoagulant
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The purpose of the present study was to compare the results obtained with a human recombinant thromboplastin (Innovin, Baxter) (IN) and a high-sensitivity rabbit brain reagent (Thromboplastin IS, Baxter) (IS), on the performance of prothrombin time (PT) test and the functional assay of factors included in the extrinsic coagulation system, in order to establish possible differences on imprecision, diagnostic accuracy and sensitivity to the oral anticoagulant defect, between the two products.Six Spanish hospital took part in the study. Plasma samples from 221 healthy subjects, 100 patients with severe liver disease, 27 with dysfibrinogenaemia, 10 with lupus anticoagulant and from 13 individuals propositus and their relatives with congenital deficiencies of the extrinsic coagulation pathway, and their relatives were studied; 188 patients stabilized on oral anticoagulant therapy and 82 on heparin therapy were also included. The in vitro effect of heparin was tested by addition of increasing amounts of heparin (0.3 to 10.0 IU/mL) to aliquots of normal plasma.Both in the intra-assay and in the inter-assay imprecision study, a better coefficient of variation was obtained with IN when the PT was performed on abnormal samples. Prothrombin time ratio from patients with liver disease had significantly higher values with IS. On the contrary, IN had a higher sensitivity in samples from patients with dysfibrinogenaemia or from those stabilized on oral anticoagulant therapy. In showed a very low sensitivity to heparin at concentrations corresponding to the therapeutic range.The results of this field study indicate that IN, compared with a high-sensitivity rabbit brain thromboplastin, is a suitable reagent for PT determination in normal subjects, patients with liver disease or with congenital deficiencies of clotting factors. It shows a higher sensitivity in cases of dysfibrinogenaemia and in patients on oral anticoagulant therapy. In addition, the recombinant reagent had better reproducibility when the PT was performed on abnormal samples, and it was hardly affected by heparin within the therapeutic range.
Thromboplastin
Prothrombin time
Oral anticoagulant
Lupus anticoagulant
Coefficient of variation
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The objective of this report is to compare the prothrombin time performed with thromboplastin of different tissues and species in patients under oral anticoagulant therapy as well as the way of expressing the results. The results showed that the ISI of the thromboplastin of human and rabbit brain are very close to the IRP BCT/253 (1.2 vs 1.1) and RBT/79 (1.3 vs 1.4), respectively. In contrast, the rabbit lung thromboplastin showed the greatest differences in the ISI values (1.6 vs 1.4) and in the CV (6.1%). The authors found significant statistical differences with the results of the prothrombin time as expressed in activity percentage (p less than 0.001) in three plasma pools of patients under different oral anticoagulant level for all thromboplastins studied. However, if the results are expressed in terms of INR, the values obtained are almost the same. The results here reported would demonstrate that the prothrombin time as INR allows the use of only one scheme for oral anticoagulant control when the thromboplastin reagent is calibrated according to the recommendations of the WHO.
Thromboplastin
Prothrombin time
Oral anticoagulant
Anticoagulant Therapy
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Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, and D-dimer assays are part of the conventional routine coagulation panel. Accurate standardization of both the preanalytical and analytical phases is pivotal to achieving accuracy and precision of results. Routine blood coagulation assays and D-dimer testing strongly influence clinical decision-making because they represent crucial steps in the diagnostic approach to thromboembolic and hemorrhagic disorders and in the monitoring of anticoagulant therapy with heparin or oral anticoagulants.
Among major determinants of preanalytical variability, sample collection exerts considerable influence on the reliability of results (1); problems arising from cumbersome blood withdrawal, inadequate filling or mixing of the tube, and inappropriate treatment of specimens are important sources of imprecision. In particular, it has been suggested that the precision of fibrinogen measurements might be influenced by procedures used for specimen collection, leading to the suggestion that the first tube of blood collected be discarded (2). To establish the potential impact of sample collection on imprecision of routine coagulation assays, we measured PT, aPTT, fibrinogen, and D-dimer in 30 consecutive patients on oral anticoagulant therapy.
The study was …
Prothrombin time
D-dimer
Coagulation testing
Oral anticoagulant
Thromboplastin
Coagulation Disorder
Blood collection
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The Ciba Corning Biotrack 512 coagulation monitor requires a minimal degree of technical expertise to operate, and is already in use for near-patient testing. This study evaluated the monitor for possible use in decentralised control of oral anticoagulant treatment. The monitor compared well with Manchester Reagent, suggesting that it could be used in areas where this thromboplastin is used for centralised control. The inability of the monitor to allow for locally determined geometric mean normal prothrombin times in the calculation of the International Normalised Ratio (INR), and possibly the high International Sensitivity Index (ISI) of the thromboplastin used with the monitor, resulted in poor comparability with some other thromboplastins, particularly Thrombotest. These problems need to be addressed if the monitor is to be used for decentralised anticoagulant control.
Thromboplastin
Oral anticoagulant
Prothrombin time
Comparability
Anticoagulant Therapy
Coagulation testing
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Most studies on the sensitivities of coagulation assays to direct oral anticoagulants (DOACs) are based on normal plasma spiked with anticoagulant in the laboratory. Recent studies have shown that reagent sensitivity varies significantly depending on whether spiked or patient samples are used. The aim of this study was to compare the sensitivities of routine coagulation assays in patient samples and commercial drug specific calibrators using commonly used activated partial thromboplastin time (APTT) and prothrombin time (PT) reagents (i.e., Actin FS and Neoplastine CI Plus for APTT and PT, respectively) in Australian laboratories. Samples collected at Pathology North Hunter (PN-H) for dabigatran (n = 39), rivaroxaban, (n = 56) or apixaban levels (n = 22) between February 2013 and November 2015 were analysed and compared to two different commercial drug specific calibrators from different manufacturers for each DOAC. Our results show that dabigatran (Hyphen and Technoclone) and rivaroxaban (Stago) calibrators tend to overestimate the APTT but are similar to patient samples for PT. A cut-off DOAC level of 50 ng/mL based on results from patient samples within the laboratory can be used as the lower limit which will result in prolongation of APTT for dabigatran (sensitivity 96%, n = 25) and PT for rivaroxaban (sensitivity 97%, n = 29), respectively. Individual laboratories should be familiar with the sensitivity of their coagulation reagents to different DOACs including differences between patient samples versus different commercial drug specific calibrators.
Apixaban
Coagulation testing
Prothrombin time
Thromboplastin
Oral anticoagulant
Thrombin time
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We have studied the effects of warfarin pretreatment on blood coagulation tests, thrombosis and endothelial damage in the rabbit after 2 h of subsequent venous stasis. We found that 3 mg/kg warfarin significantly modified the results of prothrombin time, activated partial thromboplastin time and ProComplex tests. The incidence of thrombosis was not reduced by warfarin, but the weight of the thrombi were inversely related to the effects of the drug on blood coagulation. The endothelial cells showed some degree of damage. In conclusion, warfarin neither prevents endothelial damage nor reduces the incidence of thrombosis after venous stasis, but retards the growth of thrombi.
Prothrombin time
Thromboplastin
Venous stasis
Blood stasis
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The activated partial thromboplastin time is compared with the corresponding prothrombin ratio in 6378 samples of platelet-poor plasma from 446 patients treated for a total of more than 4500 patient/months with oral anticoagulatnts. A relative decrease in the activated partial thromboplastin time following deep vein thrombosis is described, which tends to become less obvious during the first year of treatment and is greater in older patients. Although this relative decrease is also found in patients treated after cerebrovascular accidents, it is not found in patients treated after myocardial infarction or in patients with mitral valve disease treated prophylactically with long-term oral anticoagulants. It is though possible that these changes following deep vein thrombosis might be useful in helping to determine the duration of oral anticoagulant treatment.
Prothrombin time
Oral anticoagulant
Thromboplastin
Anticoagulant Therapy
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Oral anticoagulant
Anticoagulant Therapy
Coagulation testing
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Phenprocoumon
Prothrombin time
Protein C deficiency
Oral anticoagulant
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