Articles: prothrombin-time.
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Blood Coagul. Fibrinolysis · Feb 2003
Comparative StudyComparison of plasma fibrinogen by Clauss, prothrombin time-derived, and immunonephelometric assays in a general population: implications for risk stratification by thirds of fibrinogen.
There is strong evidence from meta-analyses of prospective epidemiological studies that increasing plasma fibrinogen levels are associated with increasing risk of ischaemic heart disease. It has been suggested that categorization of plasma fibrinogen by thirds of the population distribution be added to cardiovascular risk prediction equations. However, the heterogeneity of plasma fibrinogen and the resulting discrepancies between commonly performed assays may lead to differences in both mean levels and distributions, and in categorizations of populations by thirds. ⋯ The two assays of clottable fibrinogen (von Clauss and prothrombin time derived) showed similar mean values and distributions, whereas the immunonephelometric assay showed lower mean values. There was significant disagreement between all three assays in categorization of thirds of population fibrinogen distribution (kappa statistic, 0.64 von Clauss versus prothrombin time derived, 0.46 von Clauss versus immunonephelometric, and 0.51 prothrombin time derived versus immunonephelometric). We conclude that further standardization of plasma fibrinogen assays is desirable for ischaemic heart disease risk stratification, and that further studies of the causes and clinical significance of discrepancies between fibrinogen assays in the general population are indicated.
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Anesthesia and analgesia · Jan 2003
Comparative StudyAgreements between the prothrombin times of blood treated In Vitro with heparinase during cardiopulmonary bypass (CPB) and blood sampled after CPB and systemic protamine.
The prothrombin time (PT) is useful for identifying coagulation factor deficits after cardiopulmonary bypass (CPB). However, long processing times and the need for fresh frozen plasma (FFP) to be thawed cause delays in factor replacement. We hypothesized that, by treating with heparinase, blood sampled toward the end of CPB can provide PT results that help to determine the requirement for FFP after CPB. Laboratory delays can be eliminated with point-of-care monitors. We studied 158 adults undergoing nonemergent cardiac surgery. Blood taken before separation from CPB was mixed with heparinase, and PT was measured in the laboratory with a HemoTec timer. Agreements between these results and laboratory measurements of blood taken after systemic protamine were compared by using Bland and Altman plots with the threshold of +/-1.0 s. We found that the laboratory PT measurements during CPB versus after CPB were compara-ble, but the limits of agreement exceeded these thresholds. Similarly, there was unsatisfactory agreement between the HemoTec and laboratory PT results measured before, during, and after CPB. For each PT measured during CPB, the corresponding confidence interval for the postprotamine PT was calculated. During CPB, a laboratory PT of < or =16 s or > or =18 s suggests a > or =83% or > or =93% probability of not requiring or potentially requiring, respectively, FFP after CPB. We conclude that the majority of PT measurements obtained from blood taken before weaning from CPB and treated in vitro with heparinase was associated with a high probability of whether or not FFP would be needed after CPB. ⋯ Coagulation dysfunction after cardiopulmonary bypass may contribute to bleeding. Obtaining coagulation tests and fresh frozen plasma requires time and delays treatment in patients who need fresh frozen plasma. We have devised a technique to provide early estimation of postbypass coagulation status.
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The purpose of this study was to compare results obtained for the prothrombin time (PT) and the activated partial thromboplastin time (APTT) using specimens drawn with and without a discard tube in healthy adults. ⋯ Relative to sampling from a population of healthy adults, drawing a discard tube before a sodium citrate tube for coagulation testing appears to make an insignificant difference. Replication of these results with patients receiving anticoagulant therapy and/or patients with abnormal coagulation results, would offer cost savings by justifying elimination of discard tubes for blood draws for coagulation testing only. Such a change in protocol would also reduce the likelihood of nosocomial blood loss in vulnerable patient populations.
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Clin. Appl. Thromb. Hemost. · Jan 2003
Global anticoagulant effects of a synthetic anti-factor Xa inhibitor (DX-9065a): implications for interventional use.
Heparin has been conventionally used as an anticoagulant for medical and surgical indications. Because factor Xa is an essential component of the prothrombinase complex and leads to the generation of thrombin, its inhibition has become a focus of newer antithrombotic drug development. The in vitro anticoagulant profile of DX-9065a, a synthetic direct factor Xa inhibitor, was studied using activated clotting time assay, thrombelastography, and global clotting tests, such as prothrombin time (PT), activated partial thromboplastin time (aPTT), diluted aPTT, Heptest, Heptest-HI, dilute Russell's viper venom time (dRVVT), thrombin time, ecarin clotting time, and amidolytic anti-Xa assay. ⋯ DX-9065a exhibited a concentration-dependent prolongation of the PT, aPTT, diluted aPTT, Heptest, dRVVT, and reached the clotting times of 51.6, 132, 193, 47.9, 129.9 seconds, respectively, at a final concentration of 12.5 microgram/mL; compared to a control value of 10.6, 30.2, 41.9, 14, 32.2 seconds, respectively. DX-9065a did not affect the ecarin clotting time and thrombin time at concentrations up to 12.5 microgram/mL. Because DX-9065a prolonged the dRVVT, this may impact diagnostic screening of patients with systemic lupus erythematosus.
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J Extra Corpor Technol · Sep 2002
Comparative StudyComparison of five point-of-care prothrombin and activated partial thromboplastin time devices based on age of blood sample.
Delays in processing statium (STAT) blood samples have led to the production of an increasing number of point-of-care tests. Product inserts recommend measuring blood samples immediately after procurement, suggesting that delays may invalidate the test results. We studied the effect of the age of blood samples on point-of-care (POC) prothrombin time (PT) and an activated partial thromboplastin time (aPTT) result. ⋯ One device (Hemochron 801) reported results with 10-min aged blood that were statistically different from fresh blood. None of the aPTT tests results from any device produced results with aged blood that were clinically different from fresh blood. This study suggests that, in the tests evaluated, blood samples that have aged 10 or 18 min will produce clinically relevant aPTT and PT results, respectively.