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A capillary prothrombin time method was described using the Australasian Reference Thromboplastin (A.R.T.). The method was used for the control of oral anticoagulant therapy in 59 patients on 225 occasions and was found to be reliable and convenient. The capillary prothrombin ratio could be correlated with the conventional plasma prothrombin ratio.
The potential for tertiary butylhydroquinone (TBHQ) to produce hemorrhagic death similar to that seen after butylated hydroxytoluene (BHT) treatment was tested in male rats. Groups of male rats were given three consecutive daily doses of 380, 760 or 1520 mg/kg/day BHT or 50, 100 or 150 mg/kg TBHQ. Twenty-four hours following the last dose, the rats were killed, blood was taken for prothrombin determinations and gross autopsies were performed. No evidence of hemorrhage was found in any of the animals. BHT caused a significant dose-dependent increase in prothrombin times, while the prothrombin times of the TBHQ rats were comparable to the controls. Since hypoprothrombinemia plays a major role in producing hemorrhagic death, these data indicate that the potential for THBQ to have such an effect is low.
Prothrombin complex concentrates are used in the treatment of the congenital bleeding disorders associated with Factors II, VII, IX, and X deficiencies. They have also been extensively used to treat acquired coagulation abnormalities secondary to vitamin K deficiency, warfarin ingestion, and various types of liver disease. The reported complications of prothrombin complex concentrates administration include hepatitis, anaphylaxis, and thrombosis. This paper documents the development of disseminated intravascular coagulation in association with the administration of prothrombin complex concentrates to patients with liver disease.
The reported incidence of thromboembolism in children with acute lymphoblastic leukemia (ALL) treated with L-asparaginase, vincristine, and prednisone varies from 2.4% to 11.5%. The present study was designed to prospectively evaluate the role of the TT677 methylenetetrahydrofolate reductase (MTHFR) genotype, the prothrombin G20210A mutation, the factor V G1691A mutation, deficiencies of protein C, protein S, antithrombin, and increased lipoprotein (a) concentrations in leukemic children treated according to the ALL-Berlin-Frankfurt-Muenster (BFM) 90/95 study protocols with respect to the onset of vascular events. Three hundred and one consecutive leukemic children were enrolled in this study. Fifty-five of these 301 subjects investigated had one established single prothrombotic risk factor: 20 children showed the TT677 MTHFR genotype; 5 showed the heterozygous prothrombin G20210A variant; 11 were carriers of the factor V G1691A mutation (heterozygous, n = 10; homozygous, n = 1); 4 showed familial protein C, 4 protein S, and 2 antithrombin type I deficiency; 9 patients were suffering from familially increased lipoprotein (a) [Lp(a)] concentrations (>30 mg/dL). In addition, combined prothrombotic defects were found in a further 10 patients: the FV mutation was combined with the prothrombin G20210A variant (n = 1), increased Lp(a) (n = 3), protein C deficiency (n = 1), and homozygosity for the C677T MTHFR gene mutation (n = 1). Lp(a) was combined with protein C deficiency (n = 2) and the MTHFR TT 677 genotype (n = 2). Two hundred eighty-nine of the 301 patients were available for thrombosis-free survival analysis. In 32 (11%) of these 289 patients venous thromboembolism occurred. The overall thrombosis-free survival in patients with at least one prothrombotic defect was significantly reduced compared with patients without a prothrombotic defect within the hemostatic system (P <.0001). In addition, a clear-cut positive correlation (P <.0001) was found between thrombosis and the use of central lines. However, because the prothrombotic defects diagnosed in the total childhood population studied were all found within the prevalences reported for healthy Caucasian individuals, the interaction between prothrombotic risk factors, ALL treatment, and further environmental factors is likely to cause thrombotic manifestations.
A possibility of formation of the thrombin-phosphatidyl serine and prothrombin-phosphatidyl serine complex is discussed. Prothrombin incubation with 131J-labelled phosphatidyl serine and its subsequent activation results in a formation of a thrombin-phosphatidyl serine--131J-complex. The radioactive label is also detected in the protein precipitate after thermodenaturation of thrombin preincubated with 131J-labelled phosphatidyl serine, which suggests that thrombin is firmly bound to phosphatidyl serine. The formation of the thrombin-phosphatidyl serine and prothrombin-phosphatidyl serine complex is supported by data of gel-filtration on Sephadex G-200 and acrylexes P-150 and P-60, as well as by differential spectrophotometry.
Among snake venom procoagulant proteins, group II prothrombin activators are functionally similar to blood coagulation factor Xa. We have purified and partially characterized the enzymatic properties of trocarin, the group II prothrombin activator from the venom of the Australian elapid, Tropidechis carinatus (rough-scaled snake). Prothrombin activation by trocarin is enhanced by Ca2+, phospholipids, and factor Va, similar to that by factor Xa. However, its amidolytic activity on peptide substrate S-2222 is significantly lower. We have determined the complete amino acid sequence of trocarin. It is a 46,515-Dalton glycoprotein highly homologous to factor Xa and shares the same domain architecture. The light chain possesses an N-terminal Gla domain containing 11 gamma-carboxyglutamic acid residues, followed by two epidermal growth factor (EGF)-like domains; the heavy chain is a serine proteinase. Both chains are likely glycosylated: the light chain at Ser 52 and the heavy chain at Asn 45. Unlike other types of venom procoagulants, trocarin is the first true structural homologue of a coagulation factor. It clots snake plasma and thus may be similar, if not identical, to snake blood coagulation factor Xa. Unlike blood factor Xa, it is expressed in high quantities and in a nonhepatic tissue, making snake venom the richest source of factor Xa-like proteins. It induces cyanosis and death in mice at 1 mg/kg body weight. Thus, trocarin acts as a toxin in venom and a similar, if not identical, protein plays a critical role in hemostasis.
BACKGROUND AND OBJECTIVE: Prolonged anticoagulation aiming at International Normalized Ratio (INR) values > 3.0 has been recommended for patients with thrombosis and the antiphospholipid-antibody syndrome. We evaluated the influence of anticoagulant antibodies in two different prothrombin time (PT) assays carried out on plasma from lupus anticoagulant patients on oral anticoagulation. DESIGN AND METHODS: INR values obtained with a combined (final test plasma dilution 1:20) and a recombinant (final test plasma dilution 1:3) thromboplastin were compared in 17 patients with persistent lupus anticoagulants (LA) receiving oral anticoagulant treatment and monitored for 69.8 patient-years. Doses of anticoagulant drugs were always assigned based on the results obtained with the combined thromboplastin, aiming at a target INR of 2.5 or 3.0 for patients with venous or arterial thromboembolic disease. Paired determinations with both reagents were also obtained throughout the study period in 150 patients on stable oral anticoagulation but free of antiphospholipid antibodies. Total IgG fractions were purified from selected patients to evaluate effect in the two PT assay systems. RESULTS: No patient experienced recurrence of thrombosis or major bleeding complications (95% confidence interval: 0.1-6.5 per 100 patient-years). INR values with the recombinant reagent were significantly higher than with the combined reagent in 8 LA patients (mean DINR ranging from 0.17 to 0.54) of the degree of anticoagulation was overestimated in all but one LA patients with the recombinant reagent when compared to the DINR observed in non-LA patients (-0.64 +/- 0.42). The anti-cardiolipin IgG titer (r(2) = 0.43, p = 0.004) and the anti-b(2)GPI IgG titer (r(2) = 0.30, p = 0.023) were positively associated with the mean deltaINR observed in LA patients. When added to plasmas with different levels of vitamin K-dependent factors, total IgG fractions from 6 LA patients with significant overestimation of the INR with the recombinant reagent (mean DINR ranging from 0.17 to 0.54, group 1) and from 7 LA patients with mean deltaINR < or = 0.0 (ranging from -0.25 to 0.04, group 2) reproduced the effects observed ex vivo in the two assay systems. However, when total IgG fractions were tested at the same final concentration in the two PT assay systems, there was no difference in the clotting times determined with total IgG fractions from group 1 and group 2 LA patients. Addition of negatively charged liposomes (0.4 and 0.8 mg/mL final concentrations) to platelet free plasma from LA-free patients on stable oral anticoagulation caused a 20% to 48% prolongation of the prothrombin time determined with the recombinant reagent. In contrast, no significant prolongation of the prothrombin time determined with the recombinant reagent was observed upon addition of negatively charged liposomes to plasma from group 1 LA patients. INTERPRETATION AND CONCLUSIONS: These results confirm previous suggestions of assay-dependency of INR values in LA patients on oral anticoagulation. For these patients, accurate INR values may be obtained using combined thromboplastin reagents that permit testing at high plasma dilution.
Three members of a San Antonio, Texas, family were identified with prothrombin activity levels half the normal level but to have normal levels of antigen. All exons of the prothrombin gene from the proband were sequenced. A G-to-A mutation at nucleotide 7543 was found that resulted in the substitution of His for Arg at residue 320. The Arg320-Ile321 bond is 1 of 2 sites in prothrombin cleaved by Factor Xa in the prothrombinase complex to form thrombin. Substitution of His for Arg at this site resulted in the blockage of Factor Xa cleavage, forming a dysfunctional molecule. The proband, her mother, and her maternal aunt were found to be heterozygous for this mutation. This is the first known observation of an amino acid substitution at this site that resulted in dysprothrombinemia. (Blood. 2000;95:711-714)
A new genetic anomaly predisposing to venous thrombosis was described in 1996, namely the transition of guanine (G) to adenine (A) at position 20210 in the 3-untranslated region of the prothrombin gene. This mutation is associated with high levels of plasma prothrombin and increased risk of thrombotic events in the venous system. We report the case of a man who, lacking known risk factors for thrombosis, suffered a massive pulmonary embolism and deep venous thrombosis in both lower legs. Thrombophilic analysis confirmed that the patient and close relatives were carriers of the heterozygotic 20210G/A variant of the prothrombin gene. Two relatives with the genetic defect had also suffered some type of deep venous thrombosis.
BACKGROUND: Venous thrombosis followed by pulmonary embolism is one of the most common causes of sudden death among middle-aged adults. Several inherited polymorphisms are associated with heightened risk of venous thrombosis, including mutation at position 20210 of the prothrombin gene and mutation at codon 506 of the factor V gene. METHODS: We studied mutation prevalence in 67 individuals who died of pulmonary embolism and were autopsied in a medical examiner's facility over a 5-year period. Mutations were identified by polymerase chain reaction followed by allele-specific endonuclease digestion. RESULTS: Traditional risk factors for pulmonary embolism (eg, immobility, oral contraceptive use, cancer) were identified in 75%. Heterozygous mutation of the prothrombin gene was found in 3/67 (4%), and heterozygous mutation of the factor V gene was identified in 3/66 (4%). No homozygotes or compound heterozygotes were identified. The prevalence of mutation was not significantly different from that of the general population. CONCLUSIONS: Individuals who die suddenly from pulmonary embolism are not often affected by prothrombin or factor V gene mutations. Therefore, medical examiners need not routinely test for these mutations in individuals who die of pulmonary embolism.
AIM: To estimate incidence rate of Leiden mutation in factor V gene, prothrombin gene mutation responsible for replacement of G for A in position 20210 (G20210A) of its 3'-end noncoding part in patients with systemic lupus erytheamtosus (SLE) and antiphospholipid syndrome (APS) and their relationships with antiphospholipid antibodies (aPL): lupus anticoagulant (LA) and anticardiolipin antibodies (aCL). MATERIALS AND METHODS: The trial included 33 patients (2 males and 31 females) aged 20-62 years (mean age 32.7 +/- 9.8 years). 29 patients suffered from SLE, 17 of them had also APS (criteria by G. R. V Hudhes). 3 patients had primary APS, 1 female had hemorrhagic vasculitis. IgG and IgM-aCL were detected by enzyme immunoassay. In revealing mutation, DNA was used isolated from peripheral blood by standard methods based on polymerase chain reaction (PCR). Primary screening of Leiden mutation was made according to Bertina et al. with Mnl I restrictase. The mutation was confirmed by an original technique with allele-specific primers. G20210A mutation in the prothrombin gene was determined with restrictase Taq I after introduction of artificial restriction site in PCR product. The patients were divided into 2 groups. Group 1 incorporated 12 patients with SLE without APS. Group 2--21 patients with APS (17 with SLE + APS, 3 with primary APS and 1 with hemorrhagic vasculitis). RESULTS: Patients of group 1 had neither thrombotic complications nor Leiden mutation. Two patients of group 2 had heterozygous Leiden mutation. Both females were aPL-positive and had previously recurrent thrombophlebitis. One of them had also recurrent disorders of cerebral circulation. None of the examinees had any G20210A mutations in the prothrombin gene. CONCLUSION: Detection of genetic defects in APS provide arguments in the dispute about the necessity, duration and choice of anticoagulant therapy. If patients with APL syndrome appeared to have besides aPL also genetic defects in coagulation, this will enable identification of patients at high risk of thrombosis which need permanent administration of anticoagulants among which only low-molecular ones or glycosaminoglycanes are indicated. Mutation in gene of factor V is absolute contraindication to phenilin and quamarines.
Magnesium ions were detected in sodium citrate solutions in several lots of evacuated blood collection tubes. The mean concentrations ranged between 1.3 and 1.6 mmol/L. Magnesium was also present in the rubber stoppers of the blood collection tubes and could be leached into the citrate solution. It was shown that magnesium added to citrated plasma shortened the prothrombin time of both coumarin and normal plasma. The effect of magnesium was relatively greater on coumarin than on normal plasma resulting in reduced prothrombin time ratio. Shortening of the prothrombin time was also observed when magnesium chloride was added to dialysed plasma, i.e., in the absence of citrate. These results indicate that magnesium contamination can interfere with accurate INR determination in the control of oral anticoagulant therapy.
Several members of a family from Scranton, Pennsylvania were identified to have normal levels of prothrombin antigen while their prothrombin clotting activity was approximately 50% of normal. There has been no previous history of bleeding or other clinical manifestations in this family. The genomic DNA from the proband was amplified for all exons in the prothrombin gene and analyzed by single strand conformation polymorphism (SSCP)/heteroduplex analysis followed by DNA sequence analysis and restriction enzyme digestion. A mutation at nucleotide 20040 in exon 14 was identified and confirmed by restriction enzyme digestion. This mutation results in the substitution of Thr for Lys at amino acid 556. Amino acid 556 has been reported as one of the key residues for the binding of Na+ in the thrombin portion of the protein.
A new one-stage prothrombin assay using Taipan venom is presented here. Taipan venom converts prothrombin to thrombin in the absence of all coagulation factors known up to the date. The prothrombin concentration in normal adults varied from 64.0% to 159.0% with a mean of 100.64% plus or minus 24.83%.
Prothrombin time (PT) assays are clotting methods that measure the activity of vitamin K-dependent coagulation factors (F) II, VII, and X. There are three main types of PT assays in general usage, namely the Quick assay, Owren's assay and PT dry chemistry test cards. PT assays were initially developed to monitor dose-adjustments of vitamin K antagonists such as warfarin. The aim of the present study was to investigate whether commercially available PT assays are suitable for evaluating the anticoagulant activity of direct thrombin inhibitors. Melagatran, a reversible direct thrombin inhibitor, was added to human plasma at concentrations ranging from 0.1 to 2.0 micromol/l. Seventeen different commercially available PT kits were used, including thirteen Quick reagents, two Owren reagents and two PT test cards. The sensitivity of the different reagents, expressed as the concentration of melagatran that doubled the prothrombin time (IC50) varied widely, with Thromboplastin S and Thromboplastin HS being the most sensitive (IC50 = 0.9 micromol/l). The reagents with apparently the lowest sensitivity were the two Owren reagents Nycotest PT and SPA 50 with an IC50 of 2.2 and 2.9 micromol/L, respectively. This is most likely due to a higher dilution of melagatran in these assays compared to the dilution in the Quick assays. The results were also dependent on the International Sensitivity Index (ISI) of each reagent. The concentration of melagatran that produced an International Normalized Ratio (INR) of 2 was calculated from dose-response curves for each assay, and these results revealed that reagents with a high ISI value gave an INR of 2 at much lower concentrations of melagatran (0.5-0.7 micromol/L) than those with an ISI-values around one (0.9-1.2 micromol/L). It was found that INR depends not only on the plasma concentration of melagatran, but also on the sensitivity of the PT reagent and on the final dilution of the plasma sample in the prothrombin time assay. Thus, since the same melagatran concentration can be associated with widely varying PT/INR results depending on the specific assay used it is concluded that PT assays and INR can not be used to monitor melagatran activity.
BACKGROUND AND OBJECTIVES: We evaluated a new test, based on prothrombin activation by Echis Carinatus snake venom in the absence/presence of unfractionated heparin, in patients with venous thromboembolism (VTE). DESIGN AND METHODS: The test (activated prothrombin heparin-inhibition test) was performed in 555 unselected, unrelated patients who had suffered from at least one objectively confirmed VTE and the results were compared with those obtained in 408 healthy controls. RESULTS: In 71 (12.8%) of the 555 patients the results of the test, expressed as a normalized ratio, were below the cut-off. This compared with 19 (5% by definition) results below the cut-off in the control group. The crude OR for VTE in subjects with altered vs those with normal results was 3.00 (95% CI: 1.78-5.07). ORs did not significantly change after adjustment for age (2.86, 95% CI: 1.68-4.85) and age/sex (2.80, 95% CI: 1.64-4.77) by logistic regression. After adjustment for antithrombin III, fibrinogen and prothrombin levels the risk associated with altered results remained significantly high. The overall OR for VTE in females (3.22; 95% CI: 1.53-6.75) was higher than that in males (2.69; 95% CI: 1.27-5.69). However, for both sexes there was a sharp increase in the risk of VTE associated with altered results in patients aged less than 45 years (crude OR 9.61; 95% CI: 3.38-27.3). INTERPRETATION AND CONCLUSIONS: Lower than expected thrombin inhibition by endogenous antithrombin action after full activation by heparin addition was found to be a common feature in patients who suffered from previous venous thrombotic events, and may reflect a hitherto unrecognized thrombophilic alteration.
Patients (n = 1600) from 12 European countries, scheduled for elective orthopaedic hip or knee surgery, were screened for Factor V Leiden and prothrombin gene G20210A mutations, found in 5.5% and 2.9% of the populations, respectively. All patients underwent prophylactic treatment with one of four doses of melagatran and ximelagatran or dalteparin, starting pre-operatively. Bilateral ascending venography was performed on study day 8-11. The patients were subsequently treated according to local routines and followed for 4-6 weeks postoperatively. The composite endpoint of screened deep vein thrombosis (DVT) and symptomatic pulmonary embolism (PE) during prophylaxis did not differ significantly between patients with or without these mutations. Symptomatic venous thromboembolism (VTE) during prophylaxis and follow-up (1.9%) was significantly over-represented among patients with the prothrombin gene G20210A mutation (p = 0.0002). A tendency towards increased risk of VTE was found with the Factor V Leiden mutation (p = 0.09). PE were few, but significantly over-represented in both the Factor V Leiden and prothrombin gene G20210A mutated patients (p = 0.03 and p = 0.05, respectively). However, since 90% of the patients with these genetic risk factors will not suffer a VTE event, a general pre-operative genotyping is, in our opinion, of questionable value.
We determined whether total hip arthroplasty (THA) patients could test their own prothrombin time reliably over 6 weeks of anticoagulation prophylaxis with a portable device that measures prothrombin time and whether self-testing would improve or maintain the quality of care at a lower cost than our standard procedure. Forty-six THA patients participated in the study and were compared with a matched group managed with our standard protocol using a home health-care nurse. Seven patients (15%) could not be trained to obtain the blood sample, and others required multiple finger sticks to obtain valid results. However, the results from the 29 patients completing the study showed high reliability when compared with results obtained through standard protocol. Self-testing saved about $260 per patient over the cost of venipuncture. Patient self-testing of prothrombin time using the device in this study is reliable and cost-effective for monitoring the anticoagulation status after THA in a select group of elderly patients.