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PubMed1988

Automation of the prothrombin time assay on a centrifugal analyser using two different chromogenic substrate reagents.

Methods employing chromogenic substrates for the photometric determination of prothrombin time have several advantages over conventional coagulometric methods. We evaluated the analytical qualities of two recently introduced reagents for the photometric determination of prothrombin time. The assays were performed on a centrifugal analyser. Both reagents showed good precision, even with sample volumes of 10 microliters or 12 microliters. The stability of the reagents during storage was investigated at 4 degrees C, 25 degrees C and 37 degrees C. The chromogenic reagent, which contains thromboplastin from human placenta, was compared with a coagulometric method, which includes ox-brain thromboplastin: coagulation activities calculated from International Normalized Ratio values showed good correlation and conformity over the whole test range. The other chromogenic reagent contains thromboplastin from rabbit brain; outside the therapeutic range for oral anticoagulation the results obtained with this reagent showed poor agreement with those obtained with the coagulometric method. Both chromogenic reagents were sensitive to reduced concentrations of coagulation factors of the extrinsic pathway and nearly insensitive to low factor IX concentrations. The results of the photometric test paralleled those of the clotting method during oral anticoagulation therapy.

Centrifugation↗
PubMed2000

Unintentional pediatric superwarfarin exposures: do we really need a prothrombin time?

OBJECTIVE: To determine whether routine follow-up coagulation studies are useful in children with accidental exposures to rodenticides containing superwarfarin compounds. DESIGN: Retrospective review of poison center charts involving pediatric superwarfarin exposures occurring in two 2-year periods. SETTING: An American Association of Poison Control Centers-certified regional poison control center with an annual call volume of 55 000 calls per year from a 2-state area with a combined population of 4 million people. OUTCOME MEASURES: Prothrombin times and/or international normalized ratios and reported clinical signs of excessive anticoagulation after exposure. RESULTS: Of 542 children in 4 years of data collection, follow-up prothrombin times and/or international normalized ratios measurements did not detect any significant coagulation abnormalities. No child developed bleeding complications. No child required or received antidotal treatment with vitamin K. CONCLUSION: Normal preschool-aged children with unintentional acute exposures to superwarfarin rodenticides do not require any routine follow-up laboratory studies and do not require any medical intervention.

4-Hydroxycoumarins↗
PubMed2004

[Cerebral and systemic venous thrombosis associated to prothrombin G20210 mutation: case report].

Cerebral venous thrombosis is a clinical condition of difficult diagnosis, and poor prognosis when treatment is not started early. There is a long list of causes, and hereby we describe a case associated to prothrombin G20210 mutation. A 53-year-old man, white, was admitted with status epilepticus. After seizures control, he developed intracranial hypertension, with headache and vomiting, and bilateral papilledema. His past medical and familial history were unremarkable. He was a nonsmoker, no drug and alcohol user. CT scan and MRI showed right temporal and parietal infarct with hemorrhagic transformation. Spinal tap with opening pressure of 500 mmH2O showed normal CSF examination. MRI angiography disclosed superior sinus, right transverse and sigmoid sinus complete thrombosis. He was started with heparin and oral warfarin. In spite of anticoagulation, two months later he developed deep right inferior limb thrombosis. All the initial tests were normal, and test for prothrombin G20210 mutation was positive. He needed a much higher than conventional daily dose of warfarin to keep him asymptomatic.

Anticoagulants↗
PubMed2006

Mitral valve thrombosis and infective endocarditis in a patient with prothrombin mutation.

This report deals with a 25-year-old female patient, who was admitted to a medical centre with complaints of fatigue and arthralgia. A non-homogeneous mass originating from the posterior papillary muscle and reaching the posterior and anterior cusps of the mitral valve was evident on the patient's echocardiogram. Her intractable fever, despite adequate antibiotic therapy, led us to consult with the cardiac surgeons. A mitral valve replacement was performed on the 8th day of admission. The pathological examination of the mitral valve and the vegetative lesion revealed the presence of organized thrombus and infective endocarditis. The patient had a history of oral contraceptive use for one year and at genetic examination we detected a heterozygous prothrombin mutation (G20210A). The association of infective endocarditis with native mitral valvular thrombosis in a case with prothrombin mutation and history of oral contraceptive use encouraged us to share our experience with our colleagues.

Adult↗
PubMed2006

Phenotypic Heterogeneity in Patients with Homozygous Prothrombin 20210AA Genotype. A paper from the 2005 William Beaumont Hospital Symposium on Molecular Pathology.

Venous thromboembolic events (VTEs) affect an estimated 1 in 1000 people annually, resulting in approximately 50,000 deaths, with prevalence increasing with age. The genetic contributors to thrombosis have been described and further explored within the last 15 years as molecular diagnostic techniques have become more widely used. The prothrombin G20210A mutation is the second most common inherited thrombotic risk factor after factor V Leiden. Generally present in less than 5% of the population, the mutation's prevalence varies greatly with ethnicity. The G20210A mutation confers a mildly increased thrombotic risk that is compounded by the presence of other risk factors. One striking characteristic of the G20210A mutation is the phenotypic heterogeneity of the rare homozygous cases. Forty percent of the reported homozygous cases are asymptomatic. Many of the symptomatic patients have additional risk factors that might compound the thrombotic risk. We present here a review of the literature for the homozygous prothrombin G20210A mutation and describe additional cases that exemplify the heterogeneous nature of this entity.

Adolescent↗
PubMed1980

Prothrombin times: an evaluation of four thromboplastins and four machines.

The prothrombin times of 63 patients on oral anticoagulant therapy were tested using 4 different thromboplastins; 2 rabbit brains (Simplastin & Ortho), human placenta (Thromborel) and human brain (Australasian Reference Thromboplastin--ART). Four machines measuring the one-stage prothrombin times were compared with the manual method. Each of the machines and thromboplastins showed highly reproducible and predictable results, but there were differences in thromboplastin sensitivities which would pose major therapeutic problems. A system of correcting ratios of different thromboplastins to a reference preparation would overcome these differences in thromboplastin sensitivities. All thromboplastins gave comparable results with the Clotek, MLA 600 and Coag-A-Pet machines and manual method. Cortek gave comparable ratios with the ART but not with any other thromboplastin.

Administration, Oral↗
PubMed1981

The Australasian Reference Thromboplastin: II. Are corrected prothrombin ratios valid?

A comparative study was made of 2 thromboplastins, the Australasian Reference Thromboplastin, and Simplastin, in a large group of patients on long-term Warfarin therapy. 373 individual samples were obtained. Calibration constants were obtained for those patients with prothrombin ratios within the therapeutic range, and for those well outside the therapeutic range, and found to be different. Study of the relationship between the 2 thromboplastins indicates that comparability is linear only within a specified limited range of prothrombin ratios. At the two extreme ends the relationship is curved, suggesting a logarithmic relationship. Attention is drawn to the need of caution in interpretation of corrected ratios calculated on a linear relationship especially when the ratio is above 4.0 as this may have clinical implications.

Coumarins↗
PubMed1978

Control of oral anticoagulants by the prothrombin time: a plea for uniformity.

Six trromboplastins commonly used for prothrombin time determinations were studied. Prothrombin times of patients who were receiving oral anticoagulant therapy varied widely, depending on the origin of the thromboplastins. The therapeutic range which is recommended with one thromboplastin is often quite different from that recommended with another, and as a result, the therapeutic ranges of different institutions may show no overlap. Management of patients and comparison of therapeutic results would be facilitated if all thromboplastins in use in Australia were standardized by comparison with the Australian Reference Thromboplastin.

Administration, Oral↗
PubMed1999

[Prevalence of Factor V Leiden and the G20210A mutation of the prothrombin gene in a random group of patients with thrombotic episodes].

UNLABELLED: Factor V Leiden and G20210A mutation of the prothrombin gene have been described as risk factors in thrombophilic pathologies. Our objective has been to know the prevalence of these two mutations in a group of patients with thrombophilic pathology and to compare it with its prevalence in a control group of Spanish population. PATIENTS AND METHODS: 64 patients were divided in two groups. First, 39 patients with deep venous thrombosis (DVT): 24 with an unique episode of DVT; 11 with more than one episode; 3 with DVT and pulmonary thromboembolism, and one with DVT and more than one episode of cerebral thrombosis. Second, 25 patients with other pathologies, such as pulmonary thromboembolism (9 patients), acute cerebrovascular accident (10 patients) and 6 who came to our Department because there were some carrier in their families. The 20210A allele was analyzed in 37 of the 64 patients. Some of the 64 patients had haematological determinations of the activated protein C resistance (APC resistance). As well, 103 unrelated subjects with unknown thrombotic pathologies were analyzed. RESULTS: We have found a prevalence of factor V Leiden in the group of patients of 14.1% (9 carriers in 64 patients, all of them in the first group of 39 patients with DVT) versus 1% in the control group (1 carrier in 103 controls). On the other hand, the difference between the prevalence of the 20210A allele was not statistically significant between the group of patients and the control group (2.7% vs 2.9%). In 75% of the patients no haematological results of APC resistance were obtained, generally because they were with anticoagulant treatment, and in 11.1% of the carriers the result of the determination was considered as ambiguous or false negative. CONCLUSION: Factor V Leiden is well established as risk factor in the thrombophilic pathology, but more studies are needed to know the meaning of the G20210A mutation of the prothrombin gene.

Alleles↗
PubMed1999

Factor V Leiden, prothrombin 20210G-->A and the MTHFR C677T mutations in childhood stroke.

Ischaemic stroke is a rare occurrence in children and in a proportion of cases the aetiology remains unknown. We have investigated the role of thrombophilia in the aetiology of this condition. Of 50 cases identified at two centres, 37 were available for detailed haematological analysis. No cases were identified with deficiencies of antithrombin, protein C or protein S. One case had elevated IgG anticardiolipin antibodies at low titre. The prevalence of the prothrombin 20210 G-->A mutation, factor V Leiden (FVL) mutation and the C677T mutation in the MTHFR gene was compared in cases to that observed in random unselected cord blood controls. The odds ratio for stroke was not significantly increased in carriers of the prothrombin mutation (OR 1.2; 95% CI 0.1-10.7), FVL (OR 2.5; 95% CI 0.5-13.5), or the C677T mutation (OR 1.7; 95% CI 0.6-4.5). Our findings suggest that thrombophilia may not play a significant role in the aetiology of stroke in children, although a large prospective study is required to investigate this area further.

Age Factors↗
PubMed1976

The prothrombin time test: effect of varying citrate concentration.

Blood samples from 12 normal subjects and 46 patients on oral anticoagulants were divided so that each was anticoagulated with four concentrations of trisodium citrate solution in the range 0.09-0.15 M, 9 vol blood being added to 1 vol citrate solution in each case. Citrated blood haematocrit and plasma prothrombin time was measured on each subsample; 0.025 M CaCl2-solution was used for recalcification throughout. Three laboratories participated, each using a different prothrombin-time technique.

Anticoagulants↗
PubMed1999

Homozygotes for prothrombin gene 20210 A allele in a thrombophilic family without clinical manifestations of venous thromboembolism.

BACKGROUND AND OBJECTIVE: A new genetic risk factor for venous thromboembolism has recently been described which involves a G to A transition at position 20210 in the 3' untranslated region of the prothrombin gene. To date, only a few homozygotes for this mutation have been reported and in most of cases, they suffered from thrombotic disease. Here, we describe a pedigree including both heterozygous and homozygous subjects for prothrombin (PT) 20210 A. DESIGN AND METHODS: This family was recruited in 1996 as part of our GAIT (Genetic Analysis of Idiopathic Thrombophilia) project. To qualify for the GAIT study, a pedigree was required to have at least 10 living individuals in three or more generations (i.e. extended pedigree). The pedigrees were selected through probands with idiopathic thrombophilia. A complete set of plasma and DNA determinations related to hemostasis was performed on this family. RESULTS: The plasma studies yielded normal results in all of the individuals. The family members who had a history of thromboembolism were heterozygous carriers of the PT 20210 A variant. In addition, 4 relatives who were heterozygous, and two who were homozygous for this A allele, failed to show clinical manifestations. These two homozygotes were 51 and 19 years old. INTERPRETATION AND CONCLUSIONS: This case exemplifies the complexity of thrombotic disease since individuals homozygous for a mutant gene do not exhibit symptoms while heterozygous individuals often do exhibit the disease. This case suggests that the new genetic risk factor for thrombosis (i.e. PT 20210 A) may not be as strong as most of the previously described genetic risk factors.

3' Untranslated Regions↗
PubMed1999

Lipoprotein (a) and genetic polymorphisms of clotting factor V, prothrombin, and methylenetetrahydrofolate reductase are risk factors of spontaneous ischemic stroke in childhood.

Ischemic stroke is a rare event in childhood. In approximately one third of cases no obvious underlying cause or disorder can be detected. We investigated the importance of genetic risk factors of venous thromboembolism in childhood or stroke in adulthood as risk factors for spontaneous ischemic stroke in children. One hundred forty-eight Caucasian infants and children (aged 0.5 to 16 years) with stroke and 296 age-matched controls from the same geographic areas as the patients were analyzed for increased lipoprotein (a) [Lp(a)] levels >30 mg/dL; for the presence of the factor V (FV) G1691A mutation, the prothrombin (PT) G20210A variant, and the TT677 genotype of methylenetetrahydrofolate reductase (MTHFR); and deficiencies of protein C, protein S, and antithrombin. The following frequencies (patients v controls), odds ratios (ORs), and confidence intervals (CIs) of single risk factors were found: Lp(a) >30 mg/dL (26.4% v 4.7%; OR/CI, 7.2/3.8 to 13.8; P <.0001), FV G1691A (20.2% v 4%; OR/CI, 6/2.97 to 12.1; P <.0001), protein C deficiency (6% v 0.67%; OR/CI, 9.5/2 to 44.6; P =.001), PT G20210A (6% v 1.3%; OR/CI, 4.7/1.4 to 15.6; P =.01), and the MTHFR TT677 genotype (23.6% v 10.4%; OR/CI, 2.4/1.53 to 4.5; P <.0001). A combination of the heterozygous FV G1691A mutation with increased Lp(a) (n = 11) or the MTHFR TT677 genotype (n = 5) was found in 10. 8% of cases, but only 0.3% of controls (OR/CI, 35.75/4.7 to 272; P <. 0001). Increased Lp (a) levels, the FV G1691A mutation, protein C deficiency, the prothrombin G20210A variant, and the MTHFR TT677 are important risk factors for spontaneous ischemic stroke in childhood.

Adolescent↗
PubMed1999

The VITA project: prothrombin G20210A mutation and venous thromboembolism in the general population.

Recently a new identified genetic variant in the 3'-untranslated region of the prothrombin gene (G20210A allele) associated with increased plasma prothrombin levels has been linked to an increased risk of venous thromboembolism (VTE). Most of our knowledge on the G20210A allele as a risk factor for VTE derives from a population-based case-control study and from studies on selected series of VTE patients. To determine the importance of the G20210A allele as a causative risk factor for VTE in the general population, we analyzed the cross-sectional data of the Vicenza Thrombophilia and Atherosclerosis (VITA) Project. One hundred sixteen cases of VTE, ascertained in a random fashion within the general population aged 18-65, were age and sex-matched with 232 healthy subjects. Heterozygosity for the G20210A allele was present in 4.3% of VTE cases and in 3.4% of controls, indicating a marginal increase of VTE risk in carriers of the allele (odds ratio: 1.26; 95% CI 0.4-3.9). However, the VTE risk was substantially higher in subjects with idiopathic VTE before age 45 or with recurrent, idiopathic VTE (odds ratio: 2.8; 95% CI 0.6-13.8) or in subjects with a family history of VTE (odds ratio: 7.6; 95% CI 1.8-32.8). Accordingly, our results suggest that the G20210A allele associates with VTE only in selected cases, and that screening for this genetic variant is not warranted for all patients with VTE.

3' Untranslated Regions↗
PubMed1999

[Mixed retinal thrombosis in a patient carrying prothrombin gene mutation in a homozygote state].

We reported a case of a thrombosis of the retinal and central artery and vein in a 44-year-old patient, with high-grade T-cell lymphoma. Cardiovascular family history and a medical history of cerebral ischemia caused by in situ fibrinolysis, led to perform thorough hematologic and genetic examinations. These disclosed a prothrombin gene G 20210 a variant in a homozygous state. In a heterozygous state, this mutation leads to an increase in plasma prothrombin rate of the order of 30%. Therefore, it is considered to be a major risk factor for venous thrombotic disease. Otherwise, acute leukemia or non-Hodgkin's lymphoma may induce thrombosis of retinal artery and vein by means of an optic nerve infiltration, as well as beta-thalassemia, ocular trauma and retrobulbar anesthesia. Retinal central artery and vein are seldom both involved; whereas occlusions of their branches are more frequent.

Adult↗
PubMed1999

The procoagulant state of the VX-2 tumor in rabbit lung in vivo--relative accumulation of fibrinogen, prothrombin, plasminogen, antithrombin and heparin cofactor II within the tumor.

During their growth, many malignant solid tumors elicit a hemostatic response in the host. In this report, the fluxes of various rabbit plasma hemostatic proteins into pulmonary VX-2 tumors have been measured in vivo. VX-2 cells were contained within a small rabbit plasma clot which was injected intravenously into rabbits. At 28 d, each rabbit was injected intravenously with two radiolabeled (131I, 125I) proteins selected from fibrinogen, prothrombin, antithrombin-alpha, heparin cofactor II, or plasminogen-I or -II. After allowing the labeled proteins to circulate for 10-200 min, each rabbit was perfused with Krebs-Henseleit solution and the lungs excised. Solid tumors were isolated, weighed and measured for radioactivity content. A mean of 14 tumors/pair of lungs with a mean tumor weight of 0.3 g was obtained. Radioactivity per g of tumor was related to radioactivity/ml of blood at exsanguination for each protein at each time interval. Maximum flux rates were calculated (as pmol/g of tumor/min): Fibrinogen, 65.0; prothrombin, 53.0; antithrombin-alpha, 24.1; HCII, 17.2; plasminogen-II, 5.0; and plasminogen-I, 3.2. Using immunocytochemical staining, fibrin(ogen) was distributed heterogeneously within the VX-2 tumor, appearing largely in the perinodular region and in the necrotic core. From the net fluxes of these proteins, the profile of chronic hemostasis associated with the VX-2 tumor was shown to differ markedly from the hemostatic response that occurs after an acute vascular injury.

Animals↗
PubMed2000

Thrombosis associated with the prothrombin G-->A20210 mutation in Behçet's disease.

We describe 2 cases of Behcet's disease (BD) and thrombosis who were heterozygous for the prothrombin G-->A20210 mutation. In one case, progressive uncontrolled thromboses led to death. Case-control studies are needed to support the hypothesis of the role of the prothrombin A20210 allele as a risk factor for venous thrombosis in some patients with BD.

Adult↗