Isabel Tirado

The ABO blood group genotype and factor VIII levels as independent risk factors for venous thromboembolism

Factor VIII (FVIII), von Willebrand factor (vWF) and the ABO blood groups have been associated with thrombosis. The ABO locus has functional effects on vWF and FVIII levels and is genetically correlated with FVIII, vWF and thrombosis. We carried out a case-control study to assess the role of FVIII, vWF and ABO types on thrombotic risk. We analyzed 250 patients with venous thrombosis and 250 unrelated controls. FVIII, vWF and other factors related to thrombophilia were measured, ABO groups were analyzed by genotyping. FVIII and vWF were higher in non-O individuals. Group O was more frequent in the controls (44.3% v 23.3%; difference 21.1%; 95% CI: 13.0-29.3%) and Group A in patients (59.2% v. 41.5%; difference 17.7%, 95% CI: 9.1-26.4%). Individuals carrying the A1 allele had a higher risk of thrombosis (OR 2.6; 95% CI, 1.8-3.8). The risk attributed to vWF disappeared after adjusting for the ABO group. Patients with FVIII above the 90th percentile had a high thrombotic risk (adjusted OR 3.7; 95% CI, 2.1-6.5), and a high risk of recurrence (OR 2.3; 95% CI: 1.3-4.1). In conclusion, high FVIII levels and non-O blood groups, likely those with the A1 allele, are independent risk factors for venous thromboembolism and should be considered in evaluating of thrombophilia.

Risk of Ischemic Stroke Associated With Functional Thrombin-Activatable Fibrinolysis Inhibitor Plasma Levels

Background and Purpose— Recently, a novel procarboxypeptidase B–like proenzyme, called thrombin-activatable fibrinolysis inhibitor (TAFI), has been described. It plays an important role in the delicate balance between coagulation and fibrinolysis. TAFI leads to potent inhibition of tissue plasminogen activator–induced fibrinolysis. The relevance of TAFI in thromboembolic disease is unclear. We have investigated the risk of ischemic stroke (IS) in relation to plasma levels of functional TAFI. Methods— In a case-control study, we enrolled 264 individuals; 114 had IS, and 150 were recruited as controls who were age and sex matched and had no history of arterial disease. The individuals supplied information on their personal and family histories of cardiovascular diseases and conventional cardiovascular risk factors. Functional TAFI assays were performed by use of a method based on the activation of TAFI with thrombin-thrombomodulin and the measure of the TAFI activity generated. Other hemostatic parameters assayed were factor VIIIc, anti-phospholipid antibodies,fibrinogen, factor V Leiden, and the prothrombin gene G20210A mutations (PT20210A). Results— Functional TAFI levels were significantly higher in patients with IS (113.7±25%; range, 57% to 209%) than in controls (102.6±19%). The odds ratio for IS in patients with functional TAFI levels >120% was 5.7 (95% confidence interval, 2.3 to 14.1). Conclusions— We found that functional TAFI levels in plasma (>120%) increased the risk of IS ≈6-fold. Further studies should elucidate the physiological role of TAFI in arterial disease and possibly provide clues to therapeutic approaches.

Association after linkage analysis indicates that homozygosity for the 46C-->T polymorphism in the F12 gene is a genetic risk factor for venous thrombosis.

In a family-based study called GAIT (Genetic Analysis of Idiopathic Thrombophilia) that included a genome-wide scan we demonstrated that a polymorphism (46C-->T) in the F12 locus jointly influences variability of plasma (Factor XII) FXII levels and susceptibility to thrombotic disease. It then became germane to determine the prevalence of the 46C-->T polymorphism and its relative risk of thrombotic disease. We followed up evidence for genetic linkage with a case-control study, including 250 unrelated consecutive Spanish patients suffering from venous thrombotic disease and 250 Spanish subjects matched for sex and age as a controls. We measured FXII levels and genotyped the 46C-->T polymorphism, as well as a number of classical risk factors for thrombotic disease. We confirmed that individuals with different genotypes for this polymorphism showed significant differences in their FXII levels. Most importantly, the mutated T allele in the homozygous state (genotype T/T) was associated with an increased risk of thrombosis (adjusted OR of 4.82; 95% CI 1.5-15.6), suggesting that the polymorphism itself is an independent risk factor for venous thromboembolism. This study confirms that the 46C-->T polymorphism is a genetic risk factor for venous thrombosis in the Spanish population. In addition, our results confirm that a genome-wide scan coupled with a classical case-control association study is an extremely valuable approach to identify DNA variants that affect complex diseases.

Protein S gene analysis reveals the presence of a cosegregating mutation in most pedigrees with type I but not type III PS deficiency.

DNA sequence analysis of the protein S gene (PROS1) in 22 Spanish probands with type I or III PS deficiency, has allowed the identification of 10 different mutations and 2 new sequence variants in 15 probands. Nine of the mutations, 8 of which are novel, cosegregate with type I or quantitative PS deficiency in 12 of the 13 pedigrees analyzed. One of these mutations (Q238X) also cosegregates with both type I and III PS‐deficient phenotypes coexisting in a type I/III pedigree. Another mutation identified in a pedigree with these two PS phenotypes is the missense mutation R520G, present in the homozygous form in the type I propositus and in the heterozygous form in his type III relatives. By contrast, no cosegregating PROS1 mutation has been found in any of the six families with only type III phenotypes. Three of these families, as well as the two families with type I and I/III phenotypes where no other PROS1 mutation has been identified, segregate the P allele of the S460P variant, although this allele does not always cosegregate with the deficient phenotype. From these results we conclude that while mutations in PROS1 are the main cause of type I PS deficiency, the molecular basis of the type III phenotype is probably more complex, with many cases not being explained by a PROS1 mutation. Hum Mutat 14:30–39, 1999.

Hemostatic Proteins and Their Association With Hematoma Growth in Patients With Acute Intracerebral Hemorrhage

Background and Purpose— We tested the hypothesis that proteins of hemostasia could be associated with hematoma growth (HG) in patients with acute intracerebral hemorrhage. Methods— We prospectively studied patients with spontaneous supratentorial intracerebral hemorrhage within the first 6 hours after the onset of symptoms. HG was defined as an increase >33% in the volume of hematoma on CT obtained 24 to 72 hours after the onset of symptoms in comparison with the CT obtained at admission. We collected admission and follow-up blood samples. We measured fibrinogen, factor XIII, thrombin activatable fibrinolysis inhibitor, plasminogen activator inhibitor, plasminogen, &agr;;2-antiplasmin, tissue plasminogen activator, d-dimer, thrombomodulin, thrombin–antithrombin complex, and plasmin–antiplasmin complex. Results— We included 90 patients with a mean age of 71±10.8 years; 61% were men. HG was observed in 35 (39%) of the patients. Mean baseline and follow-up protein measurements showed no difference between the groups with and without HG. The analysis of variance showed that factor XIII activity decreased in the non-HG group in the 24 to 72 hours sample, whereas it increased in the HG group (P=0.001). Conclusion— Factor XIII was the only measured protein related to HG. The levels at the follow-up sample decreased in the non-HG group and increased in the HG group. Further studies are needed to confirm this association.

Rapid detection of the 46C --> T polymorphism in the factor XII gene, a novel genetic risk factor for thrombosis, by melting peak analysis using fluorescence hybridization probes.

Factor XII (FXII) level is an important intermediate phenotype associated with thrombotic disease. The 46C --> T transition in the exon 1 of the Factor XII (F12) gene is a significant, prevalent, and independent genetic risk factor for thrombotic disease. It is also associated with interindividual variation of plasma FXII zymogen levels. The aims of this study were to develop a rapid, reproducible, and easy method for 46C --> T genotyping and to compare its reliability with the classical endonuclease digestion methodology. DNA samples from 100 subjects were genotyped for the 46C --> T transition using the classical endonuclease digestion method with Sfna I. The genotypes of three of them (each with a different 46C R T genotype) were confirmed by direct sequencing analysis. We then set out to construct a LightCycler PCR protocol to detect the 46C --> T polymorphism. This protocol was designed to combine a rapid-cycle polymerase chain reaction (PCR) with an allele-specific fluorescent probe melting for mutation detection. In the three sequenced samples, as well as in the remaining 97, the LightCycler PCR procedure unambiguously resulted in the same genotype previously observed by sequencing and endonuclease digestion. Characteristic fluorescent curves were obtained for each genotype; the first derivative of these curves had a maximum at an apparent hybridization temperature (Tm) that was specific for each probe/allele duplex. The whole process took less than 40 min. Thus, if this method is used with a rapid DNA extraction, the genotypes would be obtained within 60 min after receiving a blood sample. In conclusion, the technique presented allows for easy, reliable, and rapid detection of this polymorphism, and is suitable for typing both small and large numbers of DNA samples.

IgM anti-protein S antibodies as a risk factor for venous thrombosis.

Lupus anticoagulant (LA) and antiphospholipid antibodies (APA) are immunoglobulins directed at phospholipid-protein complexes that have been associated frequently with thrombophilia. Protein S (PS) is a protein with high affinity for phospholipids and can be a target for APA. It is a cofactor in the

Antithrombin Cambridge II mutation as a risk factor to develop cerebral venous thrombosis

Antithrombin Cambridge II mutation as a risk factor to develop cerebral venous thrombosis -

The c.1787G>T and c.1787G>A Mutations are not Found in the Prothrombin Gene in a Spanish Population

Miyawaky et al. have identified recently a new prothrombin gene mutation c.1787G>T in a Japanese family with hereditary thrombophilia [4]. This mutation is located in the last exon of the prothrombin gene resulting in Arg596Leu replacement. Djordjevic et al. [5] also have described another mutation at the same prothrombin gene position (c. 1787G>A prothrombin Belgrade) that results in aminoacid change (Arg596Gln). The mutant prothrombins were shown to have reduced activity in clotting assays and the produced thrombin was markedly resistant to inhibition by antithrombin.