Anthi Travlou

Association between the plasminogen activator inhibitor-1 4G/5G polymorphism and venous thrombosis - A meta-analysis

The effect of the 675 insertion/deletion (4G/5G) polymorphism of plasminogen activator inhibitor-1 (PAI-1) gene on the risk of venous thromboembolism (VTE) remains controversial. In this study, we performed a meta-analysis of published data regarding this issue. A comprehensive electronic search was carried out up until September 2006. A total of 22 articles were included in the analysis that was performed using random effects models. Eighteen papers, concerning patients without another known risk factor, comprised 2,644 cases and 3,739 controls. The alleles contrast (4G vs. 5G allele) yielded a statistically significant odds ratio (OR) of 1.153 (95% confidence interval [CI]: 1.068-1.246). In a sub-analysis of five studies that included 256 cases with another genetic risk factor and 147 controls, the combined per-allele OR was still significant (OR: 1.833,95% CI: 1.325-2.536). On the contrary, the analysis of five studies regarding cases with a non-genetic risk factor for VTE (antiphospholipid antibody syndrome, Behcet disease) provided insignificant results in all aspects. There was no evidence for heterogeneity and publication bias in all analyses. Based on our findings, the 4G allele appears to increase the risk of venous thrombosis, particularly in subjects with other genetic thrombophilic defects. Recommendation for detection of this polymorphism in evaluating thrombophilia in such patients might be considered.

VKORC1 and CYP2C9 allelic variants influence acenocoumarol dose requirements in Greek patients

AIM To identify the frequencies of the polymorphisms CYP2C9*2, CYP2C9*3 and VKORC1-1639 G>A in the Greek population and investigate whether these polymorphisms and patient demographics (age, sex and comedication) could explain the interindividual variability of acenocoumarol dose requirements for efficient anticoagulation. MATERIALS & METHODS CYP2C9*2 (Arg144Cys), CYP2C9*3 (Ile359Leu) and VKORC1-1639G>A allelic variants were analyzed in 98 patients treated with acenocoumarol. RESULTS Allelic frequencies of CYP2C9*2, CYP2C9*3 and VKORC1A were found to be 0.155, 0.075 and 0.485, respectively. Carriership of at least one CYP2C9*3 allele led to the most pronounced reduction in the required mean dose (p<0.0001). In contrast, the CYP2C9*2 allele played a minor role (p=0.3). VKORC1 A/A patients needed approximately a third of the dose required by wild-type patients to achieve the target INR (p<0.0001). Age was the only demographical factor significantly affecting acenocoumarol dose (p<0.0001). In a multivariable regression model, CYP2C9, VKORC1 genotypes and age explained 55% of acenocoumarol dosing variability. CONCLUSION VKORC1-1639G>A, CYP2C9*2 and CYP2C9*3 polymorphisms were found to predispose to acenocoumarol sensitivity in Greeks. Other hereditary and nongenetic parameters must be incorporated in an individualized dosing algorithm to achieve a safer anticoagulant effect.

Plasminogen activator inhibitor-1 4G/5G polymorphism and risk of ischemic stroke : a meta-analysis

This study investigated the hypothesis that the insertion/deletion (4G/5G) polymorphism of the plasminogen activator inhibitor type-1 gene affects the risk for ischemic stroke, since results concerning this association have been controversial. We therefore performed a meta-analysis of published data regarding this issue. A comprehensive electronic search was carried out until January 2006. The analysis was performed using random-effects models and meta-regression. Eighteen eligible studies were retrieved (15 case–control studies and three cohort studies). The case–control studies included 3104 cases and 4870 control individuals concerning the contrast of 4G/4G versus remaining genotypes. The 4G pooled allele frequencies in cases and controls were 54.21 and 54.75%, respectively. Overall, the per-allele odds ratio of the 4G allele was 0.98 (95% confidence interval, 0.858–1.121). Regarding genotypes, we derived nonsignificant odds ratios in all contrasts. The subanalysis including the three studies with a prospective design in the 4G/4G versus 5G/5G contrast derived a significant result (relative risk, 0.523; 95% confidence interval, 0.353–0.775), but the estimated effect size was insignificant when cohort and case–control studies were analyzed together (relative risk, 0.848; 95% confidence interval, 0.662–1.087). We failed to demonstrate a significant association between the 4G/5G polymorphism and ischemic stroke under basal conditions. Determination of plasminogen activator inhibitor type-1 function seems of much higher clinical value than determination of the 4G/5G polymorphism. The effect of this genotype on risk of ischemic stroke in acute stressful diseases and the role of cohort studies in genetic epidemiology, however, warrant further investigation.

Prevalence of Prothrombotic Polymorphisms in Greece

The aim of this study was to assess the prevalence of several polymorphisms in genes that are involved in several pathways such as hemostasis, fibrinolysis, platelet membrane receptor activity, endothelial integrity and function, lipid metabolism, and regulation of blood pressure in healthy subjects of Greek origin. Most of these polymorphisms are mainly associated with conditions such as venous thromboembolism and atherothrombosis, and their prevalence has not been studied yet in Greece. We tested 140 healthy individuals for factor V (FV)1691G/A, FV4070G/A, FII 20210G/A, factor XIII (FXIII) exon 2G/T, fibrinogen beta-455G/A, plasminogen activator inhibitor-1 (PAI-1)-675 4G/5G, human platelet antigens 1 (HPA1) a/b, apolipoprotein B (ApoB) 10708 G/A, apolipoprotein E (ApoE) E2, E3, and E4, angiotensin-converting enzyme (ACE) D/I, 5,10 methylenetetrahydrofolate reductase (MTHFR) 677C/T, and MTHFR 1298A/C polymorphisms using a PCR and reverse hybridization technique that detects all of them simultaneously. The allele frequencies observed are in accordance with those reported in other Caucasian populations and almost identical to those of East Mediterranean populations. This first report from Greece may serve as a baseline for planning further investigations of these polymorphisms in association with several clinical entities and for launching guidelines for patient testing of various disease settings in this population.

Thrombomodulin as a regulator of the anticoagulant pathway: implication in the development of thrombosis.

Thrombomodulin is a cell surface-expressed glycoprotein that serves as a cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell PC receptor. The PC pathway is a major anticoagulant mechanism that downregulates thrombin formation and hedges thrombus formation. The objectives of this review were to review recent findings regarding thrombomodulin structure, its involvement in the regulation of hemostasis and further discuss the implication, if any, of the genetic polymorphisms in the thrombomodulin gene in the risk of development of thrombosis. We performed a literature search by using electronic bibliographic databases. Although the direct evaluation of risk situations associated with thrombomodulin mutations/polymorphisms could be of clinical significance, it appears that mutations that affect the function of thrombomodulin are rarely associated with venous thromboembolism. However, several polymorphisms are reported to be associated with increased risk for arterial thrombosis. Additionally studies on knock out mice as well studies on humans bearing rare mutations suggest that thrombomodulin dysfunction may be implicated in the pathogenesis of myocardial infraction.

Antiphospholipid syndrome: a predisposing factor for early onset HELLP syndrome

Hemolysis elevated liver enzymes low platelets syndrome (HELLP) is a relatively rare pregnancy-related thrombotic microangiopathic disorder, usually observed during the third trimester. Its incidence seems to be increased in patients with antiphospholipid syndrome (APS). In this report, we describe a 33-year-old pregnant woman with previously known primary APS who developed early onset HELLP syndrome during the 15th week of gestation. We also review the literature about this interesting relationship between APS and HELLP.

The impact of the PAI-1 4G/5G polymorphism on the outcome of patients with ALI/ARDS

INTRODUCTION Increased levels of plasminogen activator inhibitor-1 (PAI-1) have been associated with worse outcome in ALI/ARDS. A single guanosine insertion/deletion (4G/5G) polymorphism in the promoter region of the PAI-1 gene, may play an important role in the regulation of PAI-1 expression. The objective of the study was to evaluate the effect of this polymorphism on the outcome of critically ill patients with ALI/ARDS. MATERIALS AND METHODS 52 consecutive ventilated patients with ALI/ARDS were studied. Bronchoalveolar lavage was performed within 48 hours from diagnosis. Measurement of plasma and BALF PAI-1 activity and D-dimers levels, and 4G/5G genotyping of PAI-1 were carried out. The primary outcome was 28-day mortality, and secondary outcomes included organ dysfunction and ventilator-free days. RESULTS 17 patients were homozygotes for the 4G allele. Severity scores were not different between subgroups upon study enrollment. 28-day mortality was 70.6% and 42.9% for the 4G-4G and the non-4G-4G patients, respectively (p=0.06). PAI-1 activity levels and D-dimer in plasma and BALF were not significantly different between the 4G-4G and the non-4G-4G subgroups. In the multivariate analysis, genotype 4G/4G was the only variable independently associated with 28-day mortality (Odds Ratio=9.95, 95% CI: 1.79-55.28, p=0.009). Furthermore, genotype 4G/4G and plasma PAI-1 activity levels were independently negatively associated with ventilator free days (p=0.033 and p=0.008, respectively). CONCLUSIONS ALI/ARDS patients, homozygous for the 4G allele of the PAI-1 gene, experienced higher 28-day mortality. This genotype was associated with a reduction in the number of days of unassisted ventilation and was inversely associated with the number of days without organ failure.

Evaluation of the role of the new INNOVANCE PFA P2Y test cartridge in detection of clopidogrel resistance

Light transmittance aggregometry (LTA) has been extensively used in monitoring clopidogrel therapy. However, the availability of simple and rapid point-of-care platelet function assays is of great clinical importance. Thus, the manufacturer of the Platelet Function Analyzer (PFA)-100 System has recently produced the INNOVANCE PFA P2Y test cartridge. We assessed the ability of this new test to reliably detect clopidogrel resistance. We enrolled 90 consecutive patients with coronary artery disease receiving chronic clopidogrel maintenance therapy in combination with aspirin. Twenty healthy volunteers served as controls. Clopidogrel resistance was simultaneously analysed by the INNOVANCE PFA P2Y test cartridge, ADP-induced LTA, the flow-cytometric vasodilator-stimulated phosphoprotein (VASP)-phosphorylation assay and the multiple electrode aggregometry (Multiplate). Agreement among the four platelet function methods by two was assessed using Cohens kappa coefficient. According to the cut-off points for clopidogrel resistance proposed by the literature, agreement was fair between INNOVANCE PFA-100 P2Y and LTA (74.4%) and Multiplate (75.6%), while poor agreement was noticed in VASP assay (63.3%). Based on cut-off points indicating a higher thrombotic risk, agreement between the PFA-100 System and the other three methods did not significantly differ compared to the previous cut-offs (72.2%, 71.1% and 55.1%, respectively). The INNOVANCE PFA-100 P2Y test seems to be comparable to other established platelet function assays in detecting clopidogrel resistance. However, the modest agreement among platelet function methods makes the performance of platelet function testing crucial with more than one technique in order to reliably identify poor responders to clopidogrel treatment.

Do different substitution patterns or plant origin in hydroxyethyl starches affect blood coagulation in vitro

The effect of hydroxyethyl starches (HES) on blood coagulation is affected by their molecular weight, their molar substitution and the C2/C6 ratio. The solutions of 6% HES 130/0.4 and 6% HES 130/0.42 have similar molecular weight and molar substitution but different C2/C6 ratio and plant origin. In the present study, the comparative effect of 6% HES 130/0.4 versus 6% HES 130/0.42 on blood coagulation was investigated in vitro. Thirty milliliter of blood was obtained from 10 healthy volunteers and was diluted by 10, 30 and 50% using either 6% HES 130/0.4 or HES 130/0.42, respectively. Blood coagulation was assessed using thrombelastography measurements (clotting time, clot formation time, maximal clot firmness and alpha-angle). The assessment of platelet function was performed with whole blood aggregometry after adding thrombin–receptor-activating protein. No differences were noted between respective dilutions of the two HES. Both colloids produced significant reductions below the reference values range in clotting time at 10, 30 and 50% dilutions. The 50% dilution of both colloids resulted in significant reduction of maximal clot firmness, alpha-angle and platelet aggregation. The present study showed that the corn-derived 6% HES 130/0.4 and the potato-derived 6% HES 130/0.42 have the same effect on blood coagulation in vitro.

Monitoring aspirin treatment in patients with thrombocytosis: Comparison of the platelet function analyzer (PFA)-100 with optical aggregometry

Aspirin provides satisfactory protection against thrombotic episodes in essential thrombocythemia (ET), but at higher platelet counts has been less effective. Our aim was to compare the platelet function analyzer (PFA)-100 with optical aggregometry in order to determine a reliable method in monitoring aspirins influence on platelet function in patients with thrombocytosis. We studied 36 patients with thrombocytosis. Sixteen of them, receiving aspirin, composed group A, while group B consisted of 20 patients not taking aspirin. In all patients, we compared the platelet function measured by classic optical aggregation tests with closure times (CT) obtained by the PFA-100. The definition of platelet responses as normal or pathological showed that PFA-100 collagen and/or epinephrine (CEPI) CTs and epinephrine-induced aggregometry is the pair of methods with the higher agreement in monitoring of platelet dysfunction due to ASA treatment (a=94%). Satisfactory results were also obtained for group B (a=81%). The comparison between PFA-100 CEPI CTs and arachidonic acid-induced aggregometry exhibited moderate agreement both in the total number of patients and in group A (a=79% and 94%, respectively). PFA-100 collagen and/or ADP (CADP) CTs and ADP-induced aggregometry were not concordant. The PFA-100 system appears to be a reliable and rapid method in the assessment of aspirins antiplatelet effect in patients with thrombocytosis. Regarding aggregometry, the selection of the inducer, its concentration and cut-off points is crucial in defining the response to antiaggregating agents. It still remains to determine whether there is any relevance between the measurements obtained by these methods and clinical outcome in thrombocythemic patients.