Activated Protein C Resistance Research Articles

The preliminary research in paroxysmal nocturnal hemoglobinuria with thrombosis

目的探讨阵发性睡眠性血红蛋白尿症（PNH）患者易发血栓的可能因素。方法回顾性分析142例PNH患者的临床资料，对3个已知血栓相关基因位点[PROC c.574_576del（rs199469469）、PROC c.565C>T（rs146922325）和THBD c.-151G>T（rs1698852）]采用Sanger法进行DNA序列检测，以性别、年龄相匹配的100名健康志愿者为正常对照。结果142例患者中，合并血栓者21例（14.8%），其中2例为动脉血栓，19例为静脉血栓，血栓组患者的中位年龄为35（20~67）岁，与非血栓组[40（7~79）岁]比较差异无统计学意义（P=0.687）；两组患者的男女比例、PNH临床分类、HGB、WBC、PLT、LDH水平差异均无统计学意义（P值均>0.05）。血栓组RBC、粒细胞CD59−、红细胞CD59−及嗜水气单胞菌溶素变异体阴性细胞（Flear−）百分率均高于非血栓组（P值分别为0.015、0.005、0.004和0.026）。PNH患者组与正常对照组、PNH血栓组与非血栓组之间蛋白C、蛋白S、抗凝血酶Ⅲ、活化蛋白C抵抗、血脂、狼疮抗凝物等常见易栓因素差异均无统计学意义（P值均>0.05）。PNH患者中，rs199469469位点突变1例（0.704%）、rs16984852位点突变2例（1.408%）、无一例发生rs146922325位点突变，所有突变者均无血栓形成；正常对照组3个位点突变率分别为2.424%、0.873%和0.974%。PNH患者组与正常对照组、PNH血栓组与非血栓组之间各位点突变率差异均无统计学意义（P值均>0.05）。结论RBC与PNH克隆大小是PNH患者发生血栓的独立危险因素。PNH患者与正常人、PHN合并血栓患者与未合并血栓患者相比，常见遗传性和后天获得性易栓因素、常见的静脉血栓3个易感基因的突变率差异均无统计学意义。

Drospirenone as estrogen-free pill and hemostasis: coagulatory study results comparing a novel 4 mg formulation in a 24 + 4 cycle with desogestrel 75 μg per day

Introduction: A novel estrogen free contraceptive pill, with drospirenone 4 mg in a dosing regimen of 24 + 4, has been developed with a pearl-index of 0.51 (95% CI 0.1054; 1.4922). The aim of the following study was to determine if 4 mg DRSP has an impact on coagulation factors and thrombotic risks in comparison with desogestrel 75 μg.Patients and methods: Thirty-nine patients received 4 mg DRSP 24 + 4 d and 29 desogestrel 75 μg per day continuously during nine complete cycles. Following hemostatic parameters were evaluated: Apc resistance, Antithrombin III, Protein C reactivity, Factor VII, Factor VIII, and d-Dimer.Results: Factor VII decreased from 1.123 to 1.066 in the DRSP group and from 1.241 to 1.034 in the desogestrel group (p = 0.0088). The difference in change of mean Protein C activity from baseline to endpoint was −0.0332 in the DRSP versus −0.157 in the desogestrel group (p = 0.0249). d-Dimer values dropped in the DRSP group from baseline values of 264.9–215.0 ng/mL, whereas in the desogestrel group there was a rise from 201.4 ng/mL to 281.5 ng/mL.Discussion: DRSP 4 mg was not associated with any meaningful changes on hemostatic parameters, indicating a lack of effect on hemostasis

Use of a systematic risk analysis method (FMECA) to improve quality in a clinical laboratory procedure.

Risk management is a set of actions to recognize or identify risks, errors and their consequences and to take the steps to counter it. The aim of our study was to apply FMECA (Failure Mode, Effects and Criticality Analysis) to the Activated Protein C resistance (APCR) test in order to detect and avoid mistakes in this process. We created a team and the process was divided in phases and sub phases. For each phase we calculated the probability of occurrence (O) of an error, the detectability score (D) and the severity (S). The product of these three indexes yields the RPN (Risk Priority Number). Phases with a higher RPN need corrective actions with a higher priority. The calculation of RPN showed that more than 20 activities have a score higher than 150 and need important preventive actions; 8 have a score between 100 and 150. Only 23 actions obtained an acceptable score lower than 100. This was one of the first experience of application of FMECA analysis to a laboratory process, and the first one which applies this technique to the identification of the factor V Leiden, and our results confirm that FMECA could be a simple, powerful and useful tool in risk management and helps to identify quickly the criticality in a laboratory process.

Multimodal Venous Thromboembolism Prophylaxis with Preoperative Thrombophilia Screening Examinations for Total Hip and Knee Arthroplasties

Objective: To evaluate the efficacy of a multimodal venous thromboembolism (VTE) prophylaxis including preoperative thrombophilia screening for total hip and knee arthroplasties (THAs and TKAs) and to consider the possibility of utilizing thrombophilic blood markers for preoperative identification of patients with high risk for VTE..Method: The physical evaluation, involving the medical history of previous VTE, recent malignancy, and preoperative prolonged immobility status, and the existence of deep venous thrombosis (DVT) detected by duplex venous ultrasonography were assessed. Then, the patients with high risk of VTE were offered an inferior vena cava (IVC) filter preoperatively. The laboratory examination of complete blood count and standard biochemistry with factor VIII, activated protein C resistance (APCR), and prothrombin gene mutation were also measured. The operations were performed under regional anesthesia in most cases, and with venous foot pump (VFP), and early mobilization and aspirin (325 mg) daily were applied postoperatively.Results: IVC filters were placed in 6, and acute DVT was detected in 5 of the total 99 cases. However, there was no critical bleeding or fatal VTE. In the blood markers, prothrombin mutation and factor VIII seemed to have a relation to DVT.Conclusion: The efficacy of our multimodal protocol was confirmed. Further research is necessary to apply factor VIII and prothrombin gene mutation as thrombophilic blood markers.

Prevalence of Factor V Genetic Variants Associated With Indian APCR Contributing to Thrombotic Risk.

Phenotypic resistance to activated protein C (APC) is a complex mechanism associated with increased thrombosis risk. Activated protein C resistance (APCR) is mainly influenced by FVLeiden mutation, and various other single nucleotide polymorphisms (SNPs) in FV gene are known to be associated with APCR. The aim of present study was to investigate the incidence and assess possible mechanisms of APCR in Indian patients with deep vein thrombosis (DVT). Three hundred and ten Doppler-proven patients with DVT were screened for APCR, and 50 APCR positive patients and 50 controls were typed for FVLeiden, Hong Kong, Cambridge, HR2 haplotype, Glu666Asp, Ala485Lys, and Liverpool using either polymerase chain reaction (PCR)-restriction fragment length polymorphism or allele specific PCR. FVLeiden was commonest cause of APCR (50%) in Indian patients with DVT being statistically significant ( P = .001) compared to controls. FV Liverpool, FV Glu666Asp and FV Ala485Lys were studied for the first time in Indian population. FV Liverpool, FV Glu666Asp, Hong Kong, and Cambridge were found to be absent. High frequency of Ala485Lys in patients shows that it might be a risk factor contributing to APCR in Indian patients with DVT. HR2 haplotype was not associated with APCR; however, presence of homozygous HR2 haplotype in patients only indicates the role it might play in Indian APCR population. In conclusion, contribution of FVLeiden causing APCR in Indian population is not as strong as previously reported in Western countries. The presence of other SNPs observed in the present study requires such studies on larger sample size to understand the molecular basis of defect.

Tissue Factor Pathway Inhibitor, Activated Protein C Resistance, and Risk of Coronary Heart Disease Due To Combined Estrogen Plus Progestin Therapy.

To examine whether tissue factor pathway inhibitor or acquired activated protein C (APC) resistance influences the increased risk of coronary heart disease (CHD) due to estrogen plus progestin therapy. Prospective nested case-control study of 205 cases of CHD and 481 matched controls in the Women's Health Initiative randomized trial of estrogen plus progestin therapy. After multivariable covariate adjustment, both baseline tissue factor pathway activity (P=0.01) and APC resistance (P=0.004) were associated positively with CHD risk. Baseline tissue factor pathway activity and APC resistance singly or jointly did not significantly modify the effect of estrogen plus progestin on CHD risk. Compared with placebo, estrogen plus progestin decreased tissue factor pathway inhibitor activity and increased APC resistance but these changes did not seem to modify or mediate the effect of estrogen plus progestin on CHD risk. Tissue factor pathway inhibitor activity and APC resistance are related to CHD risk in women, but may not explain the increased CHD risk due to estrogen plus progestin therapy. The data from this study do not support the clinical use of measuring these hemostatic factors to help stratify risk before hormone therapy. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000611.

Unusual Etiology of Acute Myocardial Infarction – Factor V Leiden Mutation

The genetic defect of coagulation factor V known as factor V Leiden produces a resistance to degradation of factor V by activated protein C (APC) and that will increase the risk of venous thromboembolism. The data on arterial thrombosis and acute myocardial infarction associated with APC resistance are still not clearly defined. We report a case of acute myocardial infarction in young patient with no cardiovascular risk factors and the etiology of the myocardial infarction was defined as acute arterial thrombosis associated with factor V Leiden defect, without any significant coronary lesions. Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:"جدول عادي"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}

Non-Factor VIII Coagulation Proteins Fail to Predict Joint Outcome in Severe Hemophilia a

Background: The Joint Outcome Study (JOS), a randomized controlled trial of prophylactic vs episodic factor VIII for treatment of severe hemophilia A, conclusively showed that children started on prophylactic factor VIII before age 30 months had better joint outcomes by age 6, as measured by MRI, joint physical exam scores, and annual number of joint bleeds(Manco-Johnson, et al, NEJM 2007). However, variation in individual outcomes existed within each treatment group that was not well-explained. We measured hemostatic and fibrinolytic factors in plasma samples from the Joint Outcome Study to determine other contributors to bleeding outcomes.Methods: Samples from 65 patients in the JOS were evaluated. Factors assayed in the University of Colorado Hemophilia & Thrombosis Treatment Center Research Laboratory included: average factor VIII (FVIII) trough (prophylaxis) or baseline (episodic) activity levels; Von Willebrand Factor antigen (VWF); tissue factor pathway inhibitor (TFPI); thrombin activatable fibrinolysis inhibitor (TAFI); factor V Leiden measured by activated protein C resistance (APC-R) assay; thrombin-antithrombin complexes (TAT); and euglobulin lysis time (ELT). Results were correlated with outcomes at age 6 years, including: number of joint bleeds, total number of bleeds, MRI score, and joint physical exam score. Joint failure on MRI was defined as an MRI score of 7-10 out of 10 possible points on any joint. Linear regression was used to compare each variable with each outcome. Prophylactic and episodic groups were analyzed separately and together.Results: When both groups were evaluated together, linear regression showed significant inverse correlations between FVIII trough/baseline levels and either joint bleeds (Figure 1, p < 0.001), total bleeds (p < 0.0001), or total MRI score (p < 0.01), although episodic patients had significantly more bleeds and higher MRI scores than prophylaxis patients. This relationship was not seen if prophylaxis and episodic groups were evaluated separately (Table 1). Specifically, boys in the prophylaxis group showed no significant relationship between trough and bleeding or MRI outcomes when analyzed separately, likely because the rate of bleeds on prophylaxis was so low at any trough level. No significant association between factor VIII trough/baseline levels and physical exam joint scores was found. When prophylaxis and episodic groups were evaluated separately, the only significant association between any outcome and any coagulation factor was TFPI, which unexpectedly had an inverse relationship with joint and total bleeds (Table 1). When results were stratified by joint preservation vs. joint failure on MRI, subjects with joint failure had slightly lower FVIII trough/baseline, VWF, and TAFI levels, but these results were not significant. Two children were found to have coincidental Von Willebrand disease (VWF antigen levels of 18% (episodic arm), 31% (prophylactic arm)); the child on episodic treatment suffered joint failure on MRI. Three children (2 in episodic arm and 1 in prophylaxis arm) had factor V Leiden heterozygosity, and none of these children had joint failure.Conclusion: In the closely monitored and extensively studied participants of the JOS, higher FVIII trough/baseline levels were associated with decreased bleeding rates. In contrast, physiologic variation in constitutional levels of VWF, TAFI, and TAT, while modestly and non-significantly lower in children with joint failure on MRI, did not affect bleeding rates. While it is tempting to attribute bleeding to coincidental VWD and joint preservation to factor V Leiden heterozygosity, the data are too limited for conclusions. Use of factor VIII prophylaxis remains the most powerful predictor of joint outcome in children with severe hemophilia A. [Display omitted] [Display omitted] DisclosuresShapiro:Baxalta, Novo Nordisk, Biogen,: Membership on an entity's Board of Directors or advisory committees; Bayer Healthcare, Baxalta, Biogen, CSL Behring, Daiichi Sankyo, Kedrion Biopharma, Octapharma, OPKO, ProMetic Life Sciences, PTC Therapeutics, and Selexys: Research Funding; Biogen: Speakers Bureau; Baxalta, Novo Nordisk, Biogen, ProMetic Life Sciences, and Kedrion Biopharma: Consultancy. Recht:Baxalta: Research Funding; Novo Nordisk: Research Funding; Biogen: Research Funding; Kedrion: Membership on an entity's Board of Directors or advisory committees. Brown:Baxalta: Research Funding. Leissinger:Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Baxter: Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Membership on an entity's Board of Directors or advisory committees, Research Funding; Biogen: Research Funding; Kedrion: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. Kempton:Biogen: Consultancy; Novo Nordisk: Consultancy; Baxalta: Consultancy. Lane:Bayer Pharmaceuticals: Consultancy; Baxter Healthcare: Consultancy. Manco-Johnson:CSL Behring: Honoraria; Baxalta: Honoraria; Bayer Healthcare: Honoraria, Research Funding; BiogenIdec: Honoraria; Novo Nordisk: Honoraria.

Coagulation factor V mediates inhibition of tissue factor signaling by activated protein C in mice

AbstractThe key effector molecule of the natural protein C pathway, activated protein C (aPC), exerts pleiotropic effects on coagulation, fibrinolysis, and inflammation. Coagulation-independent cell signaling by aPC appears to be the predominant mechanism underlying its highly reproducible therapeutic efficacy in most animal models of injury and infection. In this study, using a mouse model of Staphylococcus aureus sepsis, we demonstrate marked disease stage–specific effects of the anticoagulant and cell signaling functions of aPC. aPC resistance of factor (f)V due to the R506Q Leiden mutation protected against detrimental anticoagulant effects of aPC therapy but also abrogated the anti-inflammatory and mortality-reducing effects of the signaling-selective 5A-aPC variant that has minimal anticoagulant function. We found that procofactor V (cleaved by aPC at R506) and protein S were necessary cofactors for the aPC-mediated inhibition of inflammatory tissue-factor signaling. The anti-inflammatory cofactor function of fV involved the same structural features that govern its cofactor function for the anticoagulant effects of aPC, yet its anti-inflammatory activities did not involve proteolysis of activated coagulation factors Va and VIIIa. These findings reveal a novel biological function and mechanism of the protein C pathway in which protein S and the aPC-cleaved form of fV are cofactors for anti-inflammatory cell signaling by aPC in the context of endotoxemia and infection.

Factor V Leiden.

Factor V Leiden (FVLeiden ) is a common hereditary thrombophilia that causes activated protein C (APC) resistance. This review describes many of the most fascinating features of FVLeiden , including background features, mechanisms of hypercoagulability, the founder mutation concept, the "FVLeiden paradox," synergistic interaction with other thrombotic risk factors, the intertwined relationship between FVLeiden and APC resistance testing, and other, uncommon mutations implicated in causing APC resistance. In addition, there are several conditions where laboratory tests for APC resistance and FVLeiden are or can be discrepant, including lupus anticoagulants, anticoagulants such as direct thrombin inhibitors (dabigatran, argatroban, and bivalirudin) and rivaroxaban, as well as pseudohomozygous, pseudo-wildtype, liver transplant, and bone marrow transplant patients. The laboratory test error rate for FVLeiden is also presented.

Non-Arteritic Anterior Ischemic Optic Neuropathy and Factor V Leiden

Non-arteritic anterior ischemic optic neuropathy (NAION) is an ischemic condition which affects the prelaminar portion of the optic nerve head. That is supplied by the ciliary arteries, and central retinal artery [1]. Yet, meaningful progress toward understanding the pathogenesis of this entity has been limited [2]. Thrombophilic disorders are proposed in the pathogenesis of NAION, such as resistance to activated protein C (APC resistance), protein C or S deficiency, factor V Leiden (FVL) and hyperfibrinogenemia. However, when the name of an entity itself may be a misnomer, it can be especially difficult to escape erroneous interpretations of pathophysiology. Indeed, the mechanism of this disease needs to be reanalyzed in a completely different direction. We present a case of NAION associated with FVL that we attended in our hospital and we review the literature of these two entities [2]. Non-arteritic anterior ischemic optic neuropathy (NAION) is an entity that is caused by circulatory insufficiency which affects the proximal portion of the optic nerve. NAION is characterized by the following triad: abrupt and painless loss of vision, optic disc smelling and nerve fiber bundle defects in the visual field of the affected eye. Cardiovascular risk factors and hrombophilic disorders have been proposed in the pathogenesis of NAION, such as Factor V Leiden thrombophilia (FVL). Factor V Leiden is a inherited disorder of blood clotting that predisposes to venous thrombotic events. Here, we report the case of 44-year-old female patient with NAION and activated protein C resistente (or FVL) who visited our hospital, and the diagnosis is discussed. We also review the literature of these two conditions. We suggest that physicians consider prothrombotic disorders when evaluating patients with AION, especially in atypical cases or cases occurring in young patients without classic factors of cardiovascular risk. Citation: Lorca-Barchin J, Medrano-Martinez V, Frances-Pont I, Fernandez-Izquierdo S, Mallada-Frechin J, et al. (2015) Non-Arteritic Anterior Ischemic Optic Neuropathy and Factor V Leiden. J Neurol Neurol Disord 2(3): 303.

Maximising the diagnostic potential of APTT-based screening assays for activated protein C resistance.

Activated protein C resistance (APC-R) due to FV Leiden is the most common hereditary thrombophilia. Rarer FV mutations can also confer APC-R, and acquired APC-R is encountered in a number of conditions. APC-R screening with clotting tests is common, yet they are prone to interferences and elevated baseline clotting times can invalidate testing. APTT-based classic APC-R (CAPC-R) screening, and modified screening (MAPC-R) employing dilution in FV-deficient plasma were performed on an automated analyser. Baseline clotting times and APC-R ratios of 1340 patients being screened for hereditary and acquired thrombophilia were assessed for analytical and diagnostic validity. Most patients (1117/1340) had normal baseline clotting times, and in 270 of these cases, this was despite the presence of a lupus anticoagulant (LA). FV Leiden was genetically confirmed in all patients with reduced CAPC-R and MAPC-R ratios. A subgroup with normal CAPC-R but reduced MAPC-R also identified FV Leiden, but also other patients with minimally reduced MAPC-R ratios not due to FV Leiden. Reduced CAPC-R and normal modified APC-R identified possible acquired APC-R in 49 patients. LA-positive patients with elevated baseline clotting times did not affect distinction between APC-R and normality, although therapeutic anticoagulation did invalidate CAPC-R, and occasionally MAPC-R too. Many departments only screen with MAPC-R to detect just FV mutations. Concurrent performance of CAPC-R and MAPC-R increases diagnostic capability by detecting acquired APC-R. Elevated baseline clotting times can invalidate APC-R ratios, although prolongation by LA alone may not.

Risk Factors for Thrombosis Development in Mexican Patients

To identify inherited factors: Protein C (PC), protein S (PS), antithrombin (AT), plasminogen (Plg), the activated PC resistance (APCR), prothrombin (PT) mutation G20210A (PTG20210A) and methylenetetrahydrofolate reductase C677T polymorphism (MTHFR C677T), as well as acquired-risk factors such as: diabetes mellitus, surgeries, smoking, obesity, hypertension, trauma, alcoholism, family history; and their association, in Mexican patients with diagnostic of thrombophilia. Overall, 200 patients diagnosed with thrombophilia and 100 healthy controls. Commercial kits were used for the coagulometric tests and polymerase chain reaction, restriction fragment length polymorphism for molecular alterations. Alterations were found with an estimated prevalence to PC 0.65%, AT 2.04% and Plg 2.5%, APCR 2%, PT 20210 2%, and MTHFR 65%. The C677T polymorphism of the MTHFR did not associate with acquired-risk factors so we can suppose that it is an independent risk factor. For the patients that only presented acquired-risk factors (21 of 200), the association smoking-alcoholism showed to be the cause of thrombosis with high risk. The following were also associated: smoking with AT, PC, and alcoholism; obesity with Plg; smoking with alcoholism, and PS deficiency. Risk factors for both primary and secondary and their association were present as a cause of thrombosis in the patients studied, and the possibility to suffer a recurrent thrombosis.

Activated Protein C-Resistance Determination and Vascular Access Thrombosis in Populations with High Prevalence of Factor V Leiden

Background/Aims: Factor V Leiden heterozygosity occurs in 3-8% of the general European and US populations. Activated protein C resistance (APC-R) - a non-molecular laboratory test - can efficiently demonstrate the presence of this mutation and can be performed on most coagulation analyzers. On the other hand, fistula or graft thrombosis is a common and costly complication in hemodialysis patients. Our aim was to establish the value of APC-R determination in hemodialysis patients by assessing the risk of access thrombosis in patients with increased APC-R. Methods: A total of 133 patients (81 men, mean age 64.5 ± 14.9 years and 52 women, mean age 63.6 ± 15 years) were selected. Participants were divided into 2 groups: those with access thrombosis (54 patients, 40.6%) and those with no access thrombosis (79 patients, 59.4%), and they were tested for the most common congenital or acquired thrombophilia risk factors. Results: Overall, 12 patients (9%) had an increased APC-R and 10 of them had at least 1 episode of access thrombosis (83.3%). Univariate analysis to estimate crude odds ratio (OR) showed an OR of 8.8 (95% CI 1.8-41.8) times higher risk for access thrombosis in these patients. No significant differences were found after adjusting for age, hypertension, diabetes mellitus, coronary artery disease, cerebrovascular disease, peripheral arterial disease and malignancy. Sex was also a factor influencing thrombosis, presenting a higher OR for women (OR 2.2, 95% CI 1.1-4.4). Conclusion: This study revealed a significant association between access thrombosis and increased APC-R in hemodialysis patients. This indicates that the determination of APC-R should be considered - especially, in populations with a high prevalence of Factor V Leiden - as proper anticoagulant therapy in these patients may reduce the risk of access thrombosis.

Higher levels of von Willebrand factor in patients with syncope due to orthostatic hypotension.

Orthostatic hypotension has been linked with increased mortality and cardiovascular morbidity; however, the underlying mechanisms are still unknown. The aim of the study was to assess markers of coagulability in patients with and without orthostatic hypotension who suffered transient loss of consciousness. A total of 233 consecutive patients more than 15 years old, with unexplained transient loss of consciousness, underwent head-up tilt test (HUT, Italian protocol). Blood samples were collected during supine rest before and at 3 min of 70° HUT for determination of fibrinogen, von Willebrand factor antigen (vWF:Ag) and activity (vWF:GP1bA), factor VIII (FVIII:C), lupus anticoagulant, and functional activated protein C-resistance. Orthostatic hypotension was defined as persistent decrease in SBP and/or DBP of more than 20/10 mmHg or SBP lower than 90 mmHg during passive HUT. One hundred and seventy-eight patients (81 men, 45.5%) not treated with vitamin-K antagonists were analyzed. Those with orthostatic hypotension (n = 49) were older [61 ± 18 vs. 47 ± 21 years (mean ± SD), P < 0.001], had increased C-supine (1.2 ± 0.39 vs. 1.0 ± 0.35, P = 0.001), FVIII:C-standing (1.2 ± 0.36 vs. 1.0 ± 0.34, P = 0.001), vWF:Ag-supine (1.5 ± 0.66 vs. 1.1 ± 0.44, P < 0.001), vWF:Ag-standing (1.5 ± 0.67 vs. 1.1 ± 0.46, P < 0.001), vWF:GP1bA-supine (1.5 ± 0.73 vs. 1.1 ± 0.42, P < 0.001), vWF:GP1bA-standing (1.5 ± 0.75 vs. 1.1 ± 0.42 P < 0.001), fibrinogen-standing (2.9 ± 0.53 vs. 2.7 ± 0.61, P = 0.03) but not fibrinogen-supine (2.8 ± 0.54 vs. 2.7 ± 0.61, P = 0.078) compared with patients without orthostatic hypotension. However, after adjustment for age, sex, and comorbidity, only vWF:Ag and vWF:GP1bA levels remained significantly increased in orthostatic hypotension patients. Concentration of vWF is elevated in patients with orthostatic hypotension who suffered a syncopal event. This observation may be helpful in understanding the increased risk of cardiovascular events in orthostatic hypotension.

Factors contributing to APC-resistance in women with recurrent spontaneous miscarriages: Indian perspective.

c values exceeding 95th percentile of the control population (145IU/dL), as compared to 3% in the control group (p=0.001). Mean FVIII level in control subjects was 118±14.0IUdL(-), compared with 127.7±31.2IUdL(-) in the patient group (p=0.009). Apart from FVIII, only the anti-phospholipid antibodies showed a statistically significant association with APCR phenotype (p=0.028), unlike other thrombophilic factors such as Protein C, Protein S, FV levels, HR2 haplotype or other rarer FV variants. The strong positive association of FVL mutation, anti-phospholipid antibodies and elevated FVIII levels with APCR phenotype calls for incorporating them as first line investigations in patients with recurrent spontaneous miscarriages with APCR positivity.

Prothrombotic risk factors and antithrombotic therapy in children with ischemic stroke.

Congenital and acquired prothrombotic disorders have been highlighted in a recent series of cerebrovascular stroke (CVS), with a controversial role in pathogenesis. The aim is to study some prothrombotic risk factors [activated protein C (APC) resistance, von Willebrand factor (vWF), anticardiolpin (ACL) antibodies and plasma homocysteine] in children with ischemic stroke, and to evaluate the role of aspirin and low molecular weight heparin (LMWH) in its management in relation to outcome. A total of 37 cases aged from 1 month to 15 years ( mean ± standard deviation 26.2 ± 35.7 months), diagnosed as ischemic stroke (>24 hours) were recruited. Complete blood count, prothrombin time and concentration, partial thromboplastin time, serum electrolytes, random blood sugar, C-reactive protein, electrocardiogram and echocardiography were done. Levels of APC resistance, vWF, ACL antibodies [immunoglobulin G (IgG) and immunoglobulin M (IgM)] and plasma homocysteine were estimated. A total of 25 cases received aspirin 3-5 mg /kg/d and 12 patients received LMWH as initial dose at 75 international units (IU)/kg subcutaneously (SC) then 10-25 IU/kg/day for 15 days in a nonrandomized fashion. The levels of APC resistance, vWF, ACL antibodies (IgG and IgM) and plasma homocysteine were significantly higher in stroke cases than in controls. There was no significant difference between cases treated with aspirin and those with LMWH in all prothrombotic factors. Significant positive correlations were found between vWF and ACL antibodies (IgG and IgM) levels before treatment. Significant decrease in cognitive function was detected between cases treated with LMWH and those treated with aspirin. Ischemic CVS in children is multifactorial. Thrombophilia testing should be performed in any child with CVS. Early use of aspirin improves the prognosis and has less effect on cognitive function.

Three novel variants in the coagulation factor V gene associated with deep venous thrombosis in Chilean patients with Amerindian ethnic background

BackgroundThe activated protein C (APC) resistance is the most common prothrombotic defect in thrombosis patients, mainly related with alterations in the F5 gene. In this work, we evaluated the presence of variants in the FV gene in Amerindian patients with deep venous thrombosis and APC resistance. MethodsA total of 87 patients with deep venous thrombosis (DVT) confirmed by Doppler ultrasonography, and Amerindian genetic background, were included in this study. APC resistance was assayed by clotting methods and polymorphism F51691G>A was genotyped by molecular methods. In Amerindian patients with APC resistance, the promoter region, exon 7 and exon 10 of the F5 gene were screened by PCR-SSCP and DNA sequencing. The prediction of functional effect of novel mutations was analyzed using Polyphen-2 software. ResultsIn DVT patients, 14.9% showed functional APC resistance in the absence of F51691G>A polymorphism. Interestingly, three novel missense mutations in exon 10 of F5 gene (M443L, E461Q and G493E) were identified. These genetic variants were absent in 100 healthy subjects. According to in silico analysis, the sequence variants G493E and E461Q are potentially deleterious. ConclusionsOur data shows that the APC resistance phenotype is not associated with the presence of the F51691G>A variant. We described, for the first time, the presence of three novel variants in F5 gene in Chilean patients with APC resistance. Further studies are required to investigate the real contribution of these novel mutations to the APC resistance phenotype.

The effect of dabigatran and rivarovaban on a prothrombinase-based assay for activated protein C resistance: a preliminary study in subjects heterozygous for factor V Leiden.

Oral direct inhibitors of activated factor II (FIIa), such as dabigatran, and of activated factor X (FXa), such as rivaroxaban, have the potential to interfere with the great majority of clot-based coagulation assays and some chromogenic assays, whereas these drugs would not be expected to interfere in antigen-based assays1–4. Data concerning the influence of anti-FIIa and anti-FXa on functional assays for determination of activated protein C resistance (APCr) are still rather scarce and available studies have mainly been conducted using tests based on the activated partial thromboplastin time (aPTT). Moreover the data were obtained from in vitro studies performed on plasma from normal individuals, which was spiked with variable amounts of the drugs1–4. For dabigatran there is evidence that aPTT-based APCr methods over-estimate the APCr ratio, which may lead to patients with heterozygous factor V Leiden (FVL) being misclassified as normal1–4. In contrast, for rivaroxaban there is evidence that aPTT-based APCr methods may under-estimate the APCr ratio2,3. As previously reported, in our laboratory we adopted a prothrombinase-based method to study the APCr5. Data concerning the influence of dabigatran and rivaroxaban on this assay are still rather scarce. We, therefore, report the influence of FIIa and FXa direct oral inhibitors on the APCr, evaluated with a prothrombinase assay, in a small number of FVL patients.

Prevalence and role of antithrombin III, protein C and protein S deficiencies and activated protein C resistance in Kosovo women with recurrent pregnancy loss during the first trimester of pregnancy.

CONTEXT:Several studies have reported that thrombophilia is responsible for recurrent pregnancy loss (RPL).AIMS:The aim of this study was to evaluate the prevalence and role of inherited thrombophilia in early pregnancy loss, specifically in the first trimester.MATERIALS AND METHODS:A total of 104 women (patients) with a history of two or more miscarriages during the first trimester of pregnancy and 110 women (controls) who had experienced two or more births without a miscarriage were included in this study. In both groups, we determined the biological activities of antithrombin III (ATIII) and protein C (PC) using the chromogenic method and the biological activity of protein S (PS) and the activated protein C resistance (APCR) were examined using a clotting method.RESULTS:In the patient group, deficiencies of ATIII, PC, and PS were detected in 3 (2.88%), 4 (3.85%), and 6 (5.77%) cases, respectively. In the control group, ATIII (0%) deficiencies were not detected, and deficiencies for PC (0.9%) and PS (0.9%) were each detected in 1 patient. APCR was detected in 9 patients (8.65%) and 4 control subjects (3.63%).CONCLUSION:Based on our results, we can conclude that thrombophilia is a causal factor for miscarriages in the first trimester of pregnancy, although there are the conflicting data in the literature.