Routine haemostasis testing before transplanted kidney biopsy: a cohort study.

Kidney biopsy can result in bleeding complications. Prebiopsy testing using bleeding time (BT) is controversial. New whole blood haemostasis tests, such as platelet function analyser-100 (PFA-100) and multiple electrode aggregometry (MEA), might perform better. We postulated that PFA-100 would be suitable to replace BT prebiopsy. In 154 patients, transplanted kidney biopsies were performed after measurement of bleeding time, PFA-100, MEA and mean platelet volume (MPV). Bleeding outcome (haemoglobin (Hb) drop, haematuria (±bladder catheterization), ultrasound finding of a bleeding, need for (non)surgical intervention and/or transfusion) after the biopsy was correlated to each test. Male-female ratio was 2:1. 50% had a surveillance biopsy at either three or 12 months. Around 17% (had) used acetylsalicylic acid (ASA) prebiopsy. Of 17 bleeding events, one subject needed a transfusion. Most bleeding events were Hb reductions over 1 mmol/l and all resolved uneventful. BT, PFA-100, MEA and MPV did not predict a bleeding outcome; prior ASA use however could (odds ratio 3.19; 95%-CI 1.06 to 9.61). Diagnostic performance data and Bland-Altman analysis showed that BT could not be substituted by PFA-100. ASA use was the best determinant of bleeding after kidney biopsy. Routine haemostasis testing prebiopsy has no added value.

Factor VIII gene (F8) mutation and risk of inhibitor development in nonsevere hemophilia A.

Neutralizing antibodies (inhibitors) toward factor VIII form a severe complication in nonsevere hemophilia A, profoundly aggravating the bleeding pattern. Identification of high-risk patients is hampered by lack of data that take exposure days to therapeutic factor VIII concentrates into account. In the INSIGHT study, we analyzed the association between F8 mutation and inhibitor development in patients with nonsevere hemophilia A (factor VIII 2-40 IU/dL). This analysis included 1112 nonsevere hemophilia A patients from 14 centers in Europe and Australia that had genotyped at least 70% of their patients. Inhibitor risk was calculated as Kaplan-Meier incidence with cumulative number of exposure days as the time variable. During 44 800 exposure days (median, 24 exposure days per patient; interquartile range [IQR], 7-90), 59 of the 1112 patients developed an inhibitor; cumulative incidence of 5.3% (95% confidence interval [CI], 4.0-6.6) after a median of 28 exposure days (IQR, 12-71). The inhibitor risk at 50 exposure days was 6.7% (95% CI, 4.5-8.9) and at 100 exposure days the risk further increased to 13.3% (95% CI, 9.6-17.0). Among a total of 214 different F8 missense mutations 19 were associated with inhibitor development. These results emphasize the importance of F8 genotyping in nonsevere hemophilia A.

Clot lysis phenotype and response to recombinant factor VIIa in plasma of haemophilia A inhibitor patients.

Recombinant activated factor VII (rFVIIa) is a haemostatic agent that is used for the treatment of haemophilia A patients with inhibitors. However, clinical response to rFVIIa is variable and unpredictable with currently available assays. We investigated the anti-fibrinolytic effects of rFVIIa in relation to thrombin generation (TG) and other haemostatic parameters in haemophilia A patients with inhibitors. After addition of rFVIIa to plasma, the clot-lysis assay, TF-dependent TG, TF-independent TG and parameters involved in coagulation, anticoagulation and fibrinolysis were assessed. The clot-lysis test distinguished two groups of patients: a group with a normal and a group with impaired anti-fibrinolytic response to rFVIIa. Our results showed a dose-dependent increase in TF-dependent TG and TF-independent TG in all individuals. There was a significant difference in TF-independent TG parameters between the normal and impaired response groups. In addition, there was a difference between the normal and impaired response group in prothrombin time, which could be explained by significantly higher levels of coagulation factors in the normal response group, and soluble thrombomodulin. In conclusion, we observed different in vitro responses following rFVIIa addition in plasma of patients with haemophilia A and inhibitors, which could be partially attributed to levels of procoagulant proteins and soluble thrombomodulin.

Aspirin plus heparin or aspirin alone in women with recurrent miscarriage.

BACKGROUND: Aspirin and low-molecular-weight heparin are prescribed for women with unexplained recurrent miscarriage, with the goal of improving the rate of live births, but limited data from randomized, controlled trials are available to support the use of these drugs. METHODS: In this randomized trial, we enrolled 364 women between the ages of 18 and 42 years who had a history of unexplained recurrent miscarriage and were attempting to conceive or were less than 6 weeks pregnant. We then randomly assigned them to receive daily 80 mg of aspirin plus open-label subcutaneous nadroparin (at a dose of 2850 IU, starting as soon as a viable pregnancy was demonstrated), 80 mg of aspirin alone, or placebo. The primary outcome measure was the live-birth rate. Secondary outcomes included rates of miscarriage, obstetrical complications, and maternal and fetal adverse events. RESULTS: Live-birth rates did not differ significantly among the three study groups. The proportions of women who gave birth to a live infant were 54.5% in the group receiving aspirin plus nadroparin (combination-therapy group), 50.8% in the aspirin-only group, and 57.0% in the placebo group (absolute difference in live-birth rate: combination therapy vs. placebo, -2.6 percentage points; 95% confidence interval [CI], -15.0 to 9.9; aspirin only vs. placebo, -6.2 percentage points; 95% CI, -18.8 to 6.4). Among 299 women who became pregnant, the live-birth rates were 69.1% in the combination-therapy group, 61.6% in the aspirin-only group, and 67.0% in the placebo group (absolute difference in live-birth rate: combination therapy vs. placebo, 2.1 percentage points; 95% CI, -10.8 to 15.0; aspirin alone vs. placebo -5.4 percentage points; 95% CI, -18.6 to 7.8). An increased tendency to bruise and swelling or itching at the injection site occurred significantly more frequently in the combination-therapy group than in the other two study groups. CONCLUSIONS: Neither aspirin combined with nadroparin nor aspirin alone improved the live-birth rate, as compared with placebo, among women with unexplained recurrent miscarriage. (Current Controlled Trials number, ISRCTN58496168.)

Thrombotic risk during oral contraceptive use and pregnancy in women with factor V Leiden or prothrombin mutation: a rational approach to contraception.

Current guidelines discourage combined oral contraceptive (COC) use in women with hereditary thrombophilic defects. However, qualifying all hereditary thrombophilic defects as similarly strong risk factors might be questioned. Recent studies indicate the risk of venous thromboembolism (VTE) of a factor V Leiden mutation as considerably lower than a deficiency of protein C, protein S, or antithrombin. In a retrospective family cohort, the VTE risk during COC use and pregnancy (including postpartum) was assessed in 798 female relatives with or without a heterozygous, double heterozygous, or homozygous factor V Leiden or prothrombin G20210A mutation. Overall, absolute VTE risk in women with no, single, or combined defects was 0.13 (95% confidence interval 0.08-0.21), 0.35 (0.22-0.53), and 0.94 (0.47-1.67) per 100 person-years, while these were 0.19 (0.07-0.41), 0.49 (0.18-1.07), and 0.86 (0.10-3.11) during COC use, and 0.73 (0.30-1.51), 1.97 (0.94-3.63), and 7.65 (3.08-15.76) during pregnancy. COC use and pregnancy were independent risk factors for VTE, with highest risk during pregnancy postpartum, as demonstrated by adjusted hazard ratios of 16.0 (8.0-32.2) versus 2.2 (1.1-4.0) during COC use. Rather than strictly contraindicating COC use, we advocate that detailed counseling on all contraceptive options, including COCs, addressing the associated risks of both VTE and unintended pregnancy, enabling these women to make an informed choice.

Key role of glycoprotein Ib/V/IX and von Willebrand factor in platelet activation-dependent fibrin formation at low shear flow.

A microscopic method was developed to study the role of platelets in fibrin formation. Perfusion of adhered platelets with plasma under coagulating conditions at a low shear rate (250(-1)) resulted in the assembly of a star-like fibrin network at the platelet surface. The focal fibrin formation on platelets was preceded by rises in cytosolic Ca(2+), morphologic changes, and phosphatidylserine exposure. Fibrin formation was slightly affected by α(IIb)ß(3) blockage, but it was greatly delayed and reduced by the following: inhibition of thrombin or platelet activation; interference in the binding of von Willebrand factor (VWF) to glycoprotein Ib/V/IX (GpIb-V-IX); plasma or blood from patients with type 1 von Willebrand disease; and plasma from mice deficient in VWF or the extracellular domain of GpIbα. In this process, the GpIb-binding A1 domain of VWF was similarly effective as full-length VWF. Prestimulation of platelets enhanced the formation of fibrin, which was abrogated by blockage of phosphatidylserine. Together, these results show that, in the presence of thrombin and low shear flow, VWF-induced activation of GpIb-V-IX triggers platelet procoagulant activity and anchorage of a star-like fibrin network. This process can be relevant in hemostasis and the manifestation of von Willebrand disease.

Key role of integrin α(IIb)ß (3) signaling to Syk kinase in tissue factor-induced thrombin generation.

The fibrin(ogen) receptor, integrin α(IIb)ß(3), has a well-established role in platelet spreading, aggregation and clot retraction. How α(IIb)ß(3) contributes to platelet-dependent coagulation is less well resolved. Here, we demonstrate that the potent suppressing effect of clinically used α(IIb)ß(3) blockers on tissue factor-induced thrombin generation is linked to diminished platelet Ca(2+) responses and phosphatidylserine (PS) exposure. The same blockers suppress these responses in platelets stimulated with collagen and thrombin receptor agonists, whereas added fibrinogen potentiates these responses. In platelets spreading on fibrinogen, outside-in α(IIb)ß(3) signaling similarly enhances thrombin-induced Ca(2+) rises and PS exposure. These responses are reduced in α(IIb)ß(3)-deficient platelets from patients with Glanzmann's thrombasthenia. Furthermore, the contribution of α(IIb)ß(3) to tissue factor-induced platelet Ca(2+) rises, PS exposure and thrombin generation in plasma are fully dependent on Syk kinase activity. Tyrosine phosphorylation analysis confirms a key role of Syk activation, which is largely but not exclusively dependent on α(IIb)ß(3) activation. It is concluded that the majority of tissue factor-induced procoagulant activity of platelets relies on Syk activation and ensuing Ca(2+) signal generation, and furthermore that a considerable part of Syk activation relies on α(IIb)ß(3) signaling. These results hence point to a novel role of Syk in integrin-dependent thrombin generation.

Chronic coumarin treatment is associated with increased extracoronary arterial calcification in humans.

Vascular calcification is a marker of increased cardiovascular risk. Vitamin K-dependent matrix Gla protein (MGP) is important in inhibiting calcification. Because MGP activation is vitamin K dependent, we performed a cross-sectional study investigating the relationship between the use of vitamin K antagonists and extracoronary vascular calcification. From the Dutch thrombosis services we selected 19 patients younger than 55 years who had no other cardiovascular risk factors and who had used coumarins for more than 10 years, and compared these to 18 matched healthy controls. MGP was measured, and a plain x-ray of the thighs was taken to assess femoral arterial calcifications. The odds ratio for calcification in patients versus controls was 8.5 (95% confidence interval [CI] 2.01-35.95). Coumarin use and MGP were associated with calcification, even after adjusting for other risk factors. We conclude that long-term use of coumarins is associated with enhanced extracoronary vascular calcification, possibly through the inhibition of MGP carboxylation.

Postoperative thromboembolic prophylaxis in joint replacement surgery: Guidelines and daily practice.

This is a commentary discussing the article published in Thrombosis Journal by Subramanian et al. [Thrombosis Journal 2012, 10:15].

Risk of recurrent venous thrombosis in homozygous carriers and double heterozygous carriers of factor V Leiden and prothrombin G20210A.

BACKGROUND: Homozygous or double heterozygous factor V Leiden and/or prothrombin G20210A is a rare inherited thrombophilic trait. Whether individuals with this genetic background have an increased risk of recurrent venous thrombosis is uncertain. METHODS AND RESULTS: A case-control design within a large cohort of families with thrombophilia was chosen to calculate the risk of recurrent venous thrombosis in individuals with homozygosity or double heterozygosity of factor V Leiden and/or prothrombin G20210A. Cases were individuals with recurrent venous thrombosis, and controls were those with only 1 venous thrombosis. The cohort consisted of 788 individuals with venous thrombosis; 357 had factor V Leiden, 137 had prothrombin G20210A, 27 had factor V Leiden and/or prothrombin G20210A homozygosity, and 49 had double heterozygosity for both mutations. We identified 325 cases with recurrent venous thrombosis and 463 controls with only 1 venous thrombosis. Compared with noncarriers, crude odds ratio for recurrence was 1.2 (95% confidence interval, 0.9 to 1.6) for heterozygous carriers of factor V Leiden, 0.7 (95% confidence interval, 0.4 to 1.2) for prothrombin G20210A, 1.2 (95% confidence interval, 0.5 to 2.6) for homozygous carriers of factor V Leiden and/or prothrombin G20210A, and 1.0 (95% confidence interval, 0.6 to 1.9) for double heterozygotes of both mutations. Adjustments for age, sex, family status, first event type, and concomitance of natural anticoagulant deficiencies did not alter the risk estimates. CONCLUSIONS: In this study, individuals with homozygous factor V Leiden and/or homozygous prothrombin G20210A or double heterozygous carriers of factor V Leiden and prothrombin G20210A did not have a high risk of recurrent venous thrombosis.

Early atherosclerosis exhibits an enhanced procoagulant state.

BACKGROUND: Thrombin generation in vivo may be important in regulating atherosclerotic progression. In the present study, we examined for the first time the activity and presence of relevant coagulation proteins in relation to the progression of atherosclerosis. METHODS AND RESULTS: Both early and stable advanced atherosclerotic lesions were collected pairwise from each individual (n=27) during autopsy. Tissue homogenates were prepared from both total plaques and isolated plaque layers, in which the activity of factors (F) II, X, and XII and tissue factor was determined. Microarray analysis was implemented to elucidate local messenger RNA synthesis of coagulation proteins. Part of each specimen was paraffin embedded, and histological sections were immunohistochemically stained for multiple coagulation markers with the use of commercial antibodies. Data are expressed as median (interquartile range [IQR]). Tissue factor, FII, FX, and FXII activities were significantly higher in early atherosclerotic lesions than in stable advanced atherosclerotic lesions. Endogenous thrombin potential and thrombin-antithrombin complex values consolidated a procoagulant profile of early atherosclerotic lesions (endogenous thrombin potential, 1240 nmol/L x min [IQR, 1173 to 1311]; thrombin-antithrombin complex, 1045 ng/mg [IQR, 842.6 to 1376]) versus stable advanced atherosclerotic lesions (endogenous thrombin potential, 782 nmol/L x min [IQR, 0 to 1151]; thrombin-antithrombin complex, 718.4 ng/mg [IQR, 508.6 to 1151]). Tissue factor, FVII, and FX colocalized with macrophages and smooth muscle cells. In addition, multiple procoagulant and anticoagulant proteases were immunohistochemically mapped to various locations throughout the atherosclerotic vessel wall in both early and advanced atherosclerotic stages. CONCLUSIONS: This study shows an enhanced procoagulant state of early-stage atherosclerotic plaques compared with advanced-stage plaques, which may provide novel insights into the role of coagulation during atherosclerotic plaque progression.

A lower risk of recurrent venous thrombosis in women compared with men is explained by sex-specific risk factors at time of first venous thrombosis in thrombophilic families.

Why men appear to have an increased risk of recurrent venous thrombosis compared with women is unknown. In a cohort study of families with thrombophilia, lifetime risk of recurrent venous thrombosis was assessed in men and women (n = 816). Adjusted relative risk of recurrence was 1.6 (95% CI, 1.3-2.0) in men compared with women. Women were younger at time of their first event (mean, 34 years vs 44 years; P < .001) and at time of recurrence (40 years vs 48 years, P < .001). After excluding provoked first and recurrent venous thrombosis, adjusted relative risk was 1.2 (95% CI, 0.8-1.7), although mean age at recurrence was comparable in men and women (50 years vs 49 years, P = .595). In women with a hormonal first event, median interval between first event and recurrence was 10.4 years versus 2.7 years in men (P < .001). This difference was not observed when only unprovoked events were considered (P = .938). The difference in lifetime risk of recurrent venous thrombosis between men and women in thrombophilic families can be explained by a younger age of women at time of first venous thrombosis due to hormonal risk factors, and a longer interval between a provoked first episode of venous thrombosis and recurrence in women.

Selective testing for thrombophilia in patients with first venous thrombosis: results from a retrospective family cohort study on absolute thrombotic risk for currently known thrombophilic defects in 2479 relatives.

Thrombophilia screening is controversial. In a retrospective family cohort, where probands had thrombosis and a thrombophilic defect, 2479 relatives were tested for thrombophilia. In antithrombin-, protein C-, and protein S-deficient relatives, annual incidences of venous thrombosis were 1.77% (95% CI, 1.14-2.60), 1.52% (95% CI, 1.06-2.11), and 1.90% (95% CI, 1.32-2.64), respectively, at a median age of 29 years and a positive family history of more than 20% symptomatic relatives. In relatives with factor V (FV) Leiden, prothrombin 20210G>A, or high FVIII levels, these were 0.49% (95% CI, 0.39-0.60), 0.34% (95% CI, 0.22-0.49), and 0.49% (95% CI, 0.41-0.51), respectively. High FIX, FXI, and TAFI, and hyperhomocysteinemia were not independent risk factors. Annual incidence of major bleeding in antithrombin-, protein C-, or protein S-deficient relatives on anticoagulants was 0.29% (95% CI, 0.03-1.04). Cumulative recurrence rates in relatives with antithrombin, protein C, or protein S deficiency were 19% at 2 years, 40% at 5 years, and 55% at 10 years. In relatives with FV Leiden, prothrombin 20210G>A, or high levels FVIII, these were 7%, 11%, and 25%, respectively. Considering its clinical implications, thrombophilia testing should address hereditary deficiencies of antithrombin, protein C, and protein S in patients with first venous thrombosis at young age and/or a strong family history of venous thrombosis.

Endothelial activation in lacunar stroke subtypes.

BACKGROUND AND PURPOSE: Lacunar stroke (LS) can be subtyped according to the absence (isolated lacunar infarct [ILA]) or presence of concomitant white matter lesions (WML) and/or asymptomatic lacunar infarcts. Endothelial activation is thought to play a pivotal role in the subtype with WML and/or asymptomatic lacunar infarcts. The aim of this study was to evaluate whether endothelial activation is associated with WML and/or asymptomatic lacunar infarcts in LS patients. Here, we determined levels of circulating blood markers of endothelial function in LS patients. METHODS: In 149 patients, all of whom had brain-MRI, levels of tissue plasminogen activator (tPA), plasminogen activator inhibitor type 1 (PAI-1), tPA-PAI-1 complex, von Willebrand factor, tissue factor, thrombomodulin, and coagulation factor VIII were determined. Levels of blood markers were related to subtypes of LS and adjusted for age, gender, and vascular risk factors. RESULTS: In subtypes of LS, tPA activity was increased in patients with WML (0.79 IU/mL vs 0.44 IU/mL for ILA; P=0.02) and PAI-1-antigen levels were lowest in patients with WML (27.5 ng/mL vs 44.0 ng/mL for ILA; P=0.02). The association between WML and PAI-1 remained significant after multivariable analysis (OR, 0.99; 95% CI, 0.98-1.00 per ng/mL change of PAI-1; P=0.04). CONCLUSIONS: We found further evidence for the hypothesis of endothelial activation in the subtype of LS caused by a diffuse small vessel vasculopathy, as we found higher levels of tPA in patients with concomitant extensive WML than in those with ILA. Second, low levels of PAI-1 were associated with WML. We postulate that differences in activity of components of the fibrinolytic system might contribute to WML development.

Individually tailored duration of elastic compression therapy in relation to incidence of the postthrombotic syndrome.

OBJECTIVE: We assessed whether individualized shortened duration of elastic compression stocking (ECS) therapy after acute deep venous thrombosis (DVT) is feasible without increasing the incidence of postthrombotic syndrome (PTS). METHODS: At the outpatient clinic of the Maastricht University Medical Centre, 125 consecutive patients with confirmed proximal DVT were followed for 2 years. Villalta scores were assessed on four consecutive visits; 3, 6, 12, and 24 months after the acute event. Reflux was assessed once by duplex testing. After 6 months, patients with scores

Different risk of deep vein thrombosis and pulmonary embolism in carriers with factor V Leiden compared with non-carriers, but not in other thrombophilic defects. Results from a large retrospective family cohort study.

The term factor V Leiden (FVL) paradox is used to describe the different risk of deep vein thrombosis and pulmonary embolism that has been found in carriers of FVL. In a thrombophilic family-cohort, we estimated differences in absolute risks of deep vein thrombosis and pulmonary embolism for various thrombophilic defects. Of 2,054 relatives, 1,131 were female, 41 had pulmonary embolism and 126 deep vein thrombosis. Annual incidence for deep vein thrombosis in non-carriers of FVL was 0.19% (95%CI, 0.16-0.23), and 0.41% (95%CI, 0.28-0.58) in carriers; relative risk (RR) 2.1 (95%CI, 1.4-3.2). For pulmonary embolism these incidences were similar in carriers and non-carriers 0.07%, respectively; RR 1.0 (95% CI, 0.4-2.5). When co-inheritance of other thrombophilic defects was excluded the RR for deep vein thrombosis in FVL carriers was 7.0 (95%CI, 2.3-21.7) compared to non-carriers and 2.8 (95%CI, 0.5-14.4) for pulmonary embolism. For other thrombophilic defects no such effect was observed. Thus the FVL paradox was confirmed in our study. However, a similar paradox in carriers of other thrombophilic defects was not observed.

Activated protein C protects against myocardial ischemia/ reperfusion injury via inhibition of apoptosis and inflammation.

OBJECTIVE: In spite of major advances in reperfusion therapy for patients presenting with acute coronary syndrome, long-term morbidity is still substantial. A limitation of initial treatment of myocardial ischemia is the lack of prevention of ischemia/reperfusion (I/R) injury. Activated protein C (APC), a crucial mediator in the coagulation process, plays a prominent role in the crosstalk between coagulation and inflammation and provides cytoprotective effects via inhibition of apoptosis and inflammation in several human and animal studies. METHODS AND RESULTS: APC was administered in an animal model for myocardial I/R. APC largely inhibited early myocardial I/R injury after varying reperfusion times, an effect that was absent on administration of heparin, a nonspecific anticoagulant agent. The protective effects of APC were absent in case of absence or blockade of protease activated receptor-1 (PAR-1), indicating a critical role for PAR-1 in this process. Furthermore, we showed a strong antiapoptotic effect of APC in the early phase of reperfusion combined with an antiinflammatory effect at an early stage (IL-6), as well as at a later stage (leukocyte infiltration). CONCLUSIONS: APC exerts strong protective effects on early myocardial I/R injury, primarily via inhibition of apoptosis and inflammation, which are regulated via PAR-1.

Monitoring thrombin generation: is addition of corn trypsin inhibitor needed?

Thrombin generation monitoring has the potential to be used as a clinical diagnostic tool in the near future. However, robust preanalytical conditions may be required, and one factor that has been reported is in-vitro contact activation that might influence in-vitro measurements of thrombin generation and thereby act as an unpredictable pre-analytical variable. The aim of the current study was to investigate the influence of contact activation and the necessity of corn trypsin inhibitor (CTI) to abolish contact activation in thrombin generation measurements at low tissue factor (TF) concentrations. Thrombin generation was performed using the calibrated automated thrombinoscopy (CAT), thereby determining the endogenous thrombin potential (ETP), peak height, and the lag time, in plasma obtained from healthy volunteers. Addition of CTI after plasma preparation had no significant influence on thrombin generation triggered with 0.5 pM TF or higher, as demonstrated by unaltered ETP and lag time values between analyses with and without CTI. Addition of CTI before blood collection reduced thrombin generation triggered with 0.5 pM TF: both the ETP and peak height were significantly reduced compared to no CTI addition. In contrast, thrombin generation remained unaltered at a 1 pM TF trigger or above. This study demonstrates that addition of CTI after plasma separation is not necessary when triggering with TF concentrations of 0.5 pM and higher. Furthermore, it was demonstrated that it is not needed to pre-fill blood collecting tubes with CTI when measuring thrombin generation at TF concentrations of >/=1 pM.

Absolute risk of venous and arterial thromboembolism in thrombophilic families is not increased by high thrombin-activatable fibrinolysis inhibitor (TAFI) levels.

High levels of thrombin-activatable fibrinolysis inhibitor (TAFI) are a supposed risk factor for thrombosis. However, results from previous studies are conflicting. We assessed the absolute risk of venous and arterial thromboembolism in subjects with high TAFI levels (>126 U/dl) versus subjects with normal levels, and the contribution of other concomitant thrombophilic defects. Relatives from four identical cohort studies in families with either deficiencies of antithrombin, protein C or protein S, prothrombin 20210A, high factor VIII levels, or hyperhomocysteinemia were pooled. Probands were excluded. Of 1,940 relatives, 187 had high TAFI levels. Annual incidences of venous thromboembolism were 0.23% in relatives with high TAFI levels versus 0.26% in relatives with normal TAFI levels (adjusted relative risk [RR] 0.8; 95% confidence interval [CI], 0.5-1.3). For arterial thrombosis these were 0.31% versus 0.23% (adjusted RR 1.4; 95% CI, 0.9-2.2). High levels of factor VIII, IX and XI were observed more frequently in relatives with high TAFI levels. Only high factor VIII levels were associated with an increased risk of venous and arterial thrombosis, independently of TAFI levels. None of these concomitant defects showed interaction with high TAFI levels. High TAFI levels were not associated with an increased risk of venous and arterial thromboembolism in thrombophilic families.

Thrombin generation in patients after acute deep-vein thrombosis.

Thrombin generation measurement may be of value for assessing the risk of venous thromboembolism, but its long term profile has not been assessed in patients. We evaluated thrombin generation by Calibrated Automated Thrombogram (CAT) in plasma during follow up of 104 consecutive patients after an acute episode of deep venous thrombosis. Blood was drawn three times over the course of 24 months. Thrombin generation was measured in absence and presence of thrombomodulin and compared to a reference range derived from thrombin generation curves in 137 healthy volunteers. Thrombin generation of patients showed significantly higher endogenous thrombin potential (ETP) and peak height compared to the reference population. Differences were more pronounced in assays triggered with 1 pM TF. Inhibition by thrombomodulin was attenuated in patients off anticoagulants as compared to the reference population (21% vs. 42.2%, p < 0.0001); inhibition in patients on anticoagulant treatment was less pronounced (9.7%, p < 0.0001). Protein C activity, protein S antigen as well as free protein S showed highly negative correlation with ETP in all patients. A significant negative relation was found between FVIII levels and thrombomodulin induced reduction of ETP and peak height. In conclusion, thrombin generation by CAT reflects changes in coagulation status in patients following a thromboembolic event and is most sensitive at CAT analysis triggered with 1 pM TF. A role for factor VIII as an important attributable cause of hypercoagulability is reflected by the reduced inhibitory effect of thrombomodulin at high factor VIII levels.