Addendum to “on the measurability of a function which occurs in a paper by A. C. Zaanen”

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. (Blood. 2011;118(8):2055-2061

A prothrombinase-based assay for detection of resistance to activated protein C

In this paper we present a new method for the detection of resistance to activated protein C (APC) that is based on direct measurement of the effect of APC an the cofactor activity of plasma factor Va. The factor V present in a diluted plasma sample was activated with thrombin and its sensitivity towards APC was subsequently determined by incubation with phospholipids and APC; The loss of factor Va cofactor activity was quantified in a prothrombinase system containing purified prothrombin. factor Xa and phospholipid vesicles and using a chromogenic assay for quantitation of thrombin formation. The reaction conditions were optimized in order to distinguish normal, heterozygous and homozygous APC-resistant plasmas. Maximal differences in the response of these plasmas towards ATC were observed when factor Va was inactivated by APC in the absence of protein S and when the: cofactor activity of factor Va was determined at a low factor Xa concentration (0.3 nM).Addition of 0.2 nM APC and 20 mu M phospholipid vesicles to a 1000-fold diluted sample of thrombin-activated normal plasma resulted in loss of mon than 85% of the cofactor activity factor Va within 6 min. Under the same conditions, APC inactivated similar to 60% and similar to 20% of the factor Va present in plasma samples from APC-resistant individuals that were heterozygous or homozygous for the mutation Arg(506)-->Gln in factor V, respectively. Discrimination between the plasma samples from normal and heterozygous and homozygous APC-resistant individuals was facilitated by introduction of the so-called APC-sensitivity ratio (APC-sr). The APC-sr was defined as the ratio of the factor Va cofactor activities determined in thrombin-activated plasma samples after 6 min incubation with or without 0.2 nM APC and was multiplied by as 100 to obtain integers (APC-sr = {factor Va(+APC)/factor Va(-APC)} x 100). Clear differences were observed between the APC-sr of plasmas from normal healthy volunteers (APC-sr: 8-20, n = 33) and from individuals that were heterozygous (APC-sr: 35-50, n = 17) or homozygous APC resistant (APC-sr: 82-88, n = 7). There was no mutual overlap between the APC-sr of normal plasmas and plasmas from heterozygous or homozygous APC resistant individuals (p < 0.0001), In all cases our test gave the same result as the DNA-based assay. Since the test is performed on a highly diluted plasma sample there is no interference by conditions that affect APC resistance tests that are based on clotting time determinations (e.g. coagulation factor deficiencies, oral anticoagulation, heparin treatment. the presence of lupus anticoagulants, pregnancy or the use of oral contraceptives). Furthermore, we show that part of the factor Va assay can be performed on an autoanalyzer which increases the number of plasma samples that can be handled simultaneously

Characterization of AIM2 DNA-Binding Properties and Filament Formation

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 202 1 OA, high factorVIII levels, or hyperhomocysteinemia were pooled. Probands were excluded. Of 1,940 relatives, 187 had high TAR levels. Annual incidences of venous thromboembolism were 0.23% in relatives with highTAFI levels versus 0.26% in relatives with normal TAFI levels (adjusted relative risk [RR] 0.8; 95% confidence interval [0], 0.5-1.3). For arterial thrombosis these were 0.3 1 % versus 0.23% (adjusted RR 1.4; 95% Cl, 0.9-2.2). High levels of factor VIII, IX and XI were observed more frequently in relatives with high TAR levels. Only high factor VIII levels were associated with an increased risk of venous and arterial thrombosis, independently of TAR levels. None of these concomitant defects showed interaction with high TAR levels. High TAR levels were not associated with an increased risk of venous and arterial thromboembolism in thrombophilic families

Congenital Thrombophilia and Central Venous Catheter-Related Thrombosis in Patients With Cancer

Central venous catheter (CVC)-related thrombosis is a frequently occurring complication and may cause significant morbidity in patients with cancer. The aim of this review is to discuss the main studies that examined whether a state of thrombophilia increases the risk of CVC-related thrombosis in patients with cancer. The studies were retrieved by an extensive Medline search. Patients with cancer with a CVC and a factor V Leiden mutation have a higher risk of developing CVC-related thrombosis than patients with cancer having a CVC without the mutation. The scarce information available suggests hyperhomocysteinemia to be a risk factor for CVC-related thrombosis. For other congenital thrombophilia factors, the available data are too limited to allow for any definitive conclusions to be made. Because the clinical implications of all these findings remain to be clarified, routine screening of patients with cancer having a CVC for thrombophilia cannot yet be recommended on the basis of the studies discussed

A new method to determine tissue specific tissue factor thrombomodulin activities: endotoxin and particulate air pollution induced disbalance.

ABSTRACT: BACKGROUND: Increase in tissue factor (TF) and loss in thrombomodulin (TM) antigen levels has been described in various inflammatory disorders. The functional consequences of such changes in antigen concentrations in the coagulation balance are, however, not known. This study was designed to assess the consequences of inflammation-driven organ specific functional properties of the procoagulant response. METHODS: Tissue specific procoagulant activity was assessed by adding tissue homogenate to normal human pool plasma and recording of the thrombin generation curve. The new technique was subsequently applied on two inflammation driven animal models: 1) mouse lipopolysaccharide (LPS) induced endotoxemia and 2) spontaneously hypertensive rats exposed to environmental air pollution (particulate matter (PM). RESULTS: Addition of lung tissue from untreated animals to human plasma suppressed the endogenous thrombin potential (ETP) (175 +/- 61 vs. 1437 +/- 112 nM.min for control). This inhibitory effect was due to TM, because a) it was absent in protein C deficient plasma and b) lungs from TMpro/pro mice allowed full thrombin generation (ETP: 1686 +/- 209 nM.min). The inhibitory effect of TM was lost after LPS administration to mice, which induced TF activity in lungs of C57Bl/6 mice as well as increased the ETP (941 +/- 523 vs. 194 +/- 159 nM.min for control). Another pro-inflammatory stimulus, PM dose-dependently increased TF in the lungs of spontaneously hypertensive rats at 4 and 48 hours after PM exposure. The ETP increased up to 48 hours at the highest concentration of PM (1441 +/- 289 nM.min vs. saline: 164 +/- 64 nM.min, p < 0.0001), suggesting a concentration- and time dependent reduction in TM activity. CONCLUSION: Inflammation associated procoagulant effects in tissues are dependent on variations in activity of the TF-TM balance. The application of these novel organ specific functional assays is a useful tool to monitor inflammation-driven shifts in the coagulation balance within animal or human tissues

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

ObjectiveWe 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).MethodsAt 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 ≤4 on the Villalta clinical score and in the absence of reflux were allowed to discontinue ECS therapy. If reflux was present, two consecutive scores ≤4 were needed to discontinue ECS therapy.ResultsECS therapy was discontinued in 17% of patients at 6 months, in 48% at 12 months, and in 50% at 24 months. Reflux on duplex testing was present in 74/101 (73.3%) tested patients and was not associated with the onset of PTS. At the 6-month visit, the cumulative incidence of PTS was 13.3%, at 12 months 17.0%, and at 24 months 21.1%. Varicosities/venous insufficiency (present at baseline) was significantly associated with PTS; hazard ratio 3.2 (1.2-9.1).ConclusionsPatients with a low probability for developing PTS can be identified as early as 6 months after the thrombotic event, and individualized shortened duration of ECS therapy based on Villalta clinical scores may be a safe management option. These findings need to be confirmed in a randomized clinical trial

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

<p>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.</p>