Harmonizing light transmission aggregometry in the Netherlands by implementation of the SSC-ISTH guideline.

Light transmission aggregometry (LTA) is considered the gold standard method for evaluation of platelet function. However, there are a lot of variation in protocols (pre-analytical procedures and agonist concentrations) and results. The aim of our study was to establish a national LTA protocol, to investigate the effect of standardization and to define national reference values for LTA. The SSC guideline was used as base for a national procedure. Almost all recommendations of the SSC were followed e.g. no adjustment of PRP, citrate concentration of 109 mM, 21 needle gauge, fasting, resting time for whole blood and PRP, centrifugation time, speed and agonists concentrations. LTA of healthy volunteers was measured in a total of 16 hospitals with 5 hospitals before and after standardization. Results of more than 120 healthy volunteers (maximum aggregation %) were collected, with participating laboratories using 4 different analyzers with different reagents. Use of low agonist concentrations showed high variation before and after standardization, with the exception of collagen. For most high agonist concentrations (ADP, collagen, ristocetin, epinephrine and arachidonic acid) variability in healthy subjects decreased after standardization. We can conclude that a standardized Dutch protocol for LTA, based on the SSC guideline, does not result in smaller variability in healthy volunteers for all agonist concentrations.

Monitoring of tobramycin serum concentrations in selected critically ill patients receiving selective decontamination of the digestive tract: a retrospective evaluation.

INTRODUCTION: Selective decontamination of the digestive tract (SDD) is a strategy in mechanically ventilated patients to reduce mortality. Treatment consists of enterally administered non-absorbable antibiotics, i.e., tobramycin. However, most intensive care unit (ICU) patients with SDD appear to have detectable tobramycin serum concentrations. The Rijnstate Hospital implemented a protocol for therapeutic drug monitoring (TDM) of tobramycin in patients at risk. The aim of this study was to evaluate the necessity of TDM in these patients and to optimize the current protocol. METHODS: This retrospective observational study included ICU patients with SDD treatment for ≥ 7 days and renal failure. These patients were considered eligible for monitoring of tobramycin. Tobramycin serum concentrations, relevant laboratory parameters (i.e., renal function, lactate), and patient data were extracted from the National Intensive Care Evaluation database and the hospital electronic patient data system. RESULTS: In 23 subjects, a total of 43 tobramycin serum concentrations was determined. The median tobramycin serum concentration was 0.33 (IQR 0.17-0.49) mg/L of which 12 (27.9%) samples had concentrations < 0.2 mg/L, 30 (69.8%) had concentrations 0.2-1.0 mg/L and 1 (2.3%) had a toxic concentration > 1.0 mg/L. In 3 (7.0%) cases, an intervention was conducted based on the tobramycin serum concentration. CONCLUSION: The majority (83.7%) of samples had detectable tobramycin serum concentrations. Monitoring of tobramycin serum concentrations can be considered necessary in patients at risk. However, the current protocol should be optimized to intercept patients more precise.

[Hypernatremia caused by treatment with GHB obtained via a doctor's prescription]. / Hypernatriëmie door GHB op doktersrecept.

In the last few years, gamma hydroxybutyric acid (GHB) has been used increasingly as a party drug; this has led to a marked increase in the number of requests for professional help with the treatment of GHB addiction. Pharmaceutical GHB (sodium oxybate, the sodium-salt of GHB), registered for cataplexia in narcolepsy patients, is used off-label to treat the withdrawal symptoms associated with GHB addiction. Pharmaceutical GHB has a high sodium load. In this report we present the cases of two patients who developed symptomatic hypernatremia following treatment with pharmaceutical GHB and who thereafter needed intensive care for the severe withdrawal symptoms that they experienced.

Side effects of desmopressin in patients with bleeding disorders.

INTRODUCTION: Desmopressin is frequently used in patients with bleeding disorders because of its prohaemostatic effects. In recent years desmopressin use increased due to reported high incidence of inhibitors in mild haemophilia after clotting factor infusion and the rising costs of clotting factor concentrates. The safety and frequency of side effects have hardly been assessed in well-designed studies. AIM: We therefore prospectively evaluated side effects of desmopressin in a large unselected cohort of bleeding disorder patients, who received a desmopressin test dose. METHODS: Blood was drawn prior to, one, three, six and 24 h after desmopressin. Primary outcome was change in serum sodium, haematocrit, serum- and urine osmolality, body weight and vital signs. Self-reported side effects were evaluated as secondary outcome. RESULTS: In total, 108 patients were included, median age 30 years, the majority of whom had von Willebrand disease type 1 (76%). A significant change in water balance parameters was observed. Four patients (4%) had hyponatraemia (≤135 mmol L(-1) ) after 24 h but no severe hyponatraemia occurred (≤125 mmol L(-1) ). After infusion, 41 (38%) patients were hypotensive (≤90 mmHg SBP and/or ≤60 mmHg DBP) and 10 (9%) presented with tachycardia (>100 min(-1) ). However, none of these effects sustained at 24 h. Infusion was discontinued in one patient because of tachycardia, nausea and malaise. Self-reported side effects included: headache, fatigue, flush and dizziness. CONCLUSION: Observed side effects correspond with the known antidiuretic and vasomotor effects of desmopressin. Changes in parameters were temporary and not clinically relevant. In conclusion, our study supports desmopressin use as a safe treatment option in patients with various bleeding disorders.

Full regeneration of segmental bone defects using porous titanium implants loaded with BMP-2 containing fibrin gels.

Regeneration of load-bearing segmental bone defects is a major challenge in trauma and orthopaedic surgery. The ideal bone graft substitute is a biomaterial that provides immediate mechanical stability, while stimulating bone regeneration to completely bridge defects over a short period. Therefore, selective laser melted porous titanium, designed and fine-tuned to tolerate full load-bearing, was filled with a physiologically concentrated fibrin gel loaded with bone morphogenetic protein-2 (BMP-2). This biomaterial was used to graft critical-sized segmental femoral bone defects in rats. As a control, porous titanium implants were either left empty or filled with a fibrin gels without BMP-2. We evaluated bone regeneration, bone quality and mechanical strength of grafted femora using in vivo and ex vivo µCT scanning, histology, and torsion testing. This biomaterial completely regenerated and bridged the critical-sized bone defects within eight weeks. After twelve weeks, femora were anatomically re-shaped and revealed open medullary cavities. More importantly, new bone was formed throughout the entire porous titanium implants and grafted femora regained more than their innate mechanical stability: torsional strength exceeded twice their original strength. In conclusion, combining porous titanium implants with a physiologically concentrated fibrin gels loaded with BMP-2 improved bone regeneration in load-bearing segmental defects. This material combination now awaits its evaluation in larger animal models to show its suitability for grafting load-bearing defects in trauma and orthopaedic surgery.

Presence of procoagulant peripheral blood mononuclear cells in severe COVID-19 patients relate to ventilation perfusion mismatch and precede pulmonary embolism.

PURPOSE: Pulmonary emboli (PE) contribute substantially to coronavirus disease 2019 (COVID-19) related mortality and morbidity. Immune cell-mediated hyperinflammation drives the procoagulant state in COVID-19 patients, resulting in immunothrombosis. To study the role of peripheral blood mononuclear cells (PBMC) in the procoagulant state of COVID-19 patients, we performed a functional bioassay and related outcomes to the occurrence of PE. Secondary aims were to relate this functional assay to plasma D-dimer levels, ventilation perfusion mismatch and TF expression on monocyte subsets. METHODS: PBMC from an ICU biobank were obtained from 20 patients with a computed tomography angiograph (CTA) proven PE and compared to 15 COVID-19 controls without a proven PE. Functional procoagulant properties of PBMC were measured using a modified fibrin generation time (MC-FGT) assay. Tissue factor (TF) expression on monocyte subsets were measured by flow cytometry. Additional clinical data were obtained from patient records including end-tidal to arterial carbon dioxide gradient. RESULTS: MC-FGT levels were highest in the samples taken closest to the PE detection, similar to the end-tidal to arterial carbon dioxide gradient (ETCO2 - PaCO2), a measurement to quantify ventilation-perfusion mismatch. In patients without proven PE, peak MC-FGT relates to an increase in end-tidal to arterial carbon dioxide gradient. We identified non-classical, CD16 positive monocytes as the subset with increased TF expression. CONCLUSION: We show that the procoagulant state of PBMC could aid in early detection of PE in COVID-19 ICU patients. Combined with end-tidal to ETCO2 - PaCO2 gradient, these tests could improve early detection of PE on the ICU.

Metabolic syndrome detection with biomarkers in childhood cancer survivors.

PURPOSE: Augmented survival of childhood nephroblastoma and neuroblastoma has increased long-term side effects such as metabolic syndrome (MetS). Risk stratification is difficult after abdominal radiation because waist circumference underestimates adiposity. We aimed to develop a strategy for determining MetS in irradiated survivors using an integrated biomarker profile and vascular ultrasonography. METHODS: The NCEP-ATPIII MetS-components, 14 additional serum biomarkers and 9 vascular measurements were assessed in a single-centre cohort of childhood nephroblastoma (n = 67) and neuroblastoma (n = 36) survivors and controls (n = 61). Multivariable regression models were used to study treatment effects. Principal component analysis (PCA) was used to study all biomarkers in a combined analysis, to identify patterns and correlations. RESULTS: After 27.5 years of follow-up, MetS occurred more often in survivors (14%) than controls (3%). Abdominal radiotherapy and nephrectomy, to a lesser extent, were associated with MetS and separate components and with several biomarker abnormalities. PCA of biomarkers revealed a pattern on PC1 from favourable lipid markers (HDL-cholesterol, adiponectin) towards unfavourable markers (triglycerides, LDL-cholesterol, apoB, uric acid). Abdominal radiotherapy was associated with the unfavourable biomarker profile (ß = 1.45, P = 0.001). Vascular measurements were not of added diagnostic value. CONCLUSIONS: Long-term childhood nephro- and neuroblastoma survivors frequently develop MetS. Additional assessment of biomarkers identified in PCA - adiponectin, LDL, apoB, and uric acid - may be used especially in abdominally irradiated survivors, to classify MetS as alternative for waist circumference. Vascular ultrasonography was not of added value.

The rationale and design of the PERindopril GENEtic association study (PERGENE): a pharmacogenetic analysis of angiotensin-converting enzyme inhibitor therapy in patients with stable coronary artery disease.

BACKGROUND: Angiotensin-converting enzyme (ACE) inhibitors reduce clinical symptoms and improve outcome in patients with hypertension, heart failure, and stable coronary artery disease (CAD) and are among the most frequently used drugs in these patient groups. For hypertension, treatment is guided by the level of blood pressure. In the secondary prevention setting, there are no means of guiding therapy. Prior attempts to target ACE-inhibitors to those patients that are most likely to benefit have not been successful, mainly due to the consistency in the treatment effect in clinical subgroups. Still, for prolonged prophylactic treatment with ACE-inhibitors it would be best to target treatment to only those patients most likely to benefit, which would considerably lower the number needed to treat and increase cost-effectiveness. A new approach for such "tailored-therapy" may be to integrate information on the genetic variation between patients. Until now, pharmacogenetic research of the efficacy of ACE-inhibitor therapy in CAD patients is still in a preliminary stage. METHODS: The PERindopril GENEtic association study (PERGENE) is a substudy of the EUROPA trial, a randomized double-blind placebo-controlled multicentre clinical trial which demonstrated a beneficial effect of the ACE-inhibitor perindopril in reducing cardiovascular morbidity and mortality in 12.218 patients with stable coronary artery disease (mean follow-up 4.2 years). Blood tubes were received from patients at the beginning of the EUROPA trial and buffy coats were stored at -40 degrees C at the central core laboratory. Candidate genes were selected in the renin-angiotensin-system and bradykinin pathways. Polymorphisms were selected based on haplotype tagging principles using the HapMap genome project, Seattle and other up-to-date genetic database platforms to comprehensively cover all common genetic variation within the genes. Selection also took into consideration the functionality of SNP's, location within the gene (promoter) and existing relevant literature. The main outcome measure of PERGENE is the effect of genetic factors on the treatment benefit with ACE-inhibitors. The size of this pharmacogenetic substudy allows detection with a statistical power of 98% to detect a difference in hazard ratios (treatment effect) of 20% between genotypes with minor allele frequency of 0.20 (two-sided alpha 0.05). CONCLUSION: The PERGENE study is a large cardiovascular pharmacogenetic study aimed to assess the feasibility of pharmacogenetic profiling of the treatment effect of ACE-inhibitor use with the perspective to individualize treatment in patients with stable coronary artery disease.

Association between fibrinogen and fibrinogen γ' and atherosclerotic plaque morphology and composition in symptomatic carotid artery stenosis: Plaque-At-RISK study.

INTRODUCTION: Von Willebrand Factor (VWF), ADAMTS13, fibrinogen and fibrinogen γ' are associated with an increased risk of ischemic stroke. Carotid atherosclerosis is an important risk factor for ischemic stroke. Characteristics of the vulnerable plaque; intraplaque hemorrhage (IPH), plaque ulceration and lipid-rich necrotic core (LRNC) can be visualized with imaging techniques. Since atherosclerosis might attribute to the association between coagulation factors and ischemic stroke risk, the aim of this study is to investigate the association between coagulation factors and atherosclerotic plaque characteristics in more detail. MATERIALS AND METHODS: In 182 patients of the Plaque-At-RISK study (prospective multicenter cohort study) with a recent transient ischemic attack (TIA) or ischemic stroke and a symptomatic mild-to-moderate carotid artery stenosis, we measured VWF antigen (VWF:Ag), ADAMTS13 activity, fibrinogen (Clauss), and fibrinogen γ'. Presence of plaque ulceration, IPH volume and LRNC volume were determined by Multidetector-Row Computed Tomography (MDCTA, n = 160) and Magnetic Resonance Imaging (MRI, n = 172). Linear regression analysis was used to assess the association between imaging biomarkers and coagulation factors. RESULTS: VWF:Ag or ADAMTS13 levels were not significantly associated with plaque ulceration, IPH and LRNC. We found an inverse association between fibrinogen and fibrinogen γ' and IPH volume (B = -23.40 mm3/g/L, p = 0.01 and B = -161.73 mm3/g/L, p = 0.01) and between fibrinogen and fibrinogen γ' and LRNC volume (B = -38.89 mm3 g/L, p < 0.01 and B = -227.06 mm3 g/L, p = 0.01). Additional adjustments for C-reactive protein (CRP) did not change the results. CONCLUSIONS: Fibrinogen and fibrinogen γ' are inversely associated with IPH volume and LRNC volume, independent of inflammation. CLINICAL TRIAL REGISTRATION: clinicaltrials.govNCT01208025.

Prospective evaluation of coagulopathy in multiple myeloma patients before, during and after various chemotherapeutic regimens.

BACKGROUND: Venous thromboembolism (VTE) occurs frequently in multiple myeloma patients, especially during induction treatment with thalidomide in combination with anthracyclines and/or dexamethasone. Several coagulation abnormalities have been described in untreated myeloma patients, but these have not been prospectively evaluated during and after treatment. PATIENTS AND METHODS: We performed a prospective study in 138 multiple myeloma patients in whom coagulation factor levels were evaluated longitudinally before, during induction and after intensification. Patients were randomized to induction treatment consisting of adriamycin and dexamethason, in combination with either vincristin (VAD), thalidomide (TAD), or bortezomib (PAD) followed by high-dose melphalan (HDM) and autologous stem cell transplant (ASCT). RESULTS: Factor VIII:C (FVIII:C) and von Willebrand factor (VWF) were significantly elevated before treatment (median FVIII:C 2.26U/ml, VWF:Ag 1.95 U/ml). Irrespective of the type of induction regimen, these variables increased strongly during induction therapy (FVIII:C 2.55 U/ml and VWF:Ag 2.96 U/ml). Fibrinogen also showed a significant increase after induction therapy (3.5 g/l pre-treatment and 4.0 g/l after treatment, respectively, P<0.001). This was significantly higher in TAD than VAD treated patients. Three to six month after ASCT levels of VWF and FVIII:C had decreased to values lower than observed before treatment (1.71 and 1.67 U/ml respectively). There was no correlation between the increased levels at start and the response of multiple myeloma to treatment. High levels of VWF, fibrinogen and FVIII:C before start of treatment were significantly associated with mortality. Fourteen patients (10%) developed a venous thrombotic event (VTE). The coagulation factor abnormalities before and during treatment were not associated with the development of VTE. CONCLUSION: During induction treatment several changes in coagulation factor levels are observed, which may result in a prothrombotic state. Larger studies are required to establish whether the changes in these coagulation factors during induction treatment contribute to the increased risk of venous thromboembolism in multiple myeloma patients.

Haplotypes of the fibrinogen gene and cerebral small vessel disease: the Rotterdam scan study.

OBJECTIVE: Fibrinogen levels and fibrinogen clot structure have been implicated in the pathogenesis of vascular disease. We examined fibrinogen levels and variation in fibrinogen genes (fibrinogen gamma (FGG), alpha (FGA) and beta (FGB)), which have been associated with fibrin clot structure and fibrinogen levels, in relation to cerebral small vessel disease (SVD). METHODS AND RESULTS: This study was performed as part of the Rotterdam Scan Study, a population based study in 1077 elderly patients undergoing cerebral MRI. Plasma fibrinogen levels and haplotypes were determined. We examined the association between fibrinogen levels and haplotype with silent brain infarcts and white matter lesions using logistic regression models. We constructed seven haplotypes (frequency >0.01) that describe the total common variation in the FGG and FGA genes. Haplotype 2 (GATAGTG) was associated with the presence of silent brain infarcts compared with the most frequent haplotype (GGTGGTA) (OR 1.41, 95% CI 1.03 to 1.94). Haplotype 3 (GGCGATA) was associated with periventricular white matter lesions in the highest tertile of the distribution (OR 1.40, 95% CI 1.01 to 1.92). No association was found between plasma fibrinogen levels and SVD. CONCLUSIONS: Our study provides evidence for an association of common variation in the FGG and FGA genes with cerebral SVD. It is possible that the structure of the fibrin clot rather than plasma fibrinogen levels plays a role in the pathogenesis of cerebral SVD.

Low protein Z levels but not the protein Z gene G79A polymorphism are a risk factor for ischemic stroke.

BACKGROUND: Protein Z (PZ) is a vitamin K-dependent plasma protein that plays a role in both pro-and anticoagulant pathways, but its exact physiological function remains unclear. The aim of this study was to determine the association between the G79A PZ gene polymorphism in intron F, PZ levels and the occurrence of ischemic stroke. METHODS: We performed a case-control study in 118 Caucasian patients with first ever ischemic stroke or TIA confirmed by CT, and 113 age-and sex-matched population controls. Venous blood samples for PZ levels were collected 7 to 14 days and 3 months after stroke onset. Estimates of relative risk (odds ratios) were adjusted for vascular risk factors. RESULTS: The adjusted relative risk of ischemic stroke associated with PZ levels in the lowest quartile versus the highest quartile was 3.0 (95% CI: 1.1-8.7) at 7-14 days, and 5.1 (95% CI: 1.2-21.9) at 3 months after the stroke. PZ levels in the convalescent sample were significantly lower than in the acute sample. In the convalescent sample, odds ratios increased with lower quartiles of protein Z level (test for trend p=0.02). Thirty-nine patients (33%) and 32 (28%) controls were heterozygous for the G79A PZ gene polymorphism and 4 (3%) patients and 4 (4%) controls had the AA-genotype. The PZ levels were significantly lower in subjects with the AA-genotype and intermediate in heterozygote subjects. The odds ratio of ischemic stroke associated with A-allele carriers versus GG-homozygotes was 1.2 (95% CI: 0.7-2.1). CONCLUSION: No association between the G79A PZ gene polymorphism and the occurrence of stroke was observed. However, low PZ levels are independently associated with an increased risk of ischemic stroke.

Clinically relevant differences between assays for von Willebrand factor activity.

Essentials It is unclear whether there are differences between von Willebrand factor (VWF) activity assays. We compared the four most used VWF activity assays in 661 von Willebrand disease (VWD) patients. All assays correlated excellently, but a discrepant classification was seen in 20% of patients. Differences between VWF activity assays have a large impact on the classification of VWD. SUMMARY: Background Measuring the ability of von Willebrand factor (VWF) to bind to platelets is crucial for the diagnosis and classification of von Willebrand disease (VWD). Several assays that measure this VWF activity using different principles are available, but the clinical relevance of different assay principles is unclear. Objective To compare the four most widely used VWF activity assays in a large VWD patient population. Methods We measured VWF:RCo (ristocetin to activate VWF + whole platelets), VWF:GPIbR (ristocetin + platelet glycoprotein Ib receptor [GPIb] fragments), VWF:GPIbM (gain-of-function GPIb fragments that bind VWF spontaneously without ristocetin) and VWF:Ab (monoclonal antibody directed against the GPIb binding epitope of VWF to mimic platelets) in 661 VWD patients from the nationwide 'Willebrand in the Netherlands' (WiN) Study. Results All assays correlated excellently (Pearson r > 0.9), but discrepant results led to a different classification for up to one-fifth of VWD patients. VWF:RCo was not sensitive enough to classify 18% of patients and misclassified half of genotypic 2B VWD patients, especially those with p.Arg1306Trp. VWF:GPIbR was more sensitive, accurately classified the vast majority of patients, and was unaffected by the p.Asp1472His variant that causes artificially low VWF:RCo. VWF:GPIbM was the most precise assay but misclassified over a quarter of genotypic 2A, 2B and 3 patients. VWF:Ab, often not considered an actual VWF activity assay, performed at least equally to the other assays with regard to accurate VWD classification. Conclusion Although the different VWF activity assays are often considered similar, differences between assays have a large impact on the classification of VWD.

Matrix metalloproteinase-9 gene -1562C/T polymorphism mitigates preeclampsia.

Although the aetiology of preeclampsia is unknown, there is substantial evidence that it finds its roots in abnormal placentation. Prerequisites for successful placentation include trophoblast invasion, degradation and remodelling of the uterine decidual extracellular matrix, and apoptosis without thrombosis. We tested this hypothesis by analysing the effect of functional polymorphisms in the genes coding for MMP9, MMP3 and annexin A5 on the risk of preeclampsia using a case-control design. In 163 women with preeclampsia and 163 controls we studied the association with polymorphisms in the MMP9 (-1562 C/T), MMP3 (-1612 5A/6A) and annexin A5 (-1 C/T) genes using logistic regression analysis. A lower prevalence of the rare T allele of the MMP9 (-1562 C/T) polymorphism in women with preeclampsia was found (odds ratio 0.48, 95% confidence interval 0.25-0.90). The distribution of the MMP3 (-1612 5A/6A) and annexin A5 (-1 C/T) gene polymorphisms were similar in cases and controls. Our results suggest that the MMP9-1562T allele is associated with a reduced risk of preeclampsia and therefore may protect against maladaptation of the spiral arteries and decreased decidual degradation. The elevated MMP9 concentrations reported to be associated with the -1562T allele might be essential for the development of an adequate maternal-fetal interface early in pregnancy by facilitating trophoblast apoptosis and degradation.

Monitoring of treatment with vitamin K antagonists: recombinant thromboplastins are more sensitive to factor VII than tissue-extract thromboplastins.

Essentials Differences in sensitivity to factor VII (FVII) have been suggested between thromboplastins. FVII-induced International Normalized Ratio (INR) changes differ between commercial reagents. Recombinant human thromboplastins are more sensitive to FVII than tissue-extract thromboplastins. Thromboplastin choice may affect FVII-mediated INR stability. SUMMARY: Background Differences regarding sensitivity to factor VII have been suggested for recombinant human and tissue-extract thromboplastins used for International Normalized Ratio (INR) measurement, but the evidence is scarce. Differences in FVII sensitivity are clinically relevant, as they can affect INR stability during treatment with vitamin K antagonists (VKAs). Objectives To determine whether commercial thromboplastins react differently to changes in FVII. Methods We studied the effect of addition of FVII on the INR in plasma by using three tissue-extract (Neoplastin C1+, Hepato Quick, and Thromborel S) and three recombinant human (Recombiplastin 2G, Innovin, and CoaguChek XS) thromboplastins. Three different concentrations of purified human FVII (0.006, 0.012 and 0.062 µg mL-1 plasma), or buffer, were added to five certified pooled plasmas of patients using VKAs (INR of 1.5-3.5). Changes in FVII activity were measured with two bioassays (Neoplastin and Recombiplastin), and relative INR changes were compared between reagents. Results After addition of 0.062 µg mL-1 FVII, FVII activity in the pooled plasmas increased by approximately 20% (Neoplastin) or 32% (Recombiplastin) relative to the activity in pooled normal plasma. All thromboplastins showed dose-dependent INR decreases. The relative INR change in the pooled plasmas significantly differed between the six thromboplastins. No differences were observed among recombinant or tissue-extract thromboplastins. Pooled results indicated that the FVII-induced INR change was greater for recombinant than for tissue-extract thromboplastins. Conclusions Differences regarding FVII sensitivity exist between various thromboplastins used for VKA monitoring. Recombinant human thromboplastins are more sensitive to FVII than tissue-extract thromboplastins. Therefore, thromboplastin choice may affect FVII-mediated INR stability.

Fibrin structure and wound healing.

Fibrinogen and fibrin play an important role in blood clotting, fibrinolysis, cellular and matrix interactions, inflammation, wound healing, angiogenesis, and neoplasia. The contribution of fibrin(ogen) to these processes largely depends not only on the characteristics of the fibrin(ogen) itself, but also on interactions between specific-binding sites on fibrin(ogen), pro-enzymes, clotting factors, enzyme inhibitors, and cell receptors. In this review, the molecular and cellular biology of fibrin(ogen) is reviewed in the context of cutaneous wound repair. The outcome of wound healing depends largely on the fibrin structure, such as the thickness of the fibers, the number of branch points, the porosity, and the permeability. The binding of fibrin(ogen) to hemostasis proteins and platelets as well as to several different cells such as endothelial cells, smooth muscle cells, fibroblasts, leukocytes, and keratinocytes is indispensable during the process of wound repair. High-molecular-weight and low-molecular-weight fibrinogen, two naturally occurring variants of fibrin, are important determinants of angiogenesis and differ in their cell growth stimulation, clotting rate, and fibrin polymerization characteristics. Fibrin sealants have been investigated as matrices to promote wound healing. These sealants may also be an ideal delivery vehicle to deliver extra cells for the treatment of chronic wounds.

Genetic influence on thrombotic risk markers in the elderly--a Danish twin study.

OBJECTIVE: Several hemostatic variables are identified as cardiovascular risk markers. In young and middle-aged individuals, plasma concentrations of these variables are partly determined by genetic factors. The genetic contribution to cardiovascular disease (CVD) decreases with increasing age, and it is therefore important to determine the heritability of hemostasis also in the elderly. METHODS: The heritability of plasma levels of factor VII, fibrinogen, tissue factor, tissue factor pathway inhibitor, von Willebrand factor, thrombin activatable fibrinolysis inhibitor (TAFI), and D-dimer was determined in 130 monozygotic and 155 dizygotic same-sex twin pairs, aged 73-94 years, who participated in the Longitudinal Study of Aging of Danish Twins. Furthermore, we determined the influence of promoter polymorphisms in corresponding genes on the plasma level variation. RESULTS: Genetic factors accounted for 33% (D-dimer) to 71% (TAFI) of the variation in plasma levels. Polymorphisms were associated with concentrations of FVII and TAFI in sib-pair based analyses, but in linkage analyses the polymorphisms did not explain a significant part of the genetic variation for any of the variables. CONCLUSIONS: Concentrations of hemostatic variables have a substantial genetic variation in the elderly, but in this study the promoter polymorphisms only explained a minimal part of this variation.

Molecular weight fibrinogen variants determine angiogenesis rate in a fibrin matrix in vitro and in vivo.

BACKGROUND: During wound repair, fibrin acts both as a barrier to prevent blood loss and as a temporary matrix for the invasion and ingrowth of endothelial and tissue cells. A well-controlled angiogenesis process in the fibrinous exudate matrix is crucial for optimal wound healing. The composition and structure of the fibrin matrix are important determinants of the invasion of endothelial cells and capillary-tube formation into the matrix. OBJECTIVE: Fibrinogen circulates in a high and low molecular weight form (HMW and LMW, respectively) and the purpose of this study was to investigate how fibrin matrices from these naturally occurring fibrinogen variants influence angiogenesis. Angiogenesis was studied using an in vitro model in which human microvascular endothelial cells (hMVEC) were cultured on three-dimensional fibrin matrices from different fibrinogen forms, and using two in vivo mouse models. RESULTS: The in vitro angiogenesis in an HMW-fibrin matrix shows increased cell and tubular structure ingrowth compared with unfractionated fibrin matrix (median increase 58%, range 46-234%). The ingrowth of tubular structures in an LMW-fibrin matrices is decreased when compared with unfractionated fibrin (median decrease 70%, range 67-100%). Similar results were observed for in vivo angiogenesis. CONCLUSIONS: The naturally occurring fibrinogen variants HMW- and LMW-fibrin modulate the angiogenic capacity of endothelial cells in fibrin matrices. The different effects of the molecular weight fibrinogen variants provide further insight in the matrix characteristics in angiogenesis and could possibly be applied in the context of tissue engineering and wound healing.

No effect of C-reactive protein on early atherosclerosis development in apolipoprotein E*3-leiden/human C-reactive protein transgenic mice.

OBJECTIVE: C-reactive protein (CRP) has been associated with risk of cardiovascular disease. It is not clear whether CRP is causally involved in the development of atherosclerosis. Mouse CRP is not expressed at high levels under normal conditions and increases in concentration only several-fold during an acute phase response. Because the dynamic range of human CRP is much larger, apolipoprotein E*3-Leiden (E3L) transgenic mice carrying the human CRP gene offer a unique model to study the role(s) of CRP in atherosclerosis development. METHODS AND RESULTS: Atherosclerosis development was studied in 15 male and 15 female E3L/CRP mice; E3L transgenic littermates were used as controls. The mice were fed a hypercholesterolemic diet to induce atherosclerosis development. Cholesterol exposure did not differ between E3L/CRP and E3L mice. Plasma CRP levels were on average 10.2+/-6.5 mg/L in male E3L/CRP mice, 0.2+/-0.1 mg/L in female E3L/CRP mice, and undetectable in E3L mice. Quantification of atherosclerosis showed that lesion area in E3L/CRP mice was not different from that in E3L mice. CONCLUSIONS: This study demonstrates that mildly elevated levels of CRP in plasma do not contribute to the development of early atherosclerosis in hypercholesterolemic E3L/CRP mice.

OC-10 - Disseminated intravascular coagulation at diagnosis strongly predicts both arterial and venous thrombosis in acute myeloid leukemia patients.

INTRODUCTION: Acute myeloid leukemia (AML) is associated with a slightly increased risk of VTE with an incidence of 1.7-8.9%, but only limited data are available. The mechanism of the occurrence of thrombosis in hematological disorders is still unresolved. Disseminated intravascular coagulation (DIC) is associated with VTE and bleeding in acute promyelocytic leukemia and acute lymphoblastic leukemia. Although DIC has also been reported in AML, no data exist on the relationship between DIC and VTE in AML patients. AIM: We hypothesized that the presence of DIC at diagnosis of AML may contribute to the risk of both venous and arterial thrombosis in AML. Therefore we studied a large cohort of adult patients with newly diagnosed AML aged <65 years by measuring DIC parameters at diagnosis prior to treatment and assessing the occurrence of both venous and arterial thrombosis during follow up. The findings of this study were validated in a second large cohort of patient with newly diagnosed AML aged >60 years. MATERIALS AND METHODS: In a prospective study we analysed markers of DIC and their association with the occurrence of thrombosis during follow up in a cohort of 272 young AML patients (aged 18-65) and a validation cohort of 132 elderly AML patients (aged >60) patients that were all treated with intensive chemotherapy. DIC parameters (fibrinogen, D-dimer, alpha-2-antiplasmin, antitrombin, prothrombin time and platelets) were measured at presentation with AML before start of induction chemotherapy. The DIC score according to the International Society of Thrombosis and Haemostasis DIC scoring systemwas calculated of all patients. RESULTS: The prevalence of thrombosis was 8.7% (4.7% venous, 4.0% arterial) in young patients over a median follow up of 478 days and 10.4% (4.4% venous, 5.9% arterial) in elderly patients. Most thrombotic events (66%) occurred before start of the second course of chemotherapy. The calculated DIC score significantly predicted venous and arterial thrombosis with a Hazard Ratio (HR) for a high DIC score (=>5) of 4.79 (1.71-13.45) in the cohort of young AML patients. These results were confirmed in our validation cohort of elderly AML patients. (HR 11.08 (3.23-38.06)). Of all DIC parameters D-dimer levels are most predictive for thrombosis with a HR of 12.3 (3.39-42.64) in the cohort of young AML patients and a HR of 7.82 (1.95-31.38) in the elderly cohort for a D-dimer >4.0 mg/L. CONCLUSIONS: It is concluded that both venous and arterial thrombosis occurs in around 10% of AML patients treated with intensive chemotherapy, which can be predicted by the presence of DIC, or individual DIC parameters at time of AML diagnosis.