Background Oral postmenopausal hormone therapy (HT) increases the risk of venous thrombosis (VT). We postulated that activated protein C (APC) resistance induced by HT is one of the mechanisms... Show moreBackground Oral postmenopausal hormone therapy (HT) increases the risk of venous thrombosis (VT). We postulated that activated protein C (APC) resistance induced by HT is one of the mechanisms causing VT, and also assessed the role of one of the main determinants of APC resistance (i.e., tissue factor pathway inhibitor [TFPI]).Methods We performed a nested case-control study embedded within two Women's Health Initiative hormone trials. Women were randomized to hormone therapy or placebo. Biomarkers were measured at baseline and after 1 year in 217 cases and 817 controls.Results Increased APC resistance and decreased TFPI at baseline were associated with VT (odds ratio 1.20-2.06). However, women with such prothrombotic profile at baseline did not have further increased risk of VT when randomized to HT compared with placebo. Although there was no change in APC resistance or TFPI in placebo group after 1 year, HT group showed prothrombotic changes in the biomarkers (i.e., an increase in APC resistance) (mean [standard deviation] 0.39 [0.54]) and decrease in TFPI (-0.21 [0.50]: free TFPI, -0.24 [0.22]: TFPI activity -0.22 [0.20]: total TFPI). However, HT induced prothrombotic change in biomarkers did not increase risk of VT.Conclusion Women with prothrombotic levels of APC resistance and TFPI at baseline were not at increased risk of VT when randomized to HT compared with placebo. This suggests that testing for these biomarkers before starting HT is not required. HT led to prothrombotic change in these biomarkers after one year, but this did not relate to increased risk of VT. Show less
Schmidt, D.E.; Heitink-Polle, K.M.J.; Mertens, B.; Porcelijn, L.; Kapur, R.; Schoot, C.E. van der; ... ; Haas, M. de 2021
Background In childhood immune thrombocytopenia (ITP), an autoimmune bleeding disorder, there is a need for better prediction of individual disease courses and treatment outcomes.Objective To... Show moreBackground In childhood immune thrombocytopenia (ITP), an autoimmune bleeding disorder, there is a need for better prediction of individual disease courses and treatment outcomes.Objective To predict the response to intravenous immunoglobulins (IVIg) and ITP disease course using genetic and immune markers.Methods Children aged younger than 7 years with newly diagnosed ITP (N = 147) from the Treatment With or Without IVIG for Kids with ITP study were included, which randomized children to an IVIg or observation group. A total of 46 variables were available: clinical characteristics, targeted genotyping, lymphocyte immune phenotyping, and platelet autoantibodies.Results In the treatment arm, 48/80 children (60%) showed a complete response (platelets >= 100 x 10(9)/L) that lasted for at least 1 month (complete sustained response [CSR]) and 32 exhibited no or a temporary response (absence of a sustained response [ASR]). For a biological risk score, five variables were selected by regularized logistic regression that predicted ASR vs CSR: (1) hemoglobin; (2) platelet count; (3) genetic polymorphisms of Fc-receptor (Fc gamma R) IIc; (4) the presence of immunoglobulin G (IgG) anti-platelet antibodies; and (5) preceding vaccination. The ASR sensitivity was 0.91 (95% confidence interval, 0.80-1.00) and specificity was 0.67 (95% confidence interval, 0.53-0.80). In the 67 patients of the observation arm, this biological score was also associated with recovery during 1 year of follow-up. The addition of the biological score to a predefined clinical score further improved the discrimination of favorable ITP disease courses.Conclusions The prediction of disease courses and IVIg treatment responses in ITP is improved by using both clinical and biological stratification. Show less
Huisman, M.V.; Levi, M.; Royen, E.A. van; Breederveld, C.; Buller, H.R.; Peters, M.; ... ; Agnelli, G. 2021
Background The transgender population that uses gender-affirming hormone therapy (GAHT) is rapidly growing. The (side) effects of GAHT are largely unknown. We examined the effect of GAHT on... Show moreBackground The transgender population that uses gender-affirming hormone therapy (GAHT) is rapidly growing. The (side) effects of GAHT are largely unknown. We examined the effect of GAHT on coagulation parameters associated with venous thromboembolism (VTE) risk.Methods Factor (F)II, FIX, FXI, protein (p)C and free pS, fibrinogen, hematocrit, sex hormone-binding globulin, and normalized activated protein C ratio were measured in 98 transwomen (male sex at birth, female gender identity) and 100 transmen (female sex at birth, male gender identity) before and after 12 months of GAHT (oral or transdermal estradiol and anti-androgens in transwomen, transdermal or intramuscular testosterone in transmen). Mean paired differences in coagulation measurements were estimated with 95% confidence intervals (95% CI). Differences for route of administration and age were assessed with linear regression.Results After GAHT, transwomen had more procoagulant profiles with a mean increase in FIX: 9.6 IU/dL (95% CI 3.1-16.0) and FXI: 13.5 IU/dL (95% CI 9.5-17.5), and a decrease in pC: -7.7 IU/dL (95% CI -10.1 to -5.2). Changes in measures of coagulation were influenced by route of administration (oral vs. transdermal) and age. A higher sex-hormone binding globulin level after 12 months was associated with a lower activated protein C resistance. In transmen, changes were not procoagulant overall and were influenced by age. Differences for route of administration (transdermal vs. intramuscular) were small.Conclusions GAHT in transmen was not associated with apparent procoagulant changes, which provides some reassurance regarding VTE risk. In transwomen, GAHT resulted in procoagulant changes, which likely contributes to the observed increased VTE risk. Show less
Objective This study aimed at evaluating the effect of thrombophilia on the risk of venous thromboembolism (VTE) in patients undergoing any type of orthopedic surgery.Background Patients undergoing... Show moreObjective This study aimed at evaluating the effect of thrombophilia on the risk of venous thromboembolism (VTE) in patients undergoing any type of orthopedic surgery.Background Patients undergoing orthopedic surgery are at high risk for VTE. Although patients with thrombophilia have an increased risk of VTE, it is currently unclear whether there is a synergetic effect in patients with thrombophilia who undergo orthopedic surgery.Methods Data from a large population-based case-control study (the Multiple Environmental and Genetic Assessment [MEGA] of risk factors for venous thrombosis study) were used. Odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for age, sex, and body mass index (BMI) (ORadj) were calculated for patients undergoing any orthopedic intervention.Results Of 4721 cases and 5638 controls, 263 cases and 94 controls underwent orthopedic surgery. Patients who had any orthopedic intervention in the year before the index date were at higher risk of VTE (ORadj 3.7; 95% CI, 2.9-4.8) than those who did not undergo any orthopedic surgery. There was an additionally increased risk in patients with factor V Leiden (OR 17.5, 95% CI, 4.1-73.6), non-O blood group (OR 11.2; 95% CI, 3.4-34.0), or elevated plasma levels of factor VIII (OR 18.6; 95% CI, 7.4-46.9) all relative to patients without these defects, not undergoing orthopedic surgery.Conclusions Patients with factor V Leiden, high levels of factor VIII, or blood group non-O were found to have a high risk of VTE after orthopedic surgery. Identification of these patients may enable individualized thromboprophylactic treatment to efficiently reduce VTE risk. Show less
Gal, G. le; Carrier, M.; Castellucci, L.A.; Cuker, A.; Hansen, J.B.; Klok, F.A.; ... ; ISTH CDE Task Force 2021
Clinical research in venous thromboembolism (VTE) is hindered by variability in the collection and reporting of data and outcomes. A consistent data language facilitates efficiencies, leads to... Show moreClinical research in venous thromboembolism (VTE) is hindered by variability in the collection and reporting of data and outcomes. A consistent data language facilitates efficiencies, leads to higher quality data, and permits between-study comparisons and evidence synthesis. The International Society on Thrombosis and Haemostasis (ISTH) launched an international task force of more than 50 researchers to develop common data elements for clinical research in venous thromboembolism.The project was organized in seven working groups, each focusing on a topic area: General Core Data Elements; Anticoagulation and Other Therapies; Chronic VTE and Functional Outcomes; Diagnosis of VTE; Malignancy; Perioperative; and Predictors of VTE. The groups met via teleconference to collaboratively identify key data elements and develop definitions and data standards that were structured in a project-specific taxonomy. A Steering Committee met by teleconference and in-person to determine the overall scope of the project and resolve questions arising from the working groups. ISTH held an open public comment period to enable broader stakeholder involvement and feedback. The common data elements were then refined by the working groups to create a set of 512 unique data elements that are publicly available at .The ISTH VTE Common Data Elements are intended to be a living project with ongoing curation, future expansion, and adaptation to meet the needs of the thrombosis and hemostasis research community. Show less
Wang, H.J.; Rosendaal, F.R.; Cushman, M.; Vlieg, A.V. 2020
Background: Venous thrombosis (VT) incidence increases markedly with age. Coagulation factors are also positively associated with age.Objective: To study whether higher levels of coagulation... Show moreBackground: Venous thrombosis (VT) incidence increases markedly with age. Coagulation factors are also positively associated with age.Objective: To study whether higher levels of coagulation factors II (prothrombin), VIII, IX, and XI are associated with risk of a first VT in the elderly.Methods: Four hundred and one patients and 431 control subjects aged 70 and older were included in the Age and Thrombosis, Acquired and Genetic risk factors in the Elderly (AT-AGE) study. Blood was collected 1 year after the event in patients and in all control subjects for measurement of coagulation factors. To assess the risk of VT, odds ratios (ORs) were calculated after stratification of coagulation factors in quartiles and at the 90th percentile, adjusting for potential confounders (age, sex, body mass index, and study center).Results: Mean age was 78 years (range: 70-100 years). The ORs of VT for factors in the top quartile compared with the lowest quartile were 4.5 (95% confidence interval [CI]:2.7-7.3) for factor VIII, 2.4 (95% CI:1.1-5.2) for factor IX, and 1.7 (95% CI:1.0-2.9) for factor XI. High prothrombin was not associated with an increased VT risk. There was no dose-response association between the number of high coagulation factors and VT risk. The population attributable risk (PAR) of VT was 37.6%, 23.3%, and 12.4% for factor VIII, IX, and XI, respectively.Conclusion: In this study of the elderly, higher factors VIII, IX, and XI but not prothrombin, were positively associated with the risk of VT. Show less
Background Treatment of patients with hemophilia has advanced over the past decades, but it is unknown whether this has resulted in a normal life expectancy in the Netherlands.Objective This... Show moreBackground Treatment of patients with hemophilia has advanced over the past decades, but it is unknown whether this has resulted in a normal life expectancy in the Netherlands.Objective This observational cohort study aimed to assess all-cause and cause-specific mortality in patients with hemophilia in the Netherlands between 2001 and 2018 and to compare mortality and life expectancy with previous survival assessments from 1973 onward.Patients/methods All 1066 patients with hemophilia who participated in a nationwide survey in 2001 were followed until July 2018.Results Information on 1031 individuals (97%) was available, of whom 142 (14%) deceased during follow-up. Compared with the general Dutch male population, mortality of patients with hemophilia was still increased (standardized mortality ratio: 1.4, 95% confidence interval: 1.2-1.7). Intracranial bleeding and malignancies were the most common causes of death. Estimated median life expectancy of patients with hemophilia was 77 years, 6 years lower than the median life expectancy of the general Dutch male population (83 years). Over the past 45 years, death rates of patients with hemophilia have consistently decreased, approaching the survival experience of the general population. Over the past decades, mortality due to human immunodeficiency virus and hepatitis C virus infections has decreased, death due to intracranial hemorrhages has increased, and death due to ischemic heart disease has remained consistently low over time.Conclusions Survival in patients with hemophilia in the Netherlands has improved over time but is still lower than that of the general population. Show less
Schmidt, D.E.; Edslev, P.W.; Heitink-Polle, K.M.J.; Mertens, B.; Bruin, M.C.A.; Kapur, R.; ... ; Haas, M. de 2020
Background Childhood immune thrombocytopenia (ITP) is an autoimmune bleeding disorder. The prognosis (transient, persistent, or chronic ITP) remains difficult to predict. The morbidity is most... Show moreBackground Childhood immune thrombocytopenia (ITP) is an autoimmune bleeding disorder. The prognosis (transient, persistent, or chronic ITP) remains difficult to predict. The morbidity is most pronounced in children with persistent and chronic ITP. Clinical characteristics are associated with ITP outcomes, but there are no validated multivariate prediction models.Objective Development and external validatation of the Childhood ITP Recovery Score to predict transient versus persistent ITP in children with newly diagnosed ITP.Methods Patients with a diagnosis platelet count <= 20 x 10(9)/L and age below 16 years were included from two prospective multicenter studies (NOPHO ITP study, N = 377 [development cohort]; TIKI trial, N = 194 [external validation]). The primary outcome was transient ITP (complete recovery with platelets >= 100 x 10(9)/L 3 months after diagnosis) versus persistent ITP. Age, sex, mucosal bleeding, preceding infection/vaccination, insidious onset, and diagnosis platelet count were used as predictors.Results In external validation, the score predicted transient versus persistent ITP at 3 months follow-up with an area under the receiver operating characteristic curve of 0.71. In patients predicted to have a high chance of recovery, we observed 85%, 90%, and 95% recovered 3, 6, and 12 months after the diagnosis. For patients predicted to have a low chance of recovery, this was 32%, 46%, and 71%. The score also predicted cessation of bleeding symptoms and the response to intravenous immunoglobulins (IVIg).Conclusion The Childhood ITP Recovery Score predicts prognosis and may be useful to individualize clinical management. In future research, the additional predictive value of biomarkers can be compared to this score. A risk calculator is available (). Show less
Nemeth, B.; Nelissen, R.; Arya, R.; Cannegieter, S. 2020
Venous thromboembolism (VTE) is a common complication following total hip arthroplasty (THA) and total knee arthroplasty (TKA). Many guidelines advise on the ideal pharmacological... Show moreVenous thromboembolism (VTE) is a common complication following total hip arthroplasty (THA) and total knee arthroplasty (TKA). Many guidelines advise on the ideal pharmacological thromboprophylaxis strategy; however, despite its use, approximately 1.5% of patients still develop symptomatic VTE. Considering the large number of THAs and TKAs performed worldwide (2.5 million in total), the impact of VTE following these interventions is enormous. This paper discusses a concept how to further lower rates of VTE and bleeding complications following surgery. By stratifying patients according to their risk, we can optimize the balance between VTE and bleeding for each individual. This way, low-risk patients may be safely withheld from treatment (and avoid unnecessary bleeding complications and costs), whereas high-risk patients should receive adequate therapy (for instance, an increased thromboprophylaxis dosage and duration). An individualized strategy requires a well-functioning VTE prediction model following THA and TKA to help physicians to decide on optimal thromboprophylaxis therapy. Show less
Biguzzi, E.; Siboni, S.M.; Cessie, S. le; Baronciani, L.; Rosendaal, F.R.; Vlieg, A.V.; Peyvandi, F. 2020
Background Increasing levels of von Willebrand factor (VWF) and factor VIII (FVIII:C) was associated with age in type 1 von Willebrand disease (VWD).Objectives To evaluate VWF and FVIII:C increase... Show moreBackground Increasing levels of von Willebrand factor (VWF) and factor VIII (FVIII:C) was associated with age in type 1 von Willebrand disease (VWD).Objectives To evaluate VWF and FVIII:C increase with age in a large group of patients with VWD and low levels of VWF, in whom levels were repeatedly measured.Methods Clinical charts from all patients evaluated at the A. Bianchi Bonomi Center between 1970 and 2018 were reviewed and data on VWF and FVIII:C collected. Patients affected by type 3, severe type 1 and 2N VWD were excluded. The repeated measurements were evaluated by linear mixed-effects models. A linear association between age and VWF/FVIII:C was shown after the age of 40 years in the linear mixed models and analyzed by calculating the regression slope coefficient (beta).Results A total of 617 patients were included in the study (314 type 2, 112 type 1, 181 low VWF levels), with a median age at first measurement of 28 years (interquartile range 14/42) and a mean follow-up of 16 years (standard deviation 11). VWF and FVIII:C increased with age in the whole group. The increase became linear after the age of 40 years (3.68 and 7.44 IU/dL per decade for VWF:activity and FVIII:C). In type 2, FVIII:C increased with age, whereas an increase of both VWF:activity and FVIII:C were shown in patients with type 1 VWD and low levels of VWF.Conclusions A differential increase of VWF and FVIII:C with age was shown among in different ages and types of VWD. Show less
Direct oral anticoagulants (DOACs) are increasingly used for treatment and prevention of thromboembolic diseases, used in fixed dose regimens. Although their safety and efficacy profiles are... Show moreDirect oral anticoagulants (DOACs) are increasingly used for treatment and prevention of thromboembolic diseases, used in fixed dose regimens. Although their safety and efficacy profiles are considered optimal, clinical events still occur. Given that anticoagulation treatment is a delicate balance between clotting and bleeding, it is possible that an optimal target spot exists where the effect of anticoagulation achieves both the lowest possible risk of bleeding and thrombosis. Other currently available anticoagulants (ie, vitamin K antagonists and heparins) provide important clues for this. If such a target spot exists, tailored DOAC therapy may further benefit patients. This opinion article summarizes the current available evidence that suggests that such a tailored strategy could work. It also describes research suggestions for conducting studies in patient populations such as patients with extremes of body weight or impaired kidney function to evaluate whether tailored treatment with DOACs could lead to better patient outcomes. Show less
Background Though risk for recurrent vascular events is high following ischemic stroke, little knowledge about risk factors for secondary events post-stroke exists. Objectives Coagulation factors... Show moreBackground Though risk for recurrent vascular events is high following ischemic stroke, little knowledge about risk factors for secondary events post-stroke exists. Objectives Coagulation factors XII, XI, and VIII (FXII, FXI, and FVIII) have been implicated in first thrombotic events, and our aim was to estimate their effects on vascular outcomes within 3 years after first stroke. Patients/Methods In the Prospective Cohort with Incident Stroke Berlin (PROSCIS-B) study, we followed participants aged 18 and older for 3 years after first mild to moderate ischemic stroke event or until occurrence of recurrent stroke, myocardial infarction, or all-cause mortality. We compared high coagulation factor activity levels to normal and low levels and also analyzed activities as continuous variables. We used Cox proportional hazards models adjusted for age, sex, and cardiovascular risk factors to estimate hazard ratios (HRs) for the combined endpoint. Results In total, 94 events occurred in 576 included participants, resulting in an absolute rate of 6.6 events per 100 person-years. After confounding adjustment, high FVIII activity showed the strongest relationship with the combined endpoint (HR = 2.05, 95% confidence interval [CI] 1.28-3.29). High FXI activity was also associated with a higher hazard (HR = 1.80, 95% CI 1.09-2.98), though high FXII activity was not (HR = 0.86, 95% CI 0.49-1.51). Continuous analyses yielded similar results. Conclusions In our study of mild to moderate ischemic stroke patients, high activity levels of FXI and FVIII but not FXII were associated with worse vascular outcomes in the 3-year period after first ischemic stroke. Show less
Background The role of combined prothrombotic genotypes in cancer-related venous thromboembolism (VTE) is scarcely studied. We aimed to investigate the impact of a 5-single nucleotide polymorphism ... Show moreBackground The role of combined prothrombotic genotypes in cancer-related venous thromboembolism (VTE) is scarcely studied. We aimed to investigate the impact of a 5-single nucleotide polymorphism (SNP) score on the risk of VTE in patients with and without cancer using a population-based case-cohort. Methods Cases with a first VTE (n = 1493) and a subcohort (n = 13 072) were derived from the Tromso Study (1994-2012) and the Nord-Trondelag Health Study (1995-2008). Five SNPs previously reported as a risk score were genotyped: ABO (rs8176719), F5 (rs6025), F2 (rs1799963), FGG (rs2066865), and F11 (rs2036914). Hazard ratios (HRs) for VTE were estimated according to cancer status and the number of risk alleles in the 5-SNP score (0-1, 2-3, and >= 4 alleles). Results During a median follow-up of 12.3 years, 1496 individuals were diagnosed with cancer, of whom 232 experienced VTE. The VTE risk increased with the number of risk alleles in the 5-SNP score among subjects without and with cancer. In cancer-free subjects, the HR was 2.17 (95% confidence interval [CI] 1.79-2.62) for >= 4 versus 0-1 risk alleles. In cancer patients, the corresponding HR was 1.93 (95% CI 1.28-2.91). The combination of cancer and >= 4 risk alleles yielded a 17-fold (HR 17.1, 95% CI 12.5-23.4) higher risk of VTE compared with cancer-free subjects with 0-1 risk alleles. Conclusion The risk of VTE increases with the number of prothrombotic risk alleles in subjects with and without cancer, and the combination of prothrombotic risk alleles and cancer leads to a highly elevated risk of VTE. Show less
Background In patients with non-severe hemophilia A, we lack detailed knowledge on the timing of treatment with factor VIII (FVIII) concentrates. This knowledge could provide information about the... Show moreBackground In patients with non-severe hemophilia A, we lack detailed knowledge on the timing of treatment with factor VIII (FVIII) concentrates. This knowledge could provide information about the expected treatment timing in patients with severe hemophilia A treated with non-replacement therapies. Objective To assess the FVIII treatment history in patients with non-severe hemophilia A. Methods Patients with non-severe hemophilia (baseline FVIII activity [FVIII:C] 2-40 IU/dL) were included from the INSIGHT study. The primary outcome was median age at first FVIII exposure (ED1). In a subgroup of patients for whom more detailed information was available, we analyzed the secondary outcomes: median age at first 20 EDs, annualized bleeding rate for all bleeds (ABR), joint bleeds (AJBR), and major spontaneous bleeds (ASmBR). Results In the total cohort (n = 1013), median baseline FVIII activity was 8 IU/dL (interquartile range [IQR] 4-15) and the median age at ED1 was 3.7 years (IQR 1.4-7.7). Median age at ED1 rose from 2.5 years (IQR 1.2-5.7) in patients with FVIII:C 2-5 IU/dL to 9.7 years (IQR 4.8-16.0) in patients with FVIII:C 25-40 IU/dL. In the subgroup (n = 104), median age at ED1, ED5, ED10, and ED20 was 4.0 years (IQR 1.4-7.6), 5.6 years (IQR 2.9-9.3), 7.5 years (IQR 4.4-11.3), and 10.2 years (IQR 6.5-14.2), respectively. Median ABR, AJBR, and ASmBR were 1.1 (IQR 0.5-2.6), 0.3 (IQR 0.1-0.7), and 0 (IQR 0-0), respectively. Conclusion This study demonstrates that in non-severe hemophilia A, the age at first FVIII exposure increases with baseline FVIII:C and that major spontaneous bleeds rarely occur. Show less
Background Type 3 von Willebrand's disease (VWD) patients present markedly reduced levels of von Willebrand factor and factor VIII. Because of its rarity, the bleeding phenotype of type 3 VWD is... Show moreBackground Type 3 von Willebrand's disease (VWD) patients present markedly reduced levels of von Willebrand factor and factor VIII. Because of its rarity, the bleeding phenotype of type 3 VWD is poorly described, as compared to type 1 VWD. Aims To evaluate the frequency and the severity of bleeding symptoms across age and sex groups in type 3 patients and to compare these with those observed in type 1 VWD patients to investigate any possible clustering of bleeding symptoms within type 3 patients. Methods We compared the bleeding phenotype and computed the bleeding score (BS) using the MCMDM-1VWD bleeding questionnaire in patients enrolled in the 3WINTERS-IPS and MCMDM-1VWD studies. Results In 223 unrelated type 3 VWD patients, both the BS and the number of clinically relevant bleeding symptoms were increased in type 3 as compared to type 1 VWD patients (15 versus 6 and 5 versus 3). Intracranial bleeding, oral cavity, hemarthroses, and deep hematomas were at least five-fold over-represented in type 3 VWD. A more severe bleeding phenotype was evident in patients having von Willebrand factor antigen levels < 20 IU/dL at diagnosis in the two merged cohorts. In type 3 patients, there was an apparent clustering of hemarthrosis with gastrointestinal bleeding and epistaxis, whereas bleeding after surgery or tooth extraction clusters with oral bleeding and menorrhagia. Conclusions In the largest cohort of type 3 VWD patients, we were able to describe a distinct clinical phenotype that is associated with the presence of a more severe hemostatic defect. Show less
Boer, S. de; Bowman, M.; Notley, C.; Mo, A.M.; Lima, P.; Jong, A. de; ... ; Eikenboom, J. 2020
Background Endothelial colony forming cells (ECFCs) derived from peripheral blood can be used to analyze the pathophysiology of vascular diseases ex vivo. However, heterogeneity is observed between... Show moreBackground Endothelial colony forming cells (ECFCs) derived from peripheral blood can be used to analyze the pathophysiology of vascular diseases ex vivo. However, heterogeneity is observed between ECFC clones and this variability needs to be understood and standardized for ECFCs to be used as a cell model for applications in vascular studies. Objective Determine reference characteristics of healthy control ECFCs to generate a valid ex vivo model for vascular disease. Methods Putative ECFCs (n = 47) derived from 21 individual healthy subjects were studied for cell morphology and specific cell characteristics. Clones were analyzed for the production and secretion of von Willebrand factor (VWF), cell proliferation, and the expression of endothelial cell markers. Results Based on morphology, clones were categorized into three groups. Group 1 consisted of clones with classic endothelial cell morphology, whereas groups 2 and 3 contained less condensed cells with increasing cell sizes. All clones had comparable endothelial cell surface expression profiles, with low levels of non-endothelial markers. However, a decrease in CD31 and a group-related increase in CD309 and CD45 expression, combined with a decrease in cell proliferation and VWF production and secretion, was observed in clones in group 3 and to a lesser extent in group 2. Conclusions We observed group-related variations in endothelial cell characteristics when clones lacked the classic endothelial cell morphology. Despite this variation, clones in all groups expressed endothelial cell surface markers. Provided that clones with similar characteristics are compared, we believe ECFCs are a valid ex vivo model to study vascular disease. Show less
Dam, L.F. van; Gautam, G.; Dronkers, C.E.A.; Ghanima, W.; Gleditsch, J.; Heijne, A. von; ... ; Klok, F.A. 2020
Background The diagnostic accuracy of clinical probability assessment and D-dimer testing for clinically suspected recurrent deep vein thrombosis (DVT) is largely unknown. Aim To evaluate the... Show moreBackground The diagnostic accuracy of clinical probability assessment and D-dimer testing for clinically suspected recurrent deep vein thrombosis (DVT) is largely unknown. Aim To evaluate the safety of ruling out acute recurrent DVT based on an unlikely Wells score for DVT and a normal D-dimer test. Methods This was a predefined endpoint of the Theia study in which the diagnostic accuracy of magnetic resonance direct thrombus imaging in acute recurrent ipsilateral DVT was validated. The Wells rule and D-dimer test, performed as part of the study protocol, were not used for management decisions. The primary outcome of this analysis was the incidence of recurrent DVT at baseline or during 3-month follow-up for patients with an unlikely Wells score and a normal D-dimer test. Results Results of both Wells score and D-dimer tests were available in 231 patients without anticoagulant treatment. The recurrent DVT prevalence was 45% (103/231). Forty-nine patients had an unlikely Wells score and normal D-dimer test, of whom 3 (6.1%, 95% confidence interval [CI] 1.3%-18%) had recurrent DVT at baseline/follow-up, yielding a sensitivity of 97% (95% CI 92%-99%) and specificity of 36% (95% CI 28%-45%). Thus, if clinical probability scoring and D-dimer testing would have been applied, radiological imaging could have been omitted in 21% of patients with a diagnostic failure rate of 6.1%. Conclusion By applying clinical probability scoring and D-dimer testing, radiological imaging could be spared in one fifth of patients with suspected recurrent ipsilateral DVT. However, the high failure rate does not support implementation of this strategy in daily practice. Show less
Background International normalized ratio (INR) is traceable to World Health Organization (WHO) International Standards for thromboplastins. International Standards must be used with a manual tilt... Show moreBackground International normalized ratio (INR) is traceable to World Health Organization (WHO) International Standards for thromboplastins. International Standards must be used with a manual tilt tube technique (MTT) for prothrombin time (PT) determination. An important part of the total variability of INR is due to poor harmonization of MTT across WHO reference laboratories. Objectives To determine the origins of PT differences between operators performing MTT and to develop a harmonized MTT. Methods Two workshops were held where WHO reference laboratory operators could compare their PTs using MTT and the same equipment. A harmonized MTT was used by seven operators in the second workshop. Results Differences have been observed in tilting frequency and in the height of pipetting plasma in the test tube. At the beginning of the first workshop, the tilting cycle time varied between 1.1 and 2.7 seconds. The mean PT of normal plasma obtained by pipetting plasma at the top of the tube was 14.3 seconds but was 12.9 seconds when plasma was pipetted at the bottom of the tube. When using the harmonized MTT for WHO International Standard rTF/16, the differences between operators were not greater than 1.1 seconds in normal plasma, and not greater than 1.3 seconds in patient plasma with average INR of 3.0. INR between-operator coefficient of variation was 2.3%. Conclusion Application of a harmonized MTT in three reference laboratories resulted in substantial reduction of between-operator variation of PT and INR. The harmonized MTT is proposed as Candidate Reference Measurement Procedure. Show less
Background Genome wide association studies (GWAS) identified SLC44A2 as a novel susceptibility gene for venous thrombosis (VT) and previous work established that SLC44A2 contributed to clot... Show moreBackground Genome wide association studies (GWAS) identified SLC44A2 as a novel susceptibility gene for venous thrombosis (VT) and previous work established that SLC44A2 contributed to clot formation upon vascular injury.Objective To further investigate the role of SLC44A2 in VT by utilizing SLC44A2 deficient mice (Slc44a2(-)(/)(-)) in two representative disease models.Methods Mice were included in a hypercoagulability model driven by siRNA-mediated hepatic gene silencing of anticoagulants Serpinc1 (antithrombin) and Proc (protein C) and a flow restriction (stenosis) model induced by partial ligation of the inferior vena cava.Results In the hypercoagulability model, no effect in onset was observed in Slc44a2(-)(/)(-) animals; however, a drop in plasma fibrinogen and von Willebrand factor coinciding with an increase in blood neutrophils was recorded. In the neutrophil dependent stenosis model after 48 hours, Slc44a2(-)(/)(-) mice had significantly smaller thrombi both in length and weight with less platelet accumulation as a percentage of the total thrombus area. During the initiation of thrombosis at 6 hours post-stenosis, Slc44a2(-)(/)(-) mice also had smaller thrombi both in length and weight, with circulating platelets remaining elevated in Slc44a2(-)(/)(-) animals. Platelet activation and aggregation under both static- and venous and arterial shear conditions were normal for blood from Slc44a2(-)(/)(-) mice.Conclusions These studies corroborate the original GWAS findings and establish a contributing role for SLC44A2 during the initiation of VT, with indications that this may be related to platelet-neutrophil interaction. The precise mechanism however remains elusive and warrants further investigation. Show less
