Maria Bruzelius

Studies of microparticles in patients with the antiphospholipid syndrome (APS)

Objectives: To study circulating platelet, monocyte and endothelial microparticles (PMPs, MMPs and EMPs) in patients with antiphospholipid syndrome (APS) in comparison with healthy controls. Material and method: Fifty-two patients with APS and 52 healthy controls were investigated. MPs were measured on a flow cytometer (Beckman Gallios) and defined as particles sized < 1.0 µm, negative to phalloidin, positive to lactadherin and positive to either CD42a (PMPs), CD144 (EMPs) or CD14 (MMPs). Exposure of CD142 (TF) was measured on CD144 positive MPs. Results: Total number of MPs (i.e. lactadherin positive particles) was higher in APS patients versus controls (p < 0.001). An increased number of EMPs (p < 0.001), increased TF-positive EMPs (p < 0.001) and increased MMPs (p < 0.001) were also observed. PMP numbers did not differ between the groups. None of the MP types differed in numbers between obstetric and thrombotic APS patients. Conclusion: We observed a high number of EMPs expressing TF in APS patients. The numbers of MMPs and total EMPs were also higher as compared with healthy controls but in contrast to previous reports, the number of PMPs did not differ between groups.

Management of rivaroxaban or apixaban associated major bleeding with prothrombin complex concentrates: a cohort study

There is uncertainty regarding the effectiveness and occurrence of thromboembolic events in patients treated with prothrombin complex concentrates (PCCs) for the management of major bleeding events (MBEs) on rivaroxaban or apixaban. We investigated the effectiveness of PCCs given for the management of MBEs in patients on rivaroxaban or apixaban. Between 1 January 2014 and 1 October 2016, we prospectively included patients on rivaroxaban or apixaban treated with PCCs for the management of MBEs. The effectiveness of PCCs was assessed by using the International Society of Thrombosis and Hemostasis Scientific and Standardization Subcommittee criteria for the assessment of the effectiveness of major bleeding management. The safety outcomes were thromboembolic events and all-cause mortality within 30 days after treatment with PCCs. A total of 84 patients received PCCs for the reversal of rivaroxaban or apixaban due to a MBE. PCCs were given at a median (interquartile range) dose of 2000 IU (1500-2000 IU). Intracranial hemorrhage (ICH) was the most common site of bleeding requiring reversal (n = 59; 70.2%), followed by gastrointestinal bleeding in 13 (15.5%) patients. Management with PCCs was assessed as effective in 58 (69.1%) patients and ineffective in 26 (30.9%) patients. Most patients with ineffective hemostasis with PCCs had ICH (n = 16; 61.5%). Two patients developed an ischemic stroke, occurring 5 and 10 days after treatment with PCC. Twenty-seven (32%) patients died within 30 days after a MBE. The administration of PCCs for the management of MBEs associated with rivaroxaban or apixaban is effective in most cases and is associated with a low risk of thromboembolism. Our findings are limited by the absence of a control group in the study.

Predicting venous thrombosis in women using a combination of genetic markers and clinical risk factors

Family history of venous thromboembolism (VTE) has been suggested to be more useful in risk assessment than thrombophilia testing.

A Genome-Wide Association Study Identifies KNG1 as a Genetic Determinant of Plasma Factor XI Level and Activated Partial Thromboplastin Time

Objective—Elevated plasma levels of coagulation factor XI (FXI) are implicated in the pathogenesis of venous thromboembolism and ischemic stroke, and polymorphisms in the F11 gene are associated both with risk of venous thromboembolism and an elevated plasma FXI level. Methods and Results—Here, we report the first hypothesis-free genome-wide genetic analysis of plasma FXI levels. Two genome-wide significant loci were detected in the family-based Genetic Analysis of Idiopathic Thrombophilia 1 cohort: one located in the kininogen 1 gene (KNG1) (rs710446; P=7.98×10−10) and one located in the structural F11 gene (rs4241824; P=1.16×10−8). Both associations were replicated in a second population-based Swedish cohort. A significant effect on KNG1 mRNA expression was also seen for the 2 most robustly FXI-associated single nucleotide polymorphisms located in KNG1. Furthermore, both KNG1 single nucleotide polymorphisms were associated with activated partial thromboplastin time, suggesting that FXI may be the main mechanistic pathway by which KNG1 and F11 influence activated partial thromboplastin time and risk of thrombosis. Conclusion—These findings contribute to the emerging molecular basis of venous thromboembolism and, more importantly, help in understanding the biological regulation of a phenotype that has proved to have promising therapeutic properties in relation to thrombosis.

Influence of coronary artery disease-associated genetic variants on risk of venous thromboembolism.

INTRODUCTION We investigated whether genetic variations robustly associated with coronary artery disease are also associated with risk of venous thromboembolism in a well-defined, female case-control study (n=2753) from Sweden. MATERIALS AND METHODS 39 single nucleotide polymorphisms in 32 loci associated with coronary artery disease in genome-wide association studies were identified in a literature search and genotyped in the ThromboEmbolism Hormone Study (TEHS). Association with venous thromboembolism was assessed by logistic regression. RESULTS Only rs579459 in the ABO locus demonstrated a significant association with VTE. A tentative association between ANRIL and VTE in the discovery analysis failed to replicate in a meta-analysis of 4 independent cohorts (total n=7181). CONCLUSIONS It appears that only the ABO locus is a shared risk factor for coronary artery disease and VTE.

A prospective diagnostic accuracy study evaluating rotational thromboelastometry and thromboelastography in 100 patients with von Willebrand disease.

Rotational thromboelastometry (ROTEM®) and thromboelastography (TEG®) are increasingly used in the perioperative and emergency assessment of bleeding tendencies. The diagnostic value of ROTEM and TEG for von Willebrand disease (VWD) remains to be established.

F11 is associated with recurrent VTE in women. A prospective cohort study.

Genetic associations for the reoccurrence of venous thromboembolism (VTE) are not well described. Our aim was to investigate if common genetic variants, previously found to contribute to the prediction of first time thrombosis in women, were associated with risk of recurrence. The Thromboembolism Hormone Study (TEHS) is a Swedish nationwide case-control study (2002-2009). A cohort of 1,010 women with first time VTE was followed up until a recurrent event, death or November 2011. The genetic variants in F5 rs6025, F2 rs1799963, ABO rs514659, FGG rs2066865, F11 rs2289252, PROC rs1799810 and KNG1 rs710446 were assessed together with clinical variables. Recurrence rate was calculated as the number of events over the accumulated patient-time. Cumulative recurrence was calculated by Kaplan-Meier curve. Cox proportional-hazard model was used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) between groups. A total of 101 recurrent events occurred during a mean follow-up time of five years. The overall recurrence rate was 20 per 1,000 person-years (95% CI; 16-24). The recurrence rate was highest in women with unprovoked first event and obesity. Carriers of the risk alleles of F5 rs6025 (HR=1.7 (95% CI; 1.1-2.6)) and F11 rs2289252 (HR=1.8 (95% CI; 1.1-3.0)) had significantly higher rates of recurrence compared to non-carriers. The cumulative recurrence was 2.5-fold larger in carriers of both F5 rs6025 and F11 rs2289252 than in non-carriers at five years follow-up. In conclusion, F5 rs6025 and F11 rs2289252 contributed to the risk of recurrent VTE and the combination is of potential clinical relevance for risk prediction.

Lack of association of non-synonymous FUT2 and ALPL polymorphisms with venous thrombosis.

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Whole blood ristocetin-activated platelet impedance aggregometry (Multiplate) for the rapid detection of Von Willebrand disease

Von Willebrand disease (VWD) is the most common bleeding disorder, but no bedside tests specific for Von Willebrand factor are available. The objective of this study was to evaluate the diagnostic accuracy of whole blood ristocetin-induced platelet aggregometry (WB-RIPA) in VWD. WB-RIPA was performed in VWD patients (n=100) and healthy controls (n=17) using the Multiplate® platelet impedance aggregometry platform. The diagnostic properties of the test were described as sensitivity/specificity, positive and negative predictive value, and ROC area under the curve (AUC). Patients with VWD had impaired platelet aggregation by WB-RIPA. At a cut-off of 98 U, the test sensitivity and specificity of WB-RIPA for VWD was 0.95 and 0.53. A cut-off of 60 U provided a specificity of 1.00 with reduced sensitivity of 0.76. All patients with type 3 VWD and >90 % of patients with type 2 VWD were accurately distinguished from the controls. Incorrect classifications were attributable to patients with type 1 VWD, showing partly overlapping WB-RIPA results with healthy controls. Remarkably, these patients had lower bleeding scores and higher VWF activity than other type 1 VWD patients. Overall, WB-RIPA discriminated VWD patients from healthy controls accurately with a ROC AUC of 0.94. These results show that WB-RIPA is a promising diagnostic test for VWD, especially when timely results are required. Depending on the chosen test threshold, WB-RIPA could be clinically used as a rule out test, or to suggest patients in whom further testing for VWD is warranted.

Thrombin activatable fibrinolysis inhibitor (TAFI) — A possible link between coagulation and complement activation in the antiphospholipid syndrome (APS)

BACKGROUND Thrombosis and complement activation are pathogenic features of antiphospholipid syndrome (APS). Their molecular link is Plasma carboxypeptidase-B, also known as thrombin activatable fibrinolysis inhibitor (TAFIa), which plays a dual role: anti-fibrinolytic, by cleaving carboxyl-terminal lysine residues from partially degraded fibrin, and anti-inflammatory, by downregulating complement anaphylatoxins C3a and C5a. AIM To investigate the levels of TAFI (proenzyme) and TAFIa (active enzyme) in relation to complement activation, fibrin clot permeability and fibrinolytic function in clinical and immunological subsets of 52 APS patients and 15 controls. RESULTS TAFI (p<0.001), TAFIa (p<0.05) and complement factor C5a (p<0.001) were increased, while fibrin permeability (p<0.01) was decreased and clot lysis time (CLT) was prolonged (p<0.05) in APS patients compared to controls. Furthermore, TAFIa was increased (p<0.01) in samples from APS patients affected by arterial thrombosis compared to other APS-phenotypes. Positive associations were found between TAFI and age, fibrinogen and C5a, and between TAFIa and age, fibrinogen and thrombomodulin. CONCLUSION TAFI and TAFIa levels were increased in patients with APS as a potential response to complement activation. Interestingly, TAFI activation was associated with arterial thrombotic APS manifestations. Thus, TAFIa may be considered a novel biomarker for arterial thrombosis in APS.