Bob Siegerink

Antiphospholipid antibodies and risk of myocardial infarction and ischaemic stroke in young women in the RATIO study: a case-control study

BACKGROUND Arterial thrombosis is a major clinical manifestation of the antiphospholipid syndrome, which is an autoimmune disease found mostly in young women. Although the presence of circulating antiphospholipid antibodies in individuals who have a thrombotic event is a prerequisite for the diagnosis of the antiphospholipid syndrome, the risk of arterial thrombosis associated with antiphospholipid antibodies in the general population is unclear. METHODS In RATIO (Risk of Arterial Thrombosis In relation to Oral contraceptives), a large multicentre population-based case-control study, we enrolled women aged under 50 years who were admitted to hospital at 16 centres with first ischaemic stroke or myocardial infarction between January, 1990, and October, 1995. An additional 59 women who presented with ischaemic stroke at the University Medical Centre Utrecht between 1996 and 2001 were also enrolled. Information on cardiovascular risk factors (such as oral contraceptive use, smoking, and hypertension) were assessed with a standard questionnaire. During the second phase (1998-2002), blood samples were taken to measure antiphospholipid antibody profiles (lupus anticoagulant, anticardiolipin IgG, anti-beta(2)-glycoprotein I IgG, and antiprothrombin IgG) and to determine genetic prothrombotic risk factors (factor V G1691A variant, prothrombin G20210A variant, and factor XIII 204Phe allele). FINDINGS 175 patients with ischaemic stroke, 203 patients with myocardial infarction, and 628 healthy controls were included. Patients were frequency matched with controls for age, residence area, and index year. Lupus anticoagulant was found in 30 (17%) patients with ischaemic stroke, six (3%) patients with myocardial infarction, and four (0.7%) in the control group. The odds ratio for myocardial infarction was 5.3 (95% CI 1.4-20.8), which increased to 21.6 (1.9-242.0) in women who used oral contraceptives and 33.7 (6.0-189.0) in those who smoked. The odds ratio for ischaemic stroke was 43.1 (12.2-152.0), which increased to 201.0 (22.1-1828.0) in women who used oral contraceptives and 87.0 (14.5-523.0) in those who smoked. In women who had anti-beta(2)-glycoprotein I antibodies, the risk of ischaemic stroke was 2.3 (1.4-3.7), but the risk of myocardial infarction was not increased (0.9, 0.5-1.6). Neither anticardiolipin nor antiprothrombin antibodies affected the risk of myocardial infarction or ischaemic stroke. INTERPRETATION Our results suggest that lupus anticoagulant is a major risk factor for arterial thrombotic events in young women, and the presence of other cardiovascular risk factors increases the risk even further. FUNDING Netherlands Heart Foundation and Leducq Foundation.

High VWF, low ADAMTS13, and oral contraceptives increase the risk of ischemic stroke and myocardial infarction in young women

VWF and ADAMTS13 are major determinants of platelet adhesion after vessel injury. In the present study, we aimed to determine whether VWF or ADAMTS13 plasma antigen levels influence the risks of ischemic stroke (IS) or myocardial infarction (MI) in young women and how these risks are affected by oral contraceptive (OC) use. VWF and ADAMTS13 plasma antigen levels were measured in a frequency-matched case-control study of 1018 young (18-49 years) women including 175 IS patients and 205 MI patients. Increasing levels of VWF and decreasing levels of ADAMTS13 were associated with the risk of IS and MI in a dose-dependent manner. Having both high VWF and low ADAMTS13 resulted in an odds ratio (OR) of 6.9 (95% confidence interval [95% CI], 2.0-23.0) for IS and 11.3 (95% CI, 3.6-35.2) for MI. Use of OCs increased the risk of IS and MI associated with high VWF (OR = 12; 95% CI, 5.5-26.2 and OR = 7.5, 95% CI, 3.6-15.7, respectively) and the risk of IS associated with low ADAMTS13 (OR = 5.8, 95% CI, 2.7-12.4). We conclude that high VWF and low ADAMTS13 plasma levels both increase the risk of IS and MI. The risks associated with high VWF or low ADAMTS13 levels are further increased by the use of OCs.

Intrinsic Coagulation Activation and the Risk of Arterial Thrombosis in Young Women Results From the Risk of Arterial Thrombosis in Relation to Oral Contraceptives (RATIO) Case-Control Study

Background— Classically, intrinsic coagulation proteins are thought to have a minor role in hemostasis. Recently, these proteins, especially FXII, were implicated as possible key players in the pathogenesis of arterial thrombosis. This study aims to determine the risks of arterial thrombosis conferred by increased activation of intrinsic coagulation proteins in young women and the effect of oral contraceptive use on this association. Methods and Results— The Risk of Arterial Thrombosis In relation to Oral contraceptives (RATIO) study is a population-based case-control study including young women (age 18 to 50 years) with myocardial infarction (n=205) and ischemic stroke (n=175) and 638 healthy controls. Intrinsic coagulation protein activation was determined by measuring activated protein-inhibitor complexes. This complex is with C1 esterase inhibitor (FXIIa-C1-INH, FXIa-C1-INH, Kallikrein-C1-INH) or antitrypsin inhibitor (FXIa-AT-INH). Odds ratios (ORs) and corresponding confidence intervals (95% CIs) were calculated with logistic regression. High levels of protein activation (>90th percentile of controls) showed an increased risk of ischemic stroke: FXIIa-C1-INH (OR, 2.1; 95% CI, 1.3 to 3.5), FXIa-C1-INH (OR, 2.8; 95% CI, 1.6 to 4.7), FXIa-AT-INH (OR, 2.3; 95% CI, 1.4 to 4.0), and Kallikrein-C1 (OR, 4.3; 95% CI, 2.6 to 7.2). If anything, myocardial infarction risk was only increased by Kallikrein-C1-INH (OR, 1.5; 95% CI, 0.9 to 2.5). Oral contraceptive use further increased the risks. Conclusions— High levels of activated proteins of the intrinsic coagulation system are associated with arterial thrombosis, whereas the strength of these associations differs for myocardial infarction and ischemic stroke. This contradicts similar analyses among men in the Northwick Park Heart Study. Together with the finding that oral contraceptive use further increases the risks, the question of whether the role of intrinsic coagulation proteins in the pathogenesis of arterial thrombosis is sex-specific is raised.Background— Classically, intrinsic coagulation proteins are thought to have a minor role in hemostasis. Recently, these proteins, especially FXII, were implicated as possible key players in the pathogenesis of arterial thrombosis. This study aims to determine the risks of arterial thrombosis conferred by increased activation of intrinsic coagulation proteins in young women and the effect of oral contraceptive use on this association. Methods and Results— The Risk of Arterial Thrombosis In relation to Oral contraceptives (RATIO) study is a population-based case-control study including young women (age 18 to 50 years) with myocardial infarction (n=205) and ischemic stroke (n=175) and 638 healthy controls. Intrinsic coagulation protein activation was determined by measuring activated protein-inhibitor complexes. This complex is with C1 esterase inhibitor (FXIIa-C1-INH, FXIa-C1-INH, Kallikrein-C1-INH) or antitrypsin inhibitor (FXIa-AT-INH). Odds ratios (ORs) and corresponding confidence intervals (95% CIs) were calculated with logistic regression. High levels of protein activation (>90th percentile of controls) showed an increased risk of ischemic stroke: FXIIa-C1-INH (OR, 2.1; 95% CI, 1.3 to 3.5), FXIa-C1-INH (OR, 2.8; 95% CI, 1.6 to 4.7), FXIa-AT-INH (OR, 2.3; 95% CI, 1.4 to 4.0), and Kallikrein-C1 (OR, 4.3; 95% CI, 2.6 to 7.2). If anything, myocardial infarction risk was only increased by Kallikrein-C1-INH (OR, 1.5; 95% CI, 0.9 to 2.5). Oral contraceptive use further increased the risks. Conclusions— High levels of activated proteins of the intrinsic coagulation system are associated with arterial thrombosis, whereas the strength of these associations differs for myocardial infarction and ischemic stroke. This contradicts similar analyses among men in the Northwick Park Heart Study. Together with the finding that oral contraceptive use further increases the risks, the question of whether the role of intrinsic coagulation proteins in the pathogenesis of arterial thrombosis is sex-specific is raised. # Clinical Perspective {#article-title-25}

Differences and similarities in breast cancer risk assessment models in clinical practice: which model to choose?

Abstract To show differences and similarities between risk estimation models for breast cancer in healthy women from BRCA1/2-negative or untested families. After a systematic literature search seven models were selected: Gail-2, Claus Model, Claus Tables, BOADICEA, Jonker Model, Claus-Extended Formula, and Tyrer–Cuzick. Life-time risks (LTRs) for developing breast cancer were estimated for two healthy counsellees, aged 40, with a variety in family histories and personal risk factors. Comparisons were made with guideline thresholds for individual screening. Without a clinically significant family history LTRs varied from 6.7% (Gail-2 Model) to 12.8% (Tyrer–Cuzick Model). Adding more information on personal risk factors increased the LTRs and yearly mammography will be advised in most situations. Older models (i.e. Gail-2 and Claus) are likely to underestimate the LTR for developing breast cancer as their baseline risk for women is too low. When models include personal risk factors, surveillance thresholds have to be reformulated. For current clinical practice, the Tyrer–Cuzick Model and the BOADICEA Model seem good choices.

Genetic variation in fibrinogen; its relationship to fibrinogen levels and the risk of myocardial infarction and ischemic stroke

Summary.  Background: Confounding by common causes and reverse causation have been proposed as explanations for the association between high fibrinogen levels and cardiovascular disease. Genetic variants can alter fibrinogen characteristics and are not subject to these problems. Objectives: To determine the fibrinogen plasma levels for genotypic variants in fibrinogen‐Aα (FGA Thr312Ala) and fibrinogen‐Bβ (FGB − 455G/A), and whether these variants are associated with arterial thrombosis. Methods: Fibrinogen genotypes were determined in a population‐based case–control study including women aged 18–50 years; 218 cases with myocardial infarction, 192 cases with ischemic stroke, and 769 healthy controls. Fibrinogen levels were determined in the control population. Results: The FGB − 455G/A variant increased plasma fibrinogen levels, whereas the FGA Thr312Ala variant lowered plasma fibrinogen levels, albeit to a modest extent. The risk of ischemic stroke was altered when the homozygote minor allele was compared with the homozygote major allele. The FGA Thr312Ala single‐nucleotide polymorphism (SNP) was associated with a decrease in risk [odds ratio (OR) 0.43; 95% confidence interval (CI) 0.21–0.87], whereas the FGB − 455G/A SNP might have increased the risk (OR 1.76; 95% CI 0.7–4.03). The risk of myocardial infarction was not altered for either SNP (FGA Thr312Ala, OR 0.98, 95% CI 0.40–2.40; FGB − 455G/A, OR 0.98, 95% CI 0.40–2.40). Conclusions: With the genetic variations as markers of plasma fibrinogen levels alterations, thereby ruling out confounding and reverse causation, our results suggest that plasma fibrinogen levels could play a more pronounced role as risk factors for ischemic stroke than for myocardial infarction.

Association of High Body Mass Index With Decreased Treatment Response to Combination Therapy in Recent‐Onset Rheumatoid Arthritis Patients

To assess the association between high body mass index (BMI) and treatment response in recent‐onset rheumatoid arthritis.

Where Have All the Rodents Gone? The Effects of Attrition in Experimental Research on Cancer and Stroke.

Given small sample sizes, loss of animals in preclinical experiments can dramatically alter results. However, effects of attrition on distortion of results are unknown. We used a simulation study to analyze the effects of random and biased attrition. As expected, random loss of samples decreased statistical power, but biased removal, including that of outliers, dramatically increased probability of false positive results. Next, we performed a meta-analysis of animal reporting and attrition in stroke and cancer. Most papers did not adequately report attrition, and extrapolating from the results of the simulation data, we suggest that their effect sizes were likely overestimated.

Mendelian randomization: use of genetics to enable causal inference in observational studies

The aim of aetiologic studies in epidemiology is to investigate whether factors are causally related to diseases and therefore become a potential target for therapeutic interventions. Mendelian randomization enables estimation of causal relationships in observational studies using genetic variants as instrumental variables. An instrumental variable is a variable that can be considered to mimic the coin toss in a randomized study. Given the random assignment of alleles in gamete formation, the use of genetic variants is an alternative method to control for confounding. This educational article describes the approach of Mendelian randomization, its underlying rationale and its necessary assumptions.

Plasma ADAMTS-13 levels and the risk of myocardial infarction: An individual patient data meta-analysis

Low ADAMTS‐13 levels have been repeatedly associated with an increased risk of ischemic stroke, but results concerning the risk of myocardial infarction are inconclusive.

Hypercoagulability Is a Stronger Risk Factor for Ischaemic Stroke than for Myocardial Infarction: A Systematic Review

Background and Purpose Hypercoagulability increases the risk of arterial thrombosis; however, this effect may differ between various manifestations of arterial disease. Methods In this study, we compared the effect of coagulation factors as measures of hypercoagulability on the risk of ischaemic stroke (IS) and myocardial infarction (MI) by performing a systematic review of the literature. The effect of a risk factor on IS (relative risk for IS, RRIS) was compared with the effect on MI (RRMI) by calculating their ratio (RRR = RRIS/RRMI). A relevant differential effect was considered when RRR was >1+ its own standard error (SE) or <1−SE. Results We identified 70 publications, describing results from 31 study populations, accounting for 351 markers of hypercoagulability. The majority (203/351, 58%) had an RRR greater than 1. A larger effect on IS risk than MI risk (RRE>1+1SE) was found in 49/343 (14%) markers. Of these, 18/49 (37%) had an RRR greater than 1+2SE. On the opposite side, a larger effect on MI risk (RRR<1-1SE) was found in only 17/343 (5%) markers. Conclusions These results suggest that hypercoagulability has a more pronounced effect on the risk of IS than that of MI.