Within‐person variability in measured values of multiple risk factors can bias their associations with disease. The multivariate regression calibration (RC) approach can correct for such measurement error and has been applied to studies in which true values or independent repeat measurements of the risk factors are observed on a subsample. We extend the multivariate RC techniques to a meta‐analysis framework where multiple studies provide independent repeat measurements and information on disease outcome. We consider the cases where some or all studies have repeat measurements, and compare study‐specific, averaged and empirical Bayes estimates of RC parameters. Additionally, we allow for binary covariates (e.g. smoking status) and for uncertainty and time trends in the measurement error corrections. Our methods are illustrated using a subset of individual participant data from prospective long‐term studies in the Fibrinogen Studies Collaboration to assess the relationship between usual levels of plasma fibrinogen and the risk of coronary heart disease, allowing for measurement error in plasma fibrinogen and several confounders. Copyright © 2009 John Wiley & Sons, Ltd.

One difficulty in performing meta‐analyses of observational cohort studies is that the availability of confounders may vary between cohorts, so that some cohorts provide fully adjusted analyses while others only provide partially adjusted analyses. Commonly, analyses of the association between an exposure and disease either are restricted to cohorts with full confounder information, or use all cohorts but do not fully adjust for confounding. We propose using a bivariate random‐effects meta‐analysis model to use information from all available cohorts while still adjusting for all the potential confounders. Our method uses both the fully adjusted and the partially adjusted estimated effects in the cohorts with full confounder information, together with an estimate of their within‐cohort correlation. The method is applied to estimate the association between fibrinogen level and coronary heart disease incidence using data from 154 012 participants in 31 cohorts. † One hundred and ninety‐nine participants from the original 154 211 withdrew their consent and have been removed from this analysis. Copyright © 2009 John Wiley & Sons, Ltd.

We carried out a prospective cohort study to determine whether the plasma levels of fibrinogen, plasminogen, factor VII and lipoprotein (a) are predictors of ischemic stroke and all cardiovascular disease (CVD) events. The FINRISK '92 Hemostasis Study included a random sample of 2372 participants, who were followed-up from winter 1992 to 31 December 2001. During the follow-up, 75 ischemic stroke and 145 coronary events occurred. Of these, 169 were observed among participants free of known CVD at baseline. In this group, fibrinogen and plasminogen were positively associated with the risk of a CVD event with hazard ratios of 1.22 [95% confidence interval (CI), 1.05–1.41] and 1.22 (95% CI, 1.03–1.44), respectively, after adjusting for age, sex and conventional risk factors. Factor VII:C was associated with risk of a future CVD event only among persons with positive history of CVD at baseline (hazard ratio, 1.32; 95% CI, 1.00–1.73). Factor VII antigen was not associated with CVD risk. None of the measured hemostatic factors was a predictor of ischemic stroke events, with the possible exception of lipoprotein (a), which had a borderline significant association (hazard ratio, 1.25; 95% CI, 0.99–1.58). In conclusion, the present study supports the observations that fibrinogen and plasminogen are significant predictors of CVD events, independently of conventional risk factors.

BACKGROUND:Thrombin formation during cardiac surgery could result in disordered hemostasis and thrombosis. The aim of the study was to examine the effects of aprotinin and tranexamic acid on thrombin generation and fibrinolytic activity in patients undergoing cardiac surgery.METHODS:Data were collected prospectively from 60 patients undergoing coronary artery bypass grafting using cardiopulmonary bypass (CPB). In a randomized sequence, 20 patients received aprotinin, 20 patients received tranexamic acid, and in 20 patients placebo was used.RESULTS:Significant thrombin activity was found in all the studied patients. Thrombin generation was less in the aprotinin group than in the tranexamic acid and the placebo group (thrombin/anti-thrombin III complexes 33.7 +/- 3.6, 53.6 +/- 7.0 and 44.2 +/- 5.3 microg/l 2 h after CPB and F1 + 2 fragment 1.50 +/- 0.10, 2.37 +/- 0.37 and 2.04 +/- 0.20 nmol/l 6 h after surgery, respectively). The inhibition of fibrinolysis was significant with both anti-fibrinolytic drugs (D-dimers 0.427 +/- 0.032, 0.394 +/- 0.039 and 2.808 +/- 0.037 mg/l 2 h after CPB, respectively). The generation of d-dimers was inhibited until 16 h after CPB in the aprotinin group. The plasminogen activation was significantly less in the aprotinin group (plasmin/anti-plasmin complexes 0.884 +/- 0.095, 2.764 +/- 0.254 and 1.574 +/- 0.185 mg/l 2 h after CPB, respectively).CONCLUSION:Thrombin formation is inevitable in coronary artery bypass surgery when CPB is used. The suppression of fibrinolytic activity, either with aprotinin or with tranexamic acid interferes with the hemostatic balance as evaluated by biochemical markers. Further investigations are needed to define the role of hemostatic activation in ischemic complications associated with cardiac surgery.

The laboratory diagnosis of antiphospholipid antibody syndrome currently requires two consecutive positive results in either lupus anticoagulant or anticardiolipin antibody assays. Antibodies against beta-2-glycoprotein I (abeta2-GPI) are suggested as a new marker for the syndrome. The inclusion of abeta2-GPI in the official diagnostic criteria has so far been precluded owing to lack of an international standard and also technical difficulties. Samples from 5367 consecutive patients sent to a national reference laboratory mainly because of various thrombotic events were studied. An IgG abeta2-GPI ELISA assay was performed in addition to lupus anticoagulant ( dRVVT and PTT-LA) and IgG anticardiolipin antibody determinations to evaluate patient groups in which the new assay might be of value. From a total of 90 patients, 2.2% of the samples were abeta2-GPI positive; 51 patients had abeta2-GPI as the only positive antiphospholipid antibody marker; 20 patients had had a venous thrombosis and 14 an arterial thrombosis, 4 had pregnancy complications and 2 had thrombocytopenia. Relatively young patients with cerebrovascular ischaemic events seemed especially to present sole abeta2-GPI positivity. The abeta2-GPI positivity remained fairly constant in the 23 patients from whom follow-up samples were taken. It is concluded that the IgG abeta2-GPI assay seems to be a potentially important additional diagnostic tool for the antiphospholipid antibody syndrome.

STUDY OBJECTIVE:Systemic inflammation may play an important part in the development of cardiovascular disease. It has also been shown that socioeconomic status predicts cardiovascular events independently of established risk factors. The aim of this study was to analyse the association of three sensitive markers of systemic inflammation: C reactive protein (CRP), serum amyloid A protein (SAA), and fibrinogen, with socioeconomic status.DESIGN:Cross sectional study.SETTING:Eastern and southern Finland.PARTICIPANTS:1503 men aged 45 to 74 years who participated in a cardiovascular risk factor survey in 1997. Based on the levels of education and family income, the men were classified to three socioeconomic groups.MAIN RESULTS:Mean concentrations of CRP (p for the trend <0.001), SAA (p for the trend 0.018), and fibrinogen (p for the trend <0.001) decreased substantially with increasing socioeconomic status. The trends in CRP and fibrinogen remained statistically significant after adjustment for smoking, waist to hip ratio, and prevalent longstanding diseases, and a non-significant trend was found for SAA (p for the trend 0.118). The inverse association between inflammation markers and socioeconomic status was particularly strong among the men below 60 years of age.CONCLUSIONS:Systemic inflammation is a potential mediator, especially among young and middle aged men, for the association between socioeconomic status and cardiovascular disease.

The role of paradoxical embolism through patent foramen ovale as a mechanism of cryptogenic stroke is controversial. If a venous source of emboli is relevant, prothrombotic states should be associated with patent foramen ovale and cryptogenic stroke. We assessed the occurrence of several prothrombotic states (factor V Leiden, prothrombin G20210A, deficiencies in protein S, protein C and antithrombin, lupus anticoagulant, anticardiolipin antibodies, elevated factor VIII, resistance to activated protein C) and classical risk factors for venous thrombosis in 57 adult patients with cryptogenic stroke and patent foramen ovale and in 104 matched controls. Prothrombotic states [odds ratio (OR) 2.8; 95% confidence interval (CI), 1.2-6.5; P = 0.021], migraine with aura (OR 4.4; 95% CI 1.8-10.8; P = 0.001) and classical risk factors for venous thrombosis (OR 2.5; 95% CI 1.1-5.7; P = 0.037) were independent risk factors for cryptogenic stroke. In particular factor V Leiden or prothrombin G20210A associated with cryptogenic stroke (P = 0.022) whereas other coagulation abnormalities did not (P = 0.140). Among the patients with prothrombotic states, Valsalva manoeuvre was common at onset of stroke. Our results support the possibility of paradoxical embolism behind strokes in patients with patent foramen ovale.

This case control study was designed to identify risk factors for cryptogenic brain infarction. We assessed the frequency of prothrombotic states, homocysteine, lipoprotein (a) [Lp(a)] and other lipids and the apolipoprotein E phenotype together with conventional risk factors in 46 patients (19 women and 27 men) with cryptogenic brain infarction aged from 15 to 60 years and in 104 community-based controls. Multivariate odds ratios (ORs) for risk factors and 95% CIs were calculated by logistic regression. Hypertension (OR 4.5; 95% CI, 1.5-13.2; P = 0.006), current smoking (OR 2.9; 95% CI, 1.2-6.8; P = 0.012), low HDL cholesterol (HDL-C) (OR 5.4; 95% CI, 1.1-25.5; P = 0.035) and high clotting factor VIII activity (OR 3.6; 95% CI, 1.1-12.2; P = 0.041) were variables associated with cryptogenic brain infarction. These risk factors were not equally frequent in women and men. Low HDL-C and high factor VIII activity in the women, and hypertension, current smoking and a low level of plasma folate in the men were risk factors for cryptogenic stroke. Several of the observed risk factors for cryptogenic brain infarction were lifestyle-associated, which emphasizes the role of health education in addition to pharmacological treatment in the prevention of stroke.

The arginine/glutamine (Arg/Gln) polymorphism of the factor VII (FVII) gene is associated with variation in coagulation activity (FVII:C) and antigen concentration (FVII:Ag) of the FVII protein. We estimated frequency distributions of the Arg and Gln alleles and respective genotypes in North Karelia, and evaluated the utility of this polymorphism, serum lipids, and body mass index (BMI) in the prediction of the distributions of FVII:C and FVII:Ag in a cross-sectional study and in a prospective cohort study. The sample comprised 203 males and 262 females (aged 45-64 years) who were seen twice, in 1992 and 1995. The Arg/Arg genotype and the Arg allele frequencies were among the highest reported so far (86 and 93% respectively, in men; and 89 and 94% respectively, in women). Intragenotypic means of both FVII:C and FVII:Ag were significantly higher in the Arg/Arg genotype than in the Arg/Gln genotype in both genders. Also, intragenotypic variances were different in different genotypes in females. Regression relationships between the FVII:C and FVII:Ag and serum triglyceride, and total cholesterol levels and BMI were positive in both genotypes in both genders, which has not been found in other populations. In prospective analyses, average changes in the FVII:C and FVII:Ag were genotype specific in both genders, as were also regression relationships between these changes and changes in triglyceride level in females (P = 0.065 for FVII:C and P = 0.061 for FVII:Ag). A consequence of these complex genetic architectures is that predictive utility of the Arg/Gln genotypes depends on population, gender, serum lipid levels, and BMI, and changes in these factors over time.

In the seventh national voluntary cross-sectional survey (in 1999) of Finnish patients with haemophilia A or B, type 3 von Willebrand disease or factor XIII deficiency, a plasma sample was received from 193 patients (67%). The samples were tested for hepatitis B and C, human immunodeficiency virus (HIV) and human T-cell leukaemia virus (HTLV) antibodies. Fifty-one percent of the patients were hepatitis C antibody positive and 34% hepatitis B core antibody positive. None of the patients had antibodies against HIV or HTLV. Eighteen percent of the patients had an elevated alanine aminotransferase activity. Abnormal alanine aminotransferase was significantly associated with hepatitis C seropositivity. No new seroconversions were detected among the haemophiliacs or patients with type 3 von Willebrand disease when compared with the last two surveys in 1993 and 1996, and there was no seroconversion in sole users of solvent/detergent-treated factor products. Currently, 32% of the patients use prophylactic factor treatment as their principal mode of therapy, particularly the younger patients with severe forms of the bleeding diseases.

Recent data suggest that infections, inflammation and the immune system are involved in the process of atherosclerosis. The aim of the present study was to analyze the association of coronary heart disease (CHD) with three inflammation markers, C-reactive protein (CRP), serum amyloid-A (SAA) and plasma fibrinogen. The cross-sectional study included 1400 men aged 45–74 years, who participated in a cardiovascular risk factor survey in Finland in 1997. Participants with prevalent CHD had markedly higher CRP, SAA and fibrinogen levels than participants without CHD. In logistic regression models, the age, smoking, serum cholesterol and systolic blood pressure adjusted odds ratios (2nd, 3rd and 4th quartile as compared with the 1st quartile) of CHD increased gradually with increasing quartile of CRP (1.90, 2.27, 2.64), SAA (1.68, 1.83, 2.41), and fibrinogen (1.60, 1.95, 2.14). The associations weakened somewhat after further adjustment for indicators of obesity, particularly waist hip-ratio. CRP, SAA and fibrinogen levels were markedly lower among CHD patients using cholesterol-lowering medication as compared to non-users. In conclusion, CRP, SAA and fibrinogen, which are markers of inflammation, were positively and significantly associated with prevalent CHD. Central obesity needs to be considered as a confounding factor in the observed associations. These findings support the hypothesis that cholesterol-lowering drugs have an anti-inflammatory effect.

The present study investigated the genetic basis for type II protein C deficiency in Finland, where this form has an unusually high incidence. We demonstrated that, first, a single novel mutation W380G in the protein C gene (PROC) explained 25/26 index patients, estimated to represent two thirds of all families with type II deficiency in Finland. Second, extended chromosomal conservation, i.e. a specific haplotype, around the W380G mutation was indicated in unrelated patients. Third, a local geographical origin for the W380G mutation was suggested by genealogical data. These results are in contrast to the heterogeneity in type II protein C deficiency elsewhere, but closely parallel disorders of the Finnish disease heritage. The high frequency of the type II disease can be explained by founder effect and subsequent enrichment of a single mutation in Finland. The present study also provided a simple means for genetic diagnosis of this disease and the genetic test can be included in the routine screenings in this population.

Positive association has been suggested between a variety of infections and coronary heart disease. Disturbances in blood coagulation system may form a link between infections and coronary heart disease. The aim of this study was to analyze whether chronic bronchitis, defined by the occurrence of symptoms, is associated with selected haemostatic factors in a cross-sectional population study of 2379 Finnish men and women aged between 45 and 64 years. Plasma fibrinogen level was significantly higher, 3.70 versus 3.35 g/l (P < 0.001) in men and 3.64 versus 3.44 g/l (P < 0.001) in women, among subjects with symptoms of chronic bronchitis than among those without symptoms. The association was independent of age, smoking, body mass index, physical exercise, and alcohol consumption. Also plasminogen was higher among men with symptoms than among those without but the difference disappeared after adjustment for age and smoking. Factor VII coagulant activity and factor VII antigen level did not differ between subjects with and without symptoms. Thus, fibrinogen may be associated with a possible mechanism to link chronic bronchitis to coronary heart disease risk, even though the causality of the association cannot be verified in a cross-sectional study.

The Finnish Red Cross Blood Transfusion Service has served as the national reference laboratory for haemostasis for more than 40 years and remains still the only one in the country to diagnose inherited coagulation factor deficiencies. By September 1997, 1076 patients with von Willebrand disease (vWD) were registered. The severity of bleeding symptoms leading to diagnosis varied according to the type of vWD. After prepubertal phase distinctly more female than male patients were diagnosed. The prevalence of severe type 3 vWD is 4:1 000 000.

Congenital resistance to activated protein C due to a point mutation in the factor V gene (Gln506-FV) is the most common genetic risk factor for familial venous thrombosis. Considering the central role of activated protein C as a physiological anticoagulant, the question of why the thrombotic risk associated with Gln506-FV was not more pronounced was asked. We hypothesized that in Gln506-FV heterozygotes, enhanced thrombin formation might preferentially activate protein C and thereby constitute a compensatory antithrombotic effect. We compared the circulatory level of activated protein C in twelve heterozygous carriers of Gln506-FV mutation with that in eighteen noncarriers in same families, and used prothrombin fragment 1+2 as a measure of thrombin generation. The circulating level of activated protein C was higher but not significantly different in heterozygotes compared with normal relatives. Activated protein C levels correlated strongly and positively with protein C antigen levels in both carriers (Spearman R 0.684, p < 0.05) and controls (Spearman R 0.642, p < 0.01). Correlation between activated protein C and prothrombin fragment 1+2 levels was of borderline significance (Spearman R 0.354, p = 0.055). In the current study, thrombin formation assessed by prothrombin fragment 1+2 levels was not significantly enhanced in subjects with heterozygous Gln506-FV compared with family members without the mutation. In conclusion, enhanced thrombin formation is not present in all healthy Gln506-FV heterozygotes in basal conditions. It seems that enhanced protein C activation by thrombin does not constitute a compensatory anticoagulant feedback loop in heterozygous carriers of Gln506-FV. However, the positive correlation between prothrombin fragment 1+2 and activated protein C suggests that, in healthy subjects and in basal conditions, thrombin upregulates the anticoagulant protein C pathway. Thus, it is questionable whether prothrombin fragment 1+2 can directly be used as an indicator of a hypercoagulable state.

SummaryElucidation of the key role of thrombosis in cardiovascular disease events has arisen considerable interest in hemostatic factors and in the repeatability of their determinations. Data on long-term repeatability has, however, remained scanty. We examined twice 208 men and 265 women in North Karelia, eastern Finland. The baseline examination was a part of the FINRISK 1992 Hemostasis Study and the age-range of participants was between 45-64 years. The re-examination took place three years later in 1995. Both surveys followed the same protocol and were carried out during the same season. Spearman rank correlation coefficients between 1992 and 1995 measurements of fibrinogen, factor VII coagulant activity (FVII:C), factor VII antigen (FVII:Ag), and plasminogen were among men 0.72, 0.77, 0.46 and 0.56, respectively. For total cholesterol, HDL-cholesterol, triglycerides and diastolic blood pressure the corresponding coefficients were 0.74, 0.83, 0.66, and 0.54. In women, the coefficient of fibrinogen was lower than in men, 0.62, otherwise the results were similar. Of men belonging to the highest quarter of fibrinogen, FVII:C, FVII:Ag and plasminogen in 1992, 65%, 60%, 53% and 60% belonged to the highest quarter of respective distributions also in 1995. In women, the corresponding proportions were 64%, 65%, 46% and 58%. The modest repeatability of FVII:Ag and plasminogen was mainly due to the high intraindividual variability. However, in comparisons of plasma levels between two groups, relatively small sample sizes seemed to give adequate statistical power to detect possible differences in FVII:Ag and plasminogen. In conclusion, the long-term repeatability of fibrinogen and FVII:C is similar to that of triglycerides and even better than that of diastolic blood pressure, but somewhat lower than the repeatability of total cholesterol. FVII:Ag and plasminogen did not have very good repeatability and more than one measurement of them should be considered if they are used as predictors of cardiovascular disease in prospective studies.