01/03/2010

Plasma fibrinogen level and the risk of major cardiovascular diseases and nonvascular mortality: an individual participant meta-analysis
JAMA. 2005 Oct 12;294(14):1799-809
Fibrinogen Studies Collaboration, Danesh J, Lewington S, Thompson SG, Lowe GD, Collins R, Kostis JB, Wilson AC, Folsom AR, Wu K, etc
Department of Public Health and Primary Care, University of Cambridge, Cambridge, England. john.danesh@phpc.cam.ac.uk
CONTEXT: Plasma fibrinogen levels may be associated with the risk of coronary heart disease (CHD) and stroke. OBJECTIVE: To assess the relationships of fibrinogen levels with risk of major vascular and with risk of nonvascular outcomes based on individual participant data. DATA SOURCES: Relevant studies were identified by computer-assisted searches, hand searches of reference lists, and personal communication with relevant investigators. STUDY SELECTION: All identified prospective studies were included with information available on baseline fibrinogen levels and details of subsequent major vascular morbidity and/or cause-specific mortality during at least 1 year of follow-up. Studies were excluded if they recruited participants on the basis of having had a previous history of cardiovascular disease; participants with known preexisting CHD or stroke were excluded. DATA EXTRACTION: Individual records were provided on each of 154,211 participants in 31 prospective studies. During 1.38 million person-years of follow-up, there were 6944 first nonfatal myocardial infarctions or stroke events and 13,210 deaths. Cause-specific mortality was generally available. Analyses involved proportional hazards modeling with adjustment for confounding by known cardiovascular risk factors and for regression dilution bias. DATA SYNTHESIS: Within each age group considered (40-59, 60-69, and > or =70 years), there was an approximately log-linear association with usual fibrinogen level for the risk of any CHD, any stroke, other vascular (eg, non-CHD, nonstroke) mortality, and nonvascular mortality. There was no evidence of a threshold within the range of usual fibrinogen level studied at any age. The age- and sex- adjusted hazard ratio per 1-g/L increase in usual fibrinogen level for CHD was 2.42 (95% confidence interval [CI], 2.24-2.60); stroke, 2.06 (95% CI, 1.83-2.33); other vascular mortality, 2.76 (95% CI, 2.28-3.35); and nonvascular mortality, 2.03 (95% CI, 1.90-2.18). The hazard ratios for CHD and stroke were reduced to about 1.8 after further adjustment for measured values of several established vascular risk factors. In a subset of 7011 participants with available C-reactive protein values, the findings for CHD were essentially unchanged following additional adjustment for C-reactive protein. The associations of fibrinogen level with CHD or stroke did not differ substantially according to sex, smoking, blood pressure, blood lipid levels, or several features of study design. CONCLUSIONS: In this large individual participant meta-analysis, moderately strong associations were found between usual plasma fibrinogen level and the risks of CHD, stroke, other vascular mortality, and nonvascular mortality in a wide range of circumstances in healthy middle-aged adults. Assessment of any causal relevance of elevated fibrinogen levels to disease requires additional research.
PMID: 16219884
           
Association of fibrinogen, C-reactive protein, albumin, or leukocyte count with coronary heart disease: meta-analyses of prospective studies
JAMA. 1998 May 13;279(18):1477-82
Danesh J, Collins R, Appleby P, Peto R.
Clinical Trial Service Unit and Epidemiological Studies Unit, Nuffield Department of Clinical Medicine, University of Oxford, England. john.danesh@balliol.ox.ac.uk
CONTEXT: A large number of epidemiologic studies have reported on associations between various "inflammatory" factors and coronary heart disease (CHD). OBJECTIVE: To assess the associations of blood levels of fibrinogen, C-reactive protein (CRP), and albumin and leukocyte count with the subsequent risk of CHD. DATA SOURCES: Meta-analyses of any long-term prospective studies of CHD published before 1998 on any of these 4 factors. Studies were identified by MEDLINE searches, scanning of relevant reference lists, hand searching of cardiology, epidemiology, and other relevant journals, and discussions with authors of relevant reports. STUDY SELECTION: All relevant studies identified were included. DATA EXTRACTION: The following information was abstracted from published reports (supplemented, in several cases, by the authors): size and type of cohort, mean age, mean duration of follow-up, assay methods, degree of adjustment for confounders, and relationship of CHD risk to the baseline assay results. DATA SYNTHESIS: For fibrinogen, with 4018 CHD cases in 18 studies, comparison of individuals in the top third with those in the bottom third of the baseline measurements yielded a combined risk ratio of 1.8 (95% confidence interval [CI], 1.6-2.0) associated with a difference in long-term usual mean fibrinogen levels of 2.9 pmol/L (0.1 g/dL) between the top and bottom thirds (10.3 vs 7.4 pmol/L [0.35 vs 0.25 g/dL]). For CRP, with 1053 CHD cases in 7 studies, the combined risk ratio of 1.7 (95% CI, 1.4-2.1) was associated with a difference of 1.4 mg/L (2.4 vs 1.0 mg/L). For albumin, with 3770 CHD cases in 8 studies, the combined risk ratio of 1.5 (95% CI, 1.3-1.7) was associated with a difference of 4 g/L (38 vs 42 g/L, ie, an inverse association). For leukocyte count, with 5337 CHD cases in the 7 largest studies, the combined risk ratio of 1.4 (95% CI, 1.3-1.5) was associated with a difference of 2.8 x 10(9)/L (8.4 vs 5.6 x 10(9)/L). Each of these overall results was highly significant (P<.0001). CONCLUSIONS: The published results from these prospective studies are remarkably consistent for each factor, indicating moderate but highly statistically significant associations with CHD. Hence, even though mechanisms that might account for these associations are not clear, further study of the relevance of these factors to the causation of CHD is warranted.
PMID: 9600484

Fibrinogen. Cardiovascular risk factor or marker?
Arch Cardiol Mex. 2006 Oct-Dec;76 Suppl 4:S158-72
Canseco-Avila LM, Jerjes-Sánchez C, Ortiz-López R, Rojas-Martínez A, Guzmán-Ramírez D.
Dpto. Bioquímica, Facultad de Medicina del Hospital Universitario, UANL, México.
Endothelial dysfunction and inflammation play a crucial role in all stages of atherosclerosis, from the beginning, during progression, and, finally, in its highest clinical expression: acute coronary syndromes. In this process, fibrinogen, an acute phase reactant with active participation in endothelial function, thrombosis and inflammation has proved to be an independent variable to cardiovascular risk together with its participation in resistance phenomena to different antithrombotic approaches. The reasons by which fibrinogen is elevated in cardiovascular disease and atherosclerosis are, in general, only incompletely understood; but all cells involved in the atherogenetic process are able to produce cytokines, which induce an acute phase reaction that increases fibrinogen levels in plasma. The potential pathophysiological mechanisms by which elevated fibrinogen levels mediate cardiovascular risk are multiple. Fibrinogen forms the substrate for thrombin an represents the final step in the coagulation cascade, it is essential for platelet aggregation, it modulates endothelial function, it promotes smooth muscle cell proliferation and migration, it interacts with the binding of plasmin with its receptor and, finally, it represents a major acute phase protein. Epidemiological studies have established sufficient evidence to consider fibrinogen as a strong, consistent, and independent cardiovascular risk marker or factor. Based on all these implications, the target of this review is an analysis of physiopathogenic and epidemiologic evidence searching for guidelines to establish whether fibrinogen as a risk factor or marker is the lost link between cardiovascular disease and classic risk factors. CONCLUSION: Analyses of the respective studies suggest that fibrinogen is an important and independent cardiovascular risk factor, clearly associated with conventional risk factors and genetic polymorphisms. Whether or not fibrinogen is causally involved in atherothrombogenesis still remains to be determined and despite of unsolved issues that are waiting conclusive answers, fibrinogen has emerged as an important additional marker of cardiovascular risk.
PMID: 17469344

Fibrin(ogen) in cardiovascular disease: an update
Thromb Haemost. 2003 Apr;89(4):601-9
Koenig W.
Dept. of Internal Medicine II - Cardiology, University of Ulm Medical Center, Robert-Koch Str. 8, D - 89081 Ulm/ Germany. wolfgang.koenig@medizin.uni-ulm.de
The notion that fibrinogen is strongly, consistently, and independently related to cardiovascular risk has been widely accepted. The evidence is based on numerous prospective epidemiological studies and clinical observations. In meta-analysis, an association between even modest increases (10%) in fibrinogen and future coronary heart disease (CHD) endpoints has been found with an odds ratio for CHD of 1.8; 95% CI, 1.6 to 2.0, if the top tertile of the fibrinogen distribution was compared to the bottom tertile; but fibrinogen levels were also associated with unstable and stable coronary artery disease, and coronary complications after interventions. Similar results have been obtained for incident stroke, progression of peripheral arterial disease, and finally for total mortality. The reasons however, why fibrinogen is elevated in cardiovascular disease and in atherosclerosis in general, are only incompletely understood; but all cells involved in the atherogenetic process are able to produce cytokines which induce an acute phase reaction, and thus increase fibrinogen plasma levels. The potential pathophysiological mechanisms by which elevated fibrinogen levels mediate cardiovascular risk are manyfold: It forms the substrate for thrombin and represents the final step in the coagulation cascade; it is essential for platelet aggregation; it modulates endothelial function; it promotes smooth muscle cell proliferation and migration; it interacts with the binding of plasmin with its receptor, and finally it represents a major acute phase protein. Whether or not fibrinogen is causally involved in atherothrombogenesis still remains to be determined, and even though other unsolved issues await conclusive answers, fibrinogen has emerged as an important additional marker of cardiovascular risk. PMID: 12669113

Association of fibrinogen and lipoprotein(a) as a coronary heart disease risk factor in men (The Quebec Cardiovascular Study)
Am J Cardiol. 2002 Mar 15;89(6):662-6.
Cantin B, Després JP, Lamarche B, Moorjani S, Lupien PJ, Bogaty P, Bergeron J, Dagenais GR.
Quebec Heart Institute, Ste-Foy, Quebec, Canada. Clajoie@sympatico.ca
Fibrinogen has been prospectively found to correlate with coronary heart disease (CHD) but a similar association has not been well established for lipoprotein (a) (Lp(a)). Plasma lipids, Lp(a), and fibrinogen levels were measured in 2,125 men (aged 47 to 76 years) who were free of clinical CHD. During a 5-year follow-up period, 116 first CHD events were documented. Men with CHD were older, smoked more, had a higher prevalence of diabetes, and higher levels of systolic blood pressure, cholesterol, low-density lipoprotein cholesterol, Lp(a), and fibrinogen, and lower plasma high-density lipoprotein cholesterol levels. Only fibrinogen levels in the upper tertile of the distribution compared with the lower tertiles were associated with a significant risk of CHD (adjusted risk ratio 2.5; 95% confidence interval [CI] 1.4 to 4.2; p = 0.0010). Such an association was not observed with Lp(a). To assess a possible relation between fibrinogen and Lp(a) to the risk of CHD events, men were assigned to 1 of 4 groups according to fibrinogen median levels and a Lp(a) cut-off level of 300 mg/L: group 1: fibrinogen < 4.05 g/L and Lp(a) < 300 mg/L; group 2: fibrinogen < 4.05 g/L and Lp(a) > or =300 mg/L; group 3: fibrinogen > or =4.05 g/L and Lp(a) < 300 mg/L; and group 4: fibrinogen > or =4.05 g/L and Lp(a) > or =300 mg/L. Using group 1 as a reference, a significant risk ratio was only documented in group 4 (2.5; 95% CI 1.2 to 5.1; p = 0.0132). In this population, high fibrinogen levels associated with high Lp(a) levels significantly increased the risk of CHD. PMID: 11897206