Fibrinogen

Fibrinogen (coagulation factor I) is a hepatically produced 340-kDa glycoprotein that polymerises to fibrin during clot formation and is also an acute-phase reactant. It is measured by the Clauss functional assay (clot-based) or immunoassay; typical reference range is 200-400 mg/dL (2.0-4.0 g/L). Beyond its role in haemostasis, plasma fibrinogen is an independent cardiovascular risk marker: the Fibrinogen Studies Collaboration's individual-participant meta-analysis of 154,211 adults (JAMA 2005) demonstrated a hazard ratio of approximately 2.4 (95% CI 2.3–2.6) for coronary heart disease per 1 g/L higher usual fibrinogen, with similar associations for stroke and non-vascular mortality. Major confounders include acute infection or trauma (rise within 24-48 h), smoking, pregnancy, oral estrogens, malignancy, and chronic inflammation; values can be reduced in disseminated intravascular coagulation, severe liver disease, fibrinolytic therapy and congenital hypofibrinogenaemia.