Fibrinogen is an essential protein in blood clot formation. It is one of twenty coagulation factors produced by the liver. When a blood vessel is damaged (internal or external bleeding), the various clotting factors act in cascade to eventually transform fibrinogen into fibrin filaments that will form the clot and stop the bleeding. Measuring fibrinogen is therefore used in individuals with either unexplained prolonged bleeding or clots (thromboses) when the thrombin time or aPTT results are abnormal or when there may be an innate (genetic) or acquired coagulation abnormality.
A normal fibrinogen level usually reflects normal coagulation. Chronic low levels may be due to insufficient synthesis by the liver (liver disease or severe malnutrition) or non-functional fibrinogen (genetic condition). Levels can also be acutely low in disseminated intravascular coagulation or during episodes where the body quickly rids itself of clots (abnormal or post-treatment fibrinolysis). Fibrinogen increases in a non-specific way in acute inflammatory conditions (infections, rheumatoid arthritis and other inflammations, cancers, etc.). Chronic high levels could be associated with a higher risk of cardiovascular disease.