Fibrinogen (factor I) is a glycoprotein that in vertebrates circulates in the blood. During tissue and vascular injury it is converted enzymatically by thrombin to fibrin and subsequently to a fibrin-based blood clot. Fibrinogen functions primarily to occlude blood vessels and thereby stop excessive bleeding. However, fibrinogen’s product, fibrin, binds and reduces the activity of thrombin. This activity, sometimes referred to as antithrombin I, serves to limit blood clotting. Loss or reduction in this antithrombin 1 activity due to mutations in fibrinogen genes or hypo-fibrinogen conditions can lead to excessive blood clotting and thrombosis. Fibrin also mediates blood platelet and endothelial cell spreading, tissue fibroblast proliferation, capillary tube formation, and angiogenesis and thereby functions to promote tissue revascularization, wound healing, and tissue repair.
A fibrinogen activity test is also known as a Factor I assay. It’s used to determine the level of fibrinogen in your blood. Fibrinogen, or factor I, is a blood plasma protein that’s made in the liver. Fibrinogen is one of 13 coagulation factors responsible for normal blood clotting.
When you start to bleed, your body initiates a process called the coagulation cascade, or clotting cascade. This process causes coagulation factors to combine and produce a clot that will stop the bleeding. If you don’t have enough fibrinogen or if the cascade isn’t working normally, clots will have difficulty forming. This can cause excessive bleeding.
Low fibrinogen levels can also cause thrombosis due to an increase in coagulation activity. Thrombosis refers to the formation of a blood clot inside of a blood vessel. The clot blocks the normal flow of blood through the circulatory system. This can lead to serious medical conditions such as heart attack and stroke.
Purpose of the Fibrinogen Test
Fibrinogen test may be prescribed alone or as part of a series of tests to determine the cause of abnormal bleeding.
Your doctor may prescribe fibrinogen test if you’re experiencing any of the following:
- excessive bruising
- excessive bleeding from the gums
- frequent nosebleeds
- hemorrhage of the gastrointestinal tract
- blood in the urine
- blood in the stool
- bleeding in the head
- rupture of the spleen
- abnormal results from a prothrombin time test or partial thromboplastin time test
- symptoms of disseminated intravascular coagulation, which is a condition in which small clots form throughout the body
- signs of an abnormal breakdown of fibrinogen (fibrinolysis)
- a possible acquired or inherited factor deficiency that affects how your blood clots
A fibrinogen test may also be part of a general evaluation of your risk of cardiovascular disease. People with clotting disorders can have an increased risk of heart disease and stroke.
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What are the other Names for this Test? (Equivalent Terms)
- Factor I Test
- Functional Fibrinogen Test
- Serum Fibrinogen Test
Fibrinogen Test Normal / Reference Range
Fibrinogen is a soluble protein in the plasma that is broken down to fibrin by the enzyme thrombin to form clots.
Why fibrinogen level increases?
Fibrinogen is an acute phase reactant and hence, inflammatory conditions increase fibrinogen levels. Increased fibrinogen levels may be found with:
Certain medications that you may be currently taking may influence the outcome of the test.
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