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Formal name: Factor I

At a Glance

Why Get Tested?

To determine whether your fibrinogen level is adequate to allow normal blood clotting, to help diagnose disseminated intravascular coagulation (DIC), to help determine whether you have an inherited fibrinogen deficiency or abnormality. Sometimes as a non-specific marker of inflammation in the blood. Very occasionally to help evaluate your risk of developing cardiovascular disease.

When to Get Tested?

When you have unexplained or prolonged bleeding, an abnormal prothrombin time (PT) or activated partial thromboplastin time (aPTT) test, or have a relative with a hereditary fibrinogen deficiency or abnormality. To evaluate whether certain abnormalities in a full blood count are due to inflammation or are self-generated. When your doctor wants additional information to help evaluate your risk of developing heart disease

Sample Required?

A blood sample drawn from a vein in your arm, or sometimes, via a finger prick

The Test Sample

What is being tested?

Fibrinogen is a coagulation factor, a protein that is essential for blood clot formation. It is produced by the liver and released into the circulation as needed along with over 20 other clotting factors. Normally, when a body tissue or blood vessel wall is injured a process called the coagulation cascade activates these factors. As the cascade nears completion, soluble fibrinogen (fibrinogen dissolved in fluid) is changed into insoluble fibrin threads. These threads cross-link to form a fibrin net and then stabilise at the injury site. The net adheres there, along with aggregated cell fragments called platelets, to form a stable blood clot. This barrier prevents additional blood loss and remains in place until the area has healed.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. As an alternative, particularly in paediatric care, the blood sample is drawn by quickly pricking the fingertip with a lancet.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.