Factor I
Key points
- This is a test that measures the amount of fibrinogen in the blood.
- Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand.
- For infants and children: The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust.
- This test may be performed when abnormal blood clotting is present, particularly if there is excessive bleeding.
Alternative names
Serum fibrinogen; Plasma fibrinogen; Fibrinogen; Hypofibrinogenemia test
Definition
This is a test that measures the amount of fibrinogen in the blood.
How the test is performed
Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.
A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
For an infant or young child, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
How to prepare for the test
There is no special preparation needed.
For infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:
- infant test or procedure preparation (birth to 1 year)
- toddler test or procedure preparation (1 to 3 years)
- preschooler test or procedure preparation (3 to 6 years)
- schoolage test or procedure preparation (6 to 12 years)
- adolescent test or procedure preparation (12 to 18 years)
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
This test may be performed when abnormal blood clotting is present, particularly if there is excessive bleeding.
Fibrinogen is a protein produced by the liver. Fibrinogen helps stop bleeding by helping blood clots to form. During normal blood clotting:
- Fibrinogen is broken down by an enzyme called thrombin into short fragments of fibrin. Thrombin also activates a substance called Factor XIII.
Written and revised by
David Cohen, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.