Fibrinogen
Alternative names:
factor I; hypofibrinogenemia test; plasma fibrinogen; serum fibrinogen
How the test is performed:
Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (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 tourniquet 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.
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:
Adult:
There is no special preparation.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
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 synthesized by the liver. It is used in the blood clotting process. Fibrinogen is cleaved (broken) by the enzyme thrombin to form fibrin peptides during normal coagulation (blood clotting). Thrombin also activates fibrin stabilizing factor (Factor XIII) which subsequently cross-links the fibrin monomer, thereby forming a lattice for the blood clot. Platelet aggregation at the site of injury is facilitated by binding of protein receptors in the platelet cell membranes to fibrin peptides.
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