Fibrinogen Activity Test
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
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 Activity Test
A fibrinogen activity test may be ordered alone or as part of a
series of tests to determine the cause of abnormal bleeding.
Your doctor may order a fibrinogen activity 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
Tests may also be ordered if you have:
- 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
- a possible acquired or inherited factor
deficiency that affects how your blood clots
A fibrinogen activity 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.
How Is the Test Administered?
There are no special preparations necessary for this test. Your
doctor may advise you to stop taking certain medications before this test. It’s
very important that you inform your doctor if you’re taking any blood thinners.
A healthcare provider will take a sample of blood from your arm.
They’ll clean the site with a swab of rubbing alcohol. They’ll insert the needle
into a vein, and a tube will be attached to collect the blood. The needle will
be removed when enough blood has been drawn. The site will then be covered with
a gauze pad.
This blood sample will be sent to a laboratory for analysis.
Understanding Your Test Results
The normal level of fibrinogen in the blood is between 1.5 to 3.0
grams per liter.
Abnormal results may be higher or lower than the reference range.
Abnormal results can be caused by:
- excessive fibrinogen use
- acquired or inherited fibrinogen deficiency
- abnormal fibrinolysis
Types of Fibrinogen Deficiency
The three types of fibrinogen
deficiency are afibrinogenemia, hypofibrinogenemia, and dysfibrinogenemia:
Afibrinogenemia is the total absence of fibrinogen. This disorder
out of every 10 million people. This disorder causes the most severe
bleeding out of the three forms of fibrinogen deficiency.
Hypofibrinogenemia is an abnormally low level of fibrinogen. In
this case, the test would show a level between 0.2 and 0.8 grams per liter.
This form of the deficiency is less common than afibrinogenemia and it can
cause mild to severe bleeding.
Dysfibrinogenemia is a condition in which fibrinogen levels are
normal, but the protein doesn’t function properly. Dysfibrinogenemia affects
only about one
in every 1 million people. The condition rarely causes a bleeding problem
and instead is more likely to cause thrombosis.
What Are the Risks of the Test?
As with any blood test, there are minimal risks. These include
- You may have minor bruising at the needle site.
- In very rare cases, the vein may also become
swollen after blood is drawn. Applying a warm compress several times per day
can treat this condition, which is known as phlebitis.
- Ongoing bleeding could be a problem if you have a
bleeding disorder or if you’re taking blood thinners, such as warfarin
(Coumadin) or aspirin.
- Puncture site infection is another potential
complication, noted by red swelling and possible pus formation.
What to Expect After the Test
If you have a fibrinogen deficiency, your doctor may prescribe
factor replacement treatment to control or stop the bleeding. This involves receiving
fibrinogen blood products or substitutes through your veins.
This form of treatment should be used to increase your fibrinogen
level to 1 gram per liter if you’re experiencing mild bleeding. If you’re having
severe bleeding or undergoing surgery,
your levels should be increased to 2 grams per liter.
Fibrinogen concentrate may also be administered at the following
- during surgery
- during delivery or after childbirth
- before dental surgery
- after trauma
- to prevent bleeding