Fibrinogen Activity, Clauss
Fibrinogen is essential for the formation of a blood clot. Deficiency can produce mild to severe bleeding disorders.
- How is it used?
- When is it ordered?
- What does the test result mean?
- Is there anything else I should know?
How is it used?
This testing is used to evaluate fibrinogen, a
that is essential for blood clot formation. When there is an injury and
bleeding occurs, the body forms a blood clot through a series of steps.
In one of the last steps, soluble fibrinogen is converted into
insoluble fibrin threads that crosslink together to form a net that
stabilizes and adheres at the injury site until the area has healed.
Two types of tests are available:
- A fibrinogen activity test measures the function of fibrinogen and its ability to be converted into fibrin. It is used:
- As part of an investigation of a possible bleeding disorder or inappropriate blood clot formation ()
- As a follow-up to an abnormal bleeding disorder test (prothrombin time, PT or partial thromboplastin time, PTT) and/or an episode of prolonged or unexplained bleeding
- Along with tests such as PT, PTT, platelet function tests, fibrin degradation products (FDP), and D-dimer to help diagnose disseminated intravascular coagulation (DIC) or
- Occasionally to help monitor the status of a progressive disease (such as liver disease) over time or, rarely, to monitor treatment of an acquired condition (such as DIC)
- Sometimes along with other cardiac risk markers such as C-reactive protein (CRP) to help determine a person's overall risk of developing cardiovascular disease.
This use of the test has not gained widespread acceptance though
because there are no direct treatments for elevated levels. However,
many health practitioners feel that fibrinogen activity measurements
give them additional information that may lead them to be more
aggressive in treating those risk factors that they can treat (such as
unhealthy levels of cholesterol).
- A fibrinogen antigen test is occasionally ordered as a
follow-up test to determine whether decreased fibrinogen activity is due
to insufficient fibrinogen or dysfunctional fibrinogen (caused by
inherited or acquired dysfibrinogenemia).
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When is it ordered?
A health practitioner may order a fibrinogen activity test when someone:
- Has unexplained or prolonged bleeding
- Has a
- Has an abnormal PT and PTT test result
- Has symptoms of or is undergoing treatment for DIC or
- May have an inherited or acquired coagulation factor (clotting protein) deficiency or dysfunction
- Has an acquired bleeding disorder and the person's health
practitioner wants to evaluate and monitor their clotting ability (over
A fibrinogen antigen test may be performed when someone
has a low result on a fibrinogen activity test to help determine
whether it is due to insufficient or dysfunctional fibrinogen.
High fibrinogen levels have also been associated with coronary heart disease, myocardial infarction,
and peripheral arterial disease. In some cases, fibrinogen activity
testing is performed along with other tests when a health practitioner
wants to evaluate an individual's risk of developing cardiovascular disease.
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What does the test result mean?
Fibrinogen test results are reported as the concentration of the protein in the blood. Fibrinogen activity tests are converted into concentrations for comparison with fibrinogen antigen results.
Normal fibrinogen activity results usually reflect normal blood clotting ability.
Significantly decreased fibrinogen activity may be due to decreased
or dysfunctional fibrinogen. Reduced fibrinogen activity and antigen
levels may impair the body's ability to form a stable blood clot.
low levels may be related to decreased production due to an inherited condition such as or or to an acquired condition such as end-stage liver disease or severe malnutrition.
low levels are often related to consumption of fibrinogen such as may be seen with disseminated intravascular coagulation (DIC) and ,
which occurs when the body is overactive in clearing blood clots.
Reduced fibrinogen levels may also occur following rapid, large-volume
blood transfusions and in people who are malnourished.
Sometimes a health practitioner will use a ratio of the antigen test
and the activity test. This is to help to distinguish dysfibrinogenemia
(high ratio) from hypofibrinogenemia (ratio close to 1).
Fibrinogen is an ,
meaning that fibrinogen concentrations may rise sharply in any
condition that causes inflammation or tissue damage. Elevated
concentrations of fibrinogen are not specific; that is, they do not tell
the health practitioner the cause or location of the disturbance.
Usually these elevations in the fibrinogen level are temporary,
returning to normal after the underlying condition has been resolved.
Elevated levels may be seen with:
While fibrinogen levels are elevated, a person's risk of
developing a blood clot may be increased and, over time, they could
contribute to an increased risk for developing cardiovascular disease.
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Is there anything else I should know?
Blood transfusions within the past month may affect fibrinogen test results.
Certain drugs may cause decreased levels, including anabolic
steroids, phenobarbital, streptokinase, urokinase, L-asparaginase,
tissue plasmogen activators, and valproic acid. Moderate elevations in
fibrinogen are sometimes seen with pregnancy, cigarette smoking, and with oral contraceptives or estrogen use.
is a rare coagulation disorder caused by in the
controlling the production of fibrinogen in the liver. It causes the
liver to make an abnormal, dysfunctional fibrinogen, one that resists
degradation when converted to fibrin or can not function normally in the
Dysfibrinogenemia may increase a person's risk of venous thrombosis or,
rarely, cause a mild bleeding tendency. People with fibrinogen
deficiency or dysfibrinogenemia may experience poor wound healing.
Genetic molecular testing is occasionally performed for those with inherited dysfibrinogenemia, , or to identify the genetic mutation responsible. Testing for this mutation may also be performed for other family members.
People with liver disease may develop acquired dysfibrinogenemia that could contribute to bleeding or .