Reference Range

Fibrinogen is a soluble protein in the plasma that is broken down to fibrin by the enzyme thrombin to form clots.

Fibrinogen reference ranges are as follows^[1]:

Adult: 200-400 mg/dL or 2-4 g/L (SI units)
Newborn: 125-300 mg/dL

Possible critical value: < 100 mg/dL

Interpretation

Normal fibrinogen activity results usually reflect normal blood-clotting ability.

Decreased fibrinogen levels (< 100 mg/dL) are associated with the following:^[2]

Afibrinogenemia: Chronic
Hypofibrinogenemia: Chronic
End-stage liver disease: Chronic
Severe malnutrition: Chronic
Disseminated intravascular coagulation (DIC): Acute
Abnormal fibrinolysis: Acute
Large-volume blood transfusions: Acute

Fibrinogen is an acute-phase reactant, meaning that elevated fibrinogen levels can be seen the following conditions:^{[2, 3]}

Inflammation
Tissue damage/trauma
Infection
Cancer
Acute coronary syndrome
Strokes
Inflammatory conditions

Collection and Panels

Specimen: Plasma

Container: Light blue (sodium citrate)

Collection method: Routine venipuncture

Processing: Electromagnetic mechanical clot detection/radial immunodiffusion; 2 mL from cuvette is run through an automated machine that physically detects the coagulation factor. It takes approximately 48-96 hours to produce a result.

Unacceptable conditions: Serum, hemolyzed specimens, specimens older than 24 hours

Storage: Frozen samples can last one month before degradation; ambient, 4 hours; refrigerated, 24 hours^[4]

Fibrinogen levels are typically also tested as part of the DIC panel (fibrin, fibrin monomer, platelet, prothrombin time [PT], partial thromboplastin time [PTT], international normalized ratio for prothrombin time, D-dimer).

Description

Fibrinogen is a soluble protein that is produced in the liver and released into the bloodstream. When tissue or blood vessels are damaged, the coagulation cascade is initiated by platelets, and clotting factors are activated to the site as needed, one after another.

At the end of the cascade, fibrinogen is converted to fibrin. Fibrin is an insoluble protein that forms a threaded mesh over the injury site. Thrombin is the enzyme that activates this conversion.^[3]

Indications/Applications

The fibrinogen test is used to investigate certain bleeding or clotting abnormalities, as follows:

Bleeding disorder
Thrombotic events
Suspected DIC
Abnormalities in coagulation panel (PT/PTT)
Follow-up in chronic conditions such as liver disease
Dysfibrinogenemia, in which a fibrinogen antigen test is performed to differentiate lack of protein in the system or just dysfunctional fibrinogen
Occasionally used for screening risk of coronary artery disease