Test Catalog

Test ID: FIBAG    
Fibrinogen Antigen, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluation of fibrinogen deficiency


Measuring fibrinogen in patients with elevated plasma levels of fibrin degradation products, patients receiving heparin, and in patients with antibodies to thrombin (following surgical use of topical bovine thrombin)


Identifying afibrinogenemia, hypofibrinogenemia, and dysfibrinogenemia when ordered in combination with fibrinogen activity (FIB / Fibrinogen, Plasma)

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Fibrinogen (clotting factor I) is an essential protein responsible for blood clot formation. In the final step of the coagulation cascade, thrombin converts soluble fibrinogen into insoluble fibrin strands that crosslink and form a clot.


Fibrinogen is synthesized in the liver and has a biological half-life of 3 to 5 days in the circulating plasma. Fibrinogen deficiencies can be congenital or acquired and lead to prolonged coagulation times. Isolated fibrinogen deficiency is an extremely rare inherited coagulation disorder.


Acquired fibrinogen deficiency is most commonly caused by, acute or decompensated intravascular coagulation and fibrinolysis (DIC). Other causes of fibrinogen deficiency include advanced liver disease, L-asparaginase therapy, or fibrinolytic agents (eg, streptokinase, urokinase, tissue plasminogen activator).

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

> or =18 years: 196-441 mg/dL

Reference values have not been established for patients that are less than 18 years of age.

Interpretation Provides information to assist in interpretation of the test results

This method measures the total amount of fibrinogen protein (ie, fibrinogen antigen) present in the plasma.


Adequate fibrinogen antigen levels in a context of low fibrinogen activity suggests a dysfibrinogenemia.


Fibrinogen antigen levels lower than 100 mg/dL are associated with an increased risk of bleeding.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Differentiation of congenital from acquired defects of fibrinogen requires clinical correlation and the results of standard clotting-based fibrinogen activity (FIB / Fibrinogen, Plasma) testing.


Fibrinogen is an acute phase reactant; plasma levels can be increased by inflammatory illnesses, nephrotic syndrome, liver disease, pregnancy, estrogen therapy, and/or compensated intravascular coagulation.

Clinical Reference Recommendations for in-depth reading of a clinical nature

de Moerloose P, Casini A, Neerman-Arbez M: Congenital fibrinogen disorders: an update. Semin Thromb Hemost. 2013 Sep;39(6):585-595