At a Glance
Congenital disorders of fibrinogen can be divided into afibrinogenemia (characterized by absent or trace fibrinogen in the plasma or platelets), hypofibrinogenemia (characterized by decreased fibrinogen level in the plasma) and dysfibrinogenemia (characterized by synthesis of an abnormal fibrinogen molecule that does not function properly).
Afibrinogenemia/hypofibrinogenemia clinical manifestations:
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Lifelong bleeding tendency of variable severity: umbilical cord and postcircumcision bleeding (neonate), intracerebral bleeding (infancy, childhood), easy bruising, mucosal, gastrointestinal and genitourinary hemorrhages.
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Early pregnancy spontaneous abortions, menometrorrhagia, postpartum hemorrhage.
Dysfibrinogenemia clinical manifestations:
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Mild to moderate bleeding after trauma.
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Venous or arterial thrombosis.
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Combination of thrombotic and hemorrhagic manifestations.
What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?
Tests for afibrinogenemia/hypofibrinogenemia include:
Prolonged prothrombin time (PT), partial thromboplastin time (PTT), thrombin time (TT).
Correction of the TT 1:1 mixing study.
Delayed-type hypersensitivity skin test (in patients with afibrinogenemia, show only erythema and no induration because of lack of fibrin deposition).
Fibrinogen assay by clotting and immunologic methods (show no detectable/trace fibrinogen [afibrinogenemia] or decreased fibrinogen [20-80 mg/dL, hypofibrinogenemia]).
The erythrocyte sedimentation rate (ESR; very slow, because fibrinogen is one of the main determinants of this rate).
Tests for dysfibrinogenemia include:
Prolonged thrombin time (TT), PT, and PTT.
Abnormal reptilase time (reptilase, derived from snake venom, cleaves fibrinopeptide A, resulting in the formation of clot; not affected by heparin).
Correction or noncorrection of the TT 1:1 mixing study.
Fibrinogen activity/antigen ratio decreased; liver function tests normal; inherited dysfibrinogenemia likely.
Fibrinogen immunoelectrophoresis (sometimes shows an abnormal migration in agarose gel).
Normal liver function tests and fibrin split products/D-dimer (to exclude liver disease and DIC).
Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?
Heparin, direct thrombin inhibitors (DTI), plasminogen activator, radiocontrast or topical bovine thrombine use prolonged TT.
Valproate and L-asparaginase impair the hepatic synthesis of fibrinogen.
What Lab Results Are Absolutely Confirmatory?
Fibrinogen level by clotting (measures activity) and immunologic (measures antigen) methods are confirmatory.
Definitive diagnosis depends on biochemical characterization of the fibrinogen defect, which may require amino acid sequencing.
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