Diagnosis:
Dysfibrinogenemia screening
• Dysfibrinogenemias are disorders of fibrinogen structure, which may or may not lead to abnormal function.
• Dysfibrinogenemias can be congenital or acquired. The most common causes of acquired dysfibrinogenemia are associated with liver disease.
• Among dysfibrinogenemias, 55% are asymptomatic, 25% are associated with bleeding only, and 20% are associated with thrombosis with or without bleeding.
• The thrombin time is performed by adding a low concentration of thrombin to platelet-poor plasma and measuring the time to clot formation. It is sensitive but is not a very specific test for dysfibrinogenemias. It can be prolonged in the presence of heparin, fibrin degradation products, hypofibrinogenemia, antibovine thrombin antibodies (secondary to fibrin glue), and others.
• The reptilase time is performed by adding Bothrops atrox snake venom to platelet-poor plasma and measuring the time to clot formation. Reptilase time is prolonged in similar situations such as thrombin time, but it is not sensitive to heparin inhibition. Therefore, a prolonged thrombin time with normal reptilase time suggests the presence of heparin.
• Antigenic measurement of fibrinogen can be performed with immunoassays. Decreased functional fibrinogen with normal antigenic fibrinogen suggests the presence of a functional abnormality of fibrinogen.
Hayes, T:
Dysfibrinogenemia and thrombosis. Arch Pathol Lab Med 2002;126:1387-1390.
