Acquired von Willebrand syndrome (AVWS) is a rare disorder in which laboratory findings and clinical symptoms mimic various types of von Willebrand disease (VWD). It may be suspected in a patient with abnormal VWD tests and no previous history of…
von Willebrand factor (VWF) is a large adhesive glycoprotein required for platelet adhesion to subendothelium at the site of vessel injury, platelet–platelet interaction to form the platelet plug, and stabilization of factor VIII (FVIII) in the circulation. Deficiency or defect…
Decreased fibrinogen concentration or impaired fibrinogen function can lead to hemorrhage. Thus fibrinogen testing is frequently utilized in the setting of trauma, surgery, disseminated intravascular coagulopathy, and fibrinolytic treatment to determine the need for replacement product. Congenital decreases in fibrinogen…
Coagulation factor inhibitor assays are used to identify inhibitors occurring in individuals with inherited factor deficiencies (alloantibodies) and those not congenitally deficient (autoantibodies). Alloantibodies are sought when congenitally deficient patients fail to respond to appropriate therapy. Autoantibodies are suspected when…
Coagulation factors may be measured by methods assessing both their presence, as antigens, and their ability to function, as activity. Inherited coagulation factor deficiencies may be of two types. Type I defects (quantitative) have decreased absolute amounts of the factor,…
In mixing studies, patient plasma with a prolonged activated partial thromboplastin time (PTT) or prothrombin time (PT) is mixed with normal pool plasma (NPP). PTT or PT is measured after mixing the two samples. Mixing studies are used to distinguish…
Along with prothrombin time (PT), activated partial thromboplastin time (PTT) serves as a common screening test for coagulation factor deficiencies. The test is sensitive to significantly decreased activities of so-called intrinsic (FXI, FIX, FVIII), common (FX, FV, FII, and fibrinogen),…
Prothrombin time (PT) was one of the first generated in vitro tests of the hemostasis system. It measures the time to form a fibrin clot in platelet-poor plasma stimulated with high amount of tissue factor (TF) and anionic phospholipid at the…
The human hemostasis system is complex and tightly regulated. The maintenance of adequate blood flow, interrupted only by formation of temporary thrombi localized to places of injury, requires coordination between endothelium, platelets, white blood cells, and numerous soluble plasma elements.…
Acquired coagulation factor inhibitors are autoantibodies directed against native clotting factor in persons without an underlying bleeding disorder. Although rare, these disorders can result in life-threatening hemorrhage, which can be difficult to manage. The following factor inhibitors will be discussed:…