Part of the process of blood clot formation.
Involves the adhesion, activation, and aggregation of platelets combined with von Willebrand factor to produce a temporary platelet plug.
Part of the blood clot formation process.
Activation of coagulation factors (extrinsic, intrinsic, and common pathways) to produce a stable fibrin clot.
Regulation of Coagulation System
The coagulation system and clot production is regulated by the anticoagulation system (Tissue factor pathway inhibitor, antithrombin, Protein C and Protein S)
Composed of plasminogen and t-PA.
Removes unwanted fibrin clots and restores blood vessel patency once the vascular injury has healed.
Idiopathic Thrombocytopenic Purpura (ITP)
ITP is an autoimmune disease which antibodies detectable against platelet surface antigens. May be acute, or chronic.
Treatment is steroids.
Exposure to heparin within the past 5-10 days causes antibodies to attack platelets.
Failure of platelet aggregation because of a lack of membrane receptors GPIIb/IIIa.
In the presence of normal plasma levels of fibrinogen, they have a decreased aggregation of platelets to each other (prolonged bleeding time / closure time).
Bernard Soulier Syndrome
A congenital platelet with adhesion defects.
Platelets lack membrane receptors (GP1b) for von Willebrand factor. In the presence of normal plasma levels of von Willebrand factor, there is a decreased adhesion of platelets to subendothelium (prolonged bleeding / closure time).
Platelet Function Defects - Congenital
These are rare, but should be considered.
Most platelet function defects are commonly acquired due to medication effects.
Vitamin K Deficiency
Can be a cause of an elevated PT.
Hemorrhagic Disease of the Newborn
A disease caused by insufficient Vitamin K in newborns.
Used to assess Factor VII (extrinsic pathway) and Factors II, V, X and Fibrinogen (common pathway)
Major causes of an isolated PT include Factor VII deficiency and warfarin therapy.
Type 1 VWD - Equal reductions in VWF Activity and VWF Antigen. FVIII may be normal or low.
Type 2 VWD - Greater reduction in VWF activity when compared with the reduction in VWF antigen (ratio of VWF activity to antigen <0.5-0.7). Factor VIII may be normal or low.
Type 3 VWD - Extremely low or undetectable levels of VWF antigen and activity. FVIII often <10% of normal.