Coagulation Flashcards
What happens when MTHFR decreases?
Homocystine increases
Steps of hemostasis
Primary hemostasis
Secondary hemostasis
Fibrinolysis
Steps in primary hemostasis
Vasoconstriction
Platelet adhesion
Platelet aggregation - to form primary hemostatic plug at injury site
Steps of secondary hemostasis
- Interaction of coag factors to produce fibrin (secondary hemostatic plug)
- Fibrin stabilization by FXIII
Steps in fibrinolysis
- Release tissue plasminogen activator
- Plasminogen —> plasmin
- Fibrin —> fibrin degradation products
What are the quantitative plt disorders?
Thrombocytopenia
Primary thrombocytosis
Secondary or reactive thrombocytosis
Thrombocytopenia
Decrease production, increase destruction
<30x10^9/L: petechiae, menorrhagia, spontaneous bruising
<10x10^9/L: severe spontaneous bleeding
Lab tests: Plt <150 x 10^9/L
Primary thrombocytosis
Unregulated production of megakaryocytes in BM (like ET)
Thrombosis (blood clots) or hemorrhage (damaged blood vessel)
Lab tests: >1000 x 10^9/L
Secondary or reactive thrombocytosis
Increased plt due to another condition (like hemorrhage, surgery, splenectomy)
No thrombosis or hemorrhage
Lab tests: 450-1000 x 10^9/L
Qualitative Platelet Disorders
Inherited: Bernard-Soulier syndrome, Glanzmann’s thrombasthenia, delta-storage pool disorder
Acquired
Bernard-Soulier syndrome
Lack of GP Ib/IX/V on plt surface —> no plt interaction w/ VWF —> abnormal adhesion to collagen
Glanzmann’s thrombasthenia
Deficiency or abnormality of plt membrane GP IIb/IIIa —> fibrinogen can’t attach to plt surface —> cannot do plt aggregation
delta-storage pool disorder
Dense granule deficiency —> no ADP released —> abnormal secondary aggregation with ADP & epinephrin
Acquired plt disorder
Functional plt disorder (occurs with renal failure, aspirin, etc) —> abnormal plt aggregation
Tests for platelet function
Platelet aggregation
Platelet function assay (PFA)
VWF:Ag
Platelet aggregation (plt function test)
Aggregating agent (ADP, collagen, ristocetin, epinephrine) added to plt suspension
Time it takes for plts to aggregate = increase in light transmittance
Curve = time vs % transmittance
Platelet function assay (PFA) - plt function test
Citrated WB in a capillary tube coated with ADP/collagen or epinephrine/collagen
Plts adhere and aggregate when exposed to collagen
Closure time = time it takes for plts to form a plt plug and close aperture of capillary tube
VWF:Ag
Immunologic test (ex: EIA) using monoclonal Abs to VWF
VWF needed for plts to connect to collagen (plts don’t function properly if decreased VWF — like in VWD)
Factor I
Fibrinogen
Fibrinogen —thrombin—> fibrin