Coagulation Flashcards
The APTT is normal in patients with severe deficiency of which clotting factor?
a. Factor V
b. Factor VIII
c. Factor IX
d. Factor XIII
e. von Willebrand factor (vWF)
d. Factor XIII -fibrin-stabilizing factor
The aPTT is a measure of the function of the intrinsic pathway (contact factors and Factors XI, IX, and VIII) and common pathway ( Factors X, V, and II and Fibrinogen) of coagulation.
Which coagulation factor is found in Cryoprecipitated
AHF?
a. Factor II- prothrombin
b. Factor VII- proconvertin
c. Factor IX- Christmas factor
d. Factor XI - plasma thromboplastin antecedent
e. Factor XIII - fibrin-stabilizing factor
e. Factor XIII
Cyro contains concentrated forms of Factor VIII, vWF, fibrinogen, and Factor XIII
Which is not localized or synthesized in a platelet?
a. Arachidonic acid
b. Cyclo-oxygenase
c. Prostacyclin
d. Thromboxane A2
e. Thromboxane synthetase
c. Prostacyclin
Prostacyclin, a plt aggregation inhibitor, is produced in the vascular endothelium.
What factors make up the intrinsic pathway?
contact factors and Factors XI, IX, and VIII
factors XII (Hageman factor)
XI (plasma thromboplastin antecedent)
IX (Christmas factor)
VIII (antihemophilic factor A)
What factors make up the common pathway?
Factors X, V, and II and Fibrinogen
Factor X: Also known as Stuart-Prower factor
Factor V: Also known as proaccelerin
Factor II: Also known as prothrombin
Factor I: Also known as fibrinogen
(Factor XIII: Also known as fibrin-stabilizing factor
Calcium ions: Also known as clotting factor IV)
How does the common pathway work?
Factor X is activated by either the intrinsic or extrinsic pathway
Factor Xa, Va, and calcium bind together to form a prothrombinase complex
The prothrombinase complex converts prothrombin into thrombin
Thrombin converts fibrinogen into fibrin
Thrombin also activates factor XIII, which binds with calcium to create fibrin crosslinks that stabilize the clot
What are 3 key points about the intrinsic pathway?
- Activation trigger: Exposure to collagen or other negatively charged surfaces.
- Key factors involved: Factors XII, XI, IX, and VIII.
- Function: This pathway leads to the activation of factor X, which then enters the common pathway to form a fibrin clot.
What factors make up the extrinsic pathway?
Tissue factor, factor VII, and factor X.
What are the contact factors?
Factor XII (FXII): Also known as Hageman factor (HF)
Factor XI (FXI): Also known as plasma thrombo-plastin antecedent (PTA)
Prekallikrein (PK): Also known as Fletcher factor
High molecular weight kininogen (HMWK): Also known as Fitzgerald, Flaujeac, or Williams factor
A 40 yr old man needs to have a few teeth pulled. He was dx with a bleeding disorder as a child, but can’t remember what i was. He does remember not being allowed to play outdoors with the other kids. He has received a number of blood products over the yrs, associated with trauma and medical procedures. A battery of laboratory tests demonstrates a prolonged PT, prolonged aPTT, normal thrombin time (TT), normal bleeding time, and prolonged dilute Russell viper venom time. These results are consistent with congenital deficiency of which coag factor?
a. Factor I - fibrinogen
b. Factor VII
c. Factor X
d. Factor XII
e. Factor XIII
c. Factor X
Prolongation of the PT and aPTT here, suggests a congenital deficiency within the common pathway (factors X, V, II, and I). This is further supported by the prolonged dilute Russell viper venom time- which directly activates the common pathway at Factor X; however, this was an unnecessary test that happened to be orders. The normal thrombin time rules out in the differential diagnosis; however, of these, only Factor X is listed as a choice.
Regarding prothrombin and thrombin, which statements are true?
a. The primary physiologic method of thrombin generation is via the intrinsic system.
b. Factor Va is the protease that cleaves prothrombin to thrombin
c. Thrombin generation is the major route of plt activation
d. Prothrombin is synthesized in endothelial cells.
e. Thrombin is a cofactor for protein C activation
c. Thrombin generation is the major route of plt activation
Thrombin is a stronger plt agonist that collagen, adenosine, diphosphate (ADP), or thromboxane A2. Tissuefactor/Factor VIIa-mediated generation of thrombin is the major route of plt activation
Which statement concerning Factor XII (Hageman Factor) is true?
a. It’s activation triggers the extrinsic pathway of coagulation
b. It is an important determinant of in-vitro hemostasis but is not a determinant of physiologic hemostasis
c. Deficiency of Factor XII is associated with a mild bleeding disorder
d. Deficiency of factor XII causes marked prolongation of the PT.
e. Factor XII deficiency has a prevalence of about 1:500,000p
b. It is an important determinant of in-vitro hemostasis but is not a determinant of physiologic hemostasis
What coag test measures the extrinsic pathway?
The PT
What coag test measures the intrinsic pathway?
the aPTT
Thromboelastogram (TEG) measures physical properties of a clot in whole blood by evaluating what 7 parameteres?
- R value (reaction time)
- K value (kinetics)
- alpha angle (slope of line of R and K)
- TMA (time to maximum amplitude)
- MA (maximum amplitude)
- LY30 (detects fibrinolysis) and Clot lysis time
- Kaolin and/or tissue factor
Aged serum does not contain which factors?
Factor I, II, V, VII, or XIII
Adsorbed plasma refers to plasma that was adsorbed to what?
Barium Sulfate
What factor group(s) are found in adsorbed plasma?
Factors in the contact group and fibrinogen group
Stored plasma contains all factors except?
labile factors V, and VIII.
What factor deficiency cannot be detected by either the PT or PTT?
a deficiency of Factor XIII.
A special test utilizing 5M Urea can determine qualitatively if a patient is deficient in factor XIII by observing dissolution of a clot after 24 hrs incubation.
