ASCP Coagulation

Question 1

Which coagulation factor is also known as the Leiden variant when mutated, leading to activated protein C resistance?

Accepted Answer

Factor V

Answer

Factor V Leiden is a mutated form of Factor V where arginine 506 is replaced by glutamine, making it resistant to cleavage and inactivation by activated protein C. This is the most common inherited thrombophilia.

Question 2

The PT (prothrombin time) primarily evaluates which coagulation pathway?

Accepted Answer

Extrinsic pathway

Answer

PT evaluates the extrinsic and common pathways, testing factors VII, X, V, II, and fibrinogen. It is initiated by tissue factor (thromboplastin) added in the reagent.

Question 3

Which laboratory test is most specific for monitoring unfractionated heparin therapy?

Accepted Answer

aPTT

Answer

The aPTT (activated partial thromboplastin time) is the standard monitoring test for unfractionated heparin (UFH). Therapeutic range is typically 1.5–2.5 times baseline (60–100 seconds).

Question 4

D-dimer is a fibrin degradation product that indicates:

Accepted Answer

Clot formation AND fibrinolysis

Answer

D-dimer is formed when plasmin degrades cross-linked fibrin. Its elevation indicates both thrombus formation (cross-linked fibrin was made) and fibrinolysis (that fibrin is being broken down).

Question 5

In disseminated intravascular coagulation (DIC), which set of laboratory findings is most characteristic?

Accepted Answer

High PT, low platelets, low fibrinogen, high D-dimer

Answer

DIC is characterized by simultaneous clotting and fibrinolysis: PT and aPTT are prolonged (factor consumption), platelets are low (consumed), fibrinogen is low (consumed), and D-dimer is elevated (fibrinolysis).

ASCP Practice Test

ASCP Practice Test

ASCP Coagulation