MLS Coagulation Exam| 578 QUESTIONS|
WITH COMPLETE SOLUTIONS
Course
ASCP MLS
✅ 1. Which factor is also known as anti-hemophilic factor A?
A. Factor V
B. Factor VIII ✅
C. Factor IX
D. Factor XI
Correct Answer: B. Factor VIII
Explanation: Factor VIII is essential in the intrinsic pathway and forms a complex with Factor
IX to activate Factor X. Deficiency causes Hemophilia A, the most common inherited bleeding
disorder.
✅ 2. A prolonged PT (prothrombin time) with a normal aPTT most likely
indicates a deficiency in which coagulation factor?
A. Factor VIII
B. Factor IX
C. Factor VII ✅
D. Factor XII
Correct Answer: C. Factor VII
Explanation: PT measures the extrinsic pathway (Factor VII + common pathway). A normal
aPTT rules out intrinsic pathway defects, pointing to isolated Factor VII deficiency.
✅ 3. Which test is most useful in monitoring heparin therapy?
A. PT
B. aPTT ✅
C. TT
D. D-dimer
Correct Answer: B. aPTT
Explanation: Heparin inhibits Factors IIa (thrombin) and Xa. aPTT is sensitive to these
changes, making it the go-to test for unfractionated heparin monitoring.
,✅ 4. A patient presents with deep vein thrombosis. Which test should be
performed to screen for ongoing fibrinolysis?
A. Platelet count
B. D-dimer ✅
C. Protein C level
D. INR
Correct Answer: B. D-dimer
Explanation: D-dimer is a fibrin degradation product, elevated during active clot breakdown.
It’s highly sensitive for DVT, PE, and DIC, though not specific.
✅ 5. What is the first step in the coagulation cascade common pathway?
A. Activation of Factor IX
B. Conversion of fibrinogen to fibrin
C. Activation of Factor X ✅
D. Formation of thrombin
Correct Answer: C. Activation of Factor X
Explanation: Once the intrinsic or extrinsic pathways are triggered, both converge at the
common pathway, beginning with Factor X activation, leading to thrombin formation and
fibrin clot.
✅ 6. What is the expected lab finding in a patient with von Willebrand disease?
A. Prolonged PT and normal aPTT
B. Normal PT and prolonged aPTT ✅
C. Both PT and aPTT are prolonged
D. Shortened bleeding time
Correct Answer: B. Normal PT and prolonged aPTT
Explanation: vWD affects platelet adhesion and reduces Factor VIII levels (which is bound by
vWF), prolonging aPTT, while PT remains normal.
✅ 7. Which factor is vitamin K-dependent?
A. Factor VIII
B. Factor I
,C. Factor II ✅
D. Factor XII
Correct Answer: C. Factor II (Prothrombin)
Explanation: Vitamin K is essential for synthesis of Factors II, VII, IX, and X, as well as
Protein C and S. These are inhibited by warfarin.
✅ 8. A prolonged thrombin time (TT) can indicate which condition?
A. Hemophilia B
B. Elevated fibrinogen
C. Heparin contamination ✅
D. Vitamin K excess
Correct Answer: C. Heparin contamination
Explanation: Thrombin Time assesses the conversion of fibrinogen to fibrin. Heparin
interferes with thrombin, prolonging TT significantly even in small amounts.
✅ 9. Which test is most sensitive for detecting lupus anticoagulant?
A. PT
B. Dilute Russell’s Viper Venom Test (dRVVT) ✅
C. Fibrinogen assay
D. Bleeding time
Correct Answer: B. dRVVT
Explanation: dRVVT is designed to detect lupus anticoagulant, an antiphospholipid antibody
that interferes with phospholipid-dependent coagulation steps, paradoxically causing clotting in
vivo but prolonged clotting times in vitro.
✅ 10. Which condition is associated with decreased platelet count, elevated
PT/aPTT, low fibrinogen, and high D-dimer?
A. Hemophilia A
B. Liver cirrhosis
C. Disseminated Intravascular Coagulation (DIC) ✅
D. von Willebrand disease
Correct Answer: C. DIC
Explanation: DIC is a consumptive coagulopathy: platelets and coagulation factors are used up,
, fibrinolysis is activated (↑ D-dimer), and fibrinogen drops, causing bleeding and thrombosis
simultaneously.
✅ 11. What is the function of antithrombin (AT)?
A. Activates Factor X
B. Enhances platelet aggregation
C. Inhibits thrombin and Factor Xa ✅
D. Degrades fibrinogen
Correct Answer: C.
Rationale: Antithrombin is a natural anticoagulant that inactivates thrombin (Factor IIa) and
Factor Xa, limiting clot propagation. Heparin enhances its activity.
✅ 12. Which inherited disorder is associated with a deficiency of Factor IX?
A. Hemophilia A
B. Hemophilia B ✅
C. von Willebrand disease
D. Factor V Leiden
Correct Answer: B.
Rationale: Hemophilia B, or Christmas disease, is a Factor IX deficiency, inherited in an X-
linked recessive pattern, mostly affecting males.
✅ 13. A mixing study corrects a prolonged aPTT. What does this suggest?
A. Lupus anticoagulant
B. Factor inhibitor
C. Factor deficiency ✅
D. Warfarin therapy
Correct Answer: C.
Rationale: Mixing normal plasma with patient plasma corrects aPTT if the issue is due to factor
deficiency. Lack of correction indicates an inhibitor.
✅ 14. Which reagent is required to initiate the prothrombin time (PT) test?
A. Kaolin
B. Calcium chloride
WITH COMPLETE SOLUTIONS
Course
ASCP MLS
✅ 1. Which factor is also known as anti-hemophilic factor A?
A. Factor V
B. Factor VIII ✅
C. Factor IX
D. Factor XI
Correct Answer: B. Factor VIII
Explanation: Factor VIII is essential in the intrinsic pathway and forms a complex with Factor
IX to activate Factor X. Deficiency causes Hemophilia A, the most common inherited bleeding
disorder.
✅ 2. A prolonged PT (prothrombin time) with a normal aPTT most likely
indicates a deficiency in which coagulation factor?
A. Factor VIII
B. Factor IX
C. Factor VII ✅
D. Factor XII
Correct Answer: C. Factor VII
Explanation: PT measures the extrinsic pathway (Factor VII + common pathway). A normal
aPTT rules out intrinsic pathway defects, pointing to isolated Factor VII deficiency.
✅ 3. Which test is most useful in monitoring heparin therapy?
A. PT
B. aPTT ✅
C. TT
D. D-dimer
Correct Answer: B. aPTT
Explanation: Heparin inhibits Factors IIa (thrombin) and Xa. aPTT is sensitive to these
changes, making it the go-to test for unfractionated heparin monitoring.
,✅ 4. A patient presents with deep vein thrombosis. Which test should be
performed to screen for ongoing fibrinolysis?
A. Platelet count
B. D-dimer ✅
C. Protein C level
D. INR
Correct Answer: B. D-dimer
Explanation: D-dimer is a fibrin degradation product, elevated during active clot breakdown.
It’s highly sensitive for DVT, PE, and DIC, though not specific.
✅ 5. What is the first step in the coagulation cascade common pathway?
A. Activation of Factor IX
B. Conversion of fibrinogen to fibrin
C. Activation of Factor X ✅
D. Formation of thrombin
Correct Answer: C. Activation of Factor X
Explanation: Once the intrinsic or extrinsic pathways are triggered, both converge at the
common pathway, beginning with Factor X activation, leading to thrombin formation and
fibrin clot.
✅ 6. What is the expected lab finding in a patient with von Willebrand disease?
A. Prolonged PT and normal aPTT
B. Normal PT and prolonged aPTT ✅
C. Both PT and aPTT are prolonged
D. Shortened bleeding time
Correct Answer: B. Normal PT and prolonged aPTT
Explanation: vWD affects platelet adhesion and reduces Factor VIII levels (which is bound by
vWF), prolonging aPTT, while PT remains normal.
✅ 7. Which factor is vitamin K-dependent?
A. Factor VIII
B. Factor I
,C. Factor II ✅
D. Factor XII
Correct Answer: C. Factor II (Prothrombin)
Explanation: Vitamin K is essential for synthesis of Factors II, VII, IX, and X, as well as
Protein C and S. These are inhibited by warfarin.
✅ 8. A prolonged thrombin time (TT) can indicate which condition?
A. Hemophilia B
B. Elevated fibrinogen
C. Heparin contamination ✅
D. Vitamin K excess
Correct Answer: C. Heparin contamination
Explanation: Thrombin Time assesses the conversion of fibrinogen to fibrin. Heparin
interferes with thrombin, prolonging TT significantly even in small amounts.
✅ 9. Which test is most sensitive for detecting lupus anticoagulant?
A. PT
B. Dilute Russell’s Viper Venom Test (dRVVT) ✅
C. Fibrinogen assay
D. Bleeding time
Correct Answer: B. dRVVT
Explanation: dRVVT is designed to detect lupus anticoagulant, an antiphospholipid antibody
that interferes with phospholipid-dependent coagulation steps, paradoxically causing clotting in
vivo but prolonged clotting times in vitro.
✅ 10. Which condition is associated with decreased platelet count, elevated
PT/aPTT, low fibrinogen, and high D-dimer?
A. Hemophilia A
B. Liver cirrhosis
C. Disseminated Intravascular Coagulation (DIC) ✅
D. von Willebrand disease
Correct Answer: C. DIC
Explanation: DIC is a consumptive coagulopathy: platelets and coagulation factors are used up,
, fibrinolysis is activated (↑ D-dimer), and fibrinogen drops, causing bleeding and thrombosis
simultaneously.
✅ 11. What is the function of antithrombin (AT)?
A. Activates Factor X
B. Enhances platelet aggregation
C. Inhibits thrombin and Factor Xa ✅
D. Degrades fibrinogen
Correct Answer: C.
Rationale: Antithrombin is a natural anticoagulant that inactivates thrombin (Factor IIa) and
Factor Xa, limiting clot propagation. Heparin enhances its activity.
✅ 12. Which inherited disorder is associated with a deficiency of Factor IX?
A. Hemophilia A
B. Hemophilia B ✅
C. von Willebrand disease
D. Factor V Leiden
Correct Answer: B.
Rationale: Hemophilia B, or Christmas disease, is a Factor IX deficiency, inherited in an X-
linked recessive pattern, mostly affecting males.
✅ 13. A mixing study corrects a prolonged aPTT. What does this suggest?
A. Lupus anticoagulant
B. Factor inhibitor
C. Factor deficiency ✅
D. Warfarin therapy
Correct Answer: C.
Rationale: Mixing normal plasma with patient plasma corrects aPTT if the issue is due to factor
deficiency. Lack of correction indicates an inhibitor.
✅ 14. Which reagent is required to initiate the prothrombin time (PT) test?
A. Kaolin
B. Calcium chloride
