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Question 311
Physiology → Haematology
Classification
Question
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Warfarin interferes with vitamin K-dependent gamma-carboxylation. Which complete group of coagulation factors is affected by this mechanism?
Question Stem
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Options
A
I, V, VIII and XIII
B
II, VII, IX and X
C
V, VIII, XI and XII
D
VII, VIII, XI and XIII
E
II, V, IX and XII
Explanation
Warfarin interferes with vitamin K and inhibits gamma-carboxylation of factors II, VII, IX and X. Vitamin K administration can restore a prolonged PT or high INR when vitamin K deficiency or antagonism is responsible.
Option Validity
A) This group does not match the vitamin K-dependent factors affected by warfarin. The required set comprises factors II, VII, IX and X.
C) Factors V, VIII, XI and XII are not the group undergoing vitamin K-dependent gamma-carboxylation affected by warfarin.
D) Although factor VII belongs to the required group, factors VIII, XI and XIII do not complete the vitamin K-dependent set. The complete set is II, VII, IX and X.
E) Factors II and IX are included, but factors V and XII do not complete the vitamin K-dependent group. Factors VII and X are required instead.
Further Reading
Saxena. Textbook for MRCOG-1. Physiology - Haematology - Prothrombin Time, p.72.