Vitamin K Dependent Factors — MFDS Part 1 MCQ

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ModeratePhysiologyVitamin K Dependent FactorsMFDS Part 1

Warfarin inhibits vitamin K epoxide reductase, reducing the regeneration of active vitamin K. Which set of coagulation factors consequently has impaired gamma-carboxylation and reduced biological activity?

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Correct answer: A — Factors II, VII, IX and X

The correct answer is A: factors II, VII, IX and X. Reduced vitamin K is required for gamma-carboxylation of glutamate residues in these factors, enabling calcium binding and normal biological activity. The anticoagulant proteins C and S are also vitamin K dependent, although they are not coagulation factors included in the options. Factors V and VIII are non-enzymatic coagulation cofactors and are not vitamin K dependent, making B and D incorrect despite containing some vitamin K-dependent factors. Factors XI and XII are contact-pathway proteins, factor XIII cross-links fibrin, and factor I is fibrinogen; none is vitamin K dependent. Warfarin reduces the functional activity of the vitamin K-dependent proteins by inhibiting vitamin K recycling.

Reference: East of England Neonatal Operational Delivery Network, Clinical Guideline: The routine supplementation of vitamins and iron and the management of zinc deficiency in preterm and small for gestational age infants, Vitamin K section, 2024. https://eoeneonatalpccsicnetwork.nhs.uk/wp-content/uploads/2024/03/EOE-Vitamin-Iron-guideline-March-2024.pdf