Blood and immunity: factor VII half-life: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Physiology · Blood and immunity: factor VII half-life

Sample item

A patient is started on warfarin. Within 24 to 48 hours the prothrombin time lengthens, yet full antithrombotic protection is not yet present. Which clotting factor, with the shortest half-life, accounts for this early change?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Factor VII

Warfarin impairs vitamin K dependent carboxylation of factors II, VII, IX and X and proteins C and S. Factor VII has the shortest half-life, so it falls first and prolongs the prothrombin time early. Factor II has the longest half-life, so full effect takes several days.

Option by option

  • A. Factor VII (correct)

    Correct. Factor VII falls first and drives the early rise in prothrombin time.

  • B. Factor IX

    Factor IX falls more slowly and affects the aPTT rather than the early PT.

  • C. Factor X

    Factor X also has a long half-life and falls later.

  • D. Factor II

    Factor II has the longest half-life and falls last.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Physiology questions

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Factor VII. Warfarin impairs vitamin K dependent carboxylation of factors II, VII, IX and X and proteins C and S.

Why is "Factor IX" not the answer?

Factor IX falls more slowly and affects the aPTT rather than the early PT.

Why is "Factor X" not the answer?

Factor X also has a long half-life and falls later.

Why is "Factor II" not the answer?

Factor II has the longest half-life and falls last.

What concept does this question test?

It tests Blood and immunity: factor VII half-life in Physiology. Factor VII has the shortest half-life, so it falls first and prolongs the prothrombin time early. Factor II has the longest half-life, so full effect takes several days.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Blood and immunity: factor VII half-life?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.