Blood: haemostasis: 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.

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Physiology · Blood: haemostasis

Sample item

A patient with a prolonged bleeding time, normal platelet count and normal PT has a prolonged aPTT that corrects after mixing with normal plasma. Which protein function is most plausibly deficient?

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

The answer and the reasoning

C. von Willebrand factor, which both mediates platelet adhesion and carries factor VIII

von Willebrand factor tethers platelets to subendothelial collagen through GpIb, and it also stabilises factor VIII. Deficiency therefore prolongs bleeding time and, via low factor VIII, the aPTT, while PT and platelet count stay normal.

Option by option

  • A. Fibrinogen, which cross-links platelets and forms clot

    Fibrinogen deficiency prolongs PT, aPTT and thrombin time.

  • B. Antithrombin, which inhibits thrombin

    Antithrombin deficiency causes thrombosis, not bleeding.

  • C. von Willebrand factor, which both mediates platelet adhesion and carries factor VIII (correct)

    Correct. A single defect explains both platelet and aPTT abnormalities.

  • D. Factor VII, which activates the extrinsic pathway

    Factor VII deficiency prolongs PT with a normal aPTT.

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.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is C, von Willebrand factor, which both mediates platelet adhesion and carries factor VIII. von Willebrand factor tethers platelets to subendothelial collagen through GpIb, and it also stabilises factor VIII.

Why is "Fibrinogen, which cross-links platelets and forms clot" not the answer?

Fibrinogen deficiency prolongs PT, aPTT and thrombin time.

Why is "Antithrombin, which inhibits thrombin" not the answer?

Antithrombin deficiency causes thrombosis, not bleeding.

Why is "Factor VII, which activates the extrinsic pathway" not the answer?

Factor VII deficiency prolongs PT with a normal aPTT.

What concept does this question test?

It tests Blood: haemostasis in Physiology. Deficiency therefore prolongs bleeding time and, via low factor VIII, the aPTT, while PT and platelet count stay normal.

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: haemostasis?

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.