Haematology: factor XIII deficiency: practice question

A Pathology 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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Pathology · Haematology: factor XIII deficiency

Sample item

A neonate bleeds from the umbilical stump after the cord has separated, and later shows poor wound healing. Platelet count, PT, aPTT and bleeding time are normal. Which test would establish the diagnosis?

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

The answer and the reasoning

C. Clot solubility in 5 M urea

Factor XIII cross-links fibrin, so its deficiency causes delayed bleeding, umbilical stump bleeding and poor healing with normal PT, aPTT, platelet count and bleeding time. The screening test is a clot solubility test, where the clot dissolves in urea or monochloroacetic acid, and the diagnosis is confirmed by factor XIII assay.

Option by option

  • A. Mixing study

    A mixing study evaluates a prolonged aPTT or PT, which are normal here.

  • B. Ristocetin cofactor assay

    Ristocetin cofactor activity tests von Willebrand factor, which would prolong the bleeding time.

  • C. Clot solubility in 5 M urea (correct)

    Correct. A clot lacking factor XIII cross-links dissolves in 5 M urea.

  • D. Platelet aggregometry

    Platelet aggregometry assesses platelet function disorders, which would prolong the bleeding time.

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 Pathology question

What is the answer to this Pathology question?

The best answer is C, Clot solubility in 5 M urea. Factor XIII cross-links fibrin, so its deficiency causes delayed bleeding, umbilical stump bleeding and poor healing with normal PT, aPTT, platelet count and bleeding time.

Why is "Mixing study" not the answer?

A mixing study evaluates a prolonged aPTT or PT, which are normal here.

Why is "Ristocetin cofactor assay" not the answer?

Ristocetin cofactor activity tests von Willebrand factor, which would prolong the bleeding time.

Why is "Platelet aggregometry" not the answer?

Platelet aggregometry assesses platelet function disorders, which would prolong the bleeding time.

What concept does this question test?

It tests Haematology: factor XIII deficiency in Pathology. The screening test is a clot solubility test, where the clot dissolves in urea or monochloroacetic acid, and the diagnosis is confirmed by factor XIII assay.

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 Haematology: factor XIII deficiency?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.