Vitamins: folate functional test: practice question

A Biochemistry 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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Biochemistry · Vitamins: folate functional test

Sample item

A woman has macrocytic anaemia with normal serum vitamin B12. Following an oral histidine load, which finding supports folate deficiency?

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

The answer and the reasoning

A. Increased urinary formiminoglutamate (FIGLU)

Histidine is degraded to FIGLU, which transfers its formimino group to tetrahydrofolate on the way to glutamate. In folate deficiency tetrahydrofolate is insufficient, so FIGLU accumulates and is excreted in urine after a histidine load.

Option by option

  • A. Increased urinary formiminoglutamate (FIGLU) (correct)

    FIGLU cannot be cleared without tetrahydrofolate, so it is excreted in excess.

  • B. Increased urinary xanthurenic acid

    Xanthurenic acid excretion after a tryptophan load indicates pyridoxine deficiency.

  • C. Reduced erythrocyte glutathione reductase activity coefficient

    A raised, not reduced, activity coefficient indicates riboflavin deficiency.

  • D. Increased urinary methylmalonic acid

    Methylmalonic acid is raised in vitamin B12 deficiency, which is normal here.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Increased urinary formiminoglutamate (FIGLU). Histidine is degraded to FIGLU, which transfers its formimino group to tetrahydrofolate on the way to glutamate.

Why is "Increased urinary xanthurenic acid" not the answer?

Xanthurenic acid excretion after a tryptophan load indicates pyridoxine deficiency.

Why is "Reduced erythrocyte glutathione reductase activity coefficient" not the answer?

A raised, not reduced, activity coefficient indicates riboflavin deficiency.

Why is "Increased urinary methylmalonic acid" not the answer?

Methylmalonic acid is raised in vitamin B12 deficiency, which is normal here.

What concept does this question test?

It tests Vitamins: folate functional test in Biochemistry. In folate deficiency tetrahydrofolate is insufficient, so FIGLU accumulates and is excreted in urine after a histidine load.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Vitamins: folate functional test?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.