Vitamins and minerals: Schilling test interpretation: 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 and minerals: Schilling test interpretation

Sample item

In a Schilling test, a patient with macrocytic anaemia excretes very little radiolabelled cobalamin in the urine after an oral dose. The result becomes normal when the oral dose is repeated together with intrinsic factor. What is the diagnosis?

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

The answer and the reasoning

C. Pernicious anaemia from autoimmune gastric atrophy

Cobalamin absorption needs intrinsic factor from gastric parietal cells and receptors in the terminal ileum. If adding intrinsic factor corrects urinary excretion, the defect is lack of intrinsic factor, as in pernicious anaemia. Ileal disease does not correct with intrinsic factor, overgrowth corrects after antibiotics, and pancreatic disease corrects with pancreatic enzymes.

Option by option

  • A. Terminal ileal Crohn disease with loss of absorptive receptors

    Ileal receptor loss is not fixed by intrinsic factor, because the absorptive surface is the problem.

  • B. Chronic pancreatitis with failure to release bound cobalamin

    Pancreatic insufficiency is suggested when excretion normalises with pancreatic enzyme replacement.

  • C. Pernicious anaemia from autoimmune gastric atrophy (correct)

    Correct. Correction with intrinsic factor shows that the missing component was intrinsic factor.

  • D. Small bowel bacterial overgrowth consuming the cobalamin

    Overgrowth is suggested when excretion normalises after a course of antibiotics.

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 C, Pernicious anaemia from autoimmune gastric atrophy. Cobalamin absorption needs intrinsic factor from gastric parietal cells and receptors in the terminal ileum.

Why is "Terminal ileal Crohn disease with loss of absorptive receptors" not the answer?

Ileal receptor loss is not fixed by intrinsic factor, because the absorptive surface is the problem.

Why is "Chronic pancreatitis with failure to release bound cobalamin" not the answer?

Pancreatic insufficiency is suggested when excretion normalises with pancreatic enzyme replacement.

Why is "Small bowel bacterial overgrowth consuming the cobalamin" not the answer?

Overgrowth is suggested when excretion normalises after a course of antibiotics.

What concept does this question test?

It tests Vitamins and minerals: Schilling test interpretation in Biochemistry. If adding intrinsic factor corrects urinary excretion, the defect is lack of intrinsic factor, as in pernicious anaemia. Ileal disease does not correct with intrinsic factor, overgrowth corrects after antibiotics, and pancreatic disease corrects with pancreatic enzymes.

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 Vitamins and minerals: Schilling test interpretation?

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.