Clinical biochemistry: antenatal screening: 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 · Clinical biochemistry: antenatal screening

Sample item

A 36-year-old pregnant woman has a second trimester quadruple test. Which pattern raises the risk of Down syndrome?

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

The answer and the reasoning

C. Low AFP, low unconjugated oestriol, high hCG and high inhibin A

In Down syndrome the maternal serum AFP and unconjugated oestriol are low while hCG and inhibin A are raised. Edwards syndrome shows low AFP, oestriol and hCG, with inhibin A normal or low. A high AFP suggests a neural tube defect or abdominal wall defect, or wrong dates. A screening test only modifies risk, and a high-risk result is followed by non-invasive prenatal testing or amniocentesis.

Option by option

  • A. High AFP, normal hCG and normal inhibin A

    A high AFP suggests neural tube defect, which is a different risk.

  • B. Low AFP, low unconjugated oestriol, low hCG and low inhibin A

    Low AFP, oestriol and hCG with inhibin A not raised suggest trisomy 18, not Down syndrome.

  • C. Low AFP, low unconjugated oestriol, high hCG and high inhibin A (correct)

    Correct. This is the classic Down syndrome pattern.

  • D. Normal AFP with high unconjugated oestriol and low hCG

    This mixture is not a recognised pattern for Down syndrome.

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, Low AFP, low unconjugated oestriol, high hCG and high inhibin A. In Down syndrome the maternal serum AFP and unconjugated oestriol are low while hCG and inhibin A are raised.

Why is "High AFP, normal hCG and normal inhibin A" not the answer?

A high AFP suggests neural tube defect, which is a different risk.

Why is "Low AFP, low unconjugated oestriol, low hCG and low inhibin A" not the answer?

Low AFP, oestriol and hCG with inhibin A not raised suggest trisomy 18, not Down syndrome.

Why is "Normal AFP with high unconjugated oestriol and low hCG" not the answer?

This mixture is not a recognised pattern for Down syndrome.

What concept does this question test?

It tests Clinical biochemistry: antenatal screening in Biochemistry. Edwards syndrome shows low AFP, oestriol and hCG, with inhibin A normal or low. A high AFP suggests a neural tube defect or abdominal wall defect, or wrong dates. A screening test only modifies risk, and a high-risk result is followed by non-invasive prenatal testing or amniocentesis.

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 Clinical biochemistry: antenatal screening?

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.