Clinical enzymology: cardiac markers: 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 enzymology: cardiac markers

Sample item

A 60-year-old man had an anterior myocardial infarction 4 days ago and now has recurrent chest pain. Troponin I is still elevated from the index event. Which conventional marker, because it returns to baseline within about 3 days, allows a fresh rise to be recognised?

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

The answer and the reasoning

B. CK-MB

CK-MB rises 4 to 6 hours after infarction, peaks at about 24 hours and returns to baseline in 48 to 72 hours, so a fresh rise indicates new myocardial injury. Troponins stay raised for 7 to 10 days, making a fresh rise harder to recognise in this window. LDH-1 and AST are late and non-specific.

Option by option

  • A. AST

    AST is non-specific, being raised in liver and muscle disease, and normalises over several days.

  • B. CK-MB (correct)

    Correct. CK-MB normalises quickly, so a re-rise signals reinfarction.

  • C. LDH-1

    LDH-1 peaks around day 3 and stays high for up to 10 days.

  • D. Troponin I

    Troponin I stays elevated for 7 to 10 days, so a new event can be shown only by a further significant rise, which is harder to judge than a re-rise of a marker that had normalised.

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 B, CK-MB. CK-MB rises 4 to 6 hours after infarction, peaks at about 24 hours and returns to baseline in 48 to 72 hours, so a fresh rise indicates new myocardial injury.

Why is "AST" not the answer?

AST is non-specific, being raised in liver and muscle disease, and normalises over several days.

Why is "LDH-1" not the answer?

LDH-1 peaks around day 3 and stays high for up to 10 days.

Why is "Troponin I" not the answer?

Troponin I stays elevated for 7 to 10 days, so a new event can be shown only by a further significant rise, which is harder to judge than a re-rise of a marker that had normalised.

What concept does this question test?

It tests Clinical enzymology: cardiac markers in Biochemistry. Troponins stay raised for 7 to 10 days, making a fresh rise harder to recognise in this window. LDH-1 and AST are late and non-specific.

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 Clinical enzymology: cardiac markers?

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.