Clinical biochemistry: 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 biochemistry: cardiac markers

Sample item

A 60-year-old man who had an acute myocardial infarction 3 days ago has fresh chest pain. Serum troponin I is still raised. Which marker best helps to decide whether re-infarction has occurred?

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

The answer and the reasoning

B. CK-MB

Troponins remain elevated for 7 to 14 days after an infarct, so they cannot reliably show a new event within that period. CK-MB normalises within about 2 to 3 days, so a fresh rise after normalisation suggests re-infarction. Myoglobin is early but non-specific and clears within about a day.

Option by option

  • A. Aspartate transaminase

    Aspartate transaminase is non-specific, being found in liver and muscle, and is not recommended.

  • B. CK-MB (correct)

    Correct. CK-MB falls to normal quickly, so a new rise indicates fresh myocardial injury.

  • C. Lactate dehydrogenase

    Lactate dehydrogenase stays raised for up to 10 days and is not specific to the heart.

  • D. Myoglobin

    Myoglobin has already cleared and is not specific, since skeletal muscle injury also raises it.

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. Troponins remain elevated for 7 to 14 days after an infarct, so they cannot reliably show a new event within that period.

Why is "Aspartate transaminase" not the answer?

Aspartate transaminase is non-specific, being found in liver and muscle, and is not recommended.

Why is "Lactate dehydrogenase" not the answer?

Lactate dehydrogenase stays raised for up to 10 days and is not specific to the heart.

Why is "Myoglobin" not the answer?

Myoglobin has already cleared and is not specific, since skeletal muscle injury also raises it.

What concept does this question test?

It tests Clinical biochemistry: cardiac markers in Biochemistry. CK-MB normalises within about 2 to 3 days, so a fresh rise after normalisation suggests re-infarction. Myoglobin is early but non-specific and clears within about a day.

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: 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.