Laboratory medicine: creatinine: 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 · Laboratory medicine: creatinine

Sample item

Why can serum creatinine underestimate kidney dysfunction in a frail older person with low muscle mass?

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

The answer and the reasoning

D. Creatinine generation falls with reduced muscle mass

Creatinine is generated from skeletal muscle creatine, so low muscle mass can yield a deceptively low serum creatinine despite reduced filtration. Estimated GFR formulas account for some demographic factors but have limitations.

Option by option

  • A. Creatinine rises only in nephrotic syndrome

    Creatinine rises in many forms of reduced GFR, not only nephrotic syndrome.

  • B. Muscle mass does not affect creatinine

    Muscle mass is an important determinant of creatinine.

  • C. Creatinine is made only by the liver

    Creatinine derives mainly from muscle metabolism.

  • D. Creatinine generation falls with reduced muscle mass (correct)

    Correct. Less muscle produces less creatinine generation.

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 D, Creatinine generation falls with reduced muscle mass. Creatinine is generated from skeletal muscle creatine, so low muscle mass can yield a deceptively low serum creatinine despite reduced filtration.

Why is "Creatinine rises only in nephrotic syndrome" not the answer?

Creatinine rises in many forms of reduced GFR, not only nephrotic syndrome.

Why is "Muscle mass does not affect creatinine" not the answer?

Muscle mass is an important determinant of creatinine.

Why is "Creatinine is made only by the liver" not the answer?

Creatinine derives mainly from muscle metabolism.

What concept does this question test?

It tests Laboratory medicine: creatinine in Biochemistry. Estimated GFR formulas account for some demographic factors but have limitations.

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 Laboratory medicine: creatinine?

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.