Endocrinology: HbA1c limitations: practice question

A Physiology 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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Physiology · Endocrinology: HbA1c limitations

Sample item

A diabetic patient with a recent haemolytic episode has a very low HbA1c, which does not match his high home glucose readings. What explains the mismatch?

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

The answer and the reasoning

D. Shortened red cell survival leaves less time for glucose to glycate haemoglobin

HbA1c reflects average glycaemia over about the lifespan of red cells, around 3 months. When red cells are young after haemolysis or bleeding, glycation is lower, giving a falsely low value. Fructosamine is an alternative.

Option by option

  • A. Binding of glucose to albumin

    Glucose binding to albumin gives fructosamine and not HbA1c.

  • B. Raised red cell lifespan

    Prolonged survival would raise HbA1c.

  • C. Increased insulin secretion

    Insulin secretion would not lower HbA1c relative to glucose readings.

  • D. Shortened red cell survival leaves less time for glucose to glycate haemoglobin (correct)

    Correct. Younger red cells have had less exposure to glucose.

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 Physiology question

What is the answer to this Physiology question?

The best answer is D, Shortened red cell survival leaves less time for glucose to glycate haemoglobin. HbA1c reflects average glycaemia over about the lifespan of red cells, around 3 months.

Why is "Binding of glucose to albumin" not the answer?

Glucose binding to albumin gives fructosamine and not HbA1c.

Why is "Raised red cell lifespan" not the answer?

Prolonged survival would raise HbA1c.

Why is "Increased insulin secretion" not the answer?

Insulin secretion would not lower HbA1c relative to glucose readings.

What concept does this question test?

It tests Endocrinology: HbA1c limitations in Physiology. When red cells are young after haemolysis or bleeding, glycation is lower, giving a falsely low value. Fructosamine is an alternative.

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 Endocrinology: HbA1c limitations?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.