Radiation safety and radiobiology: lymphocyte count as early indicator: practice question

A Radiology 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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Radiology · Radiation safety and radiobiology: lymphocyte count as early indicator

Sample item

After an accidental whole-body exposure, serial blood counts are used to estimate severity. Which circulating cell count falls earliest and most steeply?

ANeutrophilsBRed blood cellsCPlateletsDLymphocytes

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

The answer and the reasoning

D. Lymphocytes

Lymphocytes are highly radiosensitive and die by interphase apoptosis within hours, so the absolute lymphocyte count in the first 48 hours is a useful early guide to dose. Neutrophils may rise transiently before falling, and red cells fall last.

Option by option

A. Neutrophils
Neutrophils often increase transiently and fall later when the marrow stops producing them.
B. Red blood cells
Red cells have a long lifespan and show only a late fall.
C. Platelets
Platelets decline over days to weeks as marrow production fails.
D. Lymphocytes (correct)
Correct. Lymphocytes are lost rapidly even with low doses.

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.

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is D, Lymphocytes. Lymphocytes are highly radiosensitive and die by interphase apoptosis within hours, so the absolute lymphocyte count in the first 48 hours is a useful early guide to dose.

Why is "Neutrophils" not the answer?

Neutrophils often increase transiently and fall later when the marrow stops producing them.

Why is "Red blood cells" not the answer?

Red cells have a long lifespan and show only a late fall.

Why is "Platelets" not the answer?

Platelets decline over days to weeks as marrow production fails.

What concept does this question test?

It tests Radiation safety and radiobiology: lymphocyte count as early indicator in Radiology. Neutrophils may rise transiently before falling, and red cells fall last.

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 Radiation safety and radiobiology: lymphocyte count as early indicator?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.