Toxicology: collection of blood for alcohol analysis: practice question

A Forensic Medicine 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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Forensic Medicine · Toxicology: collection of blood for alcohol analysis

Sample item

A driver is brought after a road traffic accident and the police request blood alcohol estimation. Which collection technique is most appropriate?

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

The answer and the reasoning

B. Clean the skin with a non-alcoholic antiseptic and collect venous blood into a bottle with sodium fluoride and potassium oxalate

Skin cleaning with spirit would contaminate the sample, so a non-alcoholic antiseptic is used. Sodium fluoride prevents microbial fermentation that can generate or destroy alcohol, and potassium oxalate acts as anticoagulant. The sample is sealed, labelled and refrigerated, with consent or lawful requisition.

Option by option

  • A. Swab the skin with spirit and collect blood into a plain bottle

    Spirit contaminates the sample and an unpreserved sample can ferment.

  • B. Clean the skin with a non-alcoholic antiseptic and collect venous blood into a bottle with sodium fluoride and potassium oxalate (correct)

    Correct. Non-alcoholic cleaning with a fluoride-oxalate preservative gives a reliable sample.

  • C. Collect blood in a heparin-only tube and keep at room temperature for a week

    Unpreserved room-temperature storage allows microbial changes in alcohol content.

  • D. Collect a single urine sample after 6 hours instead of blood

    Urine lags blood and is less accurate for current impairment.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is B, Clean the skin with a non-alcoholic antiseptic and collect venous blood into a bottle with sodium fluoride and potassium oxalate. Skin cleaning with spirit would contaminate the sample, so a non-alcoholic antiseptic is used.

Why is "Swab the skin with spirit and collect blood into a plain bottle" not the answer?

Spirit contaminates the sample and an unpreserved sample can ferment.

Why is "Collect blood in a heparin-only tube and keep at room temperature for…" not the answer?

Unpreserved room-temperature storage allows microbial changes in alcohol content.

Why is "Collect a single urine sample after 6 hours instead of blood" not the answer?

Urine lags blood and is less accurate for current impairment.

What concept does this question test?

It tests Toxicology: collection of blood for alcohol analysis in Forensic Medicine. Sodium fluoride prevents microbial fermentation that can generate or destroy alcohol, and potassium oxalate acts as anticoagulant. The sample is sealed, labelled and refrigerated, with consent or lawful requisition.

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 Toxicology: collection of blood for alcohol analysis?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.