Rabies: immunoglobulin calculation: practice question

A PSM 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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PSM · Rabies: immunoglobulin calculation

Sample item

A 60-kg man is bitten on the face and hands by an unvaccinated stray dog that has run away. There are multiple deep bleeding wounds. Human rabies immunoglobulin is available. Which plan is correct?

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

The answer and the reasoning

A. 1200 IU infiltrated into and around the wounds as far as possible, any remainder given intramuscularly away from the vaccine site

Bites with bleeding wounds are category III exposures that need wound washing, a full vaccine course and rabies immunoglobulin. The dose is 20 IU/kg for human product (40 IU/kg for equine), so 20 x 60 = 1200 IU. As much as is anatomically possible is infiltrated in and around all wounds, and any remainder is given intramuscularly at a site distant from the vaccine.

Option by option

  • A. 1200 IU infiltrated into and around the wounds as far as possible, any remainder given intramuscularly away from the vaccine site (correct)

    20 IU/kg x 60 kg = 1200 IU, infiltrated locally with any remainder intramuscular at a distant site.

  • B. No immunoglobulin, since the full vaccine course alone is sufficient even for deep bleeding wounds

    Category III exposures need immunoglobulin because antibody from the vaccine appears too late to protect.

  • C. 1200 IU given entirely by deep intramuscular injection into the gluteal region, with no wound infiltration

    Giving all the immunoglobulin intramuscularly misses the local neutralisation of virus in the wounds and should not be mixed at the vaccine site.

  • D. 2400 IU of human immunoglobulin infiltrated into and around all the wounds as far as possible

    2400 IU corresponds to the 40 IU/kg equine immunoglobulin dose and is not needed for the human product.

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 PSM question

What is the answer to this PSM question?

The best answer is A, 1200 IU infiltrated into and around the wounds as far as possible, any remainder given intramuscularly away from the vaccine site. Bites with bleeding wounds are category III exposures that need wound washing, a full vaccine course and rabies immunoglobulin.

Why is "No immunoglobulin, since the full vaccine course alone is sufficient…" not the answer?

Category III exposures need immunoglobulin because antibody from the vaccine appears too late to protect.

Why is "1200 IU given entirely by deep intramuscular injection into the glute…" not the answer?

Giving all the immunoglobulin intramuscularly misses the local neutralisation of virus in the wounds and should not be mixed at the vaccine site.

Why is "2400 IU of human immunoglobulin infiltrated into and around all the w…" not the answer?

2400 IU corresponds to the 40 IU/kg equine immunoglobulin dose and is not needed for the human product.

What concept does this question test?

It tests Rabies: immunoglobulin calculation in PSM. The dose is 20 IU/kg for human product (40 IU/kg for equine), so 20 x 60 = 1200 IU. As much as is anatomically possible is infiltrated in and around all wounds, and any remainder is given intramuscularly at a site distant from the vaccine.

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 Rabies: immunoglobulin calculation?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM 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.