Blood: Bombay phenotype: 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 · Blood: Bombay phenotype

Sample item

A woman's red cells show no agglutination with anti-A, anti-B or anti-H lectin, and her serum agglutinates group A, B and O red cells. She needs a transfusion. Which blood is safe for her?

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

The answer and the reasoning

D. Blood from a donor with the Bombay phenotype

In the Bombay (hh) phenotype the H antigen precursor is not made, so A and B antigens cannot be added to red cells, which type as group O. Her serum contains anti-H in addition to anti-A and anti-B, so ordinary group O cells, which carry H antigen, are agglutinated. Only Bombay-type donor blood is compatible.

Option by option

  • A. Group O Rh-compatible blood

    Group O cells carry H antigen and would be haemolysed by her anti-H.

  • B. Group AB Rh-compatible blood

    Group AB cells carry H, A and B antigens and would be attacked by anti-H, anti-A and anti-B.

  • C. Any group after a saline-suspension crossmatch

    A crossmatch can show incompatibility but does not make unsuitable blood suitable.

  • D. Blood from a donor with the Bombay phenotype (correct)

    Correct. Cells lacking H antigen are not attacked by her anti-H antibody.

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, Blood from a donor with the Bombay phenotype. In the Bombay (hh) phenotype the H antigen precursor is not made, so A and B antigens cannot be added to red cells, which type as group O.

Why is "Group O Rh-compatible blood" not the answer?

Group O cells carry H antigen and would be haemolysed by her anti-H.

Why is "Group AB Rh-compatible blood" not the answer?

Group AB cells carry H, A and B antigens and would be attacked by anti-H, anti-A and anti-B.

Why is "Any group after a saline-suspension crossmatch" not the answer?

A crossmatch can show incompatibility but does not make unsuitable blood suitable.

What concept does this question test?

It tests Blood: Bombay phenotype in Physiology. Her serum contains anti-H in addition to anti-A and anti-B, so ordinary group O cells, which carry H antigen, are agglutinated. Only Bombay-type donor blood is compatible.

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 Blood: Bombay phenotype?

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.