Parasitology: Toxoplasma IgG avidity: practice question

A Microbiology 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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Microbiology · Parasitology: Toxoplasma IgG avidity

Sample item

A pregnant woman at 12 weeks has positive Toxoplasma IgM and IgG. IgG avidity testing shows high avidity. What does this indicate?

AConfirmed fetal infection needing urgent treatmentBA false positive from cross-reacting antibodiesCInfection acquired within the last few weeksDInfection acquired several months ago, before this pregnancy

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

The answer and the reasoning

D. Infection acquired several months ago, before this pregnancy

Low-avidity IgG appears early in infection, while high avidity develops over a few months. A high-avidity result in early pregnancy therefore dates the maternal infection to before conception, making fetal risk very low even if IgM persists.

Option by option

A. Confirmed fetal infection needing urgent treatment
Avidity dates the maternal infection and does not prove infection of the fetus.
B. A false positive from cross-reacting antibodies
Avidity testing is used to date infection and does not suggest cross-reaction.
C. Infection acquired within the last few weeks
A recent infection would give low-avidity IgG.
D. Infection acquired several months ago, before this pregnancy (correct)
Correct. High avidity effectively excludes infection within the preceding few months.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is D, Infection acquired several months ago, before this pregnancy. Low-avidity IgG appears early in infection, while high avidity develops over a few months.

Why is "Confirmed fetal infection needing urgent treatment" not the answer?

Avidity dates the maternal infection and does not prove infection of the fetus.

Why is "A false positive from cross-reacting antibodies" not the answer?

Avidity testing is used to date infection and does not suggest cross-reaction.

Why is "Infection acquired within the last few weeks" not the answer?

A recent infection would give low-avidity IgG.

What concept does this question test?

It tests Parasitology: Toxoplasma IgG avidity in Microbiology. A high-avidity result in early pregnancy therefore dates the maternal infection to before conception, making fetal risk very low even if IgM persists.

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 Parasitology: Toxoplasma IgG avidity?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.