Sexually transmitted infections: serofast state: practice question

A Dermatology 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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Dermatology · Sexually transmitted infections: serofast state

Sample item

A man treated with benzathine penicillin for secondary syphilis 12 months ago had an RPR titre fall from 1:64 to 1:4, and it has remained at 1:4 on repeat testing. He has no new lesions or neurological symptoms and no new exposure. What is this pattern called?

ABiological false-positive reactionBSerofast stateCProzone phenomenonDSerological relapse

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

The answer and the reasoning

B. Serofast state

A serofast state is a persistent low-titre non-treponemal reactivity after adequate treatment, with at least a fourfold fall but no return to non-reactivity. It is common, especially after longer disease, and needs follow-up rather than automatic retreatment. A fourfold rise suggests reinfection or relapse.

Option by option

A. Biological false-positive reaction
A biological false positive occurs in conditions such as SLE or pregnancy with a negative treponemal test.
B. Serofast state (correct)
Correct. A stable low titre after a good response to treatment is a serofast state.
C. Prozone phenomenon
Prozone phenomenon is a false-negative result from excess antibody at high titres and is solved by dilution.
D. Serological relapse
Serological relapse needs a sustained fourfold rise in titre, which has not occurred.

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 Dermatology question

What is the answer to this Dermatology question?

The best answer is B, Serofast state. A serofast state is a persistent low-titre non-treponemal reactivity after adequate treatment, with at least a fourfold fall but no return to non-reactivity.

Why is "Biological false-positive reaction" not the answer?

A biological false positive occurs in conditions such as SLE or pregnancy with a negative treponemal test.

Why is "Prozone phenomenon" not the answer?

Prozone phenomenon is a false-negative result from excess antibody at high titres and is solved by dilution.

Why is "Serological relapse" not the answer?

Serological relapse needs a sustained fourfold rise in titre, which has not occurred.

What concept does this question test?

It tests Sexually transmitted infections: serofast state in Dermatology. It is common, especially after longer disease, and needs follow-up rather than automatic retreatment. A fourfold rise suggests reinfection or relapse.

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 Sexually transmitted infections: serofast state?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology 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.