Infectious diseases: syphilis serology: practice question

A General 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.

Try it

General Medicine · Infectious diseases: syphilis serology

Sample item

A 30-year-old woman with systemic lupus erythematosus is asymptomatic. A routine VDRL test is reactive at 1:4, but the TPHA test is non-reactive. She has had no genital ulcer or rash. How should this result be interpreted?

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

The answer and the reasoning

C. Biological false-positive VDRL, so no treatment for syphilis is needed

Non-treponemal tests (VDRL, RPR) detect antibody to cardiolipin and can be falsely positive in SLE, antiphospholipid syndrome, pregnancy, malaria and other infections. A non-reactive treponemal test (TPHA) excludes syphilis because treponemal antibody persists in true infection, even after treatment. Therefore no therapy is needed.

Option by option

  • A. Previously treated syphilis with a serofast reaction

    A treated infection would leave a reactive treponemal test, whereas hers is negative.

  • B. Late latent syphilis, so weekly benzathine penicillin for three weeks is needed

    Latent syphilis is also treponemal test positive, so the three-dose course is not required.

  • C. Biological false-positive VDRL, so no treatment for syphilis is needed (correct)

    Reactive non-treponemal and negative treponemal tests in SLE are a biological false positive.

  • D. Early syphilis, so a single intramuscular dose of benzathine penicillin is needed

    Early syphilis would have a reactive treponemal test, and treatment is not warranted.

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.

More General Medicine questions

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is C, Biological false-positive VDRL, so no treatment for syphilis is needed. Non-treponemal tests (VDRL, RPR) detect antibody to cardiolipin and can be falsely positive in SLE, antiphospholipid syndrome, pregnancy, malaria and other infections.

Why is "Previously treated syphilis with a serofast reaction" not the answer?

A treated infection would leave a reactive treponemal test, whereas hers is negative.

Why is "Late latent syphilis, so weekly benzathine penicillin for three weeks…" not the answer?

Latent syphilis is also treponemal test positive, so the three-dose course is not required.

Why is "Early syphilis, so a single intramuscular dose of benzathine penicill…" not the answer?

Early syphilis would have a reactive treponemal test, and treatment is not warranted.

What concept does this question test?

It tests Infectious diseases: syphilis serology in General Medicine. A non-reactive treponemal test (TPHA) excludes syphilis because treponemal antibody persists in true infection, even after treatment. Therefore no therapy is needed.

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 Infectious diseases: syphilis serology?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General 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.