Oldies but Goodies: How should you approach a low titer +RPR?

February 5, 2010

Please enjoy a post from the Clinical Correlations Archives, first posted November 28, 2006…

45 year old male with a history of Hepatitis B ( Hep B Surf Ag + but Hep B E Ab+ and E Ag – and DNA viral load was not sent) and syphilis treated in the past. He has RPRs in the past that were 1:1 for years and then negative x 2 a year apart, the last being over two years ago. He had labs drawn last week and had an RPR of 1:4. He does report high-risk unsafe sexual activity (with female prostitutes) over the past two years. He does not recall seeing a chancre and his exam was negative. He has not tested for HIV.


1. Would you retreat?

2. Would you retreat if the RPR was 1:2? (should we consider reinfection?)

Commentary By Neal Steigbigel M.D., Professor of Medicine (Infectious Diseases/Immunology)

The RPR antibody (a non-treponemal or reaginic antibody) titer of 1:4 may be associated with:

1) reinfection syphilis (immunity brought about by previous syphilis infection is incomplete)

2) may represent a biological false positve when the titer is less than 1:8 in that this is a reagin antibody which is not specific for syphilis and and can be elevated non-specifically by conditions (particularly liver diseases, especially cirrhosis or HIV infection) that produce non-specific polyclonal increases in various antibodies.

3) persistent mild elevation from his former episode of syphilis, although the fact that it became negative prior to this last determination is somewahat against that possibility.

The patient should have a specific treponemal test performed (such as the MHA-TP test) which is specific for Treponemal infection and usually persists as positive for life. If the latter is positive in this patient that means that he has had syphilis in the past, but 1,2, and 3 above are still the possibilities which cannot be entirely resolved. That is, the patient may have late latent syphilis and if the MHA is positive and there is not documentation that he has been treated for late latent syphilis since his last sexual exposures, I would treat with benzathine penicillin G 2.4 million units im weekly for 3 weeks in the absence of a penicillin allergy. The RPR titer usually becomes negative two years after treatment. If it does not, then again the posibilities are persistent infection, reinfection or false-positive test (most likely the latter).

What would you do if the titer bounced up to 1:2 from 0?

If it fluctuates at low titer (<1:8) after the treatment that is suggested and without signs of disease I would not retreat.

What would you do in a person whose titer never falls below 1:4 and then jumps to 1:16?

That would be unlikely, but would suggest true infection requiring retreatment if the MHA was positive.