[Question #7835] RPR False Positive ? Could it be Hepc?

51 months ago

A couple of years ago I had a full panel STD test. Everything was negative except the syphilis test was RPR reactive with a titer of 1:1. I did a confirmation test (FTA-ABS) it was negative. I'm concerned maybe not enough time had elapsed for me to test positive? I was treated with doxycycline. My concern is now that maybe I had hep c and not enough time had elapsed for me to show antibodies. I have read studies online (yes i know!) that say this can cause a reactive RPR. But if it caused a reactive RPR wouldn't that mean you have the antibodies and your HCV test would show that? There seems to be new studies that say even non traumatic anal sex can transmit HCV very easily. Is this true?

H. Hunter Handsfield, MD

51 months ago

Welcome back to the forum.

It is 100% certain you do not have syphilis. The FTA-ABS test is not generally done unless RPR is posiive. However, it is well known from longstanding research that in people with newly acquired syphilis, FTA-ABS becomes positive before RPR. So you had what STD experts call a "biologic false positive" RPR, which is quite common: 1-2% of all people have it -- i.e. you're among 3-6 million Americans with BFP.

Second, if somehow you were an exception to this rule, doxycycline is 100% effective against syphilis; it is not possible you were still infected after taking doxy. So in the exceedingly unlikely case you actually had syphilis, it is now gone. But for the reasons above, you can be confident you never had it.

Interference of syphilis testing on account of HCV is rare. In any case, presumably you don't have HCV, right? If not tested for it, you might consider it for reassurance. FYI, traumatic anal sex is the ONLY way HCV is sexually transmitted, for all practical purposes; and the only population group in whom HCV is documented to be sexually transmitted is in men who have sex with men with potentially traumatic rectal exposures. (The penile exposed person is not at increased risk.) Despite common beliefs, HCV is not transmitted sexually between males and females. (The heterosexual partners of persons with HCV have no higher risk of infection than anyone else in the general population.)

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

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51 months ago

Dr. Handsfield - Thank you for your fast reply. That is reassuring about syphilis. At the time of my test, I was tested for Hep,A,B,C (I am vaccinated against A&B now). C did not show any antibodies. But I was only at 3-4 weeks of a possible remote exposure. Should I test again for hcv?My concern was that I have Hep C, it caused the "biological false positive". But, if I had that happen wouldn't I have tested positive for hcv?

H. Hunter Handsfield, MD

51 months ago

Because hepatitis C isn't really an STD, I don't have a lot of experience testing for it. But I believe 3-4 weeks was too early; it probably takes up to 6 weeks for detectable antibody to appear. On the other hand, if you're not a gay man with rectal sexual exposure, there was really no need for HCV testing anyway -- you were not at risk.

99.9% of BFPs are not the result of HCV co-infection. And yes, in that case your HCV test probably would have been positive.

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51 months ago

Thank you! My concern was a tattoo I had gotten. Foolishly I didn't realize the dangers they can have.

H. Hunter Handsfield, MD

51 months ago

My understanding is that modern tattoo methods have pretty much eliminated any risk of HCV and all other blood borne infections (assuming a legitimate tattoo parlor and not some dude who isn't properly trained).---
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