STDs Expert Forum
False Positive Herpes Culture?
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The STD Forum is intended only for questions and support pertaining to sexually transmitted diseases other than HIV/AIDS, including chlamydia, gonorrhea, syphilis, human papillomavirus, genital warts, trichomonas, other vaginal infections, nongonoccal urethritis (NGU), cervicitis, molluscum contagiosum, chancroid, and pelvic inflammatory disease (PID). All questions will be answered by H. Hunter Handsfield, M.D. or Edward W Hook, MD.

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False Positive Herpes Culture?

Is it possible to have a false positive herpes culture?  Is there any other std/infection that could cause a false positive herpes culture?  

I had a sore spot come up the morning after sex, and didnt think much of it.  It was sore for a few days and then started to hurt when urine got on it.  I had a follow up pap smear for an abnormal pap like 4-5 days after the spot came up, and my dr said it looked like herpes and did a culture and put me on Valtrex.  The culture came back positive.  This was back in July and I have had a few spots come up since then, but they are gone in 1-2 days and never scab or anything.  They also dont hurt very mcuh.  I am also having a lot of discharge and some general itching and redness.  I am just wondering if it is possible that the culture was a false positive and I actually have something else.  
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It is probable that you have genital herpes.  False positive culture results are rare, but it could happen, depending somewhat on the experience of the laboratory and the exact test methods that are used.  However, the symptoms you describe are quite typical for genital herpes, i.e. a sore spot with pain in contact with urine, lasting several days, and when a doctor believes a genital lesion looks like herpes, usually s/he is correct -- especially if s/he is experienced with herpes, like most gynecologists are.  So adding up all the evidence, almost certainly you have genital herpes.  However, the later "spots" are not herpes, which cannot cause outbreaks that last only 1-2 days.

You don't describe what virus type was isolated by culture.  If it was HSV-1 (which causes about half of all cases of initial genital herpes, usually acquired by oral sex), then you might not have any recurrent outbreaks, or only a couple outbreaks over the next year of two.  That would fit with your lack of repeat outbreaks since July, since most HSV-2 cases recur more often.  You should check with your doctor about this.  If the virus was not tested to determine type 1 or 2, you could have a blood test to determine whether you have been infected with HSV-1, HSV-2, or both.  Also, the partner you likely caught this from should be tested to determine which virus type he has.

In summary, almost certainly you have herpes.  But you need to know the virus type.  That will tell a lot about whether to expect future outbreaks and whether you are likely to have asymptomatic viral shedding, when the infection can be transmitted to sex partners without symptoms.  Feel free to return to the forum when you know which HSV type you have and I can then provide additional advice about it.

Good luck--  HHH, MD
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I was positive for HSV2, sorry that I didn’t include that in the first post.  

There are a few reasons why I still doubt that it is herpes.  The first being the spot came up the day after sex, and my gyno said that it wouldn’t show up that fast. But it had to be from that encounter, or I had it for a while and just had no symptoms, which also means that I don’t know who I got it from.  Also when I was prescribed Valtrex, it didn’t help at all, my condition actually got worse before it got better. I also had a yeast infection too. Is it common to not respond to antivirals?  

I am wondering if I should get a blood test to confirm that I am positive.  Have you ever heard of someone having a false positive culture?  

Also I am wondering what else it could be if it isn’t herpes.  
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You are correct that all those factors argue against genital herpes.  So does the fact that you have had no recurrent outbreaks despite having HSV-2; most people with initial genital HSV-2 (with symptoms) have symptomatic recurrent outbreaks within the next 6 months.  Still, false positive culture results are uncommon.

The thing to do now is have an HSV-2 blood test.  If positive, it will confirm you are infected with HSV-2.  If negative, it will strongly suggest your culture was falsely positive.
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