question about positive HSV-2 Ig G result

[dweezel]

Here's the scenario. I am a fairly sexually active male who was intimately involved with a woman on a regular basis over the past few months. During that time, she claims she was monogamous. She returned from a trip abroad and we were intimate a few days after her return. I properly used a condom, which was fully intact after intercourse. Three days later, she had an outbreak that was later confirmed by her physician to be HSV-2. He confirmed this on clinical suspicion without any cultures or blood work. She then told me that she had unprotected sex with a stranger during her trip abroad approximately two weeks before her outbreak. I went to a PCP five days after exposure and had a full STD panel including HSV 1 and 2 IgG. My HSV-1 IgG came back less than 0.9 (funny because I've had cold sores before when I was younger), and my HSV-2 IgG was 1.12. My PCP advised me to go on Valtrex over the next year to reduce the chance of an outbreak. It is now day 11 since my exposure, and I've had no symptoms so far. Is five days post-exposure enough time for me to build HSV-2 antibodies? Furthermore, is it possible that I had an HSV-2 infection prior to all this and did not know it this whole time? If so, is 1.12 a reasonable cutoff to establish a diagnosis of a prior infection. How long should I wait before I get tested again? Any other thoughts on the matter would be most appreciated. Thanks.

Dweezel

[Edward W Hook, MD]

Can you be sure - no.  What is most likely however is that you do not have HSV-2 and the result you have is a false positive.  If I were you, I would not worry about this further.  EWH

[dweezel]

So a different doc retested my HSV IgG levels about a month after my initial tests. My HSV-1 is still negative, and my HSV-2 came back at 1.07, less than my initial value. I am still asymptomatic. Is it safe to assume I'm negative for HSV-2 as well? Thanks.

[scareduncertain]

I have the same predicament..hsv 1 igg is negative and hsv 2 igg is 1.09.  i heard that false positives are either due to cross reactivity with hsv 1 or lab error.  I retested in 2 weeks in hopes for lab error and still awaiting results.  if still low...perhaps a western blot?

[Edward W Hook, MD]

Read my reply.  Possible but your risk of having a false positve is still substaantial.   EWH

[dweezel]

Is it possible for me to have aquired an HSV-2 infection prior to being with her with antibodies levels >0.9 but <2.0?

[Edward W Hook, MD]

The topic of herpes is a complex one.  The disease is common with HSV-1 being present in over 60% of adults and HSV-2 (the virus which causes most genital herpes) being present in about 1 in 5 Americans.  For both infections, the majority of people who have the infections are not aware that they are infected, either because they either acquired it without knowing in the past or because they misidentified their herpes as something else.  I will do my best to answer your questions but in general, many of these questions and information about herpes can be obtained by accessing excellent informational web sites such as the one run by the American Social Health Association (disclosure, Dr. Handsfield and I are both on the Board of Directors of ASHA).  

Herpes blood test results must be taken in context.  By that I mean that all blood tests have both false positive and false negative results from time to time (the goal is to minimize this and know when it is likely, that is a large part of my job).  Now on to you and your situation:

1.  You do not have antibodies to HSV-1.  This makes it unlikely that what you identify as cold sores are HSV-1.  In fact, it turns out that about 20-25% of genital lesions identified as genital herpes turn out to be something else.  The same is likely to be true of "cold sores".  The way to find out, if you wish to do so, is to get a culture of your "cold sore" the next time it appears (the sooner after its appearance that you are tested, the more likely the culture will be positive if this is HSV).  The Herpes Select (I presume that is the IgG test you had) detects infection in close to 95% of people with infection.  Thus there is a small chance that you have HSV-1 and negative antibody tests but it is far more likely that you don't have HSV-1 (before you ask, this does not mean you are abnormal or lacking immunity).
2.  You may not have HSV-2 either.  Your HSV IgG to HSV-2 is just above the cut off for being positive.  There is an ongoing debate in the expert community about what the cut-off for a positive Herpes Select antibody test should be with many arguing that the current cut off is too low and that, in low risk persons (thus this may pertain to you), the cut off should be in the neighborhood of 3.0.  So this could be a false positive test.  Five days would be too soon to develop a positive IgG antibody test.  If you repeat the test in about a month and it is higher (above 2.0) then you probably do have herpes.  If it is in the same low range of even negative, I doubt that you have herpes.  

Regarding valacyclovir, in my opinion, it is a bit early to start taking it until you are sure you have it.  In addition, I would advise condoms at a minimum and possibly suppressive valacyclovir for your GF although that, obviously, is up to her.

Hope this helps.  Check out the web site.  EWH