Is this a false positive? I tested Negative for HSV-1 at 8 weeks, then I tested postive at week 16.

[adnelps]

At the request of my doctor I had a complete STD panel done 8 weeks after a casual sexual encounter. Eight weeks later my doctor calls me and tells me that I should repeat the tests again just as a confirmatory measure- to give me peace of mind. Although Dr. HHH (of this forum) felt it was necessary I went ahead and did it to apease my doctor. For my first test, at 8 weeks I tested negative for everything including both HSV-1 and HSV-2. I was kind of expecting to be negative because I have not had any symptoms of HSV-1 or HSV-2  at any time, recently or throughout in my entire life- and I have been especially vigilant for symptoms during the past 16  weeks.  The results of the tests performed by LabCorp is as follows:

On 8/27/2009

HSV 1 IgG, Type Spec       (the results were  <0.91)
HSV 2 IgG, Type Spec       (the results were  <0.91)
HSV, IgM I/II Combination   (the results were 0.28)
- All were Negative

On 10/27/2009

HSV 1 IgG, Type Spec       (the results were    1.32) - Positive
HSV 2 IgG, Type Spec       (the results were  <0.91) - Negative
HSV 1 IgM Antibodies          <1:10             titer            < 1:10
HSV 2 IgM Antibodies          <1:10             titer            < 1:10

Given your expert opinion do you think this is a false positive? It seems to me that the results of the two tests that were performed the second time around contradict each other. Please let me know what you think and if its worth getting retested or just leave things the way they are.

Thanks your your invaluable service.

[H. Hunter Handsfield, M.D.]

I recognize your username but it doesn't come up on searching this forum for past threads, so I cannot review your previous question and my reply.

The performance of the HSV-1 antibody tests has not been well studied; there isn't nearly as much scientific understanding as for the HSV-2 tests.  But from what is known, it appears the test is less sensitive -- i.e. it misses lots of infections compared with the HSV-2 test.  Also, your newly positive result is very weak, so it might be a false positive result.

But my guess is that you have been infected with HSV-1 all along, most likely since you were a child, and that the initial test result just missed it.  That the IgM result remained negative suggests that you have not had a new HSV infection in the weeks since the initial test was done.  Finally, if you had a new HSV-1 infection, most likely you would have had symptoms.

If you have HSV-1, most likely it is oral and not genital, and not sexually acquired.  But there is no way to know for sure.  However, it really doesn't matter much, does it?  If it is genital, the odds are you will have few or no future outbreaks and will never transmit the infection to a sex partner.  If it is oral, and you have never had cold sores, then probably you never will.  Having a positive blood test for HSV-1 makes you just like half the US population (and 90% of people in some countries).  No big deal.  (If you like, you can search this forum for "HSV-1" to find lots of discussions about the important differences between HSV-1 and -2 and why this shouldn't be a worry for you.)

In general, HSV blood tests are not indicated unless there is rather strong suspicion of infection.  Why?  Because of exactly the sort of outcomes that you report here:  uncertain results that cause more confusion than clarity.  Although I cannot find your previous thread, apparently I advised against testing and now it seems that advice was correct.  Now, having done it anyway, you're probably going to just have to live with the uncertainty.  However, if you want to carry this out further, you could have an HSV Western blot test, which is the ultimate gold standard.  It would tell once and for all whether or not you are infected with HSV-1.  But if positive, it will not provide any additional information about when you were infected or where on your body.

Regards--  HHH, MD

[adnelps]

I have to make a correction!  I guess I was typing too fast and forgot to add the word NOT to the sentece below!  

My apologies!

Although Dr. HHH (of this forum) felt it was  NOT  necessary I went ahead and did it to apease my doctor

[H. Hunter Handsfield, M.D.]

I saw this and took it into account in my reply above.

[adnelps]

One last question. You mentioned that since the IgM results remained negative for this last lab test test (performed on 10/27/2009), it suggests that I have not had a new HSV infections in the weeks since my initial lab tests- performed on 08/27/2009. What I would like to know is; What about the initial IgM results for the test performed 8 weeks prior to that ( on 08/27/2009)? Does the negative result of that IgM lab test indicate that I had not had any new HSV infections in the 8 or so weeks prior to the performance of that particular 08/27/2009 lab test either?. I'm just curious whether I aquired HSV-1  during my  casual sexual encounter 16 weeks ago! During my childhood days, or perhaps never (as it could conceivable be a false positive).

Please educate me a little more on this matter.

As always ,

Thanks,  

[H. Hunter Handsfield, M.D.]

The IgM test is HIGHLY unreliable (just search "HSV IgM" in this fourm to see innumerable discussions).  In theory, a positive IgM with negative IgG indicates new infection.  But IgM misses lots of new infections as well.  That both IgM tests were negative suggests that you had not had a new HSV infection (either HSV-1 or 2) in the 4-6 weeks before each test.  But only "suggests" -- no firm conclusions are possible.

I already said that if you have HSV-1, it probably dates to childhood.  It is extremely unlikely you caught HSV-1 (if you are infected at all) during your sexual encounter 16 weeks previously.

If you would like to have a Western blot and report that result, I might have another comment.  But not until then.