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    What causes a false negative result for HSV-2?

Posted on Thu, 2 Jun 2016 in Sexually Transmitted Diseases
Question: Hi doctor, I would like to ask about herpes simplex virus type 2, HSV-2.

I have both HSV-1 and HSV-2 infection. I was diagnosed with genital herpes HSV-2 in 2004. I had symptoms at the time and went to do a blood test to find out what was affecting me and was found to be positive for HSV-2 antibodies (also positive for HSV-1 antibodies).

I had symptoms of genital herpes in 2004 for about 6 months when I first contracted it but have never had any symptoms since then until present.

Recently, a week ago, I went to do a blood test to check on my HSV-2 antibodies, out of curiosity and the test result came back negative. The result for my HSV-2 antibodies was 7.1 U/ml, which is negative as the reference range provided was < 16 = negative.

Can you please explain why my HSV-2 antibodies is negative now if I actually had HSV-2 in the past? Because I understand that you can never get rid of HSV-2 once you contracted it.

Another thing that I thought may have affected the HSV-2 antibody levels in my recent blood test was my antiviral medication. I developed cold sores around 13/03/2016 and after a few days of developing the symptom I decided to take antivirals, valicyclovir, to help speed up my recovery. I took valicyclovir for 2 days, i.e 16-17/03/2016 and stopped on 17/03/2016. The cold sore went away after that. I then took the blood test for HSV-2 antibodies, that I mentioned above, on 25/03/2016 . This is already about 7-8 days after my last dose of valicyclovir. So i'm thinking there shouldn't be any valicyclovir left in my system to affect the HSV-2 antibodies on my blood test on 25/03/16.

Can you please help to explain why my HSV-2 antibodies is negative? Could it possibly mean I no longer have HSV-2 in my system after all these years? Or is it normal to have a negative HSV-2 antibody level if I don’t have any recurrent active HSV-2 infection?

Thank you very much.

Answered by Dr. Kakkar S. 1 hour later
Brief Answer:
I suggest a swab test for Hsv -2 by PCR

Detailed Answer:
Hello. Thank you for writing to us

I am Dr. kakkar (dermatologist and venereologist). I have gone through your query and I have noted your concern.

Hsv once acquired stays inside body, forever. Treatment with antivirals has no effect on levels of antibodies.
I suggest you to get a more accurate test for Hsv i.e PCR for HSV-2 via a swab test. This is more accurate than a blood test for Hsv-2 antibodies. Blood test for Hsv antibodies can have false positive and false negative rates.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
Follow up: Dr. Kakkar S. 27 minutes later
Thank you Dr Kakkar.

But how do I take a swab test for HSV-2 by PCR method when I currently don't have any HSV-2 symptoms/blisters on the genitals and has never had them since 2004 until present? Or do I have to wait until I get symptoms/blisters in the future?

Is there any other accurate ways to test and confirm/rule out for HSV-2 besides the swab test by PCR, since I don't have any symptoms?

Thank you
Answered by Dr. Kakkar S. 15 hours later
Brief Answer:
A western blot for herpes would the right thing to do

Detailed Answer:

Yes, Pcr would be reliable only if you have genital lesions. In patients with active lesions it is the gold standard test for hsv. However in asymptomatic individuals serology is the only way to detect/confirm rule out hsv infection. Sometimes a single test may not be conclusive because of low index values specially in those with both hsv 1 and 2 infection. As a result rarely low index values may be reported as false positives, therefore, such low values should always be confirmed by a different test, commonly a western blot test if the earlier test was a Elisa Or immunoblot.
I suggest you to redo a western blot for Hsv if the previous screening test was an Elisa, so as to have a reliable result.

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar
Answered by
Dr. Kakkar S.


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