PCR false negative?

[talladega123]

I have a history of cold sores since childhood. I get a 2-4 a year, normally. I recently got a rash on my butt cheek that had blisters. I had very mild itchiness, no other symptoms. The blisters were scattered along the S1-S2 dermatome. I presented to the dr’s about 10-12 days after onset & assumed that they would confirm it was shingles as I had this before on the trunk around L1- it was a textbook rash and I have no doubt about that diagnosis. But this dr thought it could be HSV 1 or 2 instead. A sample was collected & tested for shingles, HSV1, & HSV2 and a pcr test was completed. They were all negative.

The dr said they could be false negatives because of the age of the lesions collected as the blisters were in the healing stage. During the 10-12 days I did take 1,000mg of valacyclovir twice for a cold sore I developed. The cold sore was standard- I had chapped lips they cracked & started a cold sore-no other oral symptoms. I couldn’t really tell if that help my butt or not. I have not had any sexual encounters in almost a year and have always used condoms for sexual intercourse(except for once over a decade ago) and never participated in anal sex. I have had less than 5 sexual partners and all were longterm and, as far as I am aware, monogamous relationships.

What is the likelihood that the tests were a false negative and I do have herpes? Should I have any further testing done?

[Terri Warren]

If you haven’t had sex in a year, you could do an IgG test since you had symptoms that were consistent with HSV. However, there are false positives on the IgG test for HSV 2 and if you have a positive that is lower than 8, I would recommend the herpes western blot for confirmation. But if negative, you can know with 92% certainty (compared to western blot) that you don’t have HSV 2. Since you’ve had cold sores since childhood, it is extremely unlikely that you have HSV 1 genitally.

Terri

[Author]

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