Equivocal LabCorp IgG + negative reflex three weeks after potential exposure

[leo_brasille]

Hi,

I’m a sexually-active 29-year-old male. In the course of recent routine STD screening (samples collected 3/15/2021), I received an equivocal HSV-2 IgG index value of 0.99 on the LabCorp HSV 1 and 2-Spec Ab, IgG, w/Rfx test (#164922). This triggered the HSV-2 IgG Supplemental Test (#163006), which came back negative.

My last unprotected sexual encounter with a partner of whose HSV status I am uncertain was on 2/21/2021, three weeks before sample collection. I have had a handful of sexual encounters since then, predominately with a condom, with the exception on two separate occasions of the brief pre-condom penetration of a partner who was, at last test, HSV-2 negative.

All partners were women. My last STD test returned results on 8/21 of last year, with an HSV-1 IgG index value of 1.29 and an HSV-2 index value of <0.91. I have never had an outbreak, although in November of last year, I observed a single non-clustered inflammation on my penis that did not blister, did not burn or itch, and was painless to the touch, although it appeared to have a comedone-like head. I have intermittently observed similar lesions since I was a young teenager, before I became sexually active. All other test results are negative.

I intend to have follow-up testing performed next week (two weeks from last sample collection), and two weeks from that date, if results are still unclear. If at any point I progress to a positive supplemental test, I will order the U. of Washington western blot.

What I am wondering, at this point, is (approximately) what percentage of people in my situation (equivocal IgG index, negative supplemental test, recent possible exposure) progress to a full positive. Additionally, while I will be taking the precaution of using condoms for all sexual encounters until a conclusive result is established — would you advise that I alert past sexual partners of my uncertain status?

[Terri Warren]

Because your most recent sexual encounter prior to taking the test was so close to the testing, you cannot know what to make of it at this point. You could be in the equivocal range because you are in the process of going from negative to positive or it could be meaningless. I think it would be good to wait 6 weeks from your most recent sexual encounter to test again. But if you are continuing to have sex, even with a condom, it’s always going to be a bit of a moving target. If you are using a condom with every encounter and condoms reduce transmission by 96%, I think it is not necessary to disclose your equivocal status at this time.

Also, your HSV 1 result is somewhat unclear as well, with such a low positive
At some point, you may wish to pursue the western blot for greater clarity

Terri

[leo_brasille]

Hi Terri,

Thanks very much! I re-tested on 4/5, six weeks out. My HSV-1 IgG index increased suddenly to 2.03 — I’m essentially indifferent to this, although I found the 0.74 index increase over three weeks somewhat surprising. My HSV-2 index has risen as well, to a point outside of the equivocal range — although minimally, at 1.29. The supplemental test came back, once again, negative. At this point, I’ll likely pursue a Western blot, but I’m curious what you make of this progression.

Also, do you have any idea what the LabCorp supplemental test actually is?

Thanks again,
Leo

[Terri Warren]

I think the LabCorp supplemental test is a membrane test that causes a color change, which I think they over-read as positive, but I’m not positive about that.
You have a low positive and definitely need a western blot as confirmation. This may well be a false positive.

Terri

[leo_brasille]

Thanks, Terri. Given the expense and hassle of the western blot, you don’t think it’s worth waiting for another few weeks, retesting, trusting the supplemental test if it’s negative, and reflexing to the western blot if it’s positive?

If/when I do get the western blot, how many weeks out from potential exposure should I be waiting?

Leo

[Author]

Posts