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Can you tell me how accurate or inaccurate you think the HerpeSelect Immunoblot is?
I had a low-positive (2.6) on the ELISA, and am thinking of getting the immunoblot, but I’m worried about cross-reactivity. Although I don’t have HSV-1 and have always tested negative for HSV-1, I did have the shingles a couple of years ago and I read that herpes zoster can cross-react with the proteins on the immunoblot and ELISA. So I guess my question is, should I go straight for the Western Blot, or the immunoblot instead? Have you heard of false-positive immunoblots? I can’t seem to find much on the internet about them because most people don’t get the immunoblot, but only the ELISA. I haven’t been with anybody sexually for years and so a low-positive ELISA with absolutely no symptoms was surprising.
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I don’t care for the immunoblot. I think it is very hard to read accurately. WE used to do it in our clinic years ago and moved to the ELISA screening test because that gave us a firm index value that could help us sort out the low positives. I do not believe that we know that varicella zoster cross reacts with the ELISA. I would most certainly skip the immunoblot and go right for the western blot for sure. The chances are excellent that the immunoblot will also be positive and then you still won’t know if this is positive due to a false positive or a real positive and have to do the western blot anyway.
Terri
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We definitely saw common protein bands being present on people who were negative for HSV 1 and 2. That was one reason we discontinued using the test. I was not aware that Focus believed that it was clear that VZV was a causative agent in common band reactivity – I know they wondered if that might be the case but since 95% of the US population has VZV antibody by age 45, I would think it would be difficult to sort that our definitively and I was not aware that they had.
If you want to get an immunoblot, go for it. Here is the guidance about that directly from the CDC STD treatment guidelines:
“Type-Specific Serologic Tests
Both type-specific and type-common antibodies to HSV develop during the first several weeks after infection and persist indefinitely. Accurate type-specific HSV serologic assays are based on the HSV-specific glycoprotein G2 (HSV-2) and glycoprotein G1 (HSV-1). Providers should only request type-specific glycoprotein G (gG)-based serologic assays when serology is performed for their patients (329-331).
Both laboratory-based assays and point-of-care tests that provide results for HSV-2 antibodies from capillary blood or serum during a clinic visit are available. The sensitivities of these glycoprotein G type-specific tests for the detection of HSV-2 antibody vary from 80%–98%; false-negative results might be more frequent at early stages of infection (330,332,333). The most commonly used test, HerpeSelect HSV-2 Elisa might be falsely positive at low index values (1.1–3.5) (334-336). Such low values should be confirmed with another test, such as Biokit or the Western blot (337). The HerpeSelect HSV-2 Immunoblot should not be used for confirmation, because it uses the same antigen as the HSV-2 Elisa. Repeat testing is indicated if recent acquisition of genital herpes is suspected. The HerpeSelect HSV-1 Elisa is insensitive for detection of HSV-1 antibody. IgM testing for HSV 1 or HSV-2 is not useful, because IgM tests are not type-specific and might be positive during recurrent genital or oral episodes of herpes (337).”
I hope hearing this from an authority other than myself helps give clarity.
Also, I am a little confused. On one post you asked me had I ever seen anyone serconvert 18 months after new infection after not seroconverting earlier and then in another post I think you mentioned an index value of 2.6?
Terri
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aaaaah, yes, I forgot about the indeterminate western blot. I knew about the rest of it but forgot about that.
I’m telling you the immunoblot is not a reliable enough test for you to freak out about.
Are you interested in doing the study for the indeterminate western blots that we have going on? If yes, then you can contact Rene at our office and she can send you a test kit and we will send one of those tubes of blood that get drawn and sent back to us for western blot. That way we can kind of kill two birds with one stone. What do you think?
Terri
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Yes, and her name is Rene, not Renegade. that might be an autocorrect. LOL
Terri
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