Can a Herpes Blood Test Be Wrong?
Yes. More often than you have been told, and in a specific, predictable way that the number on your report will reveal if you know how to read it.
I want to be careful here, because this article gets misused in both directions. Some people read something like this and talk themselves out of a true diagnosis they need to face. Others have been carrying a diagnosis for years that was never solid to begin with. Both are bad outcomes. The point is not to give you a reason to disbelieve your result. The point is to tell you which results are solid and which ones warrant a second look.
The number is doing the work
If you had an IgG blood test, your report probably carries an index value. It looks like a small decimal — 1.3, or 2.8, or 14.9 — sitting beside the word positive or negative.
The standard reading is straightforward:
- Below 0.90 — negative
- 0.90 to 1.09 — equivocal, meaning borderline
- 1.10 and above — positive
What nobody explains is that the last category is not one thing. A 1.2 and a 14.9 both print as “positive.” They are not remotely the same result.
The low band
Results between roughly 1.10 and 3.50 are described in the literature as low positive, and they are the problem.
In this range, the commonly used assays produce a substantial number of results that do not hold up when checked against a confirmatory test. How substantial depends on which study you read and on the population being tested — figures vary considerably, and the lower you sit in the band, the worse it gets. A result just over the 1.10 line is much shakier than one approaching 3.50.
The scale of it is why public health guidance recommends confirmatory testing before treating a low-positive result as a diagnosis. That recommendation exists precisely because too many people were being handed a life-changing diagnosis on the strength of a number that was never reliable enough to carry it.
Two things worth understanding about why this happens.
HSV-1 interferes with HSV-2 testing. The two viruses are closely related, and antibodies to one can produce a weak signal on the test for the other. So if you genuinely carry HSV-1 — and a very large proportion of adults do — you are more likely to see a soft false positive on HSV-2. This is the most common mechanism behind a low-positive result in someone with no symptoms and no known exposure.
Low prevalence makes it worse. The less likely you were to have the infection before the test, the more likely a weak positive is wrong. Testing someone with no symptoms and no reason to suspect anything is precisely the situation in which a marginal result should be trusted least — which is also why routine blanket herpes screening is not recommended.
Above the band
Values well above 3.50 are considerably more reliable, and most people with a strongly positive result do have the infection.
I will not tell you they are perfect, because they are not. Peer-reviewed work over the last several years has argued that the official cutoff understates the problem, and that false positives can appear across the whole reportable range rather than politely confining themselves to the low band. That is a real finding and I would rather you had it than not.
But the practical picture is this: a 14 is not a 1.4. If your number is high, the test is telling you something dependable.
Equivocal is not “nearly positive”
If your result landed between 0.90 and 1.09, you have not been given a weak yes. You have been given a result the test cannot interpret.
It may reflect very early seroconversion, in which case retesting several weeks later will resolve it upward. It may reflect background reactivity that means nothing, in which case a repeat will resolve it downward. In people with no symptoms and no known exposure, most equivocal results settle to negative on a second test.
Repeat it, on the same laboratory platform if you can. Switching between platforms produces numbers that are not directly comparable and makes the picture muddier rather than clearer.
The error runs both ways
Everything above concerns tests saying yes when the answer is no. I should tell you that in my own case the error ran the other direction entirely.
I was swabbed and told I did not have herpes. Twice. I had an obvious primary outbreak at the time. It took two years and a different hospital before a doctor looked and said plainly what it was.
I spend a good deal of my working life correcting information my patients were given by their doctors. Some of them were told a low positive was a certainty. Some were told a negative swab meant they were clear. Some were told they had “been exposed,” which is a phrase that means nothing and leaves people in a fog for years.
The lesson is not that the tests are useless. It is that the test result and the interpretation are two separate things, and the second one is where most of the damage happens.
What to do with an uncertain result
If your number is in the low band and you have no symptoms and no known exposure. This is the strongest case for confirmatory testing. Do not disclose a diagnosis to a partner on the strength of a low positive alone. That conversation is hard enough when the diagnosis is certain, and it cannot be unsaid.
If your number is in the low band and you have had symptoms consistent with herpes. Your prior likelihood is much higher, and the number means more than it would in someone with no history. Confirmation may still be worth having, but do not talk yourself out of a diagnosis that fits the clinical picture.
If your result is equivocal. Repeat it in a few weeks, same platform.
If your number is high. It is probably right. Your energy is better spent on what comes next than on chasing certainty you already have.
Confirmatory testing has narrowed recently. The rapid confirmatory assay that used to serve as an alternative has been discontinued, which leaves the Western Blot at the University of Washington standing more or less alone. Whether that is worth pursuing in your case depends on your situation, and I have set out the practical side of it — access, cost, and when I think it is not worth the trouble — here.
And if it is confirmed
Then you know, and knowing is a better place to stand than not knowing, however it feels this week.
What the number cannot tell you is anything about how this will actually go for you. Index values do not predict outbreak frequency, severity, what triggers you, or how contagious you are. They are a measure of your immune system’s antibody response, nothing more. Two people with identical results can have completely different experiences of this virus.
Your diet, age, sex, hormones, sleep, stress, emotional health, the strain you carry, and the state of your immune system all shape what happens next. That is an individual picture, and it takes an individual approach — a custom-tailored plan built around your body, rather than a supplement someone sold you because it worked for a stranger on a forum.
If you are looking at a number you cannot make sense of
Write to me. christopher.scipio@gmail.com. I read the questions myself and I answer them myself, at no charge.
If you have a confirmed result and want to work out what to do about it, we can go through your history properly.
Related: what your test results actually mean · when to get tested after exposure · is the Western Blot worth it
Christopher Scipio is a Registered Herbalist (RH, AHG) and Holistic Viral Specialist based in Vancouver, British Columbia, working with clients around the world. He has practised as a herbalist for thirty-nine years, twenty-three of them as a herpes specialist, and has lived with the virus himself for thirty-six years. He is the author of Making Peace With Herpes.