Herpes is diagnosed by examining visible sores or taking a sample for laboratory testing. Blood tests can detect antibodies toward HSV-1 or HSV-2, even between outbreaks. Most doctors can accurately diagnose HSV based on signs and symptoms, even without conducting lab tests. And, as embarrassing as it may be, the benefit to seeing your doctor for a diagnosis is that it's possible that what you think is an initial outbreak isn't. You can be infected and have no immediate symptoms. You can be symptom-free for weeks, months, and years (even decades).
Cell cultures obtained from swabbed, active blisters are the standard method for testing for HSV. First-time lesions contain a more substantial amount of virus in the cells. Recurrent lesions have a high false-negative rate, so it's essential to be tested during your first outbreak to determine the type of herpes you've contracted accurately. Knowing what kind of herpes you are dealing with is the second advantage of seeing your doctor when you're experiencing an active outbreak with visible lesions. If there are no lesions and you suspect you've contracted herpes, blood tests are available.
Your doctor can perform a blood test to determine if antibodies are present in your blood. Private blood testing is available. However, the test can yield a false negative if your infection is very recent, and they can't determine how long you've had it. They can only say you were infected at some point in your life. You'll need to ask whether they are using the IgM or the IgG test.
IgG antibodies (immunoglobulin G) and IgM antibodies (immunoglobulin M) are proteins that your immune system makes to fight off infections. IgM antibodies (immunoglobulin M) are the first antibodies your immune system makes in response to an infection. High IgM levels may indicate a recent infection. IgG, on the other hand, are secondary responders that fight off pathogens like bacteria and viruses that you've been infected with before. IgG is the most abundant antibody in your blood.
Typically, either an IgG or an IgM test is used. However, the IgM test is outdated for herpes testing. While it claims to detect antibodies soon after an initial infection, it's unreliable because it doesn't differentiate between the various herpes viruses and yields false positives. For example, you test positive for herpes, but the antibodies were for Chickenpox, not cold sores or genital herpes. Most care providers no longer request this test. They request the IgG test, which detects antibodies that can be present for a few weeks to a "lifetime" after contracting herpes. The IgG test can distinguish between HSV-1 and HSV-2 and provides an index value, a numerical indicator that reflects your test results.
- < 0.9: Negative. No antibodies detected.
- 0.9 – 1.1: Borderline. The result is unclear (which can occur when testing is done too early) and should be repeated in a few weeks.
- > 1.1 (on up): Positive. Antibodies were detected. You have the Herpes Simplex Virus. However, a low positive (1.1 to 3.5) could be a false positive. Lab tests for diagnosing herpes are not 100% accurate.
If no antibodies are detected, then you are either negative (meaning you do not have herpes) or your infection is brand new and you've tested too early. The best time to be tested for HSV is between three and four months after your first outbreak (or suspected exposure to the virus). If there are antibodies, it means your infection is not new. It means you have had herpes for at least three to four months. When you've had more than one sexual partner, this information may be helpful in understanding when you contracted herpes.
False Positives & Negatives
You've probably read claims that people were "cured" and tested negative for antibodies after trying a particular remedy. They either got tested before antibodies developed, they received a false negative, or they never had herpes to begin with.
It can take up to three months for antibodies to develop in the blood, and once they do, they typically remain present. If you have ever contracted herpes at any point in your life, you WILL test positive for antibodies after the 3-4 month mark, and you will have those antibodies for life. Even if you've never had or never have herpes symptoms (some people never do), you'll still have the antibodies.
Note: I've read there is a possibility of a false negative if you are tested after not having had an active infection for a very long time.
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