Herpes/HSV blood tests look for the body's reaction to a herpes infection rather than searching directly for the virus. Depending on the type of test used, they can take up to four months to become positive after the time of infection. If and when you have symptoms, however, the lesions can be tested as soon as they show up.
When a person becomes infected, with herpes or any other pathogen, the immune system tries to fight off the infection. Part of that process involves the production of antibodies against the infecting organism. There are several kinds of antibodies, but the two types that herpes blood tests look for are IgG and IgM. Herpes IgM antibodies usually are detectable by herpes blood tests within 7-10 days after initial infection, and levels stay high for approximately two weeks. Herpes IgG antibodies do not show up until slightly later after initial infection.
A positive herpes IgG test, if the test result is accurate, means that your body has been infected with the herpes simplex virus. Type specific herpes IgG tests can often distinguish between HSV-1 and HSV-2, but they can not detect whether a particular infection is oral or genital in the absence of symptoms. HSV-1 usually infects the mouth, causing oral herpes, and HSV-2 usually infects the genitals, but either virus can infect either location. Herpes IgG and IgM tests can only tell you that you have been infected, not where.
If you test positive for herpes IgG but not IgM, then your herpes infection is probably not recent - i.e. from the past 2 months. Individuals with recent infections are more likely to test positive for both herpes IgG and IgM or herpes IgM alone. The converse, however, isn't true. Positive herpes IgG and IgM results together do not necessarily mean you were infected recently. Between 30 and 70 percent of patients with recurrent herpes infections will test positive for herpes IgM
It is possible to have a false positive or false negative result - on either a herpes IgG or IgM test. Therefore, if your herpes blood test results do not agree with your known risk factors and sexual history, talk to your doctor about possible issues with testing. Diagnostic testing isn't perfect, but you may not be accurately assessing your risk. Many people do not understand that herpes can be transmitted even when their partner has no symptoms and does not know they are infected.
In short: IGg testing This is an explanation of how to interpret a test for herpes. There are two strains of herpes virus - HSV1, which "prefers" the mouth but can infect the genitals, and HSV2, which "prefers" the genitals but can infect the mouth.
The test doesn't measure the virus directly. It measures your immune systems response to the virus. When you get a virus, your body fights it by creating antibodies. This test measures the level of antibodies in your blood to determine if you are infected.
If for example the test shows an antibody level below 0.90, then "no" antibodies were detected and you have tested negative for herpes (you don't have herpes).
If the test shows an antibody level above 1.10 then enough antibodies were detected for this to be a positve test for herpes (you have herpes).
If the test shows an antibody level between these two numbers, then you've got an inconclusive result (equivocal). One way that this could happen is if the test was done right after you were infected, and your body is creating antibodies, but there aren't enough in your blood yet to tip you into the "positive" category. You'll probably want to get tested again in a month or so, to determine if the test was simply wrong, or if you're infected but didn't have enough antibodies in your blood to test positive yet.
