Testing for Herpes: What to Know
Herpes is a sexually transmitted infection caused by either of two different but related viruses, called herpes simplex viruses or HSV. Most genital herpes infections are from the HSV-2 virus, but the HSV-1 virus, which causes oral herpes, can be transmitted by oral sex to the genital area.
Herpes causes painful sores on or around the genitals, rectum or mouth. Herpes is very common in the United States: As many as 1 in 6 people between the ages of 14 and 49 has HSV-2. Your doctor may diagnose you by examining you when you have symptoms, but testing can confirm the diagnosis. Though herpes isn’t a serious disease, the sores can be painful and you can spread herpes if you have sex while you have sores or blisters. The sores make it easier to transmit HIV, the virus that causes AIDS.
How to Get Tested for Herpes
Even though herpes is common, testing is not a regular part of checkups with your doctor or gynecologist. The Centers for Disease Control and Prevention (CDC) recommends a genital herpes test only if you have herpes symptoms or a sexual partner who has genital herpes. However, quick and easy herpes tests are readily available through your doctor or health facility, so don’t hesitate to ask if you are concerned or notice symptoms. You can also order a home test kit, which will have instructions on how to do a finger prick to obtain a blood sample and send it to a lab for evaluation.
There are several types of tests for herpes:
- Viral culture: A healthcare worker will take fluid from a sore using a swab. Laboratory personnel will add it to a medium that can grow HSV. If no virus develops, the culture is negative. If the virus multiplies, the test is positive. The test may fail to find the virus under certain conditions, however, which is a “false negative.”
- Antigen detection test: A laboratory professional looks at cells taken from a sore under a microscope, looking for herpes antigens, which are molecules that can stimulate the body to produce an immune response.
- Antibody tests: Often referred to as a serologic herpes test, it is a blood test that looks for antibodies, which the body produces in response to antigens. These tests may not be as accurate as a viral culture. Antibodies can take time to develop so if your infection is recent, the test may not find them. Antibody tests can distinguish HSV-1 from HSV-2 infection, but there is a high rate of “false positives.” If you test positive for HSV-2 antibodies and you have a history of genital symptoms, you likely have the virus. However, if you don’t have symptoms, an HSV-2-positive result is not a diagnosis of genital herpes because of the high false-positive rate.
- Polymerase chain reaction (PCR) test: Using cells, blood or fluid from a sore, PCR tests detect the DNA of the herpes virus, and can detect the virus when there are no symptoms present. It is the most accurate of the genital herpes tests and can distinguish between HSV-1 and HSV-2. PCR is also used to test for herpes that has spread to the central nervous system; a doctor perform a lumbar puncture to sample the cerebrospinal fluid,
If you have symptoms, you will likely have a viral culture or PCR test. Blood antibody tests are generally done on people who may not have had symptoms or if the sore has already healed. Home kits for herpes testing are generally antibody tests.
Dependability of Herpes Test Results
Herpes tests can produce both false negatives and false positives. Some experts estimate that as many as half of positive blood tests may be inaccurate. Antibody tests for herpes sometimes react to related viruses, such as chickenpox or mononucleosis. If you are having an antibody test, you should wait 12 to 16 weeks after exposure so that antibodies can reach detectable levels. Bear this in mind if you are using an at-home test for herpes. Overall, antibody tests are not useful screening tests for genital herpes in the absence of symptoms (in asymptomatic people). They may be useful for people with a history of genital symptoms or who are at high risk for genital herpes, such as people who are HIV-positive.
Viral culture tests need active virus, so if the sore is small or beginning to heal, there may not be enough virus present to be detected and you could get a false negative. A viral culture may only show a positive result in about a third of tests of recurrent herpes outbreaks, meaning not your first outbreak of symptoms. Among herpes tests, you are less likely to get a false negative with the PCR test, and false positives are rare.
If you have herpes, it will not make you sick though the sores can be painful. It’s important that you know you have it so you can refrain from sexual activity when you have an outbreak and avoid infecting others.
If you need symptomatic relief, you can ask your provider who can prescribe medication for you. There is no cure for herpes but outbreaks generally become less common as people age. If you think you have herpes, tell your provider so you can discuss testing options, and if you do have it, wait until your provider tells you it is safe before you re-engage in sexual activity.