Herpes is caused by the herpes simplex virus, which comes in two strains--HSV-1 and HSV-2. Herpes can infect the mucosa of the genital tissues or the mouth and can also spread to the eyes. Herpes testing can be done to see if a patient is experiencing an active herpes outbreak, which causes sores to appear, or to see if a patient has been previously infected. Because the virus can lie dormant in the cells, there is no cure for herpes, and patients who have been infected are always at risk of having additional outbreaks.
Purpose
Herpes testing is performed on patients who are suspected of having the disease. According to Lab Tests Online, it can be done on people who have sores on their genitals or for people who have encephalitis. This is because herpes infections can cause encephalitis, especially in patients with weakened or compromised immune systems. It may also be performed on newborns who may have neonatal herpes, which is the result of the infant becoming infected during birth. Signs of neonatal herpes include skin lesions or meningitis.
Lesion Viral Culture Sampling
One method of diagnosing herpes involves looking for the virus in genital lesions. With this test the lesion itself is rubbed with a cotton swab to get a sample of the material inside the sore. According to Medline, the sample needs to have cells in it because that is where the virus resides in a herpetic lesion. The sample needs to be collected during the worst part of a potential herpes outbreak (also known as the acute phase) because this gives the test the highest sensitivity. Sometimes a sample must also be taken from the throat or eyes if those organs are suspected of being infected as well.
Culture and Testing
Once the lesion sample has been obtained, it will be sent to a lab to culture the cells in a dish with special growth media. The lab will then look for the appearance of the herpes virus or for proteins that the virus produces during infection. In some cases the lab can also test for the presence of DNA that is only found in the herpes virus. The lab can also do additional tests to determine if the virus found is of the HSV-1 or HSV-2 strains. According to Medline, results are typically available within two to four days, although results may be obtainable within 16 hours, depending on the testing method.
Interpretation
A positive result means that the patient has an active (acute) herpes infection, which means that the virus is currently replicating within the patient's cells and is responsible for the skin lesions. Negative results mean that the cultured skin cells did not yield any herpes virus. This does not necessarily mean that the patient has not been infected with herpes, because a negative result could be the result of a dormant herpes infection.
Antibody Testing
Patients can also be screened for a previous herpes infection using antibody testing. With antibody testing, a sample of the patient's blood is taken to see if it contains antibodies against the herpes virus. A positive antibody test means that the patient has been previously exposed to herpes. Patients who have been previously infected do have a risk of the virus reactivating, thereby leading to additional outbreaks.
