HSV testing is used to detect the presence of the herpes simplex virus (HSV) in those who have genital sores or encephalitis and in newborns suspected of having neonatal herpes, a rare but serious condition in which herpes is contracted during vaginal birth.
The primary methods of testing for the virus are the herpes culture and HSV DNA testing (PCR). Although it is not as sensitive, HSV antibody testing can be used to help diagnose an acute HSV infection if acute and convalescent blood samples are collected. The convalescent blood sample is collected several weeks after the acute sample, and HSV IgG antibody levels are compared to see if they have risen significantly, indicating a current infection. Antibody testing may also be used to screen certain populations, such as sexually active people, potential organ transplant recipients, and those with HIV/AIDS, for a previously contracted HSV infection.
A herpes culture (or HSV DNA testing) may be ordered when someone has a blister or vesicle on their genitals.
HSV DNA testing is ordered when a person has encephalitis that the doctor suspects may be caused by a virus.
HSV testing may be ordered regularly when a pregnant woman has herpes. A mother and newborn may be tested for HSV when a baby shows signs of HSV infection, such as meningitis or skin lesions that could be caused by the herpes virus.
HSV antibody testing is ordered primarily when someone is being screened for a previous exposure to HSV. Occasionally, acute and convalescent HSV antibody testing may be ordered when a current infection is suspected.
A doctor may also order an HSV antibody test if someone has another STD and is at risk for the infection. Risk factors include having multiple sex partners, having a sex partner with herpes, being infected with HIV, or being at risk for HIV because the person is a man who has sex with men.
A positive herpes simplex culture or HSV DNA test from a vesicle scraping indicates an active HSV-1 or HSV-2 infection. A negative test result indicates that the herpes simplex virus was not isolated but does not definitely rule out the presence of virus. If the specimen taken does not contain actively replicating virus, or if the sample was not transported under optimum conditions, no viable virus may be detectable, resulting in a false-negative result.
The presence of HSV-1 or HSV-2 IgM antibodies indicates an active or recent infection. HSV-1 or HSV-2 IgG antibodies indicate a previous infection. A significant increase in HSV IgG antibodies, measured by comparing acute and convalescent samples, indicates an active or recent infection. Negative HSV antibody results mean that it is unlikely that the person has been exposed to HSV or that the body has not had time to begin producing HSV antibodies.
The most serious, or life-threatening, HSV infections can occur in newborns who are infected during birth and in immunocompromised individuals. The lesions tend to be more extensive and persist longer than in individuals who have healthy immune systems.
Herpes can make people more susceptible to HIV infection. Likewise, it can make HIV-infected individuals more infectious. Infection with HSV can also increase HIV viral load. HSV-2 infection is a significant opportunistic infection in HIV-infected individuals; up to 90% of HIV-infected individuals are co-infected with HSV-2.
This article was last reviewed on April 25, 2013. | This article was last modified on December 29, 2014.
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