The Varicella-Zoster Antibody (IgG) test looks for antibodies in your blood that your body makes against the varicella-zoster virus. It is very contagious. Varicella-zoster virus, a herpesvirus, causes two distinct rash-associated diseases:
– chickenpox (varicella)
– shingles (herpes zoster).
First time infection: Chickenpox
When you become infected with the virus for the first time, it causes chickenpox.
Chickenpox is a highly contagious, though typically benign disease, usually contracted during childhood.
After having chickenpox, most people become immune to the virus for the rest of their life. They cannot get chickenpox again.
Virus becomes dormant: Shingles potential later in life
After the first illness, the virus becomes dormant and “hides” in nerves in your body. Later in your life, the virus can become active again. It causes a painful rash called shingles, or herpes zoster. Shingles is an extremely painful condition typically occurring in older nonimmune adults or those with impaired cellular immunity.
– Vaccinated: positive (> or =1.1 AI)
– Unvaccinated: negative (< or =0.8 AI)
A positive IgG result indicates the presence of antibodies to varicella zoster virus.
– The test cannot distinguish between past infection and current infection though, so a positive result could indicate active infection and not immunity.
– If active infection is not suspected based on your history, clinical presentation, and other laboratory results, then a positive IgG result is likely due to past infection. In such a case, the patient is presumed to be immune to varicella zoster virus.
Positive IgG and positive IgM:
A positive IgG result coupled with a positive IgM result suggests recent infection with varicella-zoster virus (VZV). This result should not be used alone to diagnose VZV infection and should be interpreted in the context of clinical presentation.
Positive IgG and negative IgM:
A positive IgG result coupled with a negative IgM result indicates previous vaccination to or infection with VZV. These individuals are considered to have protective immunity to reinfection.
Negative IgG and negative IgM:
A negative IgG result coupled with a negative IgM result indicates the absence of prior exposure to VZV and non immunity. However, a negative result does not rule-out VZV infection. The specimen may have been drawn before the appearance of detectable antibodies. Negative results in suspected early VZV infections should be followed by testing a new serum specimen in 2 to 3 weeks.
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