VZV IgG AB (VARICELLA-ZOSTER VIRUS ANTIBODY (IgG))

VZV IGG AB, Varicella-Zoster Virus Antibody (IgG); Chickenpox

Varicella is caused by the varicella-zoster virus (VZV), a member of the herpesvirus group, and is highly contagious. The most sensitive method for confirming a diagnosis of varicella is the use of polymerase chain reaction (PCR) to detect VZV in skin lesions (vesicles, scabs, maculopapular lesions). Vesicular lesions or scabs, if present, are the best for sampling. Adequate collection of specimens from maculopapular lesions in vaccinated people can be challenging. However, one study (Evaluation of Laboratory Methods for Diagnosis of Varicella) comparing a variety of specimens from the same patients vaccinated with one dose suggests that maculopapular lesions collected with proper technique can be highly reliable specimen types for detecting VZV. Other sources such as nasopharyngeal secretions, saliva, blood, urine, bronchial washings, and cerebrospinal fluid are less likely to provide an adequate sample and can often lead to false negative results.

Other viral isolation techniques for confirming varicella are direct fluorescent antibody assay (DFA) and viral culture. However, these techniques are generally not recommended because they are less sensitive than PCR and, in the case of viral culture, will take longer to generate results.

IgM serologic testing is considerably less sensitive than PCR testing of skin lesions. IgM serology can provide evidence for a recent active VZV infection, but cannot discriminate between a primary infection and reinfection or reactivation from latency since specific IgM antibodies are transiently produced on each exposure to VZV. IgM tests are also inherently prone to poor specificity.

Paired acute and convalescent sera showing a four-fold rise in IgG antibodies have excellent specificity for varicella but are not as sensitive as PCR of skin lesions for diagnosing varicella. People with a prior history of vaccination or disease history may have very high baseline titers, and may not achieve a four-fold increase in the convalescent sera. The usefulness of this method for diagnosing varicella is further limited as it requires two office visits. A single positive IgG ELISA result cannot be used to confirm a varicella case.