What laboratory tests are used to evaluate Herpes Zoster (shingles)?

From the Guidelines

Laboratory evaluation for shingles (herpes zoster) typically includes viral detection tests to confirm the diagnosis, with the most reliable test being a polymerase chain reaction (PCR) assay or direct fluorescent antibody (DFA) testing of vesicle scrapings, as defined by the presence of typical lesions with isolation of VZV, demonstration of VZV antigen by DFA or by DNA/RNA-based tests from a lesion 1. The diagnosis of herpes zoster can be classified as probable or definite, with probable diagnosis based on the presence of crops of vesicular lesions on an erythematous base, and definite diagnosis based on the presence of typical lesions with isolation of VZV, demonstration of VZV antigen by DFA or by DNA/RNA-based tests from a lesion 1. Some key laboratory tests used to evaluate herpes zoster include:

• PCR assay of fluid collected from vesicles to detect VZV DNA
• Direct fluorescent antibody (DFA) testing of vesicle scrapings to detect VZV antigen
• Tzanck smear to identify cellular changes consistent with herpesvirus infection, although it cannot distinguish between VZV and herpes simplex virus
• Serologic tests measuring VZV antibodies (IgM and IgG) to help in cases without visible lesions, although they are less useful for acute diagnosis In immunocompromised patients or those with atypical presentations, additional testing may include complete blood count and comprehensive metabolic panel to assess overall health status 1. It's worth noting that the American Society of Transplantation recommendations for screening, monitoring, and reporting of infectious complications in immunosuppression trials in recipients of organ transplantation provide guidance on the diagnosis of VZV infection, including the use of PCR and DFA testing 1. However, other studies, such as the prevention of varicella recommendations of the Advisory Committee on Immunization Practices (ACIP), focus on the prevention of varicella and the use of latex agglutination and ELISA tests to detect varicella IgG antibody, which are not directly relevant to the diagnosis of herpes zoster 1.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Laboratory Tests for Herpes Zoster (Shingles)

The following laboratory tests are used to evaluate Herpes Zoster (shingles):

• Direct immunofluorescence assay using monoclonal antibodies, such as the 3B3 antibody 2
• Polymerase chain reaction (PCR) to detect VZV DNA in cerebrospinal fluid and lesion-swab specimens 2, 3
• Tzanck test, a cytologic test that detects multinucleated giant cells in skin lesions 4, 5
• Viral culture, considered the gold standard for establishing the diagnosis of HSV infection, but also useful for diagnosing VZV infection 5
• Fluorescent antibody to membrane antigen test, a principal method for diagnosing VZV infection 5
• Serologic tests, such as enzyme immunoassay and Western blot assays, to detect IgG antibodies against VZV proteins 6, 5
• Molecular virology techniques, such as PCR, which are likely to become the diagnostic methods of choice for both HSV and VZV infections 5
• Simplexa VZV Direct Assay, a molecular assay that detects VZV DNA in cerebrospinal fluid and lesion-swab specimens 3

Comparison of Laboratory Tests

The sensitivity and specificity of these laboratory tests vary:

• PCR is found to be the most sensitive method of confirming VZV infection 2
• The Tzanck test has a sensitivity of 76.9% and a specificity of 100% 4
• The Simplexa VZV Direct Assay demonstrates near perfect agreement with composite reference methods for the detection of VZV in CSF and lesion swab specimens 3