What is the diagnostic approach for testing for Herpes Simplex Virus (HSV)?

From the Guidelines

The diagnostic approach for testing Herpes Simplex Virus (HSV) should prioritize nucleic acid amplification test (NAAT)/polymerase chain reaction (PCR) diagnostic assays for detecting HSV from clinical specimens, especially when genital ulcers are present, as they offer high sensitivity and specificity 1. When a patient presents with visible sores, a swab sample from the lesion should be taken for a viral culture or PCR test, as these methods are highly accurate for diagnosing HSV infection.

• The sensitivity and specificity of most available NAAT/PCR tests are over 90%, making them the preferred choice for diagnosis 1.
• It is essential to use assays that differentiate between HSV-1 and HSV-2 infection to provide patients with information regarding the expected natural history of genital herpes.
• If NAAT/PCR is not available due to cost or laboratory constraints, HSV culture can be performed, but it is less sensitive than NAAT/PCR, and further investigation through serology may be warranted if results are negative 1.

For individuals without symptoms but concerned about exposure, blood tests that detect HSV antibodies are recommended, particularly type-specific glycoprotein G (gG) tests that can distinguish between HSV-1 and HSV-2.

• The IgG antibody test is most reliable as it indicates past infection, while IgM tests are less useful due to cross-reactivity 1.
• Blood tests become accurate 12-16 weeks after potential exposure as antibodies need time to develop, and serologic testing should not be repeated until 12 weeks after exposure to determine if HSV-2 was acquired 1.
• Given the limitations of serologic assays, especially the low specificity of some tests, confirmatory testing with a second assay using a different gG antigen may be necessary, especially for low-positive results (index value <3.0) 1.

From the Research

Diagnostic Approach for Herpes Simplex Virus (HSV)

The diagnostic approach for testing Herpes Simplex Virus (HSV) involves several methods, including:

• Type-specific testing to distinguish HSV-1 from HSV-2, which is always recommended 2
• Polymerase Chain Reaction (PCR) for detecting HSV infections, especially for genital herpes in people with active mucocutaneous lesions 2, 3
• Viral culture, which has been the test of choice for HSV genital infection, but may be replaced by HSV PCR due to its higher rate of HSV detection 2
• Antigen detection, such as immunofluorescence test or enzyme immunoassay, which can be employed for symptomatic patients 2
• Type-specific serology based on glycoprotein G, which is used for detecting asymptomatic individuals, but widespread screening for HSV antibodies is not recommended 2, 4, 5

Serological Testing

Serological tests for HSV can accurately distinguish between HSV-1 and HSV-2, and are commercially available 4. These tests can be used to:

• Confirm a genital herpes diagnosis
• Establish diagnosis of HSV infection in patients with atypical complaints
• Identify asymptomatic carriers
• Identify persons at risk for acquiring HSV
• Screen high-risk groups, such as those with high risk for STDs and HIV infection, HIV-infected patients, and patients with sex partners with genital herpes 5

Recommendations for Testing

Recommendations for the use of type-specific HSV serological tests include:

• Screening of asymptomatic patients in high-risk groups, such as those with high risk for STDs and HIV infection, HIV-infected patients, and patients with sex partners with genital herpes 5
• Diagnostic evaluation of patients with symptoms 5
• Targeted use of HSV-2 serological tests for specific diagnostic situations and selected populations 5