HSV-2 Blood Test Ordering
Order a type-specific HSV-2 IgG antibody test using a glycoprotein G-based assay (such as HerpeSelect HSV-2 ELISA or LIAISON HSV-2 IgG chemiluminescence immunoassay) on a venous blood sample. 1, 2
Specific Test to Order
- Request type-specific HSV-2 IgG serology using glycoprotein G (gG-2) based enzyme immunoassay (EIA) or chemiluminescent immunoassay (CLIA) from venous blood 3, 1
- These assays have approximately 97% sensitivity and 98% specificity for detecting HSV-2 antibodies 3, 1
- Do NOT order HSV-2 IgM testing, as approximately one-third of patients with recurrent HSV-2 infections have IgM responses, making it a poor indicator of recent infection 3, 1
Critical Testing Caveats
Understand the "window period" limitation: A negative result within 12 weeks of potential exposure may be falsely negative, as antibodies take up to 12 weeks to develop after infection 1, 2. If recent exposure is suspected, repeat testing after 12 weeks 1, 2.
Be aware of false-positive results with low index values:
- Index values between 1.1-2.9 have only 39.8% specificity (60% are false positives) 1, 4
- Index values ≥3.0 have 78.6% specificity (21% are still false positives) 1, 4
- False positives are more common in patients with HSV-1 infection, especially at low index values 1, 4
Confirmatory Testing Algorithm
For low positive results (index value <3.0), order confirmatory testing: 1, 4, 2
- Use a second test with a different glycoprotein G antigen (such as Biokit HSV-2 rapid assay) 4, 5
- Using Biokit as confirmatory testing improves specificity from 93.2% to 98.7% compared to Western blot 4, 5
- Western blot/immunoblot is the gold standard but has limited availability 1, 4
What NOT to Order
- Do not order NAAT/PCR or viral culture from blood - these are only appropriate for active lesions, not screening 1, 2
- Do not order HSV-2 IgM - it cannot distinguish recent from recurrent infection 3, 1
- Do not order non-type-specific HSV antibody tests - they cannot differentiate HSV-1 from HSV-2 3, 2
Appropriate Use Considerations
Type-specific HSV-2 serology is recommended for: 1, 2
- Pregnant women at risk of acquiring HSV near delivery
- Men who have sex with men
- People who are HIV positive
- Sexual partners of individuals with known genital herpes
Widespread screening of the general asymptomatic population is discouraged by the US Preventive Services Task Force 1, 4, 2
Post-Test Counseling Requirements
If positive, counsel patients about: 1, 2
- Natural history of chronic, lifelong infection
- Potential for recurrent episodes
- Asymptomatic viral shedding and transmission risk
- Treatment options (episodic or suppressive therapy)
Remember: A positive test indicates past exposure and ongoing latent infection but cannot distinguish recent from long-standing infection or determine the cause of any current genital lesion. 1, 4