What is the difference between Herpes antibody and Herpes 1/2 IgG (Immunoglobulin G) testing?

Difference Between Herpes Antibody and Herpes 1/2 IgG Testing

Herpes 1/2 IgG testing is a specific type of herpes antibody test that detects type-specific glycoprotein G antibodies to differentiate between HSV-1 and HSV-2 infections, while general herpes antibody tests may not distinguish between virus types. 1

Key Differences and Testing Methods

Herpes Antibody Testing (General)

• Refers to any serologic test that detects antibodies against herpes simplex virus
• May include tests for different antibody types (IgG, IgM, IgA)
• May not differentiate between HSV-1 and HSV-2
• Includes older, less specific methods that detect antibodies to various viral proteins

Herpes 1/2 IgG Testing (Type-Specific)

• Specifically detects IgG antibodies against glycoprotein G-1 (gG-1) or glycoprotein G-2 (gG-2)
• Allows differentiation between HSV-1 and HSV-2 infections
• Available as:
  • Enzyme immunoassay (EIA)
  • Chemiluminescent immunoassay (CLIA)
  • Immunoblot tests
• Sensitivity for HSV-2 is approximately 92% 1

Clinical Applications and Limitations

When to Use Type-Specific Serology (HSV-1/2 IgG)

• Detecting asymptomatic infections
• Testing pregnant women at risk of acquiring HSV near delivery
• Testing men who have sex with men
• Testing people who are HIV positive 1

Limitations of Type-Specific Testing

• False negatives occur in 12-30% of patients with recurrent HSV-1 or HSV-2 DNA positive genital lesions 2
• HSV-1 serologic tests may have sensitivity as low as 70.2% 1
• HSV-2 serologic tests may lack specificity, particularly with low index values 1
• A single test may miss infections; using multiple tests improves detection 2

Preferred Testing Approaches

First-Line Testing for Symptomatic Patients

• For patients with active lesions, PCR/NAAT from lesion specimens is preferred over antibody testing
• PCR has highest sensitivity and specificity (>90%)
• Can differentiate between HSV-1 and HSV-2
• Provides results within approximately two hours 1

Timing of Antibody Testing

• Wait at least 12 weeks after suspected exposure before antibody testing 1
• IgM testing can help detect early seroconversion before IgG develops 3
• IgG antibodies persist long-term and indicate past or current infection

Interpreting Results

IgG Antibody Results

• Positive: Indicates current or past infection with the specific HSV type
• Negative: May indicate no infection OR false negative (especially early in infection)
• IgG1 antibodies are typically the first to appear in primary infections 4

IgM Antibody Results

• Can indicate recent infection if IgG is negative
• However, IgM is also detected in a large proportion of patients with established HSV-2 infection (29-33%) 3
• Adding IgM testing to IgG testing increases detection of early HSV-2 infection from 40-47% to 70% 3

Common Pitfalls to Avoid

• Relying on a single antibody test when clinical suspicion is high (consider using multiple test formats) 2
• Testing too early after exposure (before antibodies develop)
• Misinterpreting positive IgM as always indicating recent infection 3
• Failing to consider PCR testing when lesions are present
• Not recognizing that type-specific tests may miss 12-30% of confirmed infections 2

Remember that the World Health Organization and the American College of Physicians recommend against widespread screening for genital herpes in asymptomatic individuals 1.