What does an HSV (Herpes Simplex Virus) IgG (Immunoglobulin G) result of 20.70 indicate?

Interpreting an HSV IgG Result of 20.70

An HSV IgG result of 20.70 strongly indicates past infection with herpes simplex virus, with high specificity at this elevated index value. 1

Understanding HSV IgG Testing

• HSV-specific IgG antibodies develop within several weeks of infection and persist indefinitely, making them reliable markers of past HSV exposure 1
• Type-specific HSV IgG tests can differentiate between HSV-1 and HSV-2 infections, though the question doesn't specify which type was tested 1
• HSV IgG antibodies persist for life after infection, making them useful for determining past exposure but not distinguishing between recent or distant infections 1

Interpretation of High Index Values

• The index value of 20.70 is significantly higher than the threshold for positivity (typically >1.1 according to manufacturer specifications) 2
• Higher index values (≥3.0) for HSV IgG have substantially improved specificity (78.6%) compared to lower positive values 2, 1
• At this very high index value (20.70), the result is almost certainly a true positive, as false positives typically occur with lower index values (1.1-2.9) 2, 1

Clinical Implications

• This result indicates past infection with HSV, but cannot determine:
  • The anatomical site of infection (oral vs. genital) 3
  • Whether the infection is currently active 2
  • The timing of the initial infection 1
• The presence of HSV IgG antibodies indicates the person is at risk for viral shedding and potential transmission to partners, even without symptoms 3

Important Considerations

• PCR testing of active lesions, not serology, is the gold standard for diagnosing active HSV infections 4
• False-negative HSV antibody results can occur in 12-30% of patients with recurrent HSV infections, but false-positive results are rare with high index values like 20.70 5
• If this is an HSV-2 result, it's important to note that HSV-2 infections are predominantly genital, while HSV-1 can cause both oral and genital infections 3

Next Steps

• If the patient has active lesions, PCR testing of the lesions would provide definitive diagnosis of current infection 3, 4
• Counseling about the natural history of HSV infection, potential for recurrent episodes, asymptomatic viral shedding, and sexual transmission risk is recommended 3
• If this is a first diagnosis, type-specific testing (if not already done) would be helpful to distinguish HSV-1 from HSV-2, as this affects prognosis and counseling 3