Herpes Simplex Virus I (HSV)-IgG

Bacterial/ Viral

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Detects IgG antibodies specific to: HSV-1: Commonly causes oral herpes (cold sores)

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Herpes Simplex Virus I (HSV)-IgG Test Information Guide

Why is it done?
- Detects IgG antibodies against Herpes Simplex Virus Type 1 (HSV-1) to determine past or current infection status and immunity status
- Ordered when patients present with symptoms suggestive of HSV-1 infection such as oral herpes, recurrent mouth ulcers, or suspected encephalitis
- Used for screening pregnant women to assess risk of neonatal herpes transmission and to guide counseling regarding delivery options
- Performed to assess prior HSV-1 exposure and immunity status before organ or stem cell transplantation
- Used to differentiate between primary infection (initially negative IgG becoming positive), reactivation, or past immunity
- Indicated when patients have unclear diagnoses of fever, stomatitis, meningitis, or other neurological symptoms potentially caused by HSV-1
Normal Range
- Normal (Negative) Result: < 0.90 Index or Negative (specific cutoff values may vary by laboratory and testing methodology)
- Positive Result: ≥ 1.10 Index or Positive (indicates presence of HSV-1 IgG antibodies)
- Equivocal/Borderline Result: 0.90-1.10 Index (requires repeat testing after 2-4 weeks to determine if converting to positive)
- Units of Measurement: Index value, mIU/mL, or qualitative (Positive/Negative) depending on assay method
- Interpretation: Negative result indicates either no prior exposure to HSV-1 or testing performed too early in infection (before antibody formation). Positive result confirms prior or current HSV-1 infection and indicates immunity to reinfection.
Interpretation
- Negative IgG Result: No prior exposure to HSV-1; patient is seronegative and susceptible to infection. If acute infection is suspected, may represent very early infection before IgG develops (typically appears 1-2 weeks after symptom onset).
- Positive IgG Result: Indicates past or current HSV-1 infection with lifelong immunity; does not differentiate between primary, recurrent, or latent infection. Combined with clinical presentation and other tests (IgM, PCR, culture) can help clarify timing and status of infection.
- High Positive IgG Values: Very elevated levels may suggest recent primary infection or active/recent reactivation, particularly if IgM is also positive or clinical symptoms are present.
- Equivocal Results: Borderline or indeterminate results require repeat testing in 1-2 weeks. Seroconversion (changing from negative to positive) confirms primary infection.
- Factors Affecting Results: Immunosuppression (HIV, chemotherapy, transplant) may cause false negatives or delayed antibody production; concomitant IgM testing helps determine primary vs. recurrent infection; cross-reactivity with HSV-2 may occur in some assays; testing too early in primary infection may yield false negatives.
- Clinical Significance: Positive IgG implies protective immunity against primary HSV-1 infection but does not prevent reactivation of latent virus. Critical for assessing risk in immunocompromised patients, pregnant women, and transplant candidates.
Associated Organs
- Primary Organ Systems: Nervous system (brain, spinal cord, ganglia), skin, mucous membranes (oral and ocular), and rarely other organs. HSV-1 establishes latency in trigeminal ganglion.
- Associated Diseases and Conditions: Gingivostomatitis (primary), recurrent oral herpes, herpes encephalitis, meningitis, keratitis/conjunctivitis, neonatal herpes (severe disseminated infection), Bell's palsy (may be HSV-1 associated), erythema multiforme, eczema herpeticum (in patients with atopic dermatitis).
- Complications from HSV-1 Infection: HSV encephalitis (most common sporadic encephalitis; potential neurological sequelae including cognitive impairment and memory loss), blindness from corneal scarring, disseminated infection in immunocompromised patients, superinfection of lesions leading to bacterial infection, increased risk of transmission to neonates during delivery, potential link to Alzheimer's disease (ongoing research).
- Special Populations at Risk: Immunocompromised individuals (increased severity and dissemination), pregnant women (risk to fetus/neonate), organ transplant recipients (high morbidity risk), patients with severe atopic dermatitis, neonates (potentially severe disseminated disease).
Follow-up Tests
- HSV-1 IgM Antibody: Helps differentiate primary infection (IgM positive) from recurrent infection or latent shedding (IgM negative). Recommended if primary infection is suspected.
- HSV-1 PCR (Polymerase Chain Reaction): Gold standard for detecting active HSV-1 infection; typically performed on CSF for suspected encephalitis, lesion swabs, or other clinical specimens. Most sensitive and specific for confirming active infection.
- HSV-1 Culture: Isolation of virus from lesion fluid, mucous membranes, or other specimens; useful for confirmation but less sensitive than PCR and slower results.
- HSV-2 Serology: To differentiate HSV-1 from HSV-2 infection if both are suspected; some assays differentiate between types while others do not.
- Cerebrospinal Fluid (CSF) Analysis: Including HSV PCR, cell count, protein, and glucose if HSV encephalitis or meningitis is suspected.
- Brain MRI or CT: If encephalitis is clinically suspected; may show temporal lobe involvement characteristic of HSV encephalitis.
- Repeat HSV-1 IgG Testing: If initial result is equivocal; repeat after 2-4 weeks to detect seroconversion (indicating primary infection).
- EEG (Electroencephalography): If seizures or altered mental status present; characteristic pattern of periodic sharp wave complexes may be seen in HSV encephalitis.
- HIV Testing: If patient has risk factors or severe/recurrent HSV-1 infection, as immunocompromise increases HSV disease severity.
- Ophthalmologic Examination: If keratitis or conjunctivitis suspected; may perform viral culture or PCR from eye swabs.
Fasting Required?
- Fasting Requirement: No
- Special Instructions: Fasting is not required for this serology test. Blood sample can be drawn at any time of day without regard to food or fluid intake.
- Medications to Avoid: No medications need to be avoided before this test. Antiviral medications (acyclovir, valacyclovir) do not affect the IgG result.
- Patient Preparation: Wear comfortable clothing with sleeves that can be rolled up easily. Inform phlebotomist of any difficulties with blood draws or needle phobia. No special preparation is needed; routine blood draw procedures apply.
- Sample Collection: Serum collected via standard venipuncture into appropriate blood collection tube (typically serum separator or SST tube). Handle sample gently to prevent hemolysis. Allow blood to clot (if required by laboratory) before centrifugation. Store and transport at room temperature or refrigerate per laboratory protocol.

How our test process works!