What test should I undergo to check for herpes?

Optimal Testing for Herpes Simplex Virus

Nucleic acid amplification tests (NAATs), specifically PCR, are the preferred diagnostic method for herpes testing when active lesions are present, while type-specific serological tests should be used when no lesions are present. 1

Testing Based on Clinical Presentation

When Active Lesions Are Present:

1. First-line test: PCR (NAAT)

   • Superior sensitivity compared to viral culture (11-71% more sensitive) 1
   • Can detect and type HSV in a single reaction tube
   • Faster results (approximately two hours)
   • Remains positive longer in lesions (average 6.8 days vs 2.6 days for culture) 2
   • Less strict sample transportation requirements
   • Increases overall HSV detection rate by 24-27% compared to culture 3, 4

2. Alternative: Viral culture

   • Use only if PCR is unavailable
   • Less sensitive, especially for ulcerative lesions (70%) and crusting lesions (27%) 1
   • Results typically appear within 24-72 hours but may take up to five days
   • Advantage: allows antiviral sensitivity testing 1

3. Not recommended:

   • Direct immunofluorescence assay
   • Tzanck smear (lack sensitivity) 1

When No Active Lesions Are Present:

• Type-specific serological tests (based on glycoprotein G)
  • Sensitivity and specificity approximately 97% and 98%, respectively 1
  • Can differentiate between HSV-1 and HSV-2
  • Useful for screening and detecting newly acquired infections 1

Sampling Sites and Methods

Clinical Situation	Sampling Site	Preferred Method
Visible lesions	Vesicular rash on skin/mucosa	NAAT or antigen detection
Male patients	Urethra	NAAT or antigen detection
Female patients	Cervix/urethra	NAAT or antigen detection
Eye symptoms	Conjunctiva	NAAT or antigen detection
No visible lesions	Venous blood	Serological assays (EIAs)

Important Considerations

• Timing matters: PCR sensitivity decreases as lesions heal, but remains detectable longer than culture 2
• Type differentiation: Always use assays that differentiate between HSV-1 and HSV-2 to provide accurate information about expected natural history 1
• False negatives: May occur with healing lesions; consider serological testing if clinical suspicion remains high despite negative PCR 1
• Serological limitations:
  • HSV-1 assays may lack sensitivity, resulting in false negatives
  • Not useful for determining the site of infection (oral vs. genital)
  • Cannot distinguish between recent and old infections

Clinical Pearls

• First-episode infections typically show higher viral quantities (median 4.2 × 10^5 copies) compared to recurrent infections (1.0 × 10^4 copies) 4
• HSV-1 is more commonly the cause of first-episode genital infections (72%), while HSV-2 more commonly causes recurrent and atypical genital manifestations (73%) 4
• PCR testing becomes negative when lesions re-epithelialize 2
• Do not obtain swabs in the absence of genital ulcers due to the intermittent nature of HSV shedding 1

By following this evidence-based testing algorithm, you can ensure accurate diagnosis of herpes infections, which is crucial for appropriate treatment, counseling, and prevention of transmission.