What test is used to check for herpes?

Diagnostic Tests for Herpes Simplex Virus

Nucleic acid amplification testing (NAAT), specifically PCR, is the preferred test for diagnosing herpes simplex virus infections from active lesions due to its superior sensitivity and ability to differentiate between HSV-1 and HSV-2 in a single test. 1

Recommended Testing Approach by Clinical Presentation

For Patients with Active Lesions:

• First-line test: PCR/NAAT from lesion sample

  • Sensitivity >90% for detecting HSV 1
  • Results available within approximately 2 hours 1
  • Can differentiate between HSV-1 and HSV-2 in a single test 1
  • Requires less strict sample transportation conditions compared to culture 2

• Alternative options:

  • Antigen detection tests (DIF or EIA) if NAAT unavailable 2
  • Viral culture (traditional gold standard but less sensitive than PCR)
    • Sensitivity varies: 70% for ulcerative lesions, only 27% for crusting lesions 1
    • Results take 24-72 hours, sometimes up to 5 days 2
    • Significantly affected by sample transportation conditions 1

For Patients Without Active Lesions:

• Type-specific serological tests based on glycoprotein G 2, 3
  • Appropriate for:
    • Asymptomatic individuals at risk
    • Detecting newly acquired infections
    • Testing pregnant women at risk of acquiring HSV near delivery
    • Men who have sex with men
    • People who are HIV positive 2

Sample Collection Guidelines

• Collect samples as early as possible in lesion development 1
• Sampling sites depend on presentation:
  • Vesicular rash: Direct sampling of lesion
  • Male: Urethral sample (0.5-2 cm into urethral meatus)
  • Female: Cervical sample (2 cm into cervical canal) or vaginal wall sample 2, 1

Important Considerations and Pitfalls

• Type determination is crucial for prognosis and counseling - always use type-specific testing to distinguish HSV-1 from HSV-2 2, 3

• Timing matters: Sample collection should occur as early as possible in lesion development, as sensitivity decreases as lesions heal 1

• Avoid these common errors:

  • Using non-type-specific tests (inadequate for clinical management) 1
  • Performing NAAT/PCR in the absence of genital lesions (due to intermittent viral shedding) 1
  • Relying solely on clinical diagnosis without laboratory confirmation 1
  • Overreliance on serologic testing when lesions are present (NAAT is more appropriate) 1
  • Widespread screening for HSV antibodies (not recommended) 2

• Test limitations:

  • HSV-1 serologic assays lack sensitivity (around 70%) 1
  • HSV-2 serologic tests lack specificity (as low as 57%) 1
  • Serological tests alone cannot determine the etiology of a presenting genital lesion 2

PCR has consistently demonstrated higher rates of HSV detection compared to viral culture and is now considered the new gold standard for diagnosis of genital herpes in patients with active mucocutaneous lesions 3, 4.