What is the recommended protocol for testing for Herpes Simplex Virus (HSV)?

Testing Protocol for Herpes Simplex Virus (HSV)

Nucleic Acid Amplification Tests (NAATs) such as PCR are the gold standard for diagnosing HSV infections from active lesions due to their superior sensitivity and specificity compared to other methods. 1, 2

Testing for Active Lesions

• First-line test: NAAT/PCR is recommended as the primary diagnostic method for HSV detection from genital lesions, offering 11-71% higher sensitivity than viral culture 1
• Second-line test: Viral culture can be used if NAAT is unavailable, though it has lower sensitivity (90% for vesicular lesions, 70% for ulcerative lesions, and only 27% for crusting lesions) 1, 2
• Not recommended: Direct immunofluorescence assay and Tzanck smear lack sensitivity and should not be used for HSV diagnosis 1, 2

Sample Collection

• Vesicular lesions: Open vesicles with a sterile needle and collect fluid from the base of the lesion with a swab 1, 2
• Ulcerative lesions: Collect material directly from the base of the ulcer 1, 2
• Genital sites: For males, collect urethral swabs; for females, collect cervical/urethral swabs 1, 2
• Other sites: Samples can also be collected from conjunctiva, spinal fluid, or urine depending on clinical presentation 1, 3

Sample Handling

• For PCR: Less strict transportation conditions are acceptable 1
• For viral culture: Samples should be refrigerated during transport and processed within 24 hours to maintain viability 1, 2

Serological Testing

• When to use: Serological tests should be used when no active lesions are present, for screening high-risk individuals, or when lesion tests are negative but clinical suspicion remains high 1, 2
• Type-specific tests: Only type-specific glycoprotein G-based serologic assays should be used to differentiate between HSV-1 and HSV-2 antibodies 1, 2
• Limitations: HSV-1 serologic tests lack sensitivity (around 70%), while HSV-2 tests may have low specificity, especially with low index values (1.1-2.9 has only 39.8% specificity) 1, 4
• Interpretation: Higher index values (≥3.0) for HSV-2 tests provide better specificity (78.6%) 1
• False negatives: Commercial type-specific antibody tests can be false negative in 12-30% of patients with recurrent HSV-1 or HSV-2 DNA positive genital lesions 4

Importance of HSV Typing

• HSV typing is essential for counseling and prognosis as HSV-1 and HSV-2 have different recurrence patterns and transmission risks 1, 2
• Up to 50% of first-episode genital herpes cases are caused by HSV-1 2
• Recurrences and subclinical viral shedding are less frequent with genital HSV-1 than HSV-2 2

Clinical Pitfalls to Avoid

• Do not rely solely on clinical diagnosis without laboratory confirmation, as symptoms can mimic other conditions 1
• Do not use HSV molecular assays in the absence of genital ulcers due to intermittent viral shedding 1
• Do not use non-type-specific serologic tests as they cannot differentiate between HSV-1 and HSV-2 1, 5
• Be aware that widespread screening for HSV antibodies is not recommended in the general population 2, 5
• Consider using multiple serologic tests when results are equivocal, as a single test may yield false-negative results 4