What are the proper procedures for performing an Herpes Simplex Virus (HSV) Deoxyribonucleic Acid (DNA) test on a genitourinary skin lesion?

Proper Procedures for HSV DNA Testing on Genitourinary Skin Lesions

For optimal detection of HSV in genitourinary skin lesions, specimens should be collected from active lesions by opening vesicles with a sterile needle and collecting vesicular fluid with a cotton-wool or Dacron swab for nucleic acid amplification testing (NAAT). 1

Specimen Collection Procedure

For Vesicular Lesions:

• Open vesicles with a sterile needle
• Collect vesicular content with a cotton-wool or Dacron swab
• Introduce the swab into appropriate transport media for NAAT 1

For Ulcerative Lesions:

• The Kimura scraper should be used to sample the bases of ulcers or burst vesicles
• Before collecting, sterilize the spatula by heating in a flame and allow to cool
• Scrape the base of the lesion to collect cellular material 1

For Male Genital Lesions:

• Clean the area with a sterile gauze swab moistened in saline
• Draw back the prepuce to avoid contamination when sampling
• Collect material directly from the lesion 1

For Female Genital Lesions:

• Clean the area using a sterile gauze swab
• For vaginal/cervical lesions, insert a vaginal speculum moistened with warm water
• Clean the cervical canal opening thoroughly with a sterile gauze swab
• Collect material directly from visible lesions 1

Sample Handling

• PCR testing is the preferred method for HSV detection due to its consistently higher sensitivity compared to viral culture 2, 3
• Type-specific identification (HSV-1 vs HSV-2) is essential for proper patient counseling and prognosis 2
• Transport specimens promptly to the laboratory in appropriate viral transport media

Important Considerations

• Timing of collection is critical - early vesicular lesions yield the highest viral load
• PCR can detect HSV in lesions at all stages, but is particularly valuable for late-stage lesions where culture sensitivity drops significantly 4
• False negatives may occur if:
  • The lesion is already healing
  • Inadequate sample collection technique is used
  • Improper transport conditions are employed

Common Pitfalls to Avoid

1. Collecting from crusted lesions - These contain less viable virus; always prioritize vesicles or the base of fresh ulcers
2. Improper vesicle opening - Gently open vesicles to preserve viral material
3. Contamination with topical medications - Clean the area thoroughly before collection
4. Delayed transport - Viral viability decreases with time; expedite specimen delivery to the laboratory
5. Using inappropriate swabs - Cotton-wool or Dacron swabs are recommended; avoid calcium alginate swabs which may inhibit PCR 1

PCR-based testing has replaced viral culture as the gold standard for HSV detection from genital lesions due to its superior sensitivity and ability to provide type-specific results 3, 5. Modern multiplex PCR assays can simultaneously detect and differentiate between HSV-1 and HSV-2, which is crucial for patient counseling regarding prognosis and transmission risk 6.