What investigations should be ordered for a new penile ulcer?

Investigations for a New Penile Ulcer

For any new penile ulcer, you must order: (1) serologic test for syphilis, (2) HSV testing (preferably NAAT/PCR), and (3) HIV testing. 1, 2 These three tests form the essential baseline workup because diagnosis based on clinical examination alone is inaccurate, and these infections carry significant morbidity including increased HIV transmission risk.

Essential Testing Panel

Mandatory Tests (Order for All Patients)

• Syphilis serology - Non-negotiable baseline test 1, 2

  • Most labs now use reverse algorithm: treponemal-specific test (EIA/chemiluminescence) first, followed by RPR to confirm 3
  • If darkfield microscopy or direct immunofluorescence for Treponema pallidum is available, obtain this from ulcer exudate 1, 2

• HSV testing - Use NAAT/PCR when available (preferred over culture) 3, 4

  • NAAT/PCR has >90% sensitivity and specificity 4
  • Must differentiate HSV-1 from HSV-2 to counsel on recurrence rates (HSV-2: 90% vs HSV-1: 55%) 3
  • If only culture available, use it—but recognize sensitivity drops as ulcers heal 4
  • Do NOT use direct immunofluorescence or Tzanck smear (inadequate sensitivity) 4

• HIV testing - Critical given genital ulcers increase HIV transmission risk 1, 2

  • Retest at 3 months if initially negative 1, 2

Additional Testing Based on Epidemiology

• Culture for Haemophilus ducreyi (chancroid) - Order if:
  • You practice in an area with known chancroid prevalence 1, 2
  • Patient has painful ulcer with tender inguinal adenopathy (especially if suppurative) 1
  • Caveat: Special culture media often not commercially available; sensitivity ≤80% even with optimal media 1, 2

Important Clinical Context

Why These Tests Matter

• 3-10% of patients have multiple simultaneous infections 1
• Up to 25% of patients remain undiagnosed even after complete testing 1, 2
• Clinical diagnosis alone is frequently wrong 1, 2
• All three major causes (HSV, syphilis, chancroid) are cofactors for HIV transmission 1

Specimen Collection Technique

For HSV testing from ulcers 5:

• Open vesicles with sterile needle if present
• Swab the base of ulcers or burst vesicles (not just surface)
• Use cotton or Dacron swabs
• Apply to slide for immunofluorescence OR place in transport media for culture/NAAT

Common Pitfalls to Avoid

1. Don't wait for test results to treat - You often must initiate empiric therapy before results return 1, 2
2. Don't skip syphilis testing - This is the only test that should be done universally regardless of clinical suspicion 1, 2
3. Don't use HSV serology for acute ulcer diagnosis - Only use NAAT/PCR or culture from the lesion itself; serology cannot diagnose acute infection and has a window period up to 12 weeks 4
4. Don't forget coinfection - 10% of chancroid patients have concurrent T. pallidum or HSV 1, 2

When to Expand Testing

Consider additional workup for:

• Lymphogranuloma venereum - If patient has systemic symptoms or is MSM with rectal involvement 6
• Biopsy - If ulcer appearance atypical, not healing, or concern for malignancy (squamous cell carcinoma, premalignant lesions) 7, 8
• Bacterial culture - If secondary infection suspected 9

Follow-up Testing

If initial tests negative 1, 2:

• Repeat syphilis serology at 3 months
• Repeat HIV testing at 3 months
• Consider HSV type-specific serology if lesion testing negative but clinical suspicion high (wait 12 weeks for seroconversion) 4