What are the diagnostic tests for granuloma inguinale?

Diagnostic Tests for Granuloma Inguinale (Donovanosis)

The definitive diagnosis of granuloma inguinale requires visualization of dark-staining Donovan bodies on tissue crush preparation or biopsy of the lesion. 1

Clinical Presentation

• Granuloma inguinale presents as painless, progressive, ulcerative lesions without regional lymphadenopathy 1
• Lesions have a characteristic "beefy red appearance" and bleed easily on contact 1
• The disease is endemic in tropical and developing areas including India, Papua New Guinea, central Australia, and southern Africa 1

Diagnostic Methods

Primary Diagnostic Test

• Microscopic visualization of Donovan bodies:
  • Obtained through tissue crush preparation or biopsy of lesion 1
  • Specimens should be stained with Wright or Giemsa stain 1
  • Donovan bodies appear as dark-staining intracytoplasmic inclusions within histiocytes 1

Specimen Collection

• For tissue crush preparation:
  • Collect scraping from the lesion base 1
  • Place in formalin 1
  • Transport at room temperature within 2 hours 1
• For biopsy:
  • Sample should be taken from the advancing edge of the lesion where bacterial load is highest 1
  • Avoid necrotic areas which may have secondary bacterial infection 1

Laboratory Considerations

• The causative organism (Calymmatobacterium granulomatis, proposed reclassification as Klebsiella granulomatis) cannot be cultured on standard microbiologic media 1, 2
• Advanced laboratory techniques have been developed but are not routinely available:
  • Monocyte co-culture system has been used in research settings 3
  • Polymerase chain reaction (PCR) methods have been developed more recently 2

Differential Diagnosis

• Secondary bacterial infection may develop in lesions 1
• Lesions might be coinfected with other sexually transmitted pathogens 1
• Histopathologically, donovanosis can occasionally simulate epithelioma 4

Special Considerations

• In children, unusual presentations such as otitis media and mastoiditis have been reported, suggesting possible transmission during vaginal delivery from infected mothers 5
• Complicated cases with extensive perianal fistulas and abscesses may require surgical management in addition to antibiotic therapy 6

Diagnostic Algorithm

1. Clinical suspicion based on characteristic painless, progressive ulcerative lesions with beefy red appearance
2. Collect tissue sample through scraping or biopsy from the base or advancing edge of the lesion
3. Prepare tissue crush smear or histological sections
4. Stain with Wright or Giemsa stain
5. Examine microscopically for characteristic Donovan bodies within histiocytes
6. If initial examination is negative but clinical suspicion remains high, repeat biopsy from another site

Pitfalls and Caveats

• False negatives may occur if samples are taken from necrotic areas 1
• Secondary bacterial infection may obscure the diagnosis 1
• The organism cannot be cultured using standard microbiological techniques, making diagnosis dependent on microscopic visualization 1
• Clinical diagnosis alone is unreliable; laboratory confirmation is essential 3