Diagnosing human cutaneous leishmaniasis using fluorescence in situ hybridization.

Area of Science:

• Medical diagnostics
• Parasitology
• Infectious diseases

Background:

• Cutaneous leishmaniasis (CL) is a significant endemic disease in Sri Lanka.
• Current diagnostic methods like Giemsa-stained slit-skin-smears (SSS-Giemsa) and histology (FFPE-H&E) have limited sensitivity (40-70%).
• Polymerase chain reaction (PCR) is accurate but not widely accessible.

Purpose of the Study:

• To evaluate the sensitivity and specificity of a fluorescence in situ hybridization (FISH) assay for diagnosing CL.
• To compare FISH on skin smears (SSS-FISH) and formalin-fixed paraffin-embedded tissues (FFPE-FISH) against routine methods and PCR.

Main Methods:

• Collected samples from 123 suspected CL patients and 61 controls.
• Performed SSS-Giemsa, SSS-FISH, FFPE-H&E, and FFPE-FISH.
• Utilized PCR as the gold standard for comparison.
• Employed two cyanine 3-tagged Leishmania genus-specific probes for FISH.

Main Results:

• FFPE-FISH sensitivity was 80.9%, significantly higher than FFPE-H&E (50.4%) (p < 0.001).
• SSS-Giemsa (76.5%) and SSS-FISH (79.1%) showed similar sensitivities.
• FFPE-FISH specificity was 93.4%, while SSS-FISH was 96.7%.

Conclusions:

• Formalin-fixed paraffin-embedded FISH (FFPE-FISH) is a more accurate diagnostic tool for cutaneous leishmaniasis than standard Hematoxylin & Eosin (FFPE-H&E) staining.
• Slit-skin smear FISH (SSS-FISH) offers no diagnostic advantage over SSS-Giemsa.
• SSS-FISH may be useful in wound healing studies requiring immunological probes due to its minimally invasive nature.