Abstract:
Cutaneous leishmaniasis (CL) is endemic in Sri Lanka. Giemsa-stained slit-skin-smears (SSSGiemsa) and histology are routinely used in diagnosis with a sensitivity of 40–70%. PCR
currently has limited accessibility. Therefore, we assessed the sensitivity and specificity of a
previously described fluorescence in situ hybridization assay, on skin smears and biopsy
samples to overcome the limitations encountered with routine diagnostic methods.
Samples from a total of 123 suspected CL patients were collected and subjected to SSSGiemsa, fluorescence in situ hybridization (FISH) on slit skin smears (SSS-FISH), formalin-fixedparaffin-embedded-tissues stained with Hematoxylin & Eosin staining (FFPE-H&E) and FISH on
formalin-fixed-paraffin-embedded-tissues (FFPE-FISH). Negative controls of 61 patient samples
were collected from a CL non-endemic area and subjected to the same procedures. The gold
standard PCR was used as a comparator. For FISH, two previously described cyanine 3 tagged
Leihsmania genus-specific probes were used.
Compared to PCR, SSS-Giemsa, SSS-FISH, FFPE-H&E, and FFPE-FISH had sensitivities of 76.5%,
79.1%, 50.4% and 80.9%, respectively. Routine diagnostic tests (SSS-Giemsa and FFPE-H&E) had
a specificity of 100%. SSS-FISH and FFPE-FISH had specificities of 96.7% and 93.4%, respectively.
FFPE-FISH had a statistically significant higher diagnostic performance than FFPE-H&E
(p < 0.001). The relative performance of SSS-Giemsa, SSS-FISH and FFPE-FISH was similar
(p > 0.05 for all comparisons).
We conclude that FFPE-FISH is a more accurate diagnostic tool than FFPE–H&E. SSS-FISH did
not have an additional advantage over SSS-Giemsa in diagnosis. However, SSS-FISH could be
recommended as a minimally invasive method in studies assessing wound healing where
immunological probes are used.
