Diagnosis of cutaneous leishmaniasis: why punch when you can scrape?

Abstract

Cutaneous leishmaniasis (CL) has been introduced to the Leishmania under-endemic Lebanese population in an uncontrolled manner as a result of recent large-scale displacement of refugees from endemic Syria. Accordingly, a quick and reliable method to diagnose CL is essential. Matched punch biopsies and air-dried scrapings on 72 patients were obtained. Scrapings were collected in two forms: thick drop (N = 33) or thin smear (N = 39). Clinical information was recorded. Sections of punch biopsies and scrapings were stained and examined microscopically. Polymerase chain reaction (PCR) was performed on both scraping forms and biopsies. The diagnostic sensitivity of the tests performed revealed that microscopy in conjunction with PCR on punch biopsies was the most sensitive test (93%) overall. However, taken individually, microscopy and PCR yielded the highest sensitivities when performed on drop scrapings (63% and 85%, respectively), and not smear scrapings (38% and 56%, respectively) as compared with the punch biopsies (44% and 83%, respectively). Microscopic concordance for punch biopsies and drop scrapings was present in 25 of 33 cases. Concordance was predicted only by the high/low parasitic index (PI: 3.1 ± 1.7 and 0.4 ± 0.5, respectively; P < 0.05). Herein, we optimized a novel rapid method for reliable diagnosis of CL based on drop scrapings with good agreement with the gold standard punch biopsy technique.

Figure 1.

Nodular erythematous facial lesion in a 5-year-old child with cutaneous leishmaniasis (A). A punch biopsy (B), showing numerous amastigotes is collected in addition to thick drop and thin smear scrapings (C). Smears stained with Wright Giemsa (D), Diff quick (E), H&E (F), and Papanicolau (PAP) stain (G) are portrayed (×200).

Figure 2.

The detection rate by light microscopy showed superiority of thick drop scraping over other diagnostic techniques (P < 0.05). However, the combined detection rate by polymerase chain reaction (PCR) and light microscopy or PCR alone was relatively similar between drop scrapings and punch biopsies. Such findings suggest using thick drop scraping as a first approach towards diagnosis.