Microscopy and Polymerase Chain Reaction on Giemsa-Stained Smears: A Combined Approach for Cutaneous Leishmaniasis Diagnosis

Abstract

Microscopic examination (ME) of dermal scrapings is widely used for biological confirmation of cutaneous leishmaniasis (CL), a major health concern in North Africa. This study aims to evaluate this technique and to assess the contribution of stained smears as the DNA source for polymerase chain reaction (PCR). In total, 227 archived Giemsa-stained smears from CL-suspected patients were examined by a standardized graded microscopy followed by scraping, DNA extraction, and kinetoplast DNA real-time PCR amplification. Examination of two 100-mm2 squares for 10 minutes each identified 76 positive slides with varying parasitic loads (1 to >40 amastigotes) and amastigote detection times (range: 1 minute to 18 minutes and 10 seconds). Polymerase chain reaction was more sensitive than ME (99% versus 75.2%), detecting 25 additional positive cases with low estimated parasitic load (median: 2 parasites/slide, interquartile range: 0.5-5.7). This combined approach associates the advantages of microscopy with the increased sensitivity of PCR, being particularly interesting in ME-negative cases with strong clinical suspicion.