Reliable diagnosis of post‐kala‐azar dermal leishmaniasis (PKDL) using slit aspirate specimen to avoid invasive sampling procedures

Abstract

Confirmatory diagnosis of post-kala-azar dermal leishmaniasis (PKDL) is primarily based on invasive skin biopsy procedure. We evaluated the utility of minimally invasive slit aspirate specimen for serological and molecular diagnosis of PKDL. We compared the PKDL diagnosis using slit aspirate and skin biopsy specimens from the same patients. Serological diagnosis using rK39 strip test was performed with serum and slit aspirate sample; molecular diagnosis for parasite detection and quantification was carried out by quantitative real-time PCR (Q-PCR) with skin biopsy and slit aspirate sample. The rK39 serological strip test was positive in all PKDL cases with both slit aspirate and serum samples (n=50) and negative in all control cases (n=24), giving a sensitivity of 100% (95% CI: 92.9-100%) and a specificity of 100% (95% CI: 86.2-100%). Quantitative-PCR detected parasite in all PKDL slit aspirates (n=50, sensitivity=100%, 95% CI: 92.9-100%) and tissue biopsies (n=46, sensitivity=100%, 95% CI: 92.3-100; it was negative in all controls including dermal tissues (n=24) and slit aspirates (n=24), giving specificity of 100% (95% CI: 86.2-100%). The parasite load in tissue and slit aspirate samples was significantly (P<0.0001) correlated (r=0.82). Slit aspirates are a simpler and minimally invasive sampling technique for initial screening by serology followed by confirmatory diagnosis of PKDL with microscopy and/or Q-PCR. The simplified procedure has the potential for epidemiological studies and assessment of cure in PKDL.