Evaluation of urine for Leishmania infantum DNA detection by real-time quantitative PCR

- An optimized real-time qPCR assay was chosen for L. infantum DNA detection in urine samples.
- The chosen of the most adequate and feasible DNA extraction protocol was pivotal.
- The detection limit reached was 5 fg (~ 0.025 parasites) per μL of urine.
- Correlations with implementation of treatment were found.
- The assay indicated a good negative predictive value in urine samples from untreated suspected patients.

The availability of some sorts of biological samples which require noninvasive collection methods has led to an even greater interest in applying molecular biology on visceral leishmaniasis (VL) diagnosis, since these samples increase the safety and comfort of both patients and health professionals. In this context, this work aimed to evaluate the suitability of the urine as a specimen for Leishmania infantum kinetoplast DNA detection by real-time quantitative PCR (qPCR). Subsequent to the reproducibility analysis, the detection limit of the qPCR assay was set at 5 fg (~ 0.025 parasites) per μL of urine. From the comparative analysis performed with a set of diagnostic criteria (serological and molecular reference tests), concordance value of 96.08% was obtained (VL-suspected and HIV/AIDS patients, n = 51) (P > 0.05). Kappa coefficient (95% CI) indicated a good agreement between the test and the set of diagnostic criteria (k = 0.778 ± 0.151). The detection of Leishmania DNA in urine by qPCR was possible in untreated individuals, and in those with or without suggestive renal impairment. Fast depletion of the parasite's DNA in urine after treatment (from one dose of meglumine antimoniate) was suggested by negative qPCR results, thus indicating it as a potential alternative specimen to follow up the efficacy of therapeutic approaches. Even when evaluated in a clinically heterogeneous set of patients, the urine showed good prospect as sample for VL diagnosis by qPCR, also indicating a good negative predictive value for untreated suspected patients.