Evaluation of a serum and urine-based ELISA testing distinct antigens for the diagnosis of tegumentary leishmaniasis

Abstract

The diagnosis of tegumentary leishmaniasis (TL) is hampered by variable sensitivity and/or specificity of the tests. In this context, the identification of more refined antigens could contribute to improve the diagnostic quality, as well as the employ of less invasive biological samples. In this study, the eukaryotic initiation factor 5a (eIF5A) protein, one specific B-cell epitope predicted in the protein sequence, and a parasite antigenic preparation (SLA) were evaluated as antigens in ELISA experiments, which were reacted against paired serum and urine samples from 170 patients. ROC curves were constructed with the individual OD values and, when serum was used as analyte, eIF5a, peptide and SLA showed sensitivity of 44.0 %, 29.3 % and 29.3 %, respectively, and specificity of 100 %, 99.0 %, and 96.0 %, respectively PPV, NPV and Youden index for reIF5a were 100 %, 52.0 % and 0.44, respectively; while for peptide were of 98.0 %, 46.5 %, and 0.28, respectively; and for SLA, they were of 92.0 %, 46.0 %, and 0.26, respectively. Using urine as biological sample; eIF5a, peptide and SLA showed sensitivity of 100 %, 48.0 % and 52.0 %, respectively, and specificity of 99.1 %, 98.9 %, and 89.0 %, respectively. PPV, NPV and Youden index values for reIF5a were of 99.3 %, 100 % and 0.99, respectively; while for peptide were of 99.1 %, 54.3 %, and 0.47, respectively; and for SLA, they were of 88.0 %, 53.5 %, and 0.41, respectively. A preliminary assay using paired samples collected before and after treatment of eight patients showed a significant reduction in IgG levels when the three antigens were tested, with highest reductions found when urine was used as analyte. In this context, data suggest the use of patient urine as an alternative biological analyte for the diagnosis of TL.