The Rapid Test Based on Leishmania infantum Chimeric rK28 Protein Improves the Diagnosis of Canine Visceral Leishmaniasis by Reducing the Detection of False-Positive Dogs

Abstract

Visceral Leishmaniasis (VL) has spread to many urban centers worldwide. Dogs are considered the main reservoir of VL, because canine cases often precede the occurrence of human cases. Detection and euthanasia of serologically positive dogs is one of the primary VL control measures utilized in some countries, including Brazil. Using accurate diagnostic tests can minimize one undesirable consequence of this measure, culling false-positive dogs, and reduce the maintenance of false-negative dogs in endemic areas. In December 2011, the Brazilian Ministry of Health replaced the ELISA (EIE CVL) screening method and Indirect Immunofluorescence Test (IFI CVL) confirmatory method with a new protocol using the rapid DPP CVL screening test and EIE CVL confirmatory test. A study of diagnostic accuracy of these two protocols was done by comparing their performance using serum samples collected from a random sample of 780 dogs in an endemic area of VL. All samples were evaluated by culture and real time PCR; 766 out of the 780 dogs were tested using the previous protocol (IFI CVL + EIE CVL) and all 780 were tested using the current protocol (DPP CVL + EIE CVL). Performances of both diagnostic protocols were evaluated using a latent class variable as the gold standard. The current protocol had a higher specificity (0.98 vs. 0.95) and PPV (0.83 vs. 0.70) than the previous protocol, although sensitivity of these two protocols was similar (0.73). When tested using sera from asymptomatic animals, the current protocol had a much higher PPV (0.63 vs. 0.40) than the previous protocol (although the sensitivity of either protocol was the same, 0.71). Considering a range of theoretical CVL prevalences, the projected PPVs were higher for the current protocol than for the previous protocol for each theoretical prevalence value. The findings presented herein show that the current protocol performed better than previous protocol primarily by reducing false-positive results.

Dogs with divergent serology for visceral leishmaniasis as sources of Leishmania infection for Lutzomyia longipalpis phlebotomine sand flies – an observational study in an endemic area in Brazil

“…The current protocol presented higher specificity (0.98 vs. 0.95) and higher positive predictive value (0.83 vs. 0.70) than the previous one. The sensitivity of both protocols was similar (0.73) but a reduction in the number of false positives was observed after the change [41]. Unfortunately, alternative methods with higher sensitivity and specificity, at affordable costs for public health services, are still unavailable [20,42].…”

Clinical and immunopathological findings during long term follow-up in Leishmania infantum experimentally infected dogs

“…Anti- Leishmania antibody levels were determined by the DPP CVL (Dual-Path Platform, Bio-Manguinhos) rapid test, which detects anti rk28-antibodies, as previously described 49 . All procedures were performed in accordance with manufacturer instructions.…”

Application of theLeishmania infantum21‐kDa recombinant protein for the development of an immunochromatographic test

“…Dipsticks containing recombinant K39 (rK39) antigen and recombinant K28 (rK28) antigen are the fastest sero‐diagnostic methods used in order to diagnose VL 35,36 . Dipstick rK39 and rK28 are rapid and simple tests which are used to screen for the symptomatic phase of VL.…”