Serological diagnosis of canine leishmaniosis: comparison of three commercial ELISA tests (Leiscan®, ID Screen® and Leishmania 96®), a rapid test (Speed Leish K®) and an in-house IFAT

BACKGROUND: Speed Leish K® is used as a serological screening test for Leishmania infection prior to vaccination. Limited comparative serological studies with Speed Leish K® have been performed. The aim of this study was to evaluate the diagnostic performance of four commercially available serologic tests including ELISAs (Leiscan®, ID Screen® and Leishmania 96®), a rapid test (Speed Leish K®) and an in-house IFAT for the detection of specific antibodies against Leishmania infantum antigen in dogs in different states of infection. METHODS: Sick infected dogs (n = 36), healthy infected dogs (n = 18), L. infantum seropositive dogs with low to high levels of antibodies (n = 53), dogs seropositive to other pathogens (to evaluate cross reaction) (n = 14) and uninfected dogs from a non-endemic area (n = 50) and from an endemic area (n = 32) were analysed by the serological methods mentioned above. RESULTS: The sensitivity was as follows: ID Screen® (0.953), Leiscan® and Leishmania 96® (0.925), IFAT (0.869) and Speed Leish K® (0.636). The maximum specificity (1.000) was attained for all diagnostic tests except the Leishmania 96® (0.896) and IFAT (0.917). The accuracy was as follows: ID Screen® (0.975), Leiscan® (0.961), Leishmania 96® (0.911), IFAT (0.892) and Speed Leish K® (0.808). In relation to the area under the ROC curve (AUC-ROC), the maximum value was attained with the ID Screen® (0.993) closely followed by Leiscan® (0.990), then, Leishmania 96® (0.962), IFAT (0.926) and Speed Leish K® (0.818). For the Kappa index, the best result was obtained by the ID Screen® (0.951) followed by Leiscan® (0.921), Leishmania 96® (0.822), IFAT (0.783) and Speed Leish K® (0.622). Statistically significant differences were found between the AUC-ROC of quantitative serological tests and the only qualitative rapid test evaluated. There were also statistically significant differences between AUC-ROC of the ELISAs (ID Screen® and Leiscan®) and IFAT. CONCLUSIONS: Leiscan® and ID Screen® had superior diagnostic performance measures than IFAT and all quantitative serological tests were superior when compared to Speed Leish K®. Thus, Speed Leish K® may be considered a less valuable screening test prior to vaccination as it may result in vaccination of seropositive dogs and in some cases seropositive sick dogs.