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.