Serological diagnosis of canine leishmaniosis: comparison of three commercially available tests

Quantitative serology is an important tool in canine leishmaniosis diagnostics from clinical and epidemiological points of view. Serologic diagnosis in laboratories is traditionally carried out by immunofluorescent antibody test (IFAT), but enzyme-linked immunosorbent assays (ELISA) are being increasingly employed. Two commercially available ELISAs (LEISHMANIA-ELISA DOG® [LED] and INGEZIM LEISHMANIA® [IL]) for the detection of Leishmania infantum infection in dogs were compared with the classical IFAT technique. Ninety-two canine serum samples covering a broad range of IFAT titers were chosen for evaluation. Titers ranged from negative (<1:50) to high (>1:3,200). Statistical analysis showed high correlation between all three assays for both negative and positive IFAT-tested samples as described by respective Spearman's rank correlation coefficient (r s), but results varied for samples with inconclusive IFAT titers (1:50-1:100) with IL stating samples predominantly negative. The highest accordance was found between LED and IFAT (percentage of identical results = 83.7%; r(s) = 0.90, p < 0.0001). IL showed higher analogy with LED (accordance = 81.5%; r(s )= 0.88, p < 0.0001) than with IFAT (73.9%; r(s) = 0.80, p < 0.0001). The distribution of the different ELISA scores is discussed and grouped according to correspondent IFAT titers to familiarize practitioners with the range of these tests since antibody levels play an important role in clinical management of canine patients with L. infantum infection.