Abstract
The levels of anti-Leishmania infantum antibodies are relevant with the diagnosis and the followup of infected dogs. Both ELISA (Enzyme-Linked Immunosorbent Assay) and IFAT (Indirect Immuno-Fluorescent Antibody Test) may be employed to estimate the antibody levels in dogs, but at present, the correlation between ELISA absorbance and IFAT titer has not been investigated. In this paper, we compared the optical densities obtained with a commercial ELISA, Leiscan?(Laboratorios Dr. Esteve S.A.), versus the titers obtained by in house IFAT. We measured ELISA absorbance of: 44 IFAT negative samples coming from an endemic area; 10 negative samples coming from a non endemic area; 29 samples with an IFAT titer between 1/40 and 1/80; 10 samples with an IFAT titer of 1/160; 9 samples with an IFAT titer of 1/320; 10 samples with an IFAT titer of 1/640; 10 samples with an IFAT titer ≥ of 1/1280. Results show that: a) there is a poor correlation between IFAT titer and ELISA absorbance; b) Leiscan? is not able to distinguish between IFAT negative samples and IFAT titers up to 1:160; c) IFAT negative samples from an endemic or non endemic area show different ELISA absorbance; d) the performance of the kit may be improved by the use of a more appropriate cut-off.
Highlights
The choice of the correct cut-off is a pivotal step for the performance of Enzyme-Linked Immunosorbent Assay (ELISA); and a wrong choice will results in a misinterpretation of results
From ELISA, an advantage of an end-point Immune-Fluorescent Antibody Test (IFAT) titration is that the clinician, not the laboratory, may assign the appropriate weight to the obtained results, with the followup and the geographical area of provenience of the samples
This paper show evidence that Leiscan® is not suitable for the detection of anti-leishmania antibodies in dog serum mainly due to the inappropriate choice of the cut-off included in the kit
Summary
(2015) The Serological Diagnosis of Canine Leishmaniasis: Commercial ELISA or in House IFAT? Canine leishmaniasis is diagnosed directly through the presence of the parasite by direct microscopic examination of lymph nodes, bone marrow aspirates and/or culture of skin lesions, or indirectly by serological techniques. PCR has been described as a method sensitive enough to detect all infected individuals, results may vary according to the sampled tissue. PCR appears too sensitive for mass screening and shows a low predictive value in detecting disease [3] [4]. None of these methods is capable to give an unequivocal classification of the infected subject. A combination of serological and molecular methods may provide more reliable data
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