title: Diagnostic performance of ELISA, IFAT and Western blot for the detection of anti-Leishmania infantum antibodies in cats using a Bayesian analysis without a gold standard.
abstract: BACKGROUND
  Anti-Leishmania antibodies are increasingly investigated in cats for epidemiological studies or for the diagnosis of clinical feline leishmaniosis. The immunofluorescent antibody test (IFAT), the enzyme-linked immunosorbent assay (ELISA) and western blot (WB) are the serological tests more frequently used. The aim of the present study was to assess diagnostic performance of IFAT, ELISA and WB to detect anti-L. infantum antibodies in feline serum samples obtained from endemic (n = 76) and non-endemic (n = 64) areas and from cats affected by feline leishmaniosis (n = 21) by a Bayesian approach without a gold standard.
  
  
  METHODS
  Cut-offs were set at 80 titre for IFAT and 40 ELISA units for ELISA. WB was considered positive in presence of at least a 18 KDa band. Statistical analysis was performed through a written routine with MATLAB software in the Bayesian framework. The latent data and observations from the joint posterior were simulated in the Bayesian approach by an iterative Markov Chain Monte Carlo technique using the Gibbs sampler for estimating sensitivity and specificity of the three tests.
  
  
  RESULTS
  The median seroprevalence in the sample used for evaluating the performance of tests was estimated at 0.27 [credible interval (CI) = 0.20-0.34]. The median sensitivity of the three different methods was 0.97 (CI: 0.86-1.00), 0.75 (CI: 0.61-0.87) and 0.70 (CI: 0.56-0.83) for WB, IFAT and ELISA, respectively. Median specificity reached 0.99 (CI: 0.96-1.00) with WB, 0.97 (CI: 0.93-0.99) with IFAT and 0.98 (CI: 0.94-1.00) with ELISA. IFAT was more sensitive than ELISA (75 vs 70%) for the detection of subclinical infection while ELISA was better for diagnosing clinical leishmaniosis when compared with IFAT (98 vs 97%).
  
  
  CONCLUSIONS
  The overall performance of all serological techniques was good and the most accurate test for anti-Leishmania antibody detection in feline serum samples was WB.
authors.affiliation: Istituto Zooprofilattico Sperimentale della Sicilia, A. Mirri, Via G. Marinuzzi 3, Palermo, 90129, Italy.
authors.forename: Maria Flaminia
authors.initials: MF
authors.lastname: Persichetti
authors.affiliation: Departament de Medicina i Cirurgia Animals. Facultat de Veterinària, Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola, 08193, Barcelona, Spain.
authors.forename: Laia
authors.initials: L
authors.lastname: Solano-Gallego
authors.affiliation: Istituto Zooprofilattico Sperimentale della Sicilia, A. Mirri, Via G. Marinuzzi 3, Palermo, 90129, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Vullo
authors.affiliation: Dipartimento di Scienze Veterinarie, Università degli Studi di Messina , Polo Universitario Annunziata, Messina, 98168, Italy.
authors.forename: Marisa
authors.initials: M
authors.lastname: Masucci
authors.affiliation: Centre Hospitalier Universitaire de Nice, Faculté de Médecine, Université de Nice-Sophia Antipolis, Inserm U 1065, Hôpital de l'Archet, 151, route de Saint Antoine de Ginestière, CS 23079 06202, Nice Cedex 3, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Marty
authors.affiliation: Parasitologie-Mycologie, Hôpital de l'Archet, Centre Hospitalier Universitaire de Nice, France-MIVEGEC, UMR IRD224 - CNRS 5290 - Université de Montpellier, Montpellier Cedex 5, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Delaunay
authors.affiliation: Centro di Referenza Nazionale per le Leishmaniosi (C.Re.Na.L), Istituto Zooprofilattico Sperimentale della Sicilia, A. Mirri, Via G. Marinuzzi 3, Palermo, 90129, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Vitale
authors.affiliation: Dipartimento di Scienze Veterinarie, Università degli Studi di Messina , Polo Universitario Annunziata, Messina, 98168, Italy. mariagrazia.pennisi@unime.it.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Pennisi
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D001499:Bayes Theorem; D015153:Blotting, Western / Q000379:methods / Q000592:standards; D002371:Cat Diseases / Q000175:diagnosis* / Q000276:immunology; D002415:Cats; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000379:methods / Q000592:standards; D007074:Immunoglobulin G / Q000097:blood; D018314:Leishmania infantum / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000175:diagnosis / Q000276:immunology / Q000662:veterinary*; D008297:Male; D012015:Reference Standards; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G
keywords: Bayesian analysis; Cat; Diagnostic performance; ELISA; Gold standard; IFAT; Leishmania; Leishmaniosis; Serological diagnosis; Western blot