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ABSTRACT. de Magalhães, V.C.S., Costa, S.C.L., de Oliveira, U.V., de Almeida, C.P. & Munhoz, A.D.[Evaluation of a single serologic test in screening of crossbred dairy herd exposed to Neospora caninum]. Avaliação de um único exame sorológico na triagem de bovinos mestiços expostos à Neospora caninum. Revista Brasileira de Medicina Veterinária, 34(3):247-250, 2012. Laboratório de Análises Clínicas Veterinárias, Departamento de Ciências Agrárias e Ambientais, Universidade Estadual de Santa Cruz, Rodovia Ilhéus-Itabuna, Km 16, Salobrinho, Ilhéus, BA 45662-000, Brasil. Email: email@example.com. Crossbred animals from a dairy property with history of exposure to Neospora caninum were investigated in a longitudinal study. This study aimed to determine the relative specificity and sensitivity, positive and negative predictive values and agreement on a single sample detection of exposed and non-exposed animals to N. caninum. Blood was collected from 196 animals on three different occasions with a mean interval of 210 days between collections. The samples were examined for N. caninum using indirect fluorescent antibody test (cutoff titer 1:200). The serological results of the first sample collection were compared with those of the three consecutive collections. Positive animals were those with two or more reactive samples while negative ones were those with two or more negative samples. The sensitivity and specificity was 90.5% and 99.4%, respectively. The positive predictive value was 97.4% while the negative predictive value was 97.5%. The value of kappa was 0.92. High agreement, sensitivity and specificity suggest that a crossbred animal can be reliably characterized as exposed or non-exposed based on a single sample using a cutoff of 1:200 in the test. It is thus a valid method to determine the prevalence of N. caninum in mixed-race herds.