Abstract

SIGNORINI, M.L. et al. Herd-level predictive values and sensitivity of mastitis base on individual-animal mastitis characteristics and sample size. InVet [online]. 2008, vol.10, n.2, pp.91-102. ISSN 1668-3498.

Our objective was to build a simulation model to illustrate the difficulties in interpreting the results of intramammary infections diagnostic test and its relationship with the herd sanitary status and the sample size. Data used in this study corresponded to microbiological testing of composite milk samples of lactating cows from dairy farms located in the Provinces of Santa Fe, Córdoba and Buenos Aires (Argentina) between May 1999 and August 2007. The results reinforce the importance to be given to the type or test used to studies at herd-level and the consideration to interpreting the diseases prevalence distributions before making any extrapolation from individual diagnostic tests. To properly classify of mammary infections prevalence at herd-level, if presumed a low herd prevalence, a greater proportion of animals must be sampled and tend to use diagnostic test with high sensibility, whereas if the herd prevalence is high, the most important to consider is the diagnostic test specificity.

Keywords : Mastitis; Diagnostic test; Sensibility; Specificity; Predictive value.

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