[Influence of diagnostic tests for estimating prevalence during surveillance programs].

The influence of diagnostic tests on the estimation of the prevalence and the calculation of sample sizes with respect to different sampling schemes are presented in this paper. These sampling schemes are used for the implementation of surveillance programs. Assuming "perfect tests" (i.e. sensitivity = specificity = 100%) the calculated sample sizes, e.g. for an IBR/IPV-surveillance or a paratuberculosis survey, are half of the sample sizes considering sensitivity and specificity of the diagnostic tests. However the probability not to identify infected livestocks may be 4 times higher neglecting the test characteristics and assuming perfect tests.