Influence of diagnostic tests estimating prevalence during surveillance programs

The influence of diagnostic tests on the estimation of the prevalence and t he calculation of sample sizes with respect to different sampling schemes a re presented in this paper. These sampling schemes are used for the impleme ntation of surveillance programs. Assuming "perfect tests" (i.e. sensitivit y = specificity = 100%) the calculated sample sizes, e.g for an IBR/IPV-sur veillance or a paratuberculosis survey, are half of the sample sizes consid ering sensitivity and specificity of the diagnostic tests. However the prob ability not to identify infected livestocks may be 4 times higher neglectin g the test characteristics and assuming perfect tests.