How many cows do I need? Sample size calculations for testing co-infection using existing study data



Hickey, Graeme ORCID: 0000-0002-4989-0054, Diggle, Peter, McNeilly, Tom N, Tongue, Sue C, Chase-Topping, Margo E and Williams, Diana ORCID: 0000-0001-8186-7236
(2014) How many cows do I need? Sample size calculations for testing co-infection using existing study data. [Poster]

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Abstract

Background There is little empirical research on the co-infection of Fasciola hepatica and Escherichia coli O157 in cattle. E. coli is controlled in the gut by a Type 1 immune response, whereas F. hepatica is known to suppress these immune responses and induce an anti-inflammatory environment in the host. We evaluate the statistical feasibility of re-testing isolates from a planned UK Food Standards Agency study on E. coli prevalence for F. hepatica presence, in order to establish whether there is an association. Methods We simulate synthetic datasets representing the proposed FSA sampling strategy. Sample sizes within farms and F. hepatica infections are simulated using Beta-Binomial distributions. E. coli infections are simulated using a logistic random-intercepts model under an alternative hypothesis that the odds ratio of E. coli presence is double when F. hepatica is present, with farm- and isolate-level prevalence rates constrained to current estimates. Statistical power is calculated by fitting models to each of the simulated datasets assuming a type I error rate of 5%. Owing to the E. coli status being known in advance of the F. hepatica test, we restrict the sampling strategy to only test farms with >0% and

Item Type: Poster
Depositing User: Symplectic Admin
Date Deposited: 27 May 2015 08:12
Last Modified: 02 Apr 2021 07:17
URI: https://livrepository.liverpool.ac.uk/id/eprint/2012061