AusVet’s Evan Sergeant has now completed an internet-based epidemiological calculator for estimating disease prevalence from testing of pooled samples.
Development of the calculator was funded by the Australian Biosecurity CRC and the calculator is now available online at http://www.ausvet.com.au/pprev/
Pooled (or group) testing is a testing strategy where samples from a number of individuals are aggregated into a single sample (or pool) and multiple such pools are then tested for the disease or agent of interest. Pooling of samples for testing provides one means of substantially reducing testing costs, without necessarily sacrificing precision of resulting prevalence or confidence interval estimates. Pooled testing for prevalence estimation is particularly useful where disease prevalence is likely to be low and where test-costs are high, relative to sample-collection costs.
Statistical techniques for estimating disease prevalence from testing of pooled samples have been developed and published in the scientific literature, but are computationally complex and therefore not widely used. This calculator provides a user-friendly interface for the implementation of a number of methods for estimating prevalence, assuming fixed or variable pool size, and assuming either perfect tests or tests of imperfect and uncertain sensitivity and/or specificity. A Bayesian method is also included to allow incorporation of prior knowledge of the likely prevalence and of test performance. The calculator also includes options for estimating the required pool size and number of pools to be tested to achieve a desired level of confidence and precision when designing prevalence surveys, and for simulated sampling to evaluate precision and potential bias of alternative pooling strategies.
The Pooled Prevalence Calculator provides an invaluable resource for researchers or epidemiologists undertaking disease surveillance involving prevalence estimation at the individual level (human, animal, aquatic animal, insects or plants) using pooled samples. The system also includes a comprehensive User Guide, Glossary and example analyses based on Hendra virus in fruit bats.
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