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1-Stage Freedom analysis

Sample size for demonstration of freedom (detection of disease) using pooled testing


This utility calculates the number of pools required to be tested to provide a desired probability of detecting disease ( herd-sensitivity) at the specified design prevalence, for a large (infinite) population, using pooled testing and assuming a fixed pool size and a test of known sensitivity and 100% specificity. These analyses are an adaptation of the method from Cowling et al. (1999) (Prev Vet Med, 39:211-225), assuming known test sensitivity, perfect test specificity and 1 or more pools positive to declare a population infected (i.e. to be recognised as free there must be zero positive pools).

Inputs are the pool size used, pool-level test sensitivity, desired herd-sensitivity and design (target) prevalence. Test sensitivity is measured at the pool level (i.e. the probability that a pool will test positively if it represents one or more infected animals).

Outputs are:

  • - the number of pools of the specified size that must be tested to achieve the desired herd-sensitivity for the given design prevalence;
  • - a table and graph of various pool sizes and corresponding numbers of pools that must be tested to provide the desired herd-sensitivity for a range of design prevalence values, assuming the same test sensitivity applies to all pool sizes.


This site was created by Ausvet with funding from a range of sources. It provides a range of epidemiological tools for the use of researchers and epidemiologists, particularly in animal health.
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