AS 4659.1:2015 pdf free download – Guide to determining the equivalence of food microbiology test methods Part 1: Qualitative tests

AS 4659.1:2015 pdf free download – Guide to determining the equivalence of food microbiology test methods Part 1: Qualitative tests.
3.4 False negative
When the alternate method yields a negative result hut the reference method yields a positive result.
3.5 False positive
When the alternate method yields a positive result but the reference method yields a negative result.
NOTl: A false positive’ may he a true positive which was not detected by the reference method. Such occurrences need to he carefully verified: however, for the purpose of this Standard they will be considered fake posities because the Standard is aimed at demonstrating the equivalence of the two methods and is also applicable to the analysis of non-identical test samples. i.e. where the primary enrichment is different.
3.6 Fractional recovers’
Validation criteria that are satisfied when replicate samples of either the alternative or reference method yield 50% (range 25%—75%) positive responses.
3.7 Matrix
The food sample in which the target organism is to he detected.
3.S Presumptive
The result given by the method at a point where a decision may be made as to whether or not the matrix may contain the target organism. The method continues to confirm whether the presumptive result is in fact a positive result.
3.9 Reference culture
The culture designated in the appropriate Australian Standard method.
3.10 Reference method
The Australian Standard method against which the alternate method will he compared.
3.11 Target organism
The genus, species, antigenically, toxicologically or physiologically defined group of organisms which the reference method is designed to detect.
4 PROCFJ)tRE
4.1 Define the equivalence determination
The equivalence determination should be defined in terms of the following:
(a) The target organism’s genus, species. serotype, etc.
(h) The matrix under examination: the food and the characteristics that define it. e.g. the matrix should be defined in terms of characteristics such as p1-I, solids level, water activity, presence and composition of preservatives, season of production, brand name, etc. depending upon the nature of the matrix.
4.8 Acceptance criteria
4.8.1 General
The alternate method needs to he able to detect the target organism in all high inoculum samples and give negative results for all uninoculated controls.
The alternate method is considered to be equivalent when it is shown to yield results that are not statistically different to those obtained using the Australian Standard method.
4.8.2 Paired samples
For paired samples. acceptance criteria should be determined as follows:
Determine the total number of discordant results (V) and the number of false negative results (R) obtained using the alternate method as follows:
NOTE: Refer to Table I for guidance on how to derive the numbers for B and C.
Determine whether the disagreement between the methods is great enough so that it would be unlikely to have occurred by chance using McNemar’s test and the associated binomial probabilities.