BS ISO 22753:2021 pdf download – Molecular biomarker analysis — Method for the statistical evaluation of analytical results obtained in testing sub-sampled groups of genetically modified seeds and grains — General requirements The process of forming seed/grain groups from a series of sampling steps starting with the bulk seed/grain lot is shown in Figure 1, (1). Although the procedures for obtaining a laboratory sample from a seed/grain lot is not the subject of this document, a laboratory sample (2) from a seed/grain lot shall be obtained appropriately. The procedures can be designed according to the References [3], [6], [10], [11], [12], [15], [19] and [23]. The laboratory sample shall be thoroughly mixed and divided/reduced to create the test sample (3). Likewise, the test sample shall be thoroughly mixed (i.e. homogeneous) and divided into seed/grain groups (each group represented as an array in Figure 1, (4)) following simple random sampling principles. The seed/grain groups can vary in size from one single seed/grain up to the complete test sample (i.e. a single bulk). In most cases, multiple seed/grain groups are created from the test sample. A determined number of seeds/grains can either be obtained by weighing or a volumetric measurement, where an approximation of number is made based on a determined conversion factor (e.g. thousand seeds/grains weight). For the case that weight is used to obtain the seed/grain groups, the operator shall have an estimate of the variability introduced by using weight rather than seed/grain count. The group testing procedure described in Clause 7 is carried out on the collective qualitative (positive or negative) results for each seed/grain group. 4.3 Detection methods for the qualitative analysis of GM seed/grain in seed/grain groups In general, GMO detection methods are categorized into two classes [ 21 ] . The first class of assays targets a nucleic acid sequence for detecting GMO presence. The second class includes methods for detecting a specified protein that confers a specific transgenic trait. Detection methods from either or both classes should be selected considering fitness-for-purpose. Guidance on the selection of qualitative methods is provided in Clause 8. Further details can be found in ISO 21569 [ 4 ] and ISO 21572. 4.4 Statistical evaluation Sampling and measurement uncertainty shall be considered. Sampling uncertainty can be adequately considered using the binomial distribution [ 18 ][ 2 ] . The FPR and the FNR of the qualitative assay should be considered...
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