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Quantitation Using Informative Zeros (QUIZ): applications for determining GMO content of samples without recourse to certified reference materials

Contact: David Lee

Current EU legislations require that food above certain GMO thresholds are labeled accordingly. These are set at 0.9%, 0.5% and zero % for authorized, currently unauthorized but has passed in other recognized state and unauthorized events, respectively.

Enforcement requires the ability to determine the GMO content of foods and this is achieved using real-time PCR (rt-PCR). The reaction kinetics of the unknown sample is compared with those of a set of certified reference materials (CRMs), which consists of highly accurately determined GMO set of samples which acts as references: GMO of unknown is interpolated from those of the standards.

In a move away from the use of CRMs, NIAB has devised an alternative strategy of GMO quantification “Quantitation using informative zeros” (QUIZ) that applies most probable number statistics measure the numbers of GMO-related and reference sequences to provide an estimate of GMO content. Proof of principle of QUIZ has already been demonstrated in a Food Standards Agency-funded project (Lee et al., 2008): this follow-on project aims to apply the QUIZ method and rt-PCR to quantify the amount of GMO in different MON810- and RoundUp Ready™ soya-containing samples in two laboratories, allowing both for intra- and inter-laboratory assessment of results and comparison of the two methods for reproducibility and accuracy.

Since the accuracy of statistical methods relies on numbers, QUIZ will also explore means of extracting data from ‘preliminary experiments’. For example, determining the correct dilutions of the samples for testing requires a series of amplifications of the GMO and reference gene targets. Multiple repeats for each dilution of this process can reduce the amount of testing whilst still giving acceptably accurate results for statutory purposes.

Funding: Food Standards Agency

Collaborating Institutions: Central Science Laboratories (CSL)