The GM content in a food or feed product produced from or containing genetically modified organisms (GMO) has to be expressed in Europe in the form of a GM mass fraction. However, the most widely used quantification methods, based on PCR, are basically counting PCR-amplifiable DNA fragments in a sample extract. This paper outlines the requirements for obtaining comparable measurement results which are fit for regulatory decision-making. It introduces the concept of a reference measurement system which enables GMO analysis laboratories to relate their results to a universally accessible reference, thus establishing metrological traceability to a unique reference point. The conversion factors required for transforming data from one measurement unit into the other have to carry a minimum uncertainty and are anchored to specified certified reference materials. The establishment of such conversion factors and related calibration approaches to achieve comparable GM quantification results are sketched. Graphical abstract ᅟ.
Keywords: Conversion factor; Genetically modified organism; PCR; Quantification; Traceability; Unit of measurement.