Comparative safety assessment of genetically modified crops: focus on equivalence with reference varieties could contribute to more efficient and effective field trials

Abstract

The initial compositional analysis of plants plays an important role within the internationally harmonized comparative safety assessment approach for genetically modified plants. Current EFSA guidance prescribes two types of comparison, namely difference tests with regard to a conventional comparator or control, and equivalence tests with regard to a collection of commercial reference varieties. The experience gained so far shows that most of the statistically significant differences between the test and control can be discounted based on the fact that they are still within equivalence limits of reference varieties with a presumed history of safe use. Inclusion of a test variety and reference varieties into field trial design, and of the statistical equivalence test would already suffice for the purpose of finding relevant parameters that warrant further assessment, hence both the inclusion of a conventional counterpart and the performance of difference testing can be omitted. This would also allow for the inclusion of safety testing regimes into plant variety testing VCU (value for cultivation and use) or other, independent variety trials.

Keywords: Comparative safety assessment; Crop composition; Equivalence testing; Field trials; Genetically modified crops; Statistical analysis.

Fig. 1

The various comparisons between test, control, and reference varieties (with Capsicum varieties as a hypothetical example)

Fig. 2

Graphical display for observed differences, difference and equivalence tests (modified from EU 2013). Shown are: (horizontal lines) the confidence interval (CI) for the difference, and (vertical lines) lower and upper equivalence limits and the line of no difference. A significant difference is shown when the line of no difference is outside the CI. Equivalence is shown when the CI falls completely inside the lower and upper equivalence limit