GMO analyses

ScanBi Diagnostics bases all its GMO analyses on detection of DNA using Real-Time PCR. Real-Time PCR is by far the most sensitive GMO testing method and the only one recognised by the EU. The method is so sensitive that it can detect a single copy of DNA. High quality is very important and includes a strong focus on avoiding false negative as well as false positive results.

All ScanBi Diagnostics analyses are based on two independent sub-samples, which are analysed in parallel. A calibrant is always included in the test so that the total amount of plant DNA in the sample can be calculated. This information can be used to determine the limit of detection (LOD) in each sample analysed, which can be as low as 0.01% GM gene copies relative to the number of haploid genome copies analysed. However, ScanBi Diagnostics generally recommend reports with a LOD at 0.1%.
 

GMO analyses step-by-step

Grinding: Samples that are not liquid or powder are homogenised to particles with a size of <0.2 mm. A control is included in conjunction with homogenisation to ensure that there is no cross-contamination between samples.

DNA extraction: Two sub-samples of approx. 2 g each are used for the DNA extraction. These two sub-samples are extracted separately. The homogenisation control is extracted in parallel with the samples.

Real-Time PCR analysis: All analyses are performed by Real-Time PCR (Applied Biosystems 7900 or 7300) with the use of Taqman® chemistry. The specificity of all primers and probes is validated against certified reference material. Each sub-sample is analysed for the relevant traits. In parallel positive controls, both the reference gene and GM target are analysed in order to ensure that the desired LOD (e.g. 0.1% GM copies of the haploid genome) is reached for all samples analysed.

Qualitative analysis: This culminates in a report stating DETECTED or NOT DETECTED with the actual LOD of the sample. When traces of a GM element are detected in only one of the sub-samples, it is very important to ensure that this is not a false positive. Therefore each sub-sample is re-analysed and the answer obtained is only given if a positive result is obtained with reproducibility in both sub-samples at the desired LOD. Based on the qualitative results from a positive sample, we can provide the customer with an estimate of the content in the sample.

Quantification: Quantification includes three Real-time PCR tests of each of the two DNA sub-samples and the results are correlated to a standard curve. The limit of quantification can be as low as 0.05% GM copies of the haploid genome, but this depends on the material.
 
The samples can be processed and/or complex products. The lowest detection limit is obtained on a pure product which has not been processed.