Detection of genetically modified organisms in food: critical points for duality assurance

The detection of genetically modified organisms (GMOs) by the polymerase ch ain reaction (PCR) is a complex multiparameter problem. Therefore, a number of critical issues in respect to quality control need to be considered. Fo r practical purposes, the PCR process itself can be divided into three subp rocesses: template isolation and reaction setup (pre-PCR), PCR reaction and detection of amplification products, and data evaluation (post-PCR). Cruci al factors for the pre-PCR process are the following: homogeneity of the sa mple to be analysed, performance of template isolation and purification in terms of yield and purity, standardized process for the estimation of conce ntrations of genomic DNA and all reagents used in the reaction. For the PCR itself, crucial factors to be controlled are: setup of reactions, batch to batch variations of reagents, temperature-lime programs used for the PCR a mplification, and the performance of different types of hardware (e.g. diff erent brands of thermocyclers). The crucial factor for the post-PCR process is the detection of the amplification products of the PCR. The tremendous sensitivity of PCR methods requires a careful and consequent separation of the three processes in terms of hardware, laboratory space and sample handl ing. The avoidance of contamination is one of the most critical factors. Th e goal of quality assurance measures must be to ensure appropriate results at maximum sensitivity. The complexity of any PCR system used for the detec tion of GMOs leads to the requirement of a careful validation process for a ny laboratory using such methods. For qualitative analyses crucial validati on parameters are: specificity, selectivity, repeatability, intermediate pr ecision, reproducibility, limit of detection and robustness.