To most effectively translate basic biochemical mechanisms into reliable, consistent, and accurate analytical methods, an extensive set of controls and standards must be put in place. These operate as checks and balances that make it possible to detect and rapidly correct technical problems, operator error, inhibitor effects, and other anomalies that could lead to inaccurate results. At FoodChain ID Testing, we have designed our analytical systems to limit such problems to the greatest extent possible. However, recognizing that they may arise from time to time, we’ve implemented additional standards and controls that are capable of consistently and reliably detecting such problems when they do crop up. In this way, FoodChain ID Testing assures that the analytical results reported are maximally reliable. These standards, controls, and quality assurance procedures are discussed in the following paragraphs.
Duplicate Analyses
FoodChain ID Testing scientists carry out two independent analyses of each sample. We begin by extracting DNA from the duplicate samples independently and then carry out separate PCR analyses of the duplicate DNA preparations. The results of these analyses must agree or the entire analytical process is repeated. Such independent analyses of duplicate samples is an effective way to catch and correct a wide range of operator or human errors that inevitably arise from time to time when even the most conscientious scientist carries out complex procedures, such as those required for GMO analysis. The principle behind the use of duplicate analyses is that it is unlikely an operator will make the same mistake with both duplicates. Thus, one duplicate serves as the comparator for the other, and if both do not yield very similar results, we conclude that a mistake may have been made and the whole analysis is repeated. At that time, a repeat analysis is again carried out in duplicate, and only when comparable results are obtained with the duplicate samples are we confident that the analysis was carried out correctly.
External Standards
A series of control reactions—technically termed external standards—are run along with each set of unknowns. They consist of a series of samples of carefully defined GMO composition. When the analytical results from a series of external standards are plotted, they then serve as a reference point, or standard curve, against which samples can be compared in order to calculate the concentration of genetically modified material in the sample.
Negative Controls
As part of the external standard series we also run PCR reactions that contain DNA verified to be free of genetically modified material. These are termed negative controls. In order for any aspect of the PCR analysis to be considered valid, analysis of the negative control samples must indicate the absence of genetically modified material. This is a critical control that verifies that the reagents used in all analyses are free from contamination—such as, for example, amplicon contamination—with genetically modified material. This control is critical in detecting false positives. If results with this control come up positive, or if other results suggest the possibility of a false positive, we implement a series of additional controls and laboratory procedures that allow us to trace the source of the contamination and rapidly correct it.
